Engine Titanium Consortium - Center for Nondestructive Evaluation ...

Engine Titanium Consortium 

Quarterly Report 

January 1, 2002 – March 31, 2002 

Lisa Brasche, Bruce Thompson, ISU 

Andy Kinney, HW 

Thadd Patton, John Halase, GE 

Kevin Smith, Jeff Umbach, P&W 

on behalf of the Engine Titanium Consortium team 

June 1, 2002

Table of Contents 

TASK 1.1: NICKEL-BASED ALLOY INSPECTION ............................................................................................. 2 

SUBTASK 1.1.1: FUNDAMENTAL PROPERTY MEASUREMENTS FOR NICKEL BILLET ........................ 2 

SUBTASK 1.1.2: INSPECTION DEVELOPMENT FOR NICKEL BILLET..................................................... 13 

TASK 1.2: TITANIUM BILLET INSPECTION....................................................................................................... 20 

SUBTASK 1.2.1: INSPECTION DEVELOPMENT FOR TITANIUM BILLET................................................. 20 

TASK 1.3: TITANIUM FORGING INSPECTION .................................................................................................. 34 

SUBTASK 1.3.1: 

FUNDAMENTAL PROPERTY MEASUREMENTS FOR TITANIUM 

FORGINGS ....................................................................................................................... 34 

SUBTASK 1.3.2: INSPECTION DEVELOPMENT FOR TITANIUM FORGINGS.......................................... 54 

TASK 2.1: INSPECTION DEVELOPMENT FOR ROTATING COMPONENTS ................................................... 70 

SUBTASK 2.1.1: DEVELOPMENT OF UT CAPABILITY FOR INSERVICE INSPECTION .......................... 70 

SUBTASK 2.1.2: EDDY CURRENT PROBE EVALUATION AND IMPLEMENTATION ............................... 70 

TASK 2.2: INSPECTION DEVELOPMENT TRANSITIONS TO AIRLINE MAINTENANCE ................................ 70 

SUBTASK 2.2.1: APPLICATION OF ETC TOOLS IN OVERHAUL SHOPS – EC SCANNING.................... 70 

SUBTASK 2.2.2: HIGH SPEED BOLTHOLE EDDY CURRENT SCANNING............................................... 71 

SUBTASK 2.2.3: 

ENGINEERING STUDIES OF CLEANING AND DRYING PROCESS IN 

PREPARATION FOR FPI ................................................................................................. 77 

TASK 3.1: POD METHODOLOGY APPLICATIONS ........................................................................................... 86 

SUBTASK 3.1.1: POD OF ULTRASONIC INSPECTION OF BILLETS ........................................................ 86 

SUBTASK 3.1.2: POD OF ULTRASONIC INSPECTION OF TITANIUM FORGINGS ................................. 98 

SUBTASK 3.1.3: POD OF EDDY CURRENT INSPECTIONS IN THE FIELD.............................................. 106 

Quarterly Report – January 1, 2002 –March 31, 2002 

print date/time: 6/6/2002 - 8:39 AM – Page 1

Project 1: 

Task 1.1: 

Subtask 1.1.1: 

Production Inspection 

Nickel-based Alloy Inspection 

Fundamental Property 

Measurements for Nickel Billet 

Team Members: 

HW: Andy Kinney, Waled Hassan 

ISU: Frank Margetan, Bruce Thompson, 

Ron Roberts 

GE: Ed Nieters, Mike Gigliotti, Lee 

Perocchi, Jon Bartos, Mike Keller, Richard 

Klaassen, John Halase, Dave Copley 

PW: Jeff Umbach, Bob Goodwin, Andrei 

Degtyar, Harpreet Wasan 

Students: L. Yu 

Program initiation date: June 15, 1999 

Objectives: 

• To establish the basic ultrasonic properties of nickel-based alloy billet materials (Expected to be 

IN718, and one or more of Waspaloy, IN901, R95, or IN100) and relevant inclusions as an 

appropriate foundation for selection of ultrasonic inspection approaches. 

• To manufacture and characterize flat bottom hole (FBH), synthetic inclusion, and real defect 

standards to provide data for determining defect detectability and developing improved 

inspections. 

• To improve the understanding of the relationship of defect size, shape, and composition on 

defect detectability in Ni alloys. 

Approach: 

Alloy Selection: Several alloys have been selected for fundamental property measurements with 

IN718 selected to receive the primary focus. Alloys to be considered include Waspaloy, IN100, 

IN901, and R95. Sample design and fabrication for properties measurements will be initiated by 

the team members. A list of the types of melt-related defects encountered at the billet stage in 

Ni-based alloys, defect morphology in the forged condition, and importance to life management will 

be generated by RISC. The importance of defect parameters (size, concentration, morphology, 

presence of voids) on detectability and life will be determined through discussion with the lifing and 

materials communities. 

Sample Fabrication: The sequence of manufacturing the properties specimens and the specimen 

configuration will be planned to yield as much data as possible on properties as a function of depth 

and orientation. Novel configurations of coupons, and sequences of coupon extraction and 

characterization will be considered. Sample fabrication procedures will be coordinated with the 

Inspection Systems Capability Working Group to ensure use by both groups 

The proposed billet coupon scheme is shown in Figure 1. Because backscattered noise levels are 

strongly dependent on details of the metal microstructure, they can be used to guide the selection 

of coupon locations. From low and high noise regions, a "strip" specimen will be cut along the billet 



diameter, with transverse dimensions of 

approximately 1.5" x 1.5". This specimen 

would initially be used for property 

measurements in the axial and hoop 

directions at various depths. The strip 

specimen would then be sliced into a 

series of coupons and be used for property 

measurements in the radial direction. The 

team will agree on the final specimen 

configuration early in the program, using 

the approach described here as a starting 

point. Similar schemes will also be used 

to study ultrasonic properties in the axial 

and hoop directions as a function of 

position. Results of the anisotropy 

measurements will be provided to the 

Inspection Systems Capability Working 

Group for incorporation into the noise 

models and ultimately will be used to 

predict the change in POD as a function of 

position. The data will also provide 

guidance in design of transducers and 

optimal inspection parameters for nickel 

billet in subtask 1.1.2. 

Ultrasonic Property Measurements: 

Baseline ultrasonic properties (velocity, 

attenuation, and backscattered noise) of 

nickel billets will also be gathered for 

Axial Position 

Circumferential Position 

determination of the impact of properties on inspectability. Samples will be selected to address 

beam variability, with the expected sample set to include approximately 16 samples for each alloy. 

In Phase I, the ultrasonic properties of titanium billets were found to vary with position and 

inspection parameters, and similar variations are expected in nickel alloy billets and forgings. 

Selection of billets for properties specimens will be based on an initial screening inspection. 

Ultrasonic property measurements of the base alloys will provide the necessary noise distribution 

data for use by the Inspection Systems Capability Working Group in generating POD estimates for 

nickel billet. Signal distributions will be generated using FBH, synthetics, and the natural defects 

fabricated as defined above. Data on the natural defects will be used to develop and validate the 

flaw response and noise models and to generate the POD estimates for nickel billet in 3.1.1. 

Measurements on billet coupons will allow the team to assemble a more comprehensive picture of 

ultrasonic property variations within the billet, and to better understand the effect of these variations 

on inspectability. Correlations will be sought between the property variations with variations in the 

metal microstructure as revealed by optical micrographs and SEM studies. After assessing the 

Billet 

Hoop 

Measurement 

Axial 

measurement 

“Strip” 

Specimen 

(~ 1.5” x 1.5” x D) 

(b) 

High 

Noise 

(a) 

Radial 

Measurement 

Ref. 

Mark 

Low 

Noise 

2nd-stage coupons 

Figure 1. (a) C-scan map of backscattered noise 

versus position, showing locations of high-noise and 

low-noise "strip" specimens. (b, c). Specimen and 

smaller sub-coupons will be used to study depth 

dependence of ultrasonic properties in the three 

orthogonal inspection directions. 

(c) 



findings for the first billet studied, the coupon manufacturing procedure will be refined as necessary 

for subsequent billets and forgings. 

Synthetic Inclusion Samples: Synthetic inclusions will be embedded into Ni test standards for the 

purpose of evaluating the inspection sensitivity of ultrasonics on melt-related defects. The team will 

review the findings from the metallurgical analysis on the naturally occurring defects to identify the 

candidate inclusion types for sample manufacture. Construction methods will be developed at 

GE-CRD to chemically manufacture the synthetic inclusions and to embed the inclusions into Ni 

alloy test blocks. After the successful development of synthetic inclusion manufacturing methods, 

three blocks containing synthetic inclusions of different geometry and composition will be 

manufactured. The types of inclusions will be determined by the team based on the ability to 

manufacture the synthetic inclusions, the criticality of the defect to part life, and the sensitivity of the 

inspection to the composition and geometry of the defect type. 

The team will ultrasonically evaluate the synthetic inclusion samples to determine the sensitivity of 

the inspections for detecting and characterizing melt-related defects. This data will be used for the 

validation of computer-based flaw models and for the generation of POD curves for Ni alloy billets. 

Defect Characterization: Samples will also be acquired with real defects potentially to include dirty 

white spots, segregation (freckles), and slag (from ESR), reflecting both VIM/VAR and 

VIM/ESR/VAR material defects in 718 and Waspaloy. The initial effort will focus on evaluation of 

natural defects to establish typical compositions and properties and their detectability. Six samples 

will be evaluated using a limited ultrasonic characterization and a simplified metallographic process. 

Ultrasonic measurements will be performed at two stages: 

• original samples prior to sectioning 

• defects machined to regular shapes 

Characterization data will be used to optimize the inspection development efforts of 1.1.2, provide 

data for validation of flaw models and provide input for generation of POD for nickel billet in 3.1.1. 

Results will be included in the final report. 

Objective/Approach Amendments: Objective and approach remain as originally proposed in July 

1998. 

Progress (January 1, 2002 – March 31, 2002): 

Several consortium conference calls were conducted during the quarter to discuss the details of the 

subtask. A number of technical issues were discussed and decisions reached. The technical 

issues and discussions are summarized into two primary areas, (1) Property Measurements, and 

(2) Metallographic Microstructure which are discussed separately below. 

Property Measurements 

A primary goal of the Ni billet Fundamental Studies subtask is to determine, for representative Nialloy 

billets, the manner in which ultrasonic properties depend on inspection direction and position 

within the billet. The inspection properties of interest are the sonic velocity, attenuation, and 

backscattered grain noise level, with the latter two properties strongly dependent on the inspection 

frequency. Results of the property measurements will later be used by the Production and 



Reliability subtasks to better estimate inspection sensitivities and POD values for Nickel billet 

inspections. . 

During the quarter, work continued on four “strip coupons” cut from representative Ni alloy billets 

and designated 

• GFMA : From a high-noise site of a 10”-diameter IN718 GFM-forged billet. 

• VdieA : From a high-noise site of a 10”-diameter IN718 V-die-forged billet. 

• VdieB : From a low-noise site of the above billet. 

• WaspA : From a high-noise site of a 10”-diameter Waspaloy billet. 

Figure 1a shows the nominal geometries for each strip coupon (used for UT measurements in the 

axial and hoop directions) and the “baloney slices” that were later cut from the strip coupons (used 

for UT measurements in the radial direction). Ultrasonic data acquisition on all coupons has been 

completed, although analysis of the data is ongoing. 

Metallographic Microstructure 

A related goal of the subtask is to correlate the measured ultrasonic properties with the local billet 

microstructure. To this end, small metallographic coupons from selected billet sites have been 

polished and etched to reveal the grain structure, and grain size distributions have been measured 

from micrographs. During the Jan-Mar quarter, the majority of the research effort was spent 

completing the metallographic measurements and analyses. We now have deduced grain size 

information from 12 metallography coupons (4 sites x 3 views) for each of the four Ni-alloy strips. 

Labels and locations of the metallographic coupons in a typical strip are shown in Figure 1b. 

Two different methods, illustrated in Figure 2, were used to deduce average grain diameters from a 

given micrograph. The first, known as the Mean Chord Length (MCL) method is equivalent to: (1) 

drawing a straight line through the micrograph; (2) noting where the line crosses grain boundaries; 

(3) calculating the average length of the straight segments which lie within a single grain; and (4) 

multiplying this average chord length by 1.5 to obtain a grain diameter estimate. A computer 

program operating on a digital image of the grain boundaries is used to “draw” all possible lines in 

either the horizontal (X) or vertical (Y) direction. The conversion factor of 1.5, which translates from 

2D images to 3D diameters, is believed to be appropriate for equiaxed grains of the kind seen in 

these billets. 

In an alternative approach, known as the “P(L) Method”, one determines the probability P that a line 

segment of length L, randomly placed on the micrograph, lies entirely within a single grain . Again a 

computer program is used to generate the line segments and to decide whether a given segment 

crosses a grain boundary. Again the method can be applied separately in the X and Y directions of 

Figure 2. The X or Y analysis of a micrograph yields a probability-versus-length curve, P(L). This 

curve is then fit to an exponential function P(L) = exp(-L/b), and 2b is used as an estimate of the 

mean grain diameter. Typical measured P(L) curves do not exactly follow an exponential function, 

leading to some uncertainty in the fitting parameter “b” and the associated grain diameter estimate. 

To document this uncertainty, we perform separate fits to different regions of the measured P(L) 

curve . This is illustrated in Figure 3, where fits to the “low L’’ and “high L” halves of the data are 

shown for one case. In practice we perform separate fits to 10 overlapping regions of the 



measured P(L) curve, and tabulate the minimum, maximum, and mean values of “b” thus obtained. 

We note that P(L) curves, sometimes referred to as two-point correlation functions, are of interest 

because they appear in a direct manner in certain models of ultrasonic attenuation and 

backscattered grain noise. 

In all of the cases examined, the grain cross-sections seen in the micrographs have roughly similar 

average dimensions in the X and Y directions, indicating an equiaxed grain structure. This is 

demonstrated in Figure 4 for the MCL method. The P(L) analysis similarly finds nearly equiaxed 

grain diameters. As shown in Figures 5 and 6, the two methods generally yield similar average 

grain diameters. When a given micrograph is analyzed, the MCL estimate usually falls in between 

the minimum and maximum estimates from the P(L) method. As shown in Figure 6, the average 

grain diameter estimate from the P(L) method tends to be about 5% below that of the MCL method. 

Since the grains appear to be equiaxed and the two analysis methods yield similar diameter 

estimates, we average over the two analysis directions [X and Y] and over the two methods [MCL 

and average P(L)] to arrive at an overall grain diameter estimate for each micrograph. 

One step in the analysis of each micrograph is the construction of a tracing showing only the true 

grain boundaries. When such tracings are made, so-called “twin boundaries” are intentionally 

excluded, since it is believed that they do not significantly contribute to attenuation and backscattered 

noise. Our goal is to correlate the grain diameter estimates with ultrasonic properties. 

Absolute errors in grain diameter estimates are believed to mainly arise from two factors: (1) the 

process of identifying “non-twin” grain boundaries is somewhat subjective; and (2) a given 

micrograph containing a few hundred grains represents only a very minute fraction of the specimen 

volume that is insonified in a given ultrasonic measurement. 

During the quarter, efforts were made to correlate the measured grain diameters at various billet 

sites with the ultrasonic attenuation values measured earlier. Figure 7 displays the attenuation 

values at 7.5 MHz for all measurement sites and inspection directions. Absolute attenuation values 

are believed to be accurate to within about +/-0.0015 N/cm or +/-0.03 dB/inch. Given this level of 

accuracy, one sees that at a given site in a given specimen, the ultrasonic attenuation is quite 

isotropic. For three of the specimens (strip coupons) the attenuation drops significantly as one 

approaches the OD from the billet center. For the fourth specimen (V-die-A), the attenuation 

increases as the OD is approached. The correlation between measured attenuation values and 

measured grain diameters is shown in Figure 8. Significant scatter is seen about the general trend. 

This is believed to be primarily due to the fact that the grain size determinations were made using 

only a very small fraction of the grains contained within the ensonified volume. Nonetheless, a 

general trend is seen of the same shape as that expected for equiaxed, untextured, pure Nickel 

grains. 

In the upcoming quarter, the ongoing analysis of all backscattered grain noise data will be 

completed, and figures similar to Figures 7-8 will be generated showing the dependence of noise 

FOM on position and its correlation with average grain diameter. 



Axial 

“rough cut” coupon for 

use in metallography 

Billet 

1”-thick “slice” 

coupons 

“strip coupon” for UT 

property measurements 

possible sites for 

metallography 

Hoop 

Radial 

“Strip” 

Coupon 

(~ 2” x 2” x 10”) 

(a) 

J K 

L 

G 

H 

I 

D 

E 

F 

A 

B 

C 

Polished face: Axial 

Polished face: Radial 

Polished face: Hoop 

(b) 

10” 

Figure 1. Geometries of “strip” and “slice” coupons from Ni-alloy billets. (b) Locations and 

designations of the 12 small metallography coupons, A-L. 

100 µm 

L 

100 µm 

Twin 

boundaries 

L 

Twin 

boundaries 

Y 

S1 

Waspaloy 

Coupon K 

S2 

S3 

S4 

L 

Waspaloy 

Coupon K 

L 

L 

X 

MCL Method 

Lines are drawn. Average of the 

chord lengths (Sj) is calculated. 

P(L) Method 

For a given length L, line segments of 

that length are randomly placed on the 

image. Some cross grain boundaries, 

some do not. Count each type. 

Figure 2. The two methods used to analyze micrographs. Each method leads to an estimate of the 

average grain diameter. 



1.2 

1.0 

0.8 

V-DIE-A coupon "D" (axial view) 

Measured P(L) - x&y combined 

Low-L exponential fit (b = 11.50 microns) 

High L exponential fit (b = 9.26 microns) 

P(L) 

0.6 

0.4 

0.2 

0.0 

0 10 20 30 40 50 60 

L (microns) 

Figure 3. Examples of exponential fits to a measured P(L) curve. The blue curve is a fit to the 

lower half of the data (0 < L < 27 microns). The red curve is a fit to the upper half of the data (27 < 

L < 54 microns). 

Estimate along Y-direction . 

160 

140 

120 

100 

80 

60 

40 

20 

GRAIN DIAMETER ESTIMATES 

USING THE MCL METHOD 

GFMA 

V-DIE-A 

V-DIE-B 

WASP 

Equiaxed Grains 

(in microns) 

Estimate along Y-direction . 

40 

35 

30 

25 

20 

15 

10 

5 


USING THE MCL METHOD 

GFMA 

V-DIE-A 

V-DIE-B 

Equiaxed Grains 

(in microns) 

0 

0 20 40 60 80 100 120 140 

Estimate along X-direction 

0 

0 5 10 15 20 25 30 35 40 

Estimate along X-direction 

Figure 4. Comparisons of average grain diameters in the X and Y directions of the micrographs 

using the Mean Chord Length Method. Results are shown for analyses of 12 micrographs for each 

of 4 billet “strips”. The right-hand panel is a blow-up of the small diameter region where the IN718 

values lie. 



Ave. Grain Diameter (microns) . 

30 

25 

20 

15 

10 

5 

0 

V-die B Metallography Results 

(Sorted by increasing MCL) 

Fitting exponentials [exp(-L/b)] to 

different regions of the P(L) data 

leads to three different estimates of b: 

highest b, low est b, and average b. 

MCL = Mean Chord Length. 

D from 1.5*MCL 

D from 2*(ave b) 

D from 2*(low b) 

D from 2*(high b) 

I H L G E J C D K F A B 

Metallography Coupon 

Figure 5. Comparisons of average grain diameters as estimated by the MCL and P(L) methods. 

Results (averaged over X and Y) are shown for the 12 V-die-B micrographs. For the P(L) method, 

high, low , and average estimates are given, resulting from fitting exponentials to different regions 

of the P(L) curve. 

P(L) ESTIMATE (microns) . 

160 

140 

120 

100 

80 

60 

40 

20 

0 


(Averaged over X and Y) 

GFMA 

V-DIE-A 

V-DIE-B 

WASP 

TRENDLINE 

y = 0.9461x 

R2 = 0.9796 

0 20 40 60 80 100 120 140 160 

MCL ESTIMATE (microns) 

Figure 6. Comparisons of average grain diameters as estimated by the MCL and average-P(L) 

methods for the 4 x 12 micrographs analyzed. A best-fit trendline through the data is also shown. 



Attenuation (dB/in) . 

Waspalloy Attenuation at 7.5 MHz 

4.00 

3.50 

Axial 

3.00 

Hoop 

2.50 

Radial 

2.00 

1.50 

1.00 

0.50 

0.00 

0" 1" 2" 3" 4" 

(center) 

Measurement Site 


0.35 

0.30 

0.25 

0.20 

0.15 

0.10 

0.05 

0.00 

GFM-A Attenuation at 7.5 MHz 

Axial 

Hoop 

Radial 

0" 1" 2" 3" 4" 

(center) 



0.35 

0.30 

0.25 

0.20 

0.15 

0.10 

0.05 

0.00 

V-Die-A Attenuation at 7.5 MHz 

Axial 

Hoop 

Radial 

0" 1" 2" 3" 4" 

(center) 



V-Die-B Attenuation at 7.5 MHz 

0.16 

0.14 

0.12 

0.10 

0.08 

0.06 

0.04 

0.02 

0.00 

Axial 

Hoop 

Radial 

0" 1" 2" 3" 4" 

(center) 


Figure 7. Measured attenuation values at 7.5 MHz for the Ni billet specimens. Results are shown 

for three orthogonal inspection directions. The distance from each measurement site to the billet 

center is indicated. 

Attenuation at 7.5 MHz (dB/in) 

7 

6 

5 

4 

3 

2 

1 

Correlation Between Measured Attenuation and 

Measured Average Grain Diameter 

GFM-A 

VDIE-A 

VDIE-B 

Wasp 

JT model for pure Ni 

Waspaloy Trendline 

Note : tw in boundares 

w ere not counted as bona 

fide grain boundaries. 

Attenuation at 7.5 MHz (dB/in) 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

Correlation Between Measured Attenuation and 

Measured Average Grain Diameter 

GFM-A 

VDIE-A 

VDIE-B 

Wasp 

JT model for pure Ni 

IN718 Trendline 

Note : tw in boundares 

w ere not counted as bona 

fide grain boundaries. 

Vdie_A 

coupons 

H, I, L 

0 

0 20 40 60 80 100 120 

Estimated Grain Diameter (microns) 

0.0 

0 10 20 30 40 

Estimated Grain Diameter (microns) 

Figure 8. Correlation between measured attenuation at 7.5 MHz and estimated average grain 

diameter. Right panel shows a blow-up of the region near the plot origin. The prediction of the Joe 

Turner Attenuation Model (for pure Nickel) is shown for comparison, along with a trend lines 

through the data with the same shape as the model curve. 



Plans (April 1, 2002 – June 30, 2002): 

Ongoing analysis of all backscattered grain noise data will be completed. 

Milestones: 

Original 

Revised 

Description 

Status 

Date 

Date 

Fundamental properties of nickel billet 

3 months 6 months 

(Waspaloy) 

6 months 

(Waspaloy) 

Finalize sample configuration and manufacturing 

sequence. (All) 

Initiate sample fabrication. (GE, PW; GE to supply 

IN718, PW to supply Waspaloy) 

6 months Coordinate with RISC to generate list of 

melt-related defects and provide to Inspection 

Development and Inspection Systems Capability 

teams. Identify preferred defect types for study. 

Initiate acquisition of naturally occurring 

melt-related defects. (All) 

Complete 

Complete 

Complete 

18 months 42 months Metallographically evaluate natural defects. Synthetic defects selected 

First natural defect identified and 

evaluation initiated in Dec. 2000 

30 months Establish methods for manufacturing synthetic 

defects and for embedding synthetic and natural 

defects in IN718 (GE). 

24 months Complete property measurement samples. (GE, 

PW) 

36 months Complete synthetic inclusion standards with 

representative variation in type, geometry, and 

chemistry. (GE) 

36 months Complete characterization of property samples and 

provide to 3.1.1 for development of flaw response 

and noise models and for generation of the noise 

distribution for nickel. Includes ultrasonic velocity, 

attenuation, noise, microstructure. (ISU with 

support from GE, PW,AS) 

Coordinate results with 1.1.2 in the inspection 

design and implementation. (ISU with support from 

GE, PW,AS) 

42 months Report of ultrasonic properties (sound velocity, 

attenuation, and backscattered noise) and types of 

defects of concern in IN718 , Waspaloy, and IN901. 

(All) 

24-42 

months 

Validate noise models in cooperation with 3.1.1. 

(All) 

42 months Complete ultrasonic characterization of melt-related 

defects and provide results to 3.1.1. (All)) 

54 months Report of characterization of defects and ultrasonic 

properties (sound velocity and acoustic impedance) 

as a function of composition for defects in IN718. 

(All) 

60 months Representative sample blocks and synthetic 

inclusion samples (All) 

Complete 

Synthetic dirty white spot, freckle, 

and white spot defects prepared 

Acoustic measurements initiated at 

ISU 



Deliverables: 

Fundamental properties of nickel billet. 

Report of ultrasonic properties (sound velocity, attenuation, and backscattered noise) and types of 

defects of concern in IN718, Waspaloy, and IN901. 

Report of characterization of defects and ultrasonic properties (sound velocity and acoustic 

impedance) as a function of composition for defects in IN718. 

Representative sample blocks and synthetic inclusion samples. 

Metrics: 

Assessment of ultrasonic properties for typical nickel alloys and characterization of melt-related 

defects that support the needs of inspection development, POD estimation, and life management. 

Major Accomplishments and Significant Interactions: 

Date 

June 16, 1999 

December 21, 

1999 

Description 

Technical Kick-off Meeting in West Palm Beach, FL 

Telecon with Special Metals and Sandia National Lab personnel to discuss their experience with Ni 

defects and initiate discussions on obtaining natural Ni defect samples 

Publications and Presentations: 

Date 

Description 

2002 Pranaam Haldipur, F. J. Margetan, Linxiao Yu, and R. B. Thompson, "A study of Ultrasonic 

Property Variations Within Jet-Engine Nickel Alloy Billets", Rev. of Prog. in QNDE, Vol.21, 

eds. D.O. Thompson and D.E. Chimenti, (AIP, Melville NY, in press) 



Project 1: 

Task 1.1: 



Nickel-based Alloy Inspection 

Inspection Development for 

Nickel Billet 

Team Members: 


ISU: Ron Roberts, Bruce Thompson, Frank 

Margetan 

GE: Ed Nieters, Dave Copley, Mike Keller, 

Jon Bartos, Richard Klaassen, John Halase 



Students: none 


Objectives: 

• To apply technology developed in Phase I for titanium billet inspection to improve nickel billet 

inspection. 

• To perform factory inspection of approximately 100,000 pounds of nickel alloy billet, primarily 

INCO718, to #1 FBH sensitivity using a multizone inspection system with digital acquisition to 

provide necessary field experience that facilitates implementation decisions. 

• To determine applicability of multizone technique to Waspaloy. 

• To provide the billet industry and OEMs with demonstration of improved sensitivity inspection 

using FBH standards as the metric with a goal of #1FBH sensitivity in 10” INCO718 billets and 

#2.5FBH sensitivity in 10” Waspaloy billet. 

• To provide necessary data to the Inspection Systems Capability team for estimation of POD for 

nickel billet, including cut-up data generated in the pilot lot inspection. 

Approach: 

Initial Assessment: A kickoff meeting involving the subtask team members will be held at the 

program onset to reiterate the plans of the task and establish a means of sharing information and 

data, including necessary support of Task 3.1.1. The current plan of concentrating on INCO718 

and Waspaloy to sensitivities of #1FBH and #2.5FBH sensitivity respectively will be verified as the 

correct targets and requirements for signal-to-noise measurements will be determined. The 

number and types of calibration standards will be discussed and design of the standards will be 

initiated. Any significant change agreed on by the team will be presented to ETC management. 

Production calibration standards for the nickel alloys, presumably 10” diameter, as agreed upon in 

the initial planning meeting will be manufactured. An evaluation of current capability of 

conventional inspections will be performed as a baseline for both INCO718 and Waspaloy using the 

production calibration standards rather than relying on the nominal values stated in respective 

specifications. 



Small Diameter Billet Assessment: Assessment of small diameter inspection will also be completed 

by Honeywell. Honeywell will perform studies using billets of < 8” diameter The objective will be to 

apply technology developed in Phase II for larger Ni billet to improve nickel billet inspection in the 

stated diameter of interest to small engine manufacturers. Feasibility demonstration will be 

conducted in the laboratory environment using small nickel alloy billet and multizone transducers 

developed for the smallest of the large diameter billets. Sensitivity analysis (#FBH) will be 

conducted for various small diameter billets. A comparison will be made with the standard 

spherical focus approach. Results will be provided to the Inspection Systems Capability Working 

Group to allow POD estimates. 

Baseline Assessment: Inspection development will be performed with the calibration standards 

using existing multizone transducers to occur at PW and GE facilities to ensure hands-on 

involvement by the parties responsible for final implementation recommendations. Scans and 

associated measurements will be used to determine the focal depth of each transducer, measure 

the axial beam profile and beam cross-section, and compare these results to model predictions. 

Signal-to-noise ratio will be determined for the FBH targets. The need for new transducers will be 

evaluated based on these scans and model results. New transducers will be designed and built if 

results indicate that the existing transducers do not produce a focal zone at the required depth or of 

the required beam diameter, and if modeling indicates that significant improvement could be 

obtained by re-design. Additional funding will be sought for transducer fabrication at that time if the 

team agrees that the proposed benefits are substantial. 

Laboratory Demonstration: After inspection development for each alloy is completed, a laboratory 

demonstration of billet inspections with optimized transducers will be provided for the ETC 

members. Sensitivity to #1FBH in INCO718 and to #2.5FBH in Waspaloy will be demonstrated and 

plans made for pilot inspection. 

Factory Demonstration: A factory pilot inspection of approximately 100,000 pounds will be planned 

to determine the sensitivity level that can be consistently achieved in production and to identify any 

barriers to implementation. The first step will be for the team to identify an industry partner(s) to 

perform the pilot inspection, much as RMI worked with the consortium in Phase I in the inspection 

of titanium billet. A detailed plan will identify the particular specifications of INCO718 to be 

inspected, i.e., VIM/VAR and/or VIM/ESR/VAR, and the number of material suppliers. 

Investigations performed in the nickel fundamental studies Task 1.1.1, will provide information to 

determine the need to include two types of INCO718 in the pilot inspection. If the defect types 

found in the two materials and the ultrasonic characteristics are the same, then there will not be a 

need to include both in the factory pilot inspection. The extent of inclusion of Waspaloy will also be 

planned. Procedures for inspection, evaluation of data, and investigation of indications will be 

defined. It is expected that eight finds will be cut-up and evaluated using a process similar to that 

described in AC 33.15. It is expected that each OEM will participate in the destructive 

characterization of indications with two planned for Waspaloy and six planned for IN718. The team 

will also agree on parameters needed to determine the cost impact of implementing the higher 

sensitivity inspection as compared to conventional inspection. The pilot lot evaluation of 100,000 

pounds of billet with the optimum transducers will occur in cooperation with a multizone inspection 

source and nickel alloy material suppliers. Evaluation of 5 to 10 heats of material is expected. 



Since application of multizone technique is expected to be more straightforward for INCO718, most 

of the pilot work will be performed with that alloy. The application of #2.5FBH sensitivity to 

Waspaloy is expected to be more complex but an inspection technique should be ready to 

substitute for the last 25% of the pilot lot. The data will be evaluated and reported. Results of the 

pilot inspection and of any cut-ups will be provided to Task 3.1.1 for use in developing POD 

estimates for nickel billet. Cost and detection sensitivity assessments necessary for life 

management and implementation decisions will be gathered. Components of cost assessment will 

have been agreed on by the team and will likely include such items as system cost, longevity of 

equipment, recurring equipment costs, daily operational/inspection costs, and costs associated with 

false calls. In conjunction with the pilot lot inspection, a demonstration of the higher sensitivity 

inspection for INCO718 and Waspaloy will be presented to the OEMs and industry. A final report in 

the required FAA format will be provided. 


1998. 




issues and discussions are summarized into two primary areas, (1) Pilot Billet Inspection, and (2) 

Waspaloy Standard and discussed separately below. 

Nickel Billet Pilot Inspection 

A request was forwarded to a production facility to bid on the multizone inspection of 75,000 lbs. of 

Inconel and 25,000 lbs. of Waspaloy. The ETC will purchase the multizone inspection of this 10- 

inch diameter material calibrating on the Nickel standards developed earlier. During this pilot 

program the ETC will purchase a select number of indications found with multizone with preference 

given to those that were not rejected with conventional inspection and perform ultrasonic and 

metallographic characterization for POD studies and future inspection implementation decisions. 

As soon as the purchase order is in place the Inconel standard will be sent to the production site. 

Waspaloy Standard 

At the laboratory demonstration last quarter, the Waspaloy standard was found to have some 

surface irregularities that prompted a more detailed investigation. Surface metrology data revealed 

a periodic surface irregularity with amplitude of about 5 mils and consisting of 27 cycles around the 

circumference of the standard. Figure 1 shows the surface metrology data taken with a dial 

indicator around the circumference. The two major lobes are a result of the axial split line running 

through the center of the standard and were expected in the measurement. 

To evaluate the ultrasonic impact of this surface condition, a zone 5 transducer was used to create 

a C-scan of the machined surface on the interior of the billet standard. Figure 2 shows these 

surfaces highlighted in red. The resultant C-scan in Figure 3 shows the significant amplitude 

variation on the inner backwall caused by the surface irregularities. 



Under normal circumstances one would expect the C-scan image to show fairly uniform amplitude 

around the circumference indicating that the sound intensity was consistent. The fluctuating 

intensity seen on the C-scan is at the same frequency as the surface irregularities. 

ISU also modeled the effects of the surface on the ultrasonic signal and produced the graph in 

Figure 4. This study convinced the team to pursue having the Waspaloy standard machined or 

polished to remove the surface condition prior to using at the production site. 

Waspaloy Std. Surface Profile 

50 

Mils (1/1000 inch) 

40 

30 

20 

10 

0 

-10 

0 100 200 300 400 

Degrees 

Figure 1. Surface Profile of Waspaloy Standard 27 peaks and valleys. 

Figure 2. Diagram of Waspaloy standard highlighting inspection surface in red. 



3.15” 3.6” 

4.05” 

circumference 

axial 

Zone 5 transducer gated on FBH backwall 

Figure 3. Ultrasonic C-scan of Inner Backwall. 

Signal for 

Smooth Surface 

Figure 4. ISU model of signal strength in focal zone due to surface condition. 




Begin inspection of Inconel and Waspaloy billet with Multizone as part of the pilot lot. 

Start metallographic sectioning of indications identified in the pilot inspection. 

Milestones: 

Original 

Date 

Revised 

Date 

Description 

Nickel billet inspection development 

3 months Kickoff meeting to verify selection of materials and 

target sensitivities, initiate design of calibration 

standards and establish metrics for cost and 

sensitivity assessment. Coordination with 

Inspection Systems Capability Working Group will 

occur to ensure necessary data for later POD 

studies. (All) 

24 months Assessment of sensitivity for small diameter billet. 

Data to be provided to Task 3.1 to enable POD 

assessment. (HW) 

24 months Complete modeling and laboratory testing of 

existing transducers on calibration standards for 

INCO718 and assess need for new transducers. 

(GE, ISU). 

24 months Complete modeling and laboratory testing of 

existing transducers on calibration standards for 

Waspaloy and assess need for new transducers. 

(PW, ISU) 

Status 

Complete 

Complete 

18 months Complete calibration standards. (GE, PW) Complete 

22 months Assessment of conventional inspections for 

baseline. (GE, PW). Data to be provided to Task 

3.1 to enable POD assessment. (All) 

24 months 30 months Complete logistics of pilot lot inspection including 

establishing agreements with multizone inspection 

source and billet suppliers and establishing means 

of acquiring necessary cost data. (GE, PW) 

30 months Perform laboratory demonstration for ETC 

members. (GE, PW) 

36 months Complete factory evaluation of approximately 

100,000 pounds of billet. Perform demonstration 

for OEMs and industry at inspection facility. (GE, 

PW, ISU) 

38 months Evaluate any finds to determine necessary size 

parameters for POD assessment. (GE, ISU, PW) 

42 months Complete cost comparison of higher sensitivity 

multiple zone inspection with conventional 

inspection. (GE, PW) 

55 months Complete final report including sensitivity and cost 

comparison assessments. (All) 

55 months Report of laboratory and factory evaluations 

including sensitivity data for use by the Inspection 

Systems Capability Working Group and cost 

assessments. Calibration standards and fixed focus 

transducers. 

Complete – new transducers not 

needed to meet program goal 

Complete – new transducers not 

needed to meet program goal 

Complete 

PIA is in place. Logistics planning is 

proceeding 

Complete 



Original 

Date 

Revised 

Date 

Description 

60 months Calibration standards and fixed focus transducers 

(if fabricated). 

Status 

Deliverables: 

Laboratory demonstration and factory evaluation of multizone inspection including supplier 

demonstration. 

Report of laboratory and factory evaluations including sensitivity data for use by the Inspection 

Systems Capability Working Group and cost assessments. 

Calibration standards and fixed focus transducers. 

Metrics: 

Demonstration of #1FBH sensitivity inspection for INCO718 billet up to 10” diameter and #2.5FBH 

sensitivity for Waspaloy up to 10” diameter. 

Factory demonstration will include target of 90 cubic inches per minute scanning rate for multizone 

inspection. 


Date 

June 16, 1999 

Description 



Date 

Description 



Project 1: 

Task 1.2: 



Titanium Billet Inspection 


Titanium Billet 

Team Members: 


ISU: Bruce Thompson, Ron Roberts, Frank 

Margetan 

GE: Dave Copley, Wei Li, Mike Keller, Jon 

Bartos, Richard Klaassen, John Halase 

PW: Kevin Smith, Jeff Umbach, Bob 

Goodwin, Andrei Degtyar, Harpreet Wasan 



Objectives: 

• To provide a procedure to account for attenuation effects such that the variation between 

calibration and inspection sensitivity is minimized. 

• To demonstrate the ultrasonic equipment and techniques required to inspect titanium alloy 

billets to #1FBH sensitivity for 10” diameter and below. 

• To provide an initial assessment of sensitivity at diameters greater that 10”. 

Approach: 

Transducer Design Models: The design models will be reevaluated in detail to determine reasons 

for discrepancies between predicted and measured transducer behavior observed during Phase I 

work. This reevaluation will focus initially on assessing how well the input parameters used for the 

models represent the physical behavior of the transducers. It is planned to begin with 

characterization of piezo-electric elements prior to the addition of backing materials, and then 

attempt to compare model predictions with experiment at subsequent stages of the manufacturing 

process. This will involve working closely with a transducer manufacturer with one potential source 

identified. Based on this exercise, modifications will be made to model input parameters or to the 

model code to improve the prediction accuracy. Attention will also be paid to selection of 

transducer materials with consistent and measurable properties, for example the machining of 

lenses from solid material rather than using cast-in-place epoxy. Results will be shared with 

transducer manufacturers to allow improvements in future products both for ETC and the broader 

ultrasonic transducer user community. 

Inspection of 10” Diameter Billet: Fixed focus inspection will be the primary technique in this task. 

If this approach proves inadequate to meet program objectives, viable phased array technologies 

will be reviewed to select a candidate technique with the most potential for meeting the program 

objectives in consultation with the FAA. 

Improved fixed focus transducers for 10” diameter billet will be designed. Results from Phase I 

measurements (at 2.25” and 4.05” depths) will be used to identify the best combination of focal spot 



diameter and frequency, and this information will be used to design the complete set of 

transducers. 1 Phase I work indicates that frequency and bandwidth should be increased from those 

of the current production transducers which are 5MHz frequency and approximately 50% 

bandwidth. Two sets of the improved-design transducers will be purchased. A distance-amplitude 

correction (DAC) capability for the multizone instrumentation is being developed external to the 

ETC program with details to be shared with the ETC. This is expected to improve sensitivity by 1 or 

2 dB by ameliorating the current situation where high noise in the focal plane of the transducer 

limits sensitivity at the near and far ends of the depth-of-field. 

Laboratory Demonstration on 10” Diameter Billet: Scans will be performed on the ETC 10” 

diameter standards using the above transducers, and with DAC capability added to current 

multizone instrumentation. Work will be performed at GE QTC, with support provided to other 

Consortium members to participate in the measurements. The FBH amplitudes, noise levels, and 

FBH signal-to-noise ratios will be evaluated and compared with measurements made on production 

5MHz transducers during Phase I. A determination will be made of whether sensitivity level meets 

the #1FBH goal in all regions of the billet. Results will be provided to 3.1.1 for incorporation in the 

modeling and reliability efforts. 

Honeywell will also perform a sensitivity assessment on smaller diameter billets using billets of

system will be at GE, and evaluation of any other systems would be at a location to be agreed upon 

by the technical team. Arrangements will be made to accommodate full team participation for all of 

these evaluations. The laboratory scan results will be reviewed to identify a preferred configuration 

for factory demonstration and potential implementation. The review will consider inspection 

performance, equipment cost and complexity, operating speed, and other implementation factors. 

A hybrid system using fixed focus for the outer zones and phased array for the center will be 

considered as part of this evaluation. 

If the final approach agreed to by the technical team for factory demonstration includes phased 

arrays, additional work will be done to refine the sensor design for the selected array approach. 

Manufacturer’s engineering specifications for the array system design (element geometry, 

lens/mirror geometry, etc.) will be input into an array system computational simulation. Theoretical 

system performance will be compared to laboratory measurements of array system response. 

Discrepancies between model and experiment will be traced to underlying causes and resolved. 

Models will then be used to optimize the design and set up for specific test standards targeted for 

study including larger diameter billets. 

Factory Evaluation: The multizone configuration will be used to perform factory evaluation of five 

heats of 10” diameter titanium at a production inspection facility. Cost and detection sensitivity 

assessments necessary for life management and implementation decisions will be gathered. 

Components of cost assessment will include such items as system cost, longevity of equipment, 

recurring equipment costs, daily operational/inspection costs, and costs associated with false calls. 

Evaluation will include cut-ups of any finds. Details of metallography will depend on how many 

indications are found, but it is anticipated that all finds will be evaluated to determine cause, and 

one will be step-polished to obtain detailed sizing information. 

Factory Demonstration: An industry-wide demonstration of the multizone system will be scheduled. 

OEMs and titanium billet producers will be invited. 

Assessment of Large Diameter Billet (>10” dia): Assessment of the sensitivity at larger diameters 

will use 13” and 14” diameter standards. Existing 13” standards will be used, and a 14” chord block 

standard with near-centerline targets will be designed and built. Initial assessment will be made to 

baseline conventional inspection sensitivity either using transducers borrowed from suppliers, or by 

requesting suppliers to perform the evaluation in-house. Evaluation of zoned fixed-focus capability 

will use existing multizone transducers. Evaluation will follow a plan to be agreed by consortium 

members. If the targeted 4x sensitivity improvement over conventional inspection has been 

achieved for 13” and 14” diameters, the results will be documented and no further work pursued. If 

improvement is still needed, a plan will be formulated following the best approaches (phased array 

or improved fixed focus) identified for 10” diameter billet. The plan will be presented to the FAA as 

continued work is expected to require funding redirection. 

Attenuation Compensation Procedures: The current procedures used to measure and compensate 

for material attenuation will be evaluated and improved. The current procedure for the multizone 

inspection uses a pre-inspection of four short sections (1” long) of the billet to obtain an average 

backwall echo amplitude. This is compared with an average backwall amplitude measured on the 

calibration standard and the difference is used to calculate an attenuation compensation factor in 

decibels per inch. A transducer focused at the billet center is used to make the measurements. 



The drawback of this method is that it ignores the effects of distortion of the ultrasonic beam during 

propagation through the metal microstructure. Phase I work has shown that beam distortion can be 

a major contributor to the response from flaws and backwalls. Even when beam distortion effects 

are minor and energy loss dominates, the material attenuation is found to vary significantly with 

position in a given billet in conjunction with noise banding as was shown in Figure 6. The effects of 

noise banding and nonuniform attenuation can lead to an incorrect measurement of flaw response, 

and a true inspection sensitivity different from that assumed from calibration. The current 

attenuation compensation technique will be evaluated by applying it to several billet segments, then 

drilling a number of flat-bottom or side-drilled holes into the sections, and comparing the measured 

amplitudes of those holes to those expected from the attenuation analysis. Improvements will focus 

on selection of a transducer which will minimize the effects of beam distortion and provide an 

attenuation estimate which enables good prediction of the hole echo amplitudes. 

Billet Specification: The specification for billet inspection (AMS 2628) will be updated to reflect 

improvements achieved by this subtask. Results will also be reported in required FAA format. 


1998. 




issues and discussions are summarized into three primary areas, (1) Attenuation-Compensation, 

(2) 10” Billet Transducers and (3) 14” Chord Block Transducer and discussed separately below. 

One goal of Subtask 1.2.1 is to critically examine existing methods for attenuation compensation 

during billet inspection, and, if necessary, recommend improvements. Existing methods typically 

use the average strengths of back-wall echoes to estimate the attenuation difference between a 

billet under inspection and a calibration standard. During the Jan-Mar quarter, a series of 

experiments were performed to determine how well back-wall (BW) amplitude variations mirror the 

amplitude variations for an array of nominally-identical small internal defects. The measurements 

were carried out at GEAE and Honeywell, and results were analyzed at ISU. 

A 15”-long section of 6"-diameter Ti 6-4 billet was obtained which displayed large variations in BW 

amplitude during scanning. These variations presumably arise from differences in the local 

"effective" attenuation of the billet, with both energy loss and microstructure-induced beam 

distortion effects contributing to that attenuation. A series of #4 FBHs were drilled 0.3” deep into 

the OD of the billet, some at locations having large BW amplitudes, and others at locations having 

small BW amplitudes. The billet section was then inspected using several transducers (with 

different beam sizes at the back wall) to determine the degree of correlation between the FBH 

amplitudes and the nearby BW amplitudes. Initial measurements at GEAE used two 5-MHz fixedfocused 

transducers: (1) a multizone probe designed to focus near the center of 6"-diameter billet 

when operated at a 3” water path; and (2) a multizone probe designed to focus near the center of 

13" billet, with the water path modified to 6.6” so as to best focus the beam near the BW of the 6" 

billet under study. Additional inspections were made at Honeywell using a 114-element, 5-MHz, 

phased-array transducer. The array transducer was used to simulate inspections for two other 



fixed-focus transducers that were not readily available. We note that 6"-diameter billet was chosen 

for these initial experiments because existing transducers were available which could approximately 

focus a sound beam near the back wall in such a billet (one of the focal conditions of chief interest). 

#4 FBHs were then chosen to simulate internal defects, because such targets were large enough to 

be easily seen for the range of focal conditions being investigated. 

C-scan images for four measurement trials are shown in the upper panels of Figures 1-4, 

respectively. The upper-left panel of each figure shows the rectified peak amplitude of the BW 

echo as a function of position for a full-round inspection of the 15”-long billet section. The upperright 

panel displays images of the FBHs, obtained by performing a second scan at increased gain, 

using a time gate that enclosed the FBH echoes, but excluded the BW echoes. Annotations on the 

upper panels list the peak FBH amplitudes and the average BW amplitudes in small regions 

centered about each FBH location. In all cases, the listed amplitudes are the percentage of Full 

Screen Height (FSH). One notices in each figure that the BW and FBH both amplitudes vary 

considerably, and that large (small) FBH amplitudes are usually associated with large (small) BW 

amplitudes at similar positions. 

The correlation between FBH and BW amplitudes is further illustrated in the lower panels of Figures 

1-4. For each of the four inspections, the absolute amplitudes of the BW and FBH signals have 

been adjusted to have a mean value of 50% FSH for the suite of FBH targets. These rescaled 

amplitudes are shown in the lower-left panel, with the principal FBH targets numbered 1-13 (from 

top to bottom and left to right in the C-scan images). The lower-right panels display "correlation 

plots" of the rescaled FBH amplitudes versus the rescaled BW amplitudes. If there were perfect 

correlation between the two types of echoes, the plotted points would all fall along a straight line 

passing through the origin and having a slope of unity. In each case, a best-fit line through the 

origin is shown, and its slope is seen to be close to the ideal value of 1 in each case. Overall, the 

BW and FBH amplitudes were found to be generally well correlated, with the degree of correlation 

being largest when the beam was focused near the FBH targets. 

The results summarized in Figures 1-4 indicate that BW echoes can be used to track attenuation 

variations within a billet. Presumably, BW echoes can also be used to ascertain the attenuation 

difference between a billet under inspection and a calibration standard. Because of the significant 

variation in BW and FBH amplitudes with billet position, the results suggest that attenuation 

compensation procedures should make use of extreme BW amplitude data values rather than only 

average values. 



Back-Wall Scan 

FBH scan 

20% 

39% 

61% 

51% 

59% 

47% 

65% 64% 

20% 

7% 

23% 

20% 

47% 

49% 

93% 

80% 

75% 

55% 

68% 

34% 

38% 

30% 

73% 

59% 

13% 

22% 12% 

66% 

65% 

24% 

21% 

(a) 

(b) 

68% 

Amplitude (%FSH) 

(c) 

Comparison of Normalized 

BW and FBH variations 

(6" Multizone Probe) 

100 

BW 6"MZ 

90 

FBH 6"MZ 

80 

70 

60 

50 

40 

30 

20 

10 

Average for all sites = 50% 

0 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 


FBH Amplitude (% FSH) 

(d) 

Correlation Between Norm'ed 



100 

90 

y = 1.0243x 

80 

R 2 = 0.565 

70 

60 

50 

Trendline thru origin 

40 

30 

20 

10 

0 

0 10 20 30 40 50 60 70 80 90 100 

BW Amplitude (% FSH) 

Figure 1. Measurements on a Ti 6-4 billet segment using a 5-MHz 6”-multizone probe focused near 

the billet center. (a) C-scan of back-wall amplitude. (b) C-scan gated on FBH targets drilled into the 

billet OD. (c) Scaled BW and FBH amplitudes. (d) Correlation between BW and FBH amplitudes. 

Beam diameters (-6 dB) near the back wall are approximately 250 mils x 610 mils (axial x hoop). 

For panels (a) and (b), the horizontal direction is parallel to the billet axis. 




FBH scan 

20% 

57% 

49% 

48% 

48% 48% 

58% 59% 

22% 

13% 

18% 

20% 

28% 

31% 

79% 

64% 91% 

66% 94% 

27% 

31% 

42% 

79% 

82% 

33% 33% 

15% 

64% 70% 

22% 

19% 

(a) 

(b) 

87% 


(c) 




90 

BW 13"MZ 

80 

FBH 13"MZ 

70 

60 

50 

40 

30 

20 

10 


0 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 



(d) 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 




y = 0.9909x 

R 2 = 0.6086 


0 10 20 30 40 50 60 70 80 90 100 


Figure 2. Measurements on a Ti 6-4 billet segment using a 5-MHz 13”-multizone probe focused 

near the billet back wall, following the style of Figure 1. Beam diameters (-6 dB) near the back wall 

are approximately 150 mils x 540 mils (axial x hoop). 



56% 


84% 

FBH scan 

42% 

43% 

58% 

49% 

43% 

46% 

43% 

44% 

54% 

48% 

16% 

19% 

19% 

32% 

40% 

32% 

73% 

73% 

69% 

61% 

74% 

77% 

73% 

44% 

46% 

44% 

44% 

81% 

72% 

24% 

(a) 

(b) 



(5-MHz Phased Array; Focused in Middle; Trial 2) 



(5-MHz Phased Array; Focused in Middle; Trial 2) 

80 

80 


(c) 

70 

60 

50 

40 

30 

20 

BW PA-foc_middle 

10 

FBH PA-foc_middle 


0 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 



70 

y = 1.0117x 

60 

R 2 = 0.6684 

50 

40 

30 

20 

10 

(d) 

0 

0 10 20 30 40 50 60 70 80 90 100 



Figure 3. Measurements on a Ti 6-4 billet segment using a 5-MHz phased-array transducer 

focused near the billet center, following the style of Figure 1. Beam diameters (-6 dB) near the 

back wall are approximately 400 mils x 600 mils (axial x hoop). 



63% 


74% 

FBH scan 

58% 

40% 

64% 

60% 

59% 

57% 

42% 

61% 

68% 

47% 

33% 

37% 

35% 

37% 

57% 

56% 

64% 

71% 

68% 

55% 

69% 

66% 

64% 

48% 

49% 

46% 

38% 

66% 

66% 

36% 

(a) 


(c) 



(5-MHz Phased Array; Focused on Backwall; Trial 1) 

80 

70 

60 

50 

40 

30 

20 

10 

FBH PA-foc_at_back 


0 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 


BW PA-foc_at_back 


(b) 



(5-MHz Phased Array; Focused on Backwall; Trial 1) 

80 

70 

y = 1.005x 

R 2 60 

= 0.7744 

50 

40 

30 

(d) 


20 

10 

0 

0 10 20 30 40 50 60 70 80 90 100 


Figure 4. Measurements on a Ti 6-4 billet segment using a 5-MHz phased-array transducer 

focused near the billet back wall, following the style of Figure 1. Beam diameters (-6 dB) near the 

back wall are approximately 200 mils x 380 mils (axial x hoop). 

Evaluation of Transducers 

The two 7.5 MHzF/10 aperture elliptical transducers were evaluated in more detail than the 

preliminary evaluation reported in the previous quarterly. Frequency measurements were made 

using the echoes from #2FBH targets in 10” diameter calibration standards. Tables 1 and 2 

compares these frequency measurements with those supplied by the manufacturer, which had 

been measured on a flat brass target, located at the near focal point, in water. 

In order to assess the performance relative to the #1FBH sensitivity program goal, a number of 

scans were made using the 10 inch diameter Ti 64 ETC standards, which contain targets of various 

diameters down to 0.4 mm (1/64 inch). These scans were done as closely as possible to 

production inspection conditions, with the exceptions that the scan index was reduced to 0.01” in 

order to capture the peak signals, and the gate length was reduced where necessary to avoid back 

surface signals in the gate. For the zone 2 transducer, targets at 0.9”, 1.35” and 1.8” (start, center, 



and end of zone) were analyzed from the c-scan data. For the zone 4 transducer, targets were at 

3.15”, 3.6” (center and end of zone). In each case, there was some lateral banding of the noise 

pattern, so regions of noise in the highest and lowest bands were analyzed and are shown 

separately on the plots. Figures 5 and 6 show the target amplitudes and noise amplitudes for 

zones 2 and 4 that the zone 4 transducer was not capable of performing inspection of the material 

in the calibration standard to a 1/64 inch FBH sensitivity. The noise level in the high noise band 

was marginally above the amplitude of the 0.4 mm (1/64 inch) target at the deep end of the zone. 

We consider that a 3dB margin is required between the noise and the target amplitude in order to 

achieve the inspection sensitivity. Review of the measured frequency performance, and the 

manufacturer’s reported measurements also showed that the transducer had frequency significantly 

lower than specified (measured at 6.02, 6.25, and 6.35 MHz, versus lower specification limit of 7.0 

MHz). The transducer was returned to the manufacturer. 

The zone 2-transducer appeared marginally capable of meeting the required sensitivity. It showed 

a difference of 2.8 dB between the noise and the lowest target signal, versus the 3dB requirement. 

There is a concern that the measured bandwidth was lower than specified (48% versus lower spec 

limit of 60%), and the manufacturers reported measurement of frequency was only 6.33 MHz. 

Based on the data of Figures 5 and 6, a decision was made to pursue development of transducers 

designed with the larger F/8 aperture. Note that the original plan was to purchase sets of 

transducers with both F/10 and F/8 aperture size. The smaller F/10 transducers reported above 

were purchased with the intent of making the final decision on aperture size based on the results of 

their evaluation. 

Figure 5. Noise and target amplitude responses, zone 2 transducer. 



Figure 6. Noise and target amplitude responses, zone 4 transducer. 

Specified 

Reported by 

manufacturer 

Measured on #2FBH, 1.35” 

deep in Inconel 718 

Center freq (MHz) 7.5 ± 0.5 6.33 7.1 

Lower – 6 dB freq (MHz) 5.4 

Upper – 6 dB freq (MHz) 8.8 

Bandwidth (MHz) 3.4 

Bandwidth (%) ≥ 60 68 48 

Pulse duration (µS) 0.21 

Table 1. Frequency Measurements for Zone 2 Transducer. 



Specified 

Reported by 

manufacturer 

Measured on 

2/64 inch 

FBH, 3.15” 

deep in 

Inconel 718 

Measured on 

2/64 inch 

FBH, 3.15” 

deep in Ti 64 

Center freq (MHz) 7.5 ± 0.5 6.02 6.35 6.25 

Lower – 6 dB freq (MHz) 4.9 4.7 

Upper – 6 dB freq (MHz) 7.8 7.8 

Bandwidth (MHz) 2.9 3.1 

Bandwidth (%) ≥ 60 72 46 50 

Pulse duration (µS) 0.25 0.31 

Table 2. Frequency Measurements for Zone 4 Transducer. 


Detailed straw-man for an improved compensation procedure will be developed, and plans for a 

direct test of the new procedure will be formulated. 

Continue with purchase of F/8 aperture transducers. 

Utilize phased array to simulate the performance of the F/8 aperture and verify that the beam 

properties produced will achieve the required sensitivity 

Milestones: 

Original 

Date 

Revised 

Date 

Description 

10” diameter fixed focus 

12 months 18 months Resolve model discrepancies and design 

transducers. (ISU) 

Status 

Model discrepancies resolved— 

design activity initiated. Delay will 

not affect remainder of program 

7 months 36 months Build transducers. (GE) Zones 2 and 4 transducers received. 

First two transducers took longer to 

build than anticipated causing 

milestone slip. Ready to order 

complete set. 

29 months 38 months Complete scans on 10” standards and RDB. 

Provide data to 3.1.1 for estimation of POD. 

(GE,PW) 

30 months 39 months Review results, determine whether #1FBH goal 

was achieved. (All) 



Original 

Date 

Revised 

Date 

Description 

Status 

34 months Design and build two transducers for 14” diameter 

center zone. Evaluate performance on 14” chord 

block. (PW with support from GE) 

(30 

months) 

(33 

months) 

(39 

months) 

(42 

months) 

(48 

months) 

10” diameter phased array,(go/no go decision 

at 30 months) 

(Critical review with FAA, seek program redirection 

to develop phased arrays) (All) 

Complete preliminary phased array surveys. (PW) 

Evaluate up to three candidate phased array 

systems. 

Identify preferred configuration for factory 

evaluation system. 

Design and build improved phased array 

transducer assembly. 

Factory Evaluation / Demonstration 

36 months* 44 months Complete factory test of five heats. Conduct 

industry demonstration of #1FBH capability in 10” 

diameter. (GE, PW) 

38 months* 46 months Evaluate indication finds from factory test, 

document results. (GE, PW, ISU). 

40 months 48 months Report of laboratory and factory evaluations 


Systems Capability Working Group and cost 

comparisons for the different inspection 

approaches. (All) 

Large diameter billet 

12 months Build chord calibration standard for 14” diameter, 

near-center region. (PW) 

18 months 20 months Evaluate capability on 13” and 14” diameter using 

conventional and zoned fixed focus, determine 

improvement over conventional. Provide data to 

3.1.1 for model validation and POD estimation for 

large diameter billet. (GE, PW, ISU) 

20 months 24 months Laboratory assessment of sensitivity at diameters 

greater than 10" diameter using fixed focus 

transducers. (All) 

General issues 

28 months Complete attenuation compensation procedure in 

cooperation with 3.1.1. (ISU with support from PW 

and GE) 

30 months Procedures to account for attenuation effects that 

occur in titanium billet and thus improve the POD of 

billet inspection. (All) 

Original 

Date 

Revised 

Date 

Description 

Transducer order has been placed. 

Complete 

13” billet inspection complete at GE 

14” chord block inspection complete 

Complete at P&W 

Status 

60 months Provide revision of AMS 2628 titanium billet 

specification to SAE Committee K. 

60 months Calibration standards including 14" diameter chord 

block and transducers (fixed focus and phased 

array assemblies) as needed. 



Deliverables: 

Laboratory assessment of sensitivity at diameters greater than 10” diameter using fixed focus 

transducers. 

Procedures to account for attenuation effects that occur in titanium billet and thus improve the POD 

of billet inspection. 


Systems Capability Working Group and cost comparisons for the different inspection approaches. 

Calibration standards including 14” diameter chord block and transducers (fixed focus and phased 

array assemblies) as needed. 

Revision to AMS 2628 titanium billet specification submitted to SAS Committee K. 

Metrics: 

Achievement of #1FBH in 10” diameter billet with no significant speed reduction from current 

multizone inspection. 


Date 

June 16, 1999 

Description 



Date 

Description 



Project 1: 

Task 1.3: 



Titanium Forging Inspection 

Fundamental Property 

Measurements for Titanium 

Forgings 

Team Members: 

HW: R. Bellows, Waled Hassan 

ISU: Bruce Thompson, Frank Margetan, 

Ron Roberts, Tim Gray 

GE: Ed Nieters, Mike Gigliotti, Lee 

Perocchi, Dave Copley, Wei Li, Jon Bartos, 

Bill Leach 



Students: A. Li 


Objectives: 

• To gain the fundamental understanding of the ultrasonic properties of titanium forgings that is 

needed to provide a foundation for the development of reliable inspection methods that provide 

uniformly high sensitivity throughout the forging envelope. 

• To acquire the data necessary to relate the detectability of defects in forgings to component 

properties (flow line characteristics, surface curvature) and defect properties (size, shape, 

composition, location, and orientation) thereby providing a foundation for the design of 

improved inspections and the evaluation of inspection capability. 

Approach: 

Sample Fabrication: A critical flaw list for titanium forgings will be generated in cooperation with 

RISC including description of typical morphologies for use in the model development efforts. 

This list will be used to define a limited set of forging standards with embedded defects. 

Forging samples with varying flow line characteristics and surface curvatures, some of which will 

contain flat-bottomed holes or synthetic inclusions will be defined and manufactured. 

Deformation models will be used to predict variations in metal flow distributions and guide the 

sample development. Approximately 32 coupons from forgings with varying flow line directions, 

flow line densities, and geometrical curvatures (concave and convex) will be acquired. Samples 

available from the CBS and TRMD programs will be utilized to the extent possible. 



Ultrasonic Property Measurement: UT and material anisotropy associated with the forging process 

will be quantified by measurement of the sound speeds, attenuations, signal fluctuations and 

backscattered noise levels of the forging coupons. The measurement methods developed in Phase 

I will generally be used. As in Phase I, cube specimens cut at various locations may be used for 

initial surveys. In selected cases, novel coupon geometries will also be considered which permit 

beam propagation at various angles to the flow lines. Figure 2 displays one possible coupon 

design which allows measurements: (1) along flow lines; (2) perpendicular to flow lines; and (3) at 

oblique incidence. Such measurements will be used to establish the relationship of flow line 

direction to inspectability. The results of the experimental measurements will be used to develop 

and validate the noise models and ultimately allow consideration of the effect of forging process on 

inspection capability as part of 3.1.2. 

Measurements will be made of the 

ultrasonic scattering from the embedded 

defects, including both the synthetic hard 

alpha inclusions and the samples available 

from the CBS and TRMD programs. This 

data will be provided for further model 

validation which will in turn be utilized in 

subtasks 3.1.2 for POD determination. 

Effects of Surface Curvature: The 

relationship between surface curvature and 

inspectability will be quantified in this 

subtask. The shape of the entry surface 

influences the focusing of the sonic beam 

within the forging, and hence, affects both 

the amplitude of defect echoes and the level 

of competing grain noise. The team will 

measure the effects of surface curvature by 

using coupon designs such as that shown in 

Figure 3. Curvature corrections will be 

developed and transducer designs will be 

optimized in cooperation with 1.3.2. Models 

which predict the effects of surface 

curvature on backscattered flaw echoes, 

grain noise characteristics, and signal/noise 

ratios will be developed and validated in 

cooperation with 3.1.2. Measurements 

made using the surface-curvature 

specimens will be used to validate those 

models. The models will then be used to 

develop curvature corrections and optimized 

transducer designs for forging inspections in support of 1.3.2. 

Measurements 

parallel to 

flow lines 

FLOW LINES 

Oblique angle 

measurements 

Measurements 

perpendicular 

to flow lines 

Figure 2. Potential coupon design for forging samples. 

Octagonal shape provides entry and reflecting surfaces for 

velocity and attenuation measurements at various 

orientations to the forging flow lines. 

Initial Shape 

FBH’s 

A 

B 

C 

D 

E 

Surface 

Progression 

- 2” 

- 4” 

flat 

4” 

2” 

Figure 3. Potential design for surface curvature test 

specimens. Specimen contains flat-bottomed holes or 

other reflectors, and begins with a concave surface 

curvature which is progressively machined to arrive at 

convex entry surface. Design ensures that metal travel 

path and microstructure surrounding the reflectors remain 

unchanged in successive measurements. 




1998. 




issues and discussions are summarized into three primary areas, (1) Property Measurements, (2) 

Noise Curvature Blocks, and (3) Synthetic Inclusion Disk and discussed separately below. 

Property Measurements 

One goal of the Fundamental Studies subtask is to document the manner in which ultrasonic 

properties vary within representative Ti 6-4 forgings, and to relate those properties to the forging 

microstructure. The ultrasonic data will then be used by Subtask 1.3.2 to design new forging 

inspections which improve defect detection sensitivity four-fold: from the current #1 FBH level to a 

#1/2 FBH level. Since backscattered grain noise is primarily responsible for determining defect 

detection limits, the emphasis has been on grain noise measurement and analysis. 

The overall plan calls for UT measurements on coupons cut from selected sites in three typical Ti 6- 

4 forgings supplied by the OEMs. Approximately 8-10 coupons have now been cut from each 

forging, with coupon sites chosen to provide a range of local microstructures (based on 

backscattered noise C-scan, macroetch, and strain-map data). In previous quarters, grain noise 

studies were concluded on suites of coupons cut from forged disks provided by GE and P&W. 

During the Jan-Mar 2002 quarter, similar measurements were conducted on the coupons from the 

Honeywell (HW) forging. The noise measurement and FBH normalization procedures were 

identical to those reported in the Jan-Mar 2001 Quarterly Report. The noise measurement setup is 

shown in Figure 1, together with the coupon sites for the HW forging. 

Backscattered grain noise amplitudes for one case are shown in Figure 2. The noise C-scans for 

the HW coupons generally showed little variation with position in the hoop direction; however in 

some cases there was a strong variation with inspection direction or with radial/axial position. As 

was done earlier, each coupon was divided into quadrants of approximately uniform noise 

amplitude, and noise statistics for each quadrant were computed for the two inspection directions in 

the radial-axial plane. Gated-peak noise amplitudes were measured relative to an available #1 

FBH reference, namely a 0.5”-deep hole in an IN100 step block. ISU models were then used to 

rescale the noise data relative to a hypothetical #1 FBH in Ti 6-4 at the same average depth as the 

noise measurements. Resulting average and peak noise levels for the HW coupons are shown in 

Figure 3. 

Measured average and maximum gated-peak noise levels are compared for the three OEMsupplied 

forgings in Table 1. When averaged over all coupons and inspection directions, results for 

the three forgings were quite similar. The largest peak noise level seen in all of the cases studied 

was 6.9% of the #1 FBH reference. This occurred within Honeywell coupon #5 which was located 

in the OD portion of the forging, about midway between the “forward” and “aft” surfaces. 



When designing UT inspections of forgings, the high-noise regions are of chief interest since the 

elevated grain noise levels there can mask echoes from small or weakly reflecting defects. For this 

reason, additional UT measurements were planned for the highest-noise coupon from each forging. 

These included determination of the attenuation and the backscattered noise capacity (FOM), both 

of which are frequency-dependent. Such measurements had been performed earlier for the highnoise 

GE and P&W coupons. During the Jan-Mar quarter, similar measurements were completed 

for the highest-noise coupon from the HW forging, and results are summarized in Figures 4 and 5. 

Because the microstructure typically varies with depth, FOM values were deduced for a series of 

depths by using time gates with different centers and durations. Power law fits to the FOM-versusfrequency 

data were then made for the depth zone having the highest noise capacity. Table 2 

summarizes the pertinent UT properties for the highest-noise zones of the high-noise coupons from 

the GE, P&W, and HW forgings. As expected from Table 1, the measured FOM value was largest 

for the Honeywell high-noise coupon. 

Note that the differences in FOM values in Table 2 are greater than the corresponding differences 

in peak noise values listed in Table 1. This is chiefly because, in the survey measurements leading 

to Table 1, only gated-peak noise amplitudes were measured, and the focal spot of the transducer 

was not necessarily located in the depth zone where the noise capacity was greatest. For Table 2, 

however, noise A-scan data was analyzed in a manner that identified the depth zone with the 

greatest noise capacity. 

The properties listed in Table 1 can be used as inputs to computer models that simulate ultrasonic 

inspections of forgings. Examples of such simulations for one proposed inspection scheme can be 

found in an article written for the 2001 QNDE conference held in Brunswick, Maine: “Survey of 

Ultrasonic Properties of Aircraft Engine Titanium Forgings”, by L. Yu, F. J. Margetan, R. B. 

Thomson, and A. Degtyar. 

During the quarter, we continued efforts to relate the observed noise variations in the Ti 6-4 forging 

coupons to available microstructural data. The latter includes forging strain map information as 

calculated using DEFORM. One display of the strain data for the Honeywell forging is shown in 

Figure 6. It shows the manner in which ellipsoidal elements in the billet are deformed by the multistep 

forging process. The billet elements were chosen to have 5:1 aspects ratios, with the long 

dimension aligned with the billet axis, to approximately simulate billet macrograins. Efforts to 

correlate absolute noise levels with properties of the deformed ellipsoids seen in Figure 6 were not 

very successful. However, a clear correlation was seen between the local ellipsoid properties and 

the local noise anisotropy. The noise anisotropy (NA) is defined as the ratio of the average gatedpeak 

noise values for C-scans made from two orthogonal directions. For coupons that are not 

“tilted” with respect to the symmetry axis of the forging, the NA equals the “axial” noise level divided 

by the “radial” noise level. If the shapes of macrograins in the forging mimic the shapes of the 

ellipsoidal elements output by the DEFORM calculation, then the noise anisotropy is expected to 

correlate with the ellipsoid projection ratio defined in the right-hand panel of Figure 6. For the 

Honeywell forging, a positive correlation is seen between the NA and projection ratio (Figure 7). 

However, the degree of correlation is not as high as seen earlier for the P&W forging. A similar 

study comparing noise anisotropy and ellipsoid deformation is planned for the GE forging if suitable 

DEFORM calculations can be obtained. 



(a) 

Transducer is: 

15 MHz 

0.5”-Diameter 

F = 3.5 in. 

0.0 

0.2 

0.4 

0.6 

0.8 

1.0 1.0 

Coupons measure 

1.25” x 1.25” x 2.0”. 

Each of the four 

large surfaces was 

scanned. 

Gated region for 

C-scan images of 

gated peak noise. 

Relative inspection 

sensitivity with depth 

within gate. 

(Via noise models.) 

Focused 1/4 way down 

(b) 

ID 

9 

1.75” 

7.63” 

AFT 

1.25” / 2 

1 

3 

2 

10 

4 

5 

6 

7 8 

Sonic shape. 

FWD 

HW Ti 6-4 Forging 

OD 

Figure 1. (a) Setup for backscattered noise measurements on forging coupons. (b): Coupon 

locations for the Honeywell forging. 

(a) 

Side 2 

(AFT) 

Side 1 

Side 3 

(OD) 

(hoop) 

(c) 

ID 

(side 4) 

H# 

AFT 

(side 2) 

5 

6 

4 

1 

3 2 

8 7 

FWD 

(side 5) 

engraved 

label 

OD 

(side 1) 

0% 100% 

(b) 

Thru OD 

Tic marks 

are 0.5” 

apart 

Cropped 

region used 

for noise 

statistics 

Specimen, 

inspection 

direction 

and 

absolute 

gain 

setting. 

Side 2 - AFT 

(Side 3 – hoop) 

H3 Side 1, 37dB 

Side 5 - FWD 

Avg.: 2.58% 2.13% 3.03% 

Peak: 10.4% 6.11% 10.4% 

Full 

image 

Left 

half 

Right 

half 

Inspection 

entry 

surface 

“Hoop” edge 

(Side 3) is 

always at the 

bottom of the 

image, 

allowing the 

other edges to 

be readily 

identified. 

“Edge effects” 

Table lists average 

and maximum 

gated-peak noise 

amplitude, as a 

percentage of the 

amplitude of the #1 

FBH in IN100 at 

the same water 

path and gain. 

Amplitudes are 

computed for the 

reduced-area 

region (illustrated 

above) with “edge 

effects” cropped. 

Figure 2. Details of backscattered grain noise measurements on the Honeywell forging coupons. 

(a) Designation of inspection surfaces. (b) Noise C-scan and summary table for a typical case 

(inspection through OD face of coupon #3). (c) For a given coupon, results are tabulated for 8 

combinations of inspection direction and coupon quadrant. 



Measured Noise Levels in Honeywell Ti 6-4 Forging Coupons 

Noise Level 

(100 = #1 FBH in Ti 6-4) . 

8.00 

7.00 

6.00 

5.00 

4.00 

3.00 

2.00 

1.00 

Red: Peak Noise 

Blue: Ave. Noise 

Honeywell Forging 

9 

AFT 

1 

10 

4 

6 

7 8 

FWD 

AFT 

(side 2) 

5 

6 

2 

5 

3 

OD 

0.00 

3 4 5 6 7 8 

12 3 4 5 6 7 8 12 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 

H1 

H2 

H3 

H4 

H6 

H8 

Coupon, and Quadrant 

Coupon, Inspection Direction, and Quadrant 

H5 

H7 

ID 

(side 4) 

4 

1 

3 2 

8 7 

FWD 

(side 5) 

OD 

(side 1) 

Figure 3. Comparison of peak (red) and average (blue) gated-peak noise levels in the Honeywellsupplied 

Ti 6-4 forging coupons. Noise levels are relative to the amplitude of a (hypothetical) #1 

FBH located at the same depth in Ti 6-4 material. For each coupon eight values are shown, 

corresponding to different combinations of inspection directions and analysis quadrant. 

AFT 

Honeywell Coupon#5 Side 4 Attenuation 

9 

1 

2 

10 

4 

6 

5 

3 

OD 

Attenuation (Nepers/cm) 

0.05 

0.04 

0.03 

0.02 

0.01 

Full scan region 

Reduced scan region 

Power Law Fit 

fit is 0.00082 x freq 1.343 

7 8 

FWD 

0.00 

4 6 8 10 12 14 16 18 

Frequency (MHz) 

Figure 4. Measured average attenuation curve and associated power-law fit for the highest-noise 

coupon from the Honeywell Ti 6-4 forging. The large arrow in the cross-sectional drawing of the 

forging identifies the coupon and inspection direction. A 10-MHz, 0.25”-diameter planar probe was 

used. Average results are shown for the full scan region (central 1.5” x 0.75” of the entry surface) 

and for a reduced-area region (central 1.25” x 0.50”). Multiply attenuation values by 22.06 to 

change to dB/inch units. 



FOM (std. units) 

0.20 

0.18 

0.16 

0.14 

0.12 

0.10 

0.08 

0.06 

H5 Side 4 FOM (using meas. atten) 

Gate #1 

Gate#2 

Gate#3 

Gate#4 

Gate#5 

gate#6 

0.04 

0.02 

0.00 

5.0 10.0 15.0 20.0 

Frequency (MHz) 

RMS Noise (Volts) 

0.030 

0.025 

0.020 

0.015 

0.010 

0.005 

HW5 Side 4 RMS Noise 

Gate Center Duration 

G1 2.61 us (0.32”) 2.55 us 

G2 3.61 us (0.44”) 1.27 us 

G3 4.61 us (0.56”) 1.27 us 

G4 5.61 us (0.69”) 1.27 us 

G5 6.61 us (0.81”) 1.27 us 

G6 3.90 us (0.48”) 5.11 us 

G1 

G2 

G3 

G6 

G4 

G5 

0.000 

0 1 2 3 4 5 6 7 8 9 10 

Time after Front Wall Echo (usec) 

Figure 5. Measured grain-noise FOM values, as functions of frequency, for the Honeywell highnoise 

forging coupon. The largest FOM values were seen for analysis Gate #3, centered about 

0.56” below the entry surface. The locations of the various gates used in the analysis of noise A- 

scans are shown in the rightmost panel which displays the measured rms noise level as a function 

of time. A 15-MHz, F7 focused transducer was used, and the peak in the rms noise curve 

corresponds to scattering by grains located in the focal zone. 



Noise Anisotropy is 

defined as: 

9 

1 

10 

4 

6 

2 

5 

3 

Noise Inspected From Axial Direction 

Noise Inspected From Radial Direction 

We attempt to correlate NA with Y/X : 

Axial 

Radial 

7 8 

Elliptical 

Strain element 

X 

Figure 6. Left: DEFORM calculation showing how 5:1 elliptical elements in the billet are 

transformed by the forging process from the initial billet to the final forged shape. (Only a portion of 

the billet is shown. Right: Definitions of the noise anisotropy and the ellipse projection ratio. 

Y 

NA (Axial Noise / Radial Noise) . 

Relationship between Noise Anisotropy and Forging 

Deformation (Starting from 5:1Ellipsoid) 

5.0 

sample#1 

sample#2 

sample#3 

sample#4 

sample#6 

sample#8 

4.0 

sample#5 

sample#7 

sample#9 

3.0 

2.0 

1.0 

Horizontal coordinate is the projection of 

the ellipse onto the axial inspection 

direction divided by the projection onto 

the radial inspection direction. 

0.0 

0 1 2 3 4 5 6 

Ellipse Projection Ratio 

Honeywell Forging Coupons 

Trendline 

NA (Axial Noise / Radial Noise) . 

2.5 

2.0 

1.5 

1.0 

0.5 

Relationship between Noise Anisotropy and Forging 

Deformation (Starting from 5:1Ellipsoid) 

P&W Forging Coupons 

Trendline 

sample#1 

sample#2 

sample#4 

sample#5 

sample#6 

sample#7 

sample#8 

0.0 

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 

Ellipse Projection Ratio 

Figure 7. Correlation between noise anisotropy and ellipse projection ratio for the Honeywell and 

P&W forgings. Each plotted point represents measurements within one quadrant of one forging 

coupon. 



Peak> Range of Ave. Range of Peak 

GE: 0.81% 2.03% 0.2% - 1.9% 0.5% - 6.1% 

PW: 0.83% 2.31% 0.4% - 1.8% 0.7% - 5.5% 

HW: 0.88% 2.36% 0.4% - 2.5% 0.6% - 6.9% 

(#1 FBH in Ti 6-4 = 100%) 

Table 1. Comparison of average and maximum gated-peak noise voltages seen in the suites of 

coupons from the GE, P&W, and HW forgings. The first two columns list the average and 

maximum values for a given forging, averaged over all coupons, inspection directions, and analysis 

quadrants. The last two columns list the ranges of measured values for average and peak noise in 

each forging. 

Table 2. Comparison of UT properties for the high-noise coupons from the Pratt&Whitney, General 

Electric, and Honeywell Ti 6-4 forgings. 

Noise Curvature Blocks 

PW GE HW 

velocity (cm/usec): 0.622 0.618 0.621 

density (gm/cc): 4.43 4.43 4.43 

attenuation power law * : 6.83E-4*freq^1.79 4.31E-5*freq^2.26 8.20E-4*freq^1.34 

attenuation at 10 MHz: 0.93 dB/inch 0.17 dB/inch 0.40 dB/inch 

FOM power law * : 1.61E-3*freq^1.25 2.95E-3*freq^0.896 4.15E-3*freq^1.078 

Meas. FOM at 10 MHz: 0.027 0.021 0.047 

* For power laws, units are N/cm for attenuation, and 

cm^-0.5 for FOM, with the frequency input in MHz. 

Six “noise curvature blocks” were made to investigate the manner in which surface curvature 

influences inspection sensitivity in forgings. A principal use of the blocks will be to test models that 

predict the characteristics of backscattered grain seen during forging inspections. The six blocks, 

each measuring approximately 1.6” x 5.9” x 2” (axial x radial x hoop) were fabricated by 

Pratt&Whitney from one of their Ti 6-4 forgings. The location of each block within the forging 

cross-section is shown in Figure 8a. For five of the blocks, the upper surface in Figure 10a is 

curved, while the sixth block has a flat upper surface. Although each block was cut from the same 

position in the radial/axial plane of the forging, the blocks, of necessity, had different angular 

positions, as shown in Figure 8b. Since microstructural variations in the hoop direction of a forging 

are often minor, it was hoped that this construction method would produce six blocks with nearly 

identical microstructures. 



Preliminary measurements of backscattered noise levels through the (lower) flat surfaces of the 

blocks were carried out early in the quarter. Selected results are shown in Figure 9. Although the 

average noise levels were generally similar from block-to-block, the differences were deemed to be 

large enough to require further measurement and documentation. In addition, the preliminary 

measurements revealed that the flat block, which was cut from the forging at a later date than the 

other five coupons, had been cut out “upside down” (i.e., with “TOP” and “BOT” faces reversed in 

Figure 8). This error, and the fact that the noise level in the ID portion of the forging increases from 

“TOP” to “BOT” is responsible for the large difference seen in the right-hand portion of Figure 9 

between the noise level in the flat block and those of the other five coupons. Although unfortunate, 

this fabrication error was not deemed to be a major problem for testing the noise models. The 

principal noise measurements could be confined to the thicker zones of the blocks, and the flat 

block could simply be “flipped” when measurements were made. 

During the quarter, additional noise measurements were made through the flat surfaces of the 

blocks to: (1) carefully document the effect of microstructural differences between blocks; and (2) to 

test noise model predictions for inspections through flat surfaces. The measurements themselves, 

and subsequent analysis to calculate relevant noise statistics, were performed at Pratt&Whitney. 

Additional analyses and model predictions were then carried out at ISU. 

This second round of measurements was made using a “characterized” 10-MHz transducer whose 

effective focal properties had been carefully determined (effective diameter = 0.344”; geometric 

focal length = 3.95”). Measurements through the flat surfaces of the blocks were made for two 

water paths: 2.4”, which put the actual focal spot just under the entry surface; and 1.0”, which put 

the focal spot approximately 0.5” deep in the metal. In each case the probe was scanned over a 3” 

x 0.5” (radial x hoop) region using a step size of 0.015” in each direction. The noise A-scans 

acquired at each site were stored for later processing. Each day that noise data was acquired, a 

reference echo from a #1 FBH in a calibration block was also measured. The reference echo was 

used to correct for minor differences in measurement system efficiency from one measurement trial 

to the next. In addition, the electronic noise level was measured so that it could be properly 

accounted for when noise model predictions were compared with experiment. 

The manner in which the measured noise level depends upon depth is shown in Figures 10 and 11 

for the 2.4” and 1.0” water paths, respectively. In the left-hand panels, the rms noise levels, 

averaged over the lateral scan positions, are shown for each block. Block-to-block differences in 

noise levels can be seen which presumably result from variations in the forging microstructure with 

circumferential position. Also shown in Figures 10 and 11 are rms noise levels predicted using an 

ISU model. The model assumes a uniform microstructure, and requires ultrasonic velocity, 

attenuation, and grain noise Figure-of-Merit (FOM) values as inputs. Initial guesses for the model 

inputs were obtained by averaging values measured in a suite of smaller coupons cut from one 

section of the same forging (see Figure 8b). The estimated FOM value was then increased by 10% 

to bring the predicted rms noise level more into line with the average of the measurements on the 

six noise curvature blocks. In Figures 10-11, there is good agreement between the model 

prediction and the average experimental result in the central depth region, i.e., away from the 

influences of the front-wall and back-wall echoes. Also note that the location and width of the focal 

maximum in Figure 11 is well predicted by the theory. 



The average noise characteristics, as reflected by the rms-noise-versus-depth curves, are 

somewhat different for the different blocks. For each block the following procedure was used to 

determine a depth-dependent “microstructure difference factor”. (1) The measured rms-noiseversus 

depth curve was adjusted to remove the (minor) effect of electronic noise. (2) 

The six rms noise curves (one for each block) were averaged to determine the mean curve for the 

suite of coupons. This was done separately for each inspection water path. (3) The rms noise 

curve for a given coupon was divided by the mean curve to determine the fractional deviation from 

the mean at each metal depth. As shown in Figure 12, these difference factors were found to be 

nearly identical for the two inspections at different water paths, indicating that they do indeed arise 

from microstructural variations. (4) The difference factors measured for a given block using the 2.4” 

and 1.0” water paths were then averaged. In future analyses of grain noise measured through the 

curved surfaces of the blocks, these difference factors will be used (with the distance scale 

inverted) to “correct” noise quantities for microstructural differences. Remaining differences in 

noise properties will then presumable be due to surface curvature effects. 

From the stored grain noise A-scans, other noise statistics can be readily computed. For example, 

for one typical block, Figure 13 shows gated-peak noise C-scans reconstructed from the flatsurface 

A-scan data for four choices of the time gate. As the gate is widened, keeping its center at 

the same depth, the average noise is seen to increase, as expected. Similar C-scan images were 

generated for all six coupons, and the average and maximal noise amplitude in each image was 

tabulated. Results are shown in graphical form in Figure 14-15, where they are compared to the 

predictions of the ISU noise model (rightmost portion of each plot). The model the does a good job 

of predicting the average gated peak noise amplitude for each of the four gates. However, the 

theory tends to underestimate the maximum noise amplitude seen in a given C-scan. The current 

noise model assumes a uniform “average” microstructure. The actual microstructure of a typical 

block varies only modestly with axial depth, but varies quite significantly with radial position, as can 

be seen in Figure 13. In the future the model for gated-peak noise statistics will be modified to 

account for such microstructural variations. This should improve predictions of maximal gated-peak 

noise amplitudes. 



6.8” 

ID 

“Side 5” = “BOT” 

OD 

CURVED 

SURFACE 

1.64” 

0.49” 

0.75” 

0.49” 

1.5” 

#1 FBH 

“Side 2” = “TOP” 

0.1” 

(a) 

3.4” 

3.4” 

This side of the block 

will be rounded to ensure 

that the length of the block is 6.8” 

convex 4.0 

4 

The interior 

edges may be 

lopped to ensure 

that all 5 blocks 

fit within the 

forging 

3 

convex 10.0 

5 

200 o 

(ref. gap) 

Material not available 

from this section 

Small coupons for 

earlier property 

measurements 

260 o 

2” 

Flat block was 

later machined 

from one of the 

remaining 

wedges 

concave 8.0 

2 

1 

(b) 

concave 2.0 

concave 0.75 

(c) 

Figure 8. Positions of noise curvature blocks relative to the original P&W Ti 6-4 forging. (a)-(b): 

Locations of the curved blocks in the radial-axial (a) and radial-hoop (b) planes. (c) The flat block 

was machined later from one of the remaining wedges, and is slightly shorter in the radial direction. 

Curved blocks have radii of curvature of 0.75” concave, 2” concave, 8” concave, 4” convex, and 10” 

convex, respectively. 



Noise C-scans through the “Flat Surfaces” of the Six Specimens 

10 MHz, 0.375”D, focal depth in water = 2.65”, Amp=7, Damping=1, Pulse Width = 20ns 

Waterpath = 1.0in, Focus ≈ 0.5” deep, Gain = 57.0dB, Gate delay = 0.3in, Gate Range = 0.4in 

OD 

Thicker region 

Thinner region 

ID 

22.4% 

10.0” Radius Convex Block 

28.4% 

18.8% 

4.0” Radius Convex Block 

27.2% 

17.1% 

Flat Reference Block 

14.1% 

22.9% 

0.75” Radius Concave Block 

32.8% 

23.3% 


32.3% 

19.9% 


30.5% 

Figure 9. Preliminary C-scans showing gated-peak grain noise levels measured through the flat 

surfaces of the six noise curvature blocks. Average noise levels as a percentage of full screen 

height are listed. 

Noise Measurements thru Flat Entry Surfaces 

2.4" water path; 57 dB 



RMS Grain Noise (% of FSH) . 

12 

Flat, FBHs in back 

Flat, FBHs in front 

0.75 cv 2.0 cv 

10 

8.0 cv 4.0 cx 

10.0 cx Theory 

8 

Model assumes: FOM = 1.1* (5.6E-4*freq^1.25) 

Atten = 5.7E-4*freq^1.8 

6 

4 

2 

Exp. values corrected for electronic 

noise and Ref signal differences 

0 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 


12 

Theory 

Exp. Ave. 

10 



8 

6 

4 

2 

Exp. values correctedfor electronic 

noise and Ref signal differences 

0 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 

Metal Depth (inches) 


Figure 10. Comparison of measured and predicted rms grain noise levels for inspections through 

the flat surfaces of the six noise curvature blocks using a 2.4” water path. Left-hand panel displays 

the measured noise levels for the six blocks individually, while the right-hand panel displays their 

average. 








14 

12 

10 

Flat, FBHs in back 

Flat, FBHs in front 

0.75 cv 2.0 cv 

8.0 cv 4.0 cx 

10.0 cx Theory 

8 

6 

4 

2 

Exp. values corrected 


for electronic noise 


0 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 



14 

Theory 

Exp. Ave. 

12 

Exp. values corrected 

for electronic noise 

10 

8 

6 

4 

2 



0 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 


Figure 11. Comparison of measured and predicted rms grain noise levels for inspections through 

the flat surfaces of the six noise curvature blocks using a 1.0” water path. Left-hand panel displays 

the measured noise levels for the six blocks individually, while the right-hand panel displays their 

average. 

Coupon Noise / Average 

(a) 

Coupon Noise / Average . 

1.80 

1.60 

1.40 

1.20 

1.00 

RMS grain noise in Ti noise curvature blocks 

measured from flat side, water path = 2.4" 

Normalized by average over six coupons. 

flat with FBHs in back 

0.75 cv 

2.0 cv 

8.0 cv 

4.0 cx 

10.0 cx 

0.80 

(5 and 0.62 dB corrections to "flat") 

0.60 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 

1.4 

1.3 

1.2 

1.1 

Depth (inches) 

RMS grain noise in Ti noise curvature blocks measured from 

flat side, normalized by average over six coupons. 

4.0 cx- 1.0" 

4.0 cx - 2.4" 

4.0 cx - ave. 

1.0 

0.9 

0.8 

4.0” – Convex Specimen 

0.7 

(c) 

0.6 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 


Coupon Noise / Average 

Coupon Noise / Average . 

1.80 

1.60 

1.40 

1.20 

1.00 

0.80 

(b) 

(d) 

RMS grain noise in Ti noise curvature blocks 

measured from flat side, water path = 1" 

Normalized by average over six coupons. 

flat with FBHs in back 

0.75 cv 

2.0 cv 

8.0 cv 

4.0 cx 

10.0 cx 

0.60 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 

1.4 

1.3 

1.2 

1.1 

1.0 

0.9 

0.8 

0.7 


RMS grain noise in Ti noise curvature blocks measured from 

flat side, normalized by average over six coupons. 

0.75” – Concave Specimen 

0.6 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 


0.75 cv - 1.0" 

0.75 cv - 2.4" 

0.75 cv - ave. 

Figure 12. (a)-(b): Microstructure difference factors, as functions of depth, measured using water 

paths of 2.4” and 1.0”, respectively. (c)-(d): More detailed views of the microstructure correction 

factors for two of the blocks. 



4.0” Convex Block; Flat Side Inspection; 1.0” Water Path 

Depth Zone 

Gate 1 

0.8”-1.0” 

Gate 2 

0.7”-1.1” 

Gate 3 

0.6”-1.2” 

Gate 4 

0.5”-1.3” 

OD 

ID 

Figure 13. Gated peak noise C-scan images for four choices of the time gate (or depth zone). 

Results are shown for one of the noise curvature blocks inspected at a 1” water path. 



% FSH 

25 

20 

15 

10 

Noise Measurements from flat side, water path = 1" 

Average Gated Peak Noise, Gain = 57 dB, I3 probe 

Gate1 

Gate 2 

Gate 3 

Gate 4 

5 

0 

Flat with 

FBH in 

back 

Flat with 

FBH in 

front 

0.75" 

concave 

2.0" 

concave 

8.0" 

concave 

4.0" 

convex 

10.0" 

convex 

THEORY 

% FSH 

25 

20 

15 

10 

5 

Noise Measurements from flat side,water path=2.4" 

Average Gated Peak Noise, Gain = 57 dB, I3 probe 

Gate1 

Gate 2 

Gate 3 

Gate 4 

0 

Flat with 

FBH in 

back 

Flat with 

FBH in 

front 

0.75" 

concave 

2.0" 

concave 

8.0" 

concave 

4.0" convex 10.0" 

convex 

THEORY 

Figure 14. Measured and predicted average amplitudes in gated-peak noise C-scan images. 

Results are shown for the four choices of the time gate (or depth zone) for each inspection water 

path. 



% FSH 

Noise Measurements from flat side, water path = 1" 

Maximum Gated Peak Noise, Gain = 57 dB, I3 probe 

80 

60 

40 

Gate1 

Gate 2 

Gate 3 

Gate 4 

20 

0 

Flat with 

FBH in 

back 

Flat with 

FBH in 

front 

0.75" 

concave 

2.0" 

concave 

8.0" 

concave 

4.0" 

convex 

10.0" 

convex 

THEORY 

% FSH 

80 

60 

40 

20 

Noise Measurements from flat side,water path=2.4" 

Maximum Gated Peak Noise, Gain = 57 dB, I3 probe 

Gate1 

Gate 2 

Gate 3 

Gate 4 

0 

Flat with 

FBH in 

back 

Flat with 

FBH in 

front 

0.75" 

concave 

2.0" 

concave 

8.0" 

concave 

4.0" convex 10.0" 

convex 

THEORY 

Figure 15. Measured and predicted maximum amplitudes in gated-peak noise C-scan images. 

Results are shown for the four choices of the time gate (or depth zone) for each inspection water 

path. 

Synthetic Inclusion Disk 

Machining of the forging continued following the initial evaluation of the as-forged piece described 

in the previous quarterly report. Mike Gigliotti (GE-CRD) requested that the machined forging be 

delivered to him with an excess material envelope of 0.25” on the outer diameter and 0.1” on the 

forward and aft faces, outside the planned final dimensions. The machining and ultrasonic 

inspection were planned in two stages. Initially the outside diameter (face UG) and four flat faces 



(UO, US, UM, UH) were machined, and were inspected ultrasonically (see figure 16 for 

identification of faces). Then the remaining faces were machined, with the exception of the bore 

UZ, since the piece will be delivered with a solid bore. 

Figure 16. Configuration and face identification of the synthetic inclusion forging. 


Property Measurements Continue efforts to relate grain noise variations within forgings to forging 

strain variations as predicted using DEFORM. 

Noise Curvature Blocks: Perform grain noise measurements through the curved surfaces of the 

blocks. Compare RMS and gated-peak noise statistics, corrected for microstructural differences to 

the predictions of the ISU model. 

Synthetic Inclusion Disk: The remaining faces of the machined forging will be inspected 

ultrasonically. The data will be analyzed to verify that the noise levels and noise distributions make 

it a suitable piece for the synthetic inclusion forging. It will then be delivered to GE CR&D for 

continued machining into its final form. 

Milestones: 

Original 

Date 

Revised 

Date 

Description 

Status 

Flaw and sample definition 

3 months Generate critical flaw list for titanium forgings in 

cooperation with RISC and provide to 3.1.2. (All) 

4 months Utilize deformation model predictions to guide 

sample development. (PW with support from ISU) 

6 months 11 months Provide list of samples and sample geometry to be 

developed for forging property measurements. 

(ISU with support from GE, PW) 

Complete 

Complete 

Complete 



Original 

Revised 

Description 

Status 

Date 

Date 

Sample fabrication 

12-30 

months 

Acquire/fabricate the necessary samples. (GE with 

support from PW, AS) 

Complete 

Fundamental property measurements 

12 - 36 

months 

Acquire velocity, attenuation, backscattered noise, 

and defect-echo data necessary to assess the 

effects of microstructural anisotropy and surface, 

curvature, etc., on forging inspections. (ISU with 

support from GE, PW, AS) 

18 months 24 months Provide velocity data for incorporation into the 

noise model. (ISU with support from GE, PW, AS) 

Complete techniques for curvature correction 

approaches. (All) 

24 months Provide surface curvature data for development of 

curvature correction factors. Provide data to 1.3.2 

for transducer design optimization. (ISU with 

support from GE, PW, AS) 

24 - 39 

months 

Validate noise models in cooperation with 3.1.2. 

(All) 

45 months Report of the effects of anisotropy and surface 

curvature on inspection sensitivity for typical 

titanium forgings used in aircraft engines. 

45 months Initiate final report. (All) 

45 months Techniques used to correct for geometry effects 

including curvature correction factors. 

54 months Complete final report. (All) 

60 months Representative sample blocks of forging material or 

fundamental property measurements. 

Primary measurements required to 

assess effects of microstructural 

anisotropy completed using 

property/flow line blocks). For 

surface curvature effects see below 

Complete 

Complete 

Work initiated using “Noise 

Curvature Blocks” to assess 

combined effects of surface 

curvature and microstructure on 

inspections, and to validate noise 

models. 

Deliverables: 

Techniques to correct for geometry effects including curvature correction factors. 

Report of effect of anisotropy and surface curvature on inspection sensitivity for typical titanium 

forgings used in aircraft engines. 

Representative sample blocks of forging material or fundamental property measurements. 



Metrics: 

Assessments of the effects of microstructural anisotropy and surface curvature on inspection 

sensitivity for typical titanium forgings, supporting the needs of inspection development, POD 

estimation, and life management tasks. 

Comparisons of inspections using standard and optimized transducer designs, quantifying the 

improvement in detection sensitivity. 


Date 

June 16, 1999 

Description 



Date 

2002 

Description 

L. Yu, F.J. Margetan, R.B. Thompson and A. Degtyar, “Survey of Ultrasonic Properties of Aircraft 

Engine Titanium Forgings”, Rev. of Prog. in QNDE, Vol.21, eds. D.O. Thompson and D.E. 

Chimenti, (AIP, Melville NY, in press) 



Project 1: 

Task 1.3: 



Titanium Forging Inspection 


Titanium Forgings 

Team Members: 

HW: Andy Kinney, Tim Duffy, Waled 

Hassan 

ISU: Tim Gray, Bruce Thompson, Frank 

Margetan, Ron Roberts 

GE: Dave Copley, Ed Nieters, Wei Li, Bob 

Gilmore, , Jon Bartos, , Richard Klaassen, 

Mike Keller, John Halase 


Degtyar, Harpreet Wasan, Dave Raulerson 



Objectives: 

• To develop a high sensitivity ultrasonic inspection of titanium forgings utilizing a 1/128” (#½) 

FBH calibration target, digital C-scan image acquisition, and signal-to-noise rejection criteria 

target without significant cost increase. 

• To demonstrate the new technique in a production environment over an extended period to 

determine its feasibility (both cost and readiness) as a production inspection. 

Approach: 

Forging Selection and Preparation: Select one representative forging design from each of the 

OEMs for use throughout the duration of this subtask (both inspection development and 

demonstration). Selection criteria will include: 

• forging shapes that address generic concerns such as effects of curvature, surface condition, 

and part thickness 

• forging material and microstructure 

• forging cost 

• production volume and schedule 

Sensitivity and coverage maps will be developed for the selected forgings using model-based tools. 

CAD files will be provided to ISU by each of the OEMs for the selected forging geometries. 

Particular attention will be given to the effect of curved surfaces on inspection sensitivity relative to 

flat surface sensitivity. Calibration standards will be designed to cover the range of metal travel and 

curvatures found on the selected forgings. Plans include two sets of standards in order to support 

multiple member involvement. 

Transducer Design Models: Fixed focus and phased array transducer design models will be 

reevaluated in detail to determine reasons for discrepancies between predicted and measured 

subsurface focused transducer behavior observed during Phase I work. This reevaluation will focus 

initially on assessing how well the input parameters used for the models represent the physical 



ehavior of the transducers. This effort will begin as part of Task 1.1 and 1.2 which will concentrate 

on fixed focus transducers. Two blocks (one for fixed-focus and one for phased array) suitable for 

the evaluation of subsurface focused transducers will be manufactured to provide experimental 

data with consideration given to samples available in 1.3.1. Based on this exercise, modifications 

will be made to model input parameters or to the model code to improve the prediction accuracy. 

Attention will also be paid to selection of transducer materials with consistent and measurable 

properties, for example the machining of lenses from solid material rather than using cast-in-place 

epoxy. Coordination with transducer and system vendors is expected with the objective of ensuring 

that results of this effort impact the performance characteristics of future products used in jet engine 

inspection. 

Surface Finish Effects: The effect of surface finish on inspectability will be determined. Surface 

finish requirements are anticipated to be more stringent at the higher sensitivity inspections 

necessary for forgings (compared to billet) and will be a focus of study in this subtask. Empirical 

and theoretical approaches will be used to assess the relationship between surface finish and 

inspectability. Empirical studies will be limited to 100 machining passes spread across five 13” 

diameter by 2” thick pancake samples. Results will be implemented in the UT modeling tools. 

Transducer Design and Selection: The ultrasonic beam properties (frequency, depth-of-field, 

diameter, bandwidth, mode, etc.) required to produce an acceptable 1/128” FBH calibration (FBH 

@ 80%, Ti grain noise < 50%) will be defined. Fixed focus transducers for flat entry surfaces will be 

designed, manufactured, and evaluated using appropriate ETC test specimens as necessary. An 

assessment of the transducers (producing the above determined ultrasonic beam properties) 

necessary to inspect the three OEM forgings will be made. Any additional required transducers will 

be designed and manufactured. A commercial source for such transducers will be established. 

Productivity Improvement: It was shown in Phase I that inspection sensitivity improvements will, in 

general, increase the time required for the inspection. Fixed-focus transducer inspection 

approaches have the advantage of being expandable (in an economical fashion) to include the 

collection of data from multiple transducers simultaneously. This approach has the potential to 

offset the productivity losses which will likely occur from the increased inspection sensitivity 

required by this task. In order to meet the inspection time goals for this task, a study will be made 

of the OEM forgings to determine potential areas of productivity improvement. A maximum 

productivity approach will be defined and developed for evaluation in the laboratory demonstration. 

Fixed Focus Laboratory Testbed: Laboratory testbed for the development and evaluation of the 

fixed-focus inspection approach for a 1/128” FBH calibration forging inspection with digital C-scan 

data acquisition and SNR based rejection criterion will be established. Additional transducers 

necessary to inspect the OEM forgings will be designed, manufactured and tested. Scan plans for 

the selected OEM forgings will be developed with model-based support. A limited number (1-2) of 

each of the selected forgings will be inspected per the scan plan. Performance of the fixed focus 

inspection approach for forging inspection will be documented. Alternative inspection technologies 

will be identified using the experience base of the four partners, as well as NTIAC. 

Phased Array Inspection: An evaluation will be made of available phased array technology to 

determine which are potentially production-ready and capable. At this time, the digital focused 

array transducer system DFATS annular phased array and the R/D Tech 2D array are known as 



possible candidates. Development work on these approaches will be limited to building one sensor 

assembly for each approach if suitable sensors are not already available at the OEMs. Evaluation 

will be performed on appropriate ETC test specimens with both flat and curved sound entry 

surfaces. It is expected that phased array approaches will be necessary to arrive at the necessary 

sensitivity through curved surfaces. Arrangements will be made to accommodate full team 

participation for all of these evaluations. The results will be reviewed to identify a preferred 

alternative inspection technology. The review will consider inspection performance, equipment cost 

and complexity, operating speed, potential for productivity improvements, and other implementation 

factors. 

Phased Array Laboratory Testbed: A laboratory testbed for the development and evaluation of the 

alternative inspection approach for a 1/128” FBH calibration forging inspection with digital C-scan 

data acquisition and SNR based rejection criterion will be established. Additional transducers 

necessary to inspect the OEM forgings will be designed, manufactured and tested. Scan plans for 

the selected OEM forgings will be developed. A limited number (1-2) of each of the selected 

forgings will be inspected per the scan plan. The full description of the testbed is not known at this 

time because of its dependence on the initial assessment. An amendment and appropriate request 

for funding will be prepared in consultation with the FAA when the details are completed. 

Factory Testbed, Evaluation and Demonstration: The laboratory results from the fixed-focus and 

alternative inspection method will be reviewed to identify a preferred configuration for factory 

demonstration and potential implementation. The review will consider inspection performance, 

equipment cost and complexity, operating speed, and other implementation factors. A hybrid 

system using fixed focus and an alternative inspection technology will be considered as part of this 

evaluation. The chosen configuration will be used to perform factory evaluation of 30 forgings at a 

production inspection facility. A production testbed with digital C-scan data acquisition will be 

established for the evaluation of the 1/128” FBH calibration forging inspection technique. (This may 

include the purchase of additional capital equipment if none is present at production inspection 

facility or available for loan from a consortium member.) Scan plans for the selected OEM forgings 

will be written by the respective OEM with ISU providing support using the inspectability model 

tools. Attention will be given to maximize productivity (to minimize any cycle time impact caused by 

the higher sensitivity) for the inspection during the production testbed design and scan plan 

development. Any additional transducers required to implement the scan plans will be designed 

using the transducer design models and built using commercial sources. A total of 30 forgings (10 

from each OEM) will be inspected over the course of 10 months. Noise levels with respect to the 

calibration target, and actual inspection time in hours will be documented for each forging and 

provided to task 3.1.2. Any detections will be first reported to the responsible OEM. Up to six 

indications (from up to three separate forgings) which fail the proposed acceptance limits will be 

destructively evaluated to determine their cause. Funds to purchase these forgings are not 

included in the current proposal but will require an amendment at the time. The actual hours for the 

conventional production inspection of these forgings will be gathered and compared to the time of 

the 1/128” FBH inspection to establish a per part cost difference. Additional cost components will 

include items such as system cost, longevity of equipment, recurring equipment costs, and costs 

associated with false calls. An industry demonstration will be held to provide the results to the other 



OEMs and the forging industry. A final report summarizing the results of the technical effort and the 

final factory demonstration will be written in the required FAA format. 


1998. 


Significant progress was made towards the goal of achieving #1/2 FBH sensitivity in Ti-6-4 forgings. 

Progress was made in both defining the inspection parameters and the supporting tasks of creating 

calibration standards and defining surface condition requirements with additional details provided 

below. 

Calibration Standards 

The team agreed on a final design for the standards that will make them more generic rather than 

useful for a single inspection scenario. Initially, the standards were to reflect the requirements of 

the three OEM forgings to be used in this program. The zones that were initially defined were from 

the inspection of these three forgings and are dependent on the noise in the coupons made from 

sample forgings. The team agreed it would be a mistake to create the calibration standards just for 

zones defined for those samples. Instead, the standards will have FBHs placed at fairly fine 

increments, 0.05”, so that zones can be defined and setups made for a variety of zone depths for a 

range of forging geometries. 

Four blocks will be required to accomplish 0.05” steps to a depth of 4.0”. The first depth, however, 

will be at 0.06” to meet current near surface setup requirements. The second hole depth is at 0.10” 

and all subsequent hole depths are at incremental depths of 0.05”. The design of the first block is 

shown in Figure 1. GE has had all 4 blocks machined with the steps and plans are in place to have 

the FBHs drilled. The completion of the standards is expected to be within the revised milestone 

date of month 36. 



Forging Calibration Standard #1 

1.75" 

.300" 

7.0" 

0.216 

.300" 

1.156" 

holes drilled .156" deep 

02/13/2002 

Figure 1. One of the four blocks comprising the set of calibration standards for zoned forging 

inspections. 

Analysis of supplier capability to create FBHs was tested with the sample of 2” cube material made 

from powder Ti-6-4. Several attempts at analyzing the condition of the holes was presented in 

earlier reports that included replication and laser profilometry analysis. During this reporting period, 

GE has carried out metallographic analysis of the holes to complete the evaluation. The analysis 

was completed in 2 steps. First, the block was ground to a thickness that is 5 to 10 mils above the 

bottom of the hole. This view allowed measurement of the roundness of the hole including focus to 

the bottom of the hole. The second step consisted of transverse polishing to evaluate flatness of 

the bottom of the hole. Figure 2 shows a representative example of the analysis that was 

performed on several holes that were produced by 2 suppliers. The result of this analysis is that 

the 2 suppliers that made FBHs for this study are equally capable of providing the features that 

were requested. One of the suppliers is able to provide smaller holes with their equipment. 

Historically, only one of the suppliers was used for calibration standards and this study shows that a 

second supplier is also capable. 



#1 FBH 

2A Top 

2A Side 

1A 1B 1C 

2A 2B 2C 

3A 3B 3C 

2A Bottom 

Figure 2. Sample of metallographic evaluation of FBHs. 



Surface Finish Studies 

The plans for the surface finish study have been refined during this reporting period with 

significant input by the three OEMs. GE has primary responsibility for this activity and will 

initiate the execution of the plan. While the plan is not quite finalized, the sequence of events 

is as follows – 

(1) GE has FBHs placed in the pancake, performs UT characterizing of the holes, applies the 

1 st set of machining passes, acquires profiles of the machining grooves, and performs UT 

with specified transducers, 

(2) P&W performs UT inspection of the 1 st machined surface, applies the 2 nd set of machining 

passes, and performs UT inspection of the 2 nd machined surface, 

(3) GE acquires profiles of the 2 nd machined surface, and performs UT inspection of the 2 nd 

machined surface, 

(4) Honeywell performs UT inspection of the 2 nd surface, applies the 3 rd set of machining 

grooves, and performs UT inspection of the 3 rd surface, 

(5) GE performs UT inspection of the 3 rd surface finish, and acquires profiles of the 3 rd 

machined surface, 

(6) Data is analyzed by the team to relate surface finish conditions to near surface resolution 

and to signal to noise ratio. Hopefully, a relationship can also be established between 

feedrate and front surface signal ringdown. 

Some of the details that are yet to be worked out include identification of the transducers to be 

used, which feedrates to use, what is the minimum UT data that should be collected at each 

site, and how should the machinists requirements be controlled/recorded. 

Beam Properties 

A goal of subtask 1.3.2 is to design an inspection scheme that achieves #1/2 FBH sensitivity in Ti 

forgings. When designing a zoning scheme and choosing transducers, one of the key steps is to 

define the requirements of the ultrasonic pulse volume. It has been shown theoretically and verified 

experimentally that the signal-to-noise (S/N) ratio is approximately inversely proportional to the 

square root of the pulse volume. Thus, to meet the subtask goal, one needs to define the 

restrictions on the pulse volume that provide acceptable S/N ratios for a #1/2 FBH inspection. 

During the previous and current quarters such data was acquired at GE-QTC. Signal-to-peak-noise 

ratios were measured using several transducers with different focal characteristics to achieve a 

wide range of pulse-volume values. The measurements were performed on the highest noise 

“property” coupons from each OEM’s Ti 6-4 forging. Two of the three coupons had arrays of #1 

FBH drilled into them, and one of the holes in the PW coupon served as a reference against which 

peak noise values were measured. The data acquired using an F6 transducer with the beam 

focused on the FBHs is shown at Figure 3. The gain was selected such that the response from 

#1/2 FBH would be at 80% Full Screen Height (FSH). The peak noise was measured for each of 



the high-noise coupons shown in the figure, resulting in 30.6%, 43.0% and 36% for the PW, HW 

and GE coupons respectively. 

In addition to the S/N measurements, sonic pulse volumes were also measured. First, the –6dB 

beam diameter at the FBH depth was determined from a fine increment C-scan of the reference 

hole in the PW coupon. Figure 4 illustrates the beam diameter determination for the same 

example, leading to a value of 39.4 mils. Secondly, as illustrated in Figure 5, the pulse duration 

was measured by finding the –6 dB points for the envelope function of the rectified FBH echo, and 

this duration was translated to a pulse length in metal. For the case shown, the pulse length was 

36.7 mils, leading to a measured pulse volume of (π/4)(39.4 mils) 2 (36.7mils) = 44,600 cubic mils. 

Peak noise vs. pulse volume for all measurements is summarized in Figure 6. 

PW8 

Max. noise 

30.6% 

HW5 

Max noise 

43% 

GE6 

Max. noise 

36% 

#1/2 FBH ~ 80% 

Figure 3. Example of S/N measurements in high-noise forging coupons. Here the FBH holes are 

located at the focus of an F6 transducer. 



Figure 4. Beam diameter determination for the case of an F6 transducer focused on the FBHs. All 

pixels with amplitudes within 6 dB of the maximum are located, and their joint area is measured. 

125 

F6 - Reference Waveform at Focus 

100 

F6-0dB-Rect 

F6-0dB-Env 

Amplitude 

75 

50 

25 

0 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 

Microseconds 

Figure 5. Pulse duration determination for the case of an F6 transducer focused at the FBH depth. 

The full width of the envelope at the –6 dB level (50% of maximum) is 0.150 microseconds. 



Peak-Noise-to-Signal (% FSH) 

80.0 

70.0 

60.0 

50.0 

40.0 

30.0 

20.0 

10.0 

0.0 

Peak Noise Levels for 

Ti 6-4 High Noise Coupons 

#1 FBH at 12 dB above 80% 

or at 318.5% on this scale 

56.6% (3 dB below 80%) 

For each specimen, 

Rule-of-Thumb would 

predict a straight line 

passing thru origin. 

Slope dependent on FOM 

PW8 

HW5 

GE6 

F5 @ 0dB 

F5 @ -3dB 

F6 @ 0dB 

F6 @ -3dB 

F8 @ 0dB 

1.6 usec time gate 

0 100 200 300 

Sqrt (Pulse Volume in cubic mils) 

#1/2 FBH 

approx at 80% 

on this scale. 

Figure 6. Peak noise vs. pulse volume measurements performed at GE-QTC. PW8, HW5, and 

GE6 denote the highest noise coupons cut from three Ti 6-4 forgings. 

From Figure 6 one can conclude that choosing the square root of pulse volume to be 240 mils 3/2 or 

smaller likely ensures that the peak noise is at least 3 dB below the response from a #1/2 FBH for 

the “noisiest” PW and GE coupons. For this choice, the peak noise in the noisiest HW coupon 

would be near to but slightly above the 3dB level. If we assume that the typical pulse duration is 

equal to 37 mils (average of measured values) the limitation on the beam diameter would be about 

( π × ) ⎤ 

1/2 

240 ⎡⎣4 / 37 ⎦ or about 45 mils. Thus, we estimate that a forging inspection which achieves 

#1/2 FBH sensitivity, requires a beam diameter that does not exceed 45 mils at any depth within the 

region of interest. 

Our next objective was to design an inspection that covered 3.2” of material depth using the 

minimum number of zones and ensuring that the beam diameter did not exceed 0.045” at any 

depth. We note that 3.2” is the maximum depth required to inspect forgings selected for this task 

from all OEMs. An optimization procedure was employed to determine the maximum zone size and 

to design a transducer for each zone. First the water path was fixed at 3” with the transducer 

diameter and focal length treated as unknown “fitting” parameters. Since the entry surface is flat for 

this exercise, one needs to consider spherically focused probes only. 

The beam diameter for a given transducer at a given depth was calculated using the Gaussian- 

Hermite beam model developed by Iowa State University. It was determined that a 7/16”-wide zone 



size was adequate to support a 0.045” maximal beam diameter. Eight such zones are needed to 

cover 3.2” of material and nine zones would cover almost 4”. If the water path were fixed such an 

inspection would require nine different transducers. We determined that by varying the water path 

one transducer could be used to inspect three zones. Thus, for nine zones, three transducers are 

required. The parameters of these three probes are listed in Table 1. These are the transducers 

originally designed for zones 2, 5 and 8 for the original inspection scheme that used a fixed 3” water 

path. For example, the zone 2 transducer (transducer #1 in Table 1) can also inspect zones 1 and 3 

with 4.8” and 1.2” water paths respectively. The final inspection scheme that utilizes three 

transducers is presented in Table 2. For this scheme, the on-axis profile (of pressured squared) is 

shown in Figure 7. The amplitude of an echo from a small defect is approximately proportional to 

pressure squared, so Figure 7 displays the manner in which defect signal amplitude depends on 

depth when the proposed scheme is used without a DAC. 

On-axis profile for 3-transducer 7/16" zone design 

Ammplitude 

8E-04 

7E-04 

6E-04 

5E-04 

4E-04 

3E-04 

2E-04 

1E-04 

Zone1 

Zone2 

Zone3 

Zone4 

Zone5 

Zone6 

Zone7 

Zone8 

Zone9 

0E+00 

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 

Depth, in 

Figure 7. Predicted on-axis, pressure-squared, beam profile for each zone using the 3-transducer 

7/16” zone inspection scheme. 

The designed optimal transducers have diameters that are not exactly multiples of 1”. However, by 

slightly varying the water paths, we believe the inspection can be performed by three F6 

transducers with diameters of 1”, 2” and 3”. The 1” diameter F6 transducer is already available, 

and the 2” diameter transducer has been ordered. The intent is to test the proposed inspection for 

the first 6 zones during the next quarter. Based on those results the decision will be made on how 

to proceed. The use of a DAC to produce a uniform amplitude for #1/2 FBHs throughout a zone will 

also be investigated in the upcoming quarter. 



Probe 

Diameter, 

in 

Probe 

Diameter, cm 

Probe Radius 

of Curvature, in 

Probe Radius 

of Curvature, 

cm 

Transducer #1 0.92 2.34 5.77 14.66 

Transducer #2 1.88 4.78 11.22 28.50 

Transducer #3 2.80 7.11 16.70 42.42 

Table 1. Designed transducer parameters. 

7/16" Zone Size, 3-transducer inspection, 4" coverage 

Zone From To Transducer # Water path, in Water path, cm 

in in 

Maximum beam 

diameter within 

the zone, in 

1 0.0000 0.4375 1 4.8 12.19 0.046 

2 0.4375 0.8750 1 3.0 7.62 0.045 

3 0.8750 1.3125 1 1.2 3.05 0.045 

4 1.3125 1.7500 2 4.8 12.19 0.045 

5 1.7500 2.1875 2 3.0 7.62 0.044 

6 2.1875 2.6250 2 1.2 3.05 0.044 

7 2.6250 3.0625 3 4.8 12.19 0.045 

8 3.0625 3.5000 3 3.0 7.62 0.044 

9 3.5000 3.9375 3 1.2 3.05 0.044 

Table 2. Designed inspection scheme to achieve #1/2 FBH sensitivity throughout 4” of Ti 6-4 

forging material. The scheme uses three transducers and has nine zones, each 7/16” wide.. Each 

transducer covers three zones using three different water paths. 

Phased Array Inspection Development 

Significant progress was made on the design of the phased array transducer that will be used to 

make a test of #1/2 FBH inspection sensitivity with currently available technology. In addition to 

discussion at the monthly conference call, a separate conference call was held with a subteam to 

discuss the transducer design that is being performed at ISU. The design has progressed to a 

state allowing discussion with transducer manufacturers for placement of an order by P&W. 

Figure 8 shows the most recent design for the F6 transducer that will allow focussing to a depth of 

3.2 inches as required by the selection of the OEM forgings for inspection demonstration in this 

sub-task. Several modifications of the design have occurred and these were due primarily to 

compromises that had to be made from the ideal design to allow for the limitations of existing 



phased array instruments. The design modifications were made after extensive discussions by ISU 

with the primary equipment manufacturer. 

Figure 8. Schematic drawing of 128 element transducer for forging inspection. 

P&W has begun the purchase of the transducer with discussions with two manufacturers and will 

contact the third know manufacturer of phased array transducers at the start of the next quarter. 


Complete calibration standards. 

Order 2” and 3” diameter transducers for complete 9 zone inspection. 

Continue inspection development with DAC tests for individual zones. 

Select supplier and place order for phased array transducer. 

First machining and sonic measurements will be performed for the surface finish study samples 



Milestones: 

Original 

Date 

Revised 

Date 

Description 

General Issues 

3 months 7 months Finalize selection of OEM forging samples for 

study. CAD files will be provided to ISU for 

generation of sensitivity and coverage maps. (HW, 

GE, PW) 

3 months Complete design of transducer design model 

sample blocks. (GE with support of HW, ISU, PW) 

15 months 18 months Complete manufacture of transducer design model 

sample blocks. (GE) 

24 months Finalize and transition transducer design models to 

OEMs. (ISU) 

24 months -30 Review fundamental property data from 1.3.1 for 

transducer design optimization. (ISU) 

29 months ? Complete model assessment of inspection 

sensitivity for OEM forgings including POD 

considerations in cooperation with 3.1.2. (ISU with 

support from HW, GE, PW) 

Fabrication of calibration standards 

15 months Complete calibration standard design. (All) 

24 months 36 Complete manufacture of calibration standards. 

(GE) 

Surface finish studies 

36 months 

Generation of samples and collection of empirical 

data for surface finish studies (GE) 

39 months 

Determine surface finish requirements for 1/128” 

FBH forging inspection. (All) 

42 months 

Implementation of empirical results from surface 

finish results in UT model tools. (ISU) 

42 months 

Review curvature correction approaches from 1.3.1 

(All) 

Titanium forging fixed-focus inspection 

development 

24 months 30 Complete definition of transducer beam properties 

required for a 1/128” FBH calibration in Ti-6Al-4V. 

(ISU, GE, PW and HW) 

33 months 

Complete any needed new transducers. Establish 

commercial sources for transducers. (GE) 

------------------------------------------------------------------- 

44 

Complete definition of maximum productivity fixed 

focus inspection approach. (GE with support from 

PW, AS, ISU) 

Status 

complete 

complete 

Task cancelled – results not needed 

to resolve transducer model 

problems 

complete 

An additional sample may be 

required 

Alignment with 3.1.2 will follow 

restart of that task 

complete 

Raw material delivered 

Final definition depends on 

completion of noise analysis 

The second half was moved to 44 

months. 

39 months Establish fixed focus laboratory testbed. (GE) 

40 months Finalize scan plans for OEM forgings. (All) 

42 months Conduct laboratory inspection of high sensitivity 

zoned inspection on six OEM forgings. Provide 

data to 3.1.2 for model validation and POD 

prediction. (All) 

43 months Laboratory demonstration of fixed focus high 

iti it f i i ti f fl t f 



Original 

Date 

Revised 

Date 

Description 

sensitivity forging inspection for flat surfaces. 

44 months Complete definition of maximum productivity fixed 

focus inspection approach (GE with support from 

PW, HW, ISU) 

Titanium forging phased array inspection 

development 

36 months Complete evaluation of up to 3 candidate phased 

inspection techniques. (All) 

37 months Review results and select phased array inspection 

technique to pursue. (All) 

39 months Establish phased array inspection technique and 

laboratory testbed. (TBD) 

40 months Complete modified phased array inspection scan 

plans for OEM forgings. (All) 

42 months Conduct laboratory inspection of six OEM forgings 

using phased array approach as required. Provide 

data to 3.1.2 for model validation and POD 

prediction. (All) 

43 months Laboratory demonstration of high sensitivity forging 

inspection utilizing an alternative technique for 

curved entry surface inspection. 

Factory Evaluation / Demonstration 

43 months Review results of laboratory inspections performed 

with fixed focus and the alternative technique. 

Define high sensitivity forging inspection for factory 

demonstration. (All) 

49 months Establish production testbed for high sensitivity 

forging inspection. (GE with support from PW and 

AS) 

49 months Finalize scan plans for OEM forgings. (All) 

57 months Complete production inspection for 30 forgings (10 

from each OEM). Provide data to 3.1.2 for model 

validation and POD prediction. (All) 

57 months Factory demonstration of high sensitivity forging 

inspection including digital C-scan data acquisition 

performed on 30 separate forgings. 

59 months Evaluate indication finds from production test, 

document results. Provide data to 3.1.2 for model 

validation and POD prediction. (All) 

60 months Report of laboratory and factory evaluations 


System Capability Working Group and cost 

comparisons for the different inspection 

approaches. 

Status 

This milestone was separated from a 

33 month milestone with multiple 

tasks. 

Deliverables: 

Transducer design models (both fixed-focus and phased array) transitioned to the OEMs. 

Calibration standards and transducers as needed. 

Laboratory demonstration of fixed focus high sensitivity forging inspection for flat surfaces. 



Laboratory demonstration of high sensitivity forging inspection utilizing an alternative technique for 

curved entry surface inspection. 

Factory demonstration of high sensitivity forging inspection including digital C-scan data acquisition 

performed on 30 separate forgings. 


Systems Capability Working Group and cost comparisons for the different inspection approaches. 

Metrics: 

Demonstration of 1/128” (#½) FBH sensitivity inspection with digital C-scan data acquisition and 

SNR-based reject criterion for representative titanium forgings using zoned inspection approach 

with inspection speed comparable to current inspections. 


Date 

June 16, 1999 

Description 



Date 

Description 



Task 2: 

Task 2.1: 


Inservice Inspection 


Rotating Components 

Development of UT Capability 

for Inservice Inspection 

Team Members: 

HW: Prasanna Karpur, Andy Kinney 

ISU: Tim Gray, Bruce Thompson 

GE: Tony Mellors 

PW: John Lively, Dave Raulerson, Rob 

Stephan, Jeff Umbach, Dave Bryson, Anne 

D’Orvilliers 

Program status: June 15, 1999. The FAA contracting office suspended new work on this subtask, 

effective March 16, 2000. All milestones were significantly effected. Deliverables originally 

proposed will not be provided unless/until FAA direction to resume effort on this task. 

Task 2: 

Task 2.1: 




Rotating Components 

Eddy Current Probe Evaluation 

and Implementation 

Team Members: 

HW: A. Kinney, T. Duffy 

GE: W. Bantz, J. Collins, D. Copley, B. 

McKnight, T. Mellors, S. Nath 

ISU: L. Brasche, N. Nakagawa 

PW: D. Raulerson, J. Lively, R. Stephan 




Task 2: 

Task 2.2: 



Inspection Development 

Transitions to Airline 

Maintenance 

Application of ETC Tools in 

Overhaul Shops - EC Scanning 

Team Members: 

HW: Jim Hawkins, Jim Ohm, Tim Duffy, 

Andy Kinney 

ISU: L. Brasche, N. Nakagawa 

GE: Julia Collins, Tony Mellors, Shridhar 

Nath 

PW: Kevin Smith, Dave Bryson, Anne 

D’Orvilliers, Rob Stephan, Dave Raulerson, 

John Lively 






Task 2: 

Task 2.2 





Maintenance 

High Speed Bolthole Eddy 

Current Scanning 

Team Members: 

HW: Tim Duffy, Jim Ohm, Waled Hassan 

ISU: Lisa Brasche 

GE: Tony Mellors, Shridhar Nath, Jon 

Bartos 

PW: Kevin Smith, Dave Bryson, Rob 

Stephan 

Students: None 


Objectives: 

To develop common fixtures to reduce inspection variables and arrive at a standardized inspection 

technique. 

To measure the process capability. 

To utilize this information to develop an industry best practice document. 

Approach: 

Evaluation of Existing Processes: Efforts will concentrate on process improvements for and 

standardization of high speed bolt hole scanning. A detailed evaluation of existing OEM inspection 

processes and needs will be conducted. Current equipment and tooling will be analyzed to provide 

a baseline of existing inspection processes and their limitations. The data will be analyzed for 

potential process improvements and identification of common tooling approaches. A survey of 

available commercial tooling will be included as part of the assessment and included in the baseline 

as possible. 

Development of Common Tooling: The efforts will then be focused on the detailed design and 

fabrication of common tooling with an emphasis placed on variability reduction and defect 

detectability improvements. An inspection demonstration will be conducted on a sample set of 

hardware from each of the industrial members for validation of process development. A 

comparison to the baseline data will be made. Working with task 3.1.3 an evaluation of the process 

POD will be conducted on existing bolt hole reliability specimens. 

Development of Common Process: A common inspection technique and best practices document 

will be developed. Currently AS4787, Eddy Current Inspection of Circular Holes in Nonferrous 

Metallic Aircraft Engine Hardware, serves as a standard for hole inspection. This document will be 

revised to reflect the results of the ETC effort. Recommendations for equipment improvements will 

be supplied to vendors and implications for further study will be provided to the FAA. 




1998. 


The subtask was realigned during this quarter. A revised plan was generated and is reflected in the 

“Milestones” section below. The technical team supporting this subtask held several conference 

calls leading to significant technical progress . The following represents a summary of the 

accomplishments: 

Bolt hole Simulator Design: The design of the bolt hole simulator is complete. This piece will be 

used to precisely fixture round bolt hole specimens (see Figure 1) in a circular layout as they would 

be for a typical rotating engine component. This piece will be able to hold twenty-five 1.875” 

diameter specimens having a 0.250-inch thickness. The bolt hole diameter within these circular 

specimens will be 0.460 inches. The layout aligns the specimens in a precise circular pattern with 

the bolt holes within 0.002 inches of geometric center. When specimens are aligned, they can be 

locked into position to prevent rotation and lift-out during scanning. 

Probe Translation Device: A preliminary design is complete. This device is required to precisely 

position and translate a rotating eddy current probe through boltholes of various diameters in critical 

engine rotating hardware. These probes will be mounted to off-the-shelf high-speed eddy current 

bolt hole rotating drivers and are used for detecting cracks along the length of the bolt holes. There 

are various probe-rotating drivers available and the device is designed to be able 

Figure 1. FML100146 Eddy Current Bolt hole Crack Specimen Design. 



to firmly fixture and work with a number of these rotating drivers. Schematics or actual rotating 

drivers were made available for this design. The probe translation device will be adaptable to 

different engine part numbers. Figure 2 shows a schematic of the preliminary design of the probe 

translation device. The following requirements were imposed during the design process: 

1. Fixtured alignment to control wobble of probe while translating through a part 

2. Fine X-Y plane adjustment to center probe within bolt hole diameter 

3. Machine control of probe travel through bolt holes by means of selectable fixed transverse 

speeds of zero, 0.100, and 0.200 inches/second in a helical scan pattern 

4. Rapid adjustable automatic translation retraction to a start next scan position 

5. Scan limit switch to prevent excess travel of probe 

6. Minimum of three inches of probe translation travel 

7. Slip clutch to prevent burn-out of translation motor 

8. Use of exchangeable bolt-on adapter plates for fit to specific parts/bolt hole patterns 

9. Adaptability to Uniwest probe rotating driver, Roman Elotest, Foerster, Zetec, etc as provided. 

10. There can be no electrical interference caused the probe translation device on the eddy current 

inspection process including data acquisition. 

11. Manufacturing cost less than $10,000 

Part Adapter Plate: In order to adapt the proposed bolt hole scanning system design to various 

parts and for the inspection of each hole, the ability to manually lift the instrument and secure it for 

the next bolt hole must be present. This will be accomplished through an exchangeable adapter 

plate designed for that purpose. These adapter plates shall bolt to the bottom of the translation 

device. To precisely adjust the eddy-current probe within a bolt hole, a fine X-Y adjustment that can 

also lock the probe into the correct position within the hole is provided. Figure 3 shows an example 

of an adapter plate that is currently in use in production. Our plan includes the design and 

manufacturing of two such adapter plates for pre-selected industry applications. The selection of 

these applications in underway and once finalized the design of these adapter plates will be 

completed. 



Figure 2. A preliminary design of the probe translation device. 

Figure 3. An example of an adapter plate that is currently in use. 




• Finalize the design of the probe translation device and complete manufacture. 

• Identify two industry bolt hole configurations for the inspection assessment study and design 

and manufacture the needed adapter plates. 

• Manufacture the part simulator fixture 

• Obtain a documented and larger population POD specimen set for use in tooling assessment 

Milestones: 

Original 

Revised 

Description 

Status 

Date 

Date 

0 –12 

months 

Evaluate existing OEM techniques. (All) 

Complete 

12 –30 

months 

12-32 

months 

Develop common tooling. (Honeywell with support 

from GE, PW) 

In progress 

• Define common tooling requirements 

• Design and build prototype tooling 

• Design tests for tooling assessment 

Perform tooling assessment 

30-36 

months 

32-38 

months 

Develop common inspection technique. (Honeywell 

with support from GE, PW) 

•Perform demonstration on sample hardware 

36 –48 

months 

38-48 

months 

Determine improved process capability (Honeywell 

with support from GE, PW) 

• Evaluate process PODs 

• Revise AS4787 

Deliverables: 

Common fixture for reduced inspection variability. 

Common high speed bolt hole eddy current inspection technique through revision of AS4787. 

Report of process capability and reliability. 

Metric: 

Common practices and tooling required to achieve a demonstrated 30 mil crack detectability and 

4:1 signal-to-noise in a common bolt hole geometry 


Date 

June 17, 1999 

March 22, 2000 

Description 

Technical Kick-off Meeting at West Palm Beach, FL 

TOGAA review at Honeywell in Phoenix, AZ 




Date 

Description 



Project 2: 

Task 2.2: 





Maintenance 

Engineering Studies of Cleaning 

and Drying Process in 

Preparation for FPI 

Team Members: 

HW: Andy Kinney, James Hawkins, Tim 

Duffy 

ISU: Brian Larson, Rick Lopez, Lisa 

Brasche 

GE: Terry Kessler, Charlie Loux, Jon 

Bartos 

PW: Anne D'Orvilliers, Brian MacCracken, 

Kevin Smith, Jeff Stevens, John Lively 

Students: S. Gorman, L. Rohrhey, and Y. Wang 

Program initiation date: February 7, 2000 

Objectives: 

• To establish a quantifiable measure of cleanliness including the minimum condition to allow 

effective inspection processing. 

• To establish the effect of local etching on detectability and provide guidance on best practices 

for removal of local surface damage from FOD and other surface anomalies. 

• To determine the effect of chemical cleaning, mechanical cleaning, and drying processes on the 

detectability of LCF cracks in titanium and nickel alloys that would be typical in field run 

hardware. 

• To update existing specifications to reflect the improved processes and provide best practices 

documents for use by the OEMs and airlines. 

Approach: 

The overall approach to the FPI studies is shown in the following flowchart with details provided in 

the text that follows. 

Literature and Industry Survey: The effects of cleanliness, cleaning method, and drying method on 

penetrant inspectability will be evaluated. As a first step, a review of the literature related to FPI 

processes and cleaning and drying methods will be conducted. Literature related to cleaning 

processes as well as NDE processes will be reviewed. Existing CASR literature review data will 

serve as a starting point. 

A survey of current practices used by the OEMs, airlines, and third party maintenance shops will be 

conducted to determine the existing “state of the practice”. Potential partners will be identified for 

participation in the follow on studies on fielded hardware. A team meeting will be held to identify 

the cleaning methods and drying methods to be studied and the contaminants of concern. Other 

organizations not participating in ETC will be invited to attend the meeting and coordination with 

other relevant programs will be maintained. A design of experiments approach will be considered 

in order to optimize the use of the results. A set of 40 specimens, 20 titanium and 20 nickel will be 

generated by CASR staff. 



Survey of common 

practices (industry) 

Survey of existing data 

(literature) 

Identify drying 

methods for study 

Identify cleaning 

methods for study 

Identify typical 

contaminants of 

concern 

Define and acquire 

crack samples for 

baseline studies 

Identify engine run 

hardware for use 

in cleanability 

studies 

Study to detemine 

"how clean is 

clean"; "how clean 

is needed" 

Use metrics 

established 

by 

MacCracken/ 

Kessler 

Assess methods 

at airline shops; 

compare against 

baseline sample 

Matrix of cleaning 

process effectivity 

vs contaminant 

Engineering study 

to determine effect 

of drying method 

on detectability 

(t and T) for 

oven drying 

flash drying and air 

drying 

Utilize lcf samples 

to extent possible; 

study on 

components 

required to 

address thermal 

mass issues 

Engineering study 

to determine effect 

of cleaning on 

detectability 

Potential variables: 

aqueous degreasers 

ultrasonic cleaners 

plastic media blast 

water jet blast 

solvent cleaners 

etching processes (local only) 

chemical cleaners 

vapor degreasers 

Utilize lcf crack samples to 

assess detectability; effect of 

cleaner on background, wetting 

characteristics, residual stress, 

etc. 

Matrix of drying 

process vs 

detectability 

Matrix of cleaning 

process vs 

detectability 

Develop best 

practices 

document and 

necessary spec 

changes 

Figure 1. Program Plan for “Engineering Studies of Cleaning and Drying Process in Preparation for 

FPI”. 



Assessment of Cleanliness on Inspectability: A major concern for the inspector is the cleanliness of 

the part to be inspected and the impact that surface condition will have on detectability, with the 

question often being asked, “How clean is clean?” Some effort has been undertaken to provide 

guidance in this area in the most recent version of SAS 2647. An engineering study will be 

performed to assess the utility of these metrics through on-site evaluation at airline shops using 

field run hardware. LCF blocks will be used to establish a baseline and for comparison across test 

sites. A matrix will be generated that establishes the effectiveness of various cleaning methods in 

removing general classes of typical contaminants. It is expected that various operational 

conditions, types of cleaner equipment/systems, cleaner type, cleaner concentration, process 

parameters, and alloy types will be considered. Appropriate data will be gathered on the field 

systems used in the study such as chemical concentration of the cleaning solutions, temperature, 

etc to allow comparison between systems and to approved process parameters. Guidance on the 

effect of cleanliness on penetrant inspectability will be provided in the form of a cleanliness matrix 

that summarizes cleaning process effectivity for various contaminants. 

Assessment of the Effect of Cleaning Method on Inspectability: Given a definition of the required 

cleanliness from the effort above, an engineering study to arrive at the effect of cleaning methods 

on detectability will be performed using LCF blocks. Potential cleaning methods to be considered 

include 

♦ aqueous degreasers 

♦ ultrasonic cleaners 

♦ plastic media blast 

♦ water jet blast 

♦ solvent cleaners 

♦ etching processes (local only) 

♦ chemical cleaners for both Ti and Ni 

♦ vapor degreasers 

Local etching of FOD and other local anomalies to remove smeared metal and improve crack 

detectability is a common practice. An evaluation to define optimal local etching practices will be 

performed. Parameters within the global cleaning process which may need to be considered 

consist of degree of agitation, time spent in tanks, degree of concentration and post-clean, 

particulate size and content, pressure, etc. The effect of cleaning methods on background, wetting 

characteristics, residual stress, and crack detectability will be assessed. A matrix will be generated 

which establishes the detectability as a function of the selected cleaning processes and provided as 

a final product of the study. 

Assessment of the Drying Method on Inspectability: Once the part is appropriately cleaned, it is 

essential that all fluids be removed from any rejectable defects such that penetrant solution can 

easily enter the flaw. Definition and adherence to appropriate drying times and temperatures is 

critical to the overall effectiveness of the FPI process. An engineering study will be performed to 

establish the optimal drying process parameters. Potential drying methods to be considered 



include air drying, oven drying, and flash drying. Initial studies will utilize lcf blocks with final 

recommendations to be based on actual engine hardware. A matrix that defines the effect of drying 

parameters on detectability will be generated. 

Development of Best Practices Document: The final stage of the work will be generation of a best 

practices document that provides guidance to the OEMs and airlines and will allow for any 

necessary specification changes. An assessment will be made of the need for further work such as 

a formal POD study and recommendations provided. 

Objective/Approach Amendments: Objective and approach were discussed and details were 

added to the approach in the February 2000 kick-off meeting. 


The third and final testing session for this study was held at Delta February 4-7. Honeywell 

completed the “baked on” contamination process which lead to oxidation/scale, soot, and 

coke/varnish as specified by the team. All planned cleaning methods of the baked on 

contamination was completed at the Delta Airlines engine shop and at Northwest Airlines (wet-glass 

beading) both in Atlanta. 

Additionally, follow-up studies identified from results of the first cleaning run which occurred in 

October at Delta were made. These include additional samples with penetrating oil contamination. 

Some specimens were involved in various other cleaning trials including the use of vapor 

degreasing, acidic scale conditioner, acetone and permanganate. 

Part two of the cleaning studies at Delta included evaluation of the cleaning methods listed below 

for each of the contaminate types. In cases where unsatisfactory cleaning results were found for a 

particular contaminate/cleaning method combination, as determined by photometer brightness 

numbers, the sample was then cleaned by another method. 

• Oxidation of nickel specimens 

C3 – Alkaline De-rust Solution A 

C7a – Ultrasonic w/Alkaline De-rust Solution B 

B2 – Wet Glass Bead 

B5 – Aluminum Oxide 500 grit 

• Oxidation and scale of titanium specimens 

C2a – Alkaline De-rust Solution A 

C2b – Alkaline De-rust Solution B 

B2 – Wet Glass Bead 

B5 – Aluminum Oxide 500 grit 

• Soot on titanium 

C1 – Aqueous degreaser 

C2a – Alkaline De-rust Solution A 



C2b – Alkaline De-rust Solution B 

C5 – Alkaline Gel Cleaner 

B1– Plastic media blast (at 80 and 40 psi) for 30 sec 

• Soot on nickel-based specimens 



B1– Plastic media blast (at 80 and 40 psi) for 30 sec 

• Varnish/Coke on nickel-based specimens 


C5 – Alkaline Gel Cleaner 


B1– Plastic media blast (40 psi) for 30 sec 

Visually, almost all of the specimens were evaluated as having a surface that appeared to be clean 

following the initial cleaning attempt. At the very least, two out of the three specimens for a 

particular contaminate/cleaning method combination were assessed as visually clean. However, 

crack crevice cleaning as evaluated by brightness was a different story. Many of the specimens 

showed reduced brightness with respect to baseline brightness and in some cases no indication 

could be discerned either by photometer or by a more sensitive though qualitative visual black light 

examination. 

The C4 four-step alkaline process for nickel-based materials (alkaline rust remover, acidic scale 

conditioner, alkaline permanganate, alkaline rust remover) proved successful for removing all three 

contaminants from the cracks and restoring much of the baseline fluorescent brightness. It was 

somewhat less effective on nickel oxidation. However, no cleaning process for titanium proved as 

effective as the four-step for nickel-based materials. 

For removal of oxidation on titanium, the cleaning difficulty was partly due to the higher degree of 

oxidation with to the nickel-based material. Oxidation on the titanium was estimated to be 

equivalent to 5,000 hours of engine run. It represents a heavy amount of oxidation that is now 

being seen on some of the hotter running titanium components. 

In addition, the method for producing soot by suspending specimens, crack opening down, over hot 

oil produced a blackened surface having somewhat of a sheen rather than a matte black finish. 

This condition would more likely be found on turbine engine hot section parts, but probably not on 

titanium cold section parts. The contaminant condition proved more resistant to some of the 

cleaning methods than typical soot. 

There were sometimes apparent inconsistent results for a particular contaminant/cleaning method 

that may be related to three different crack sizes being used. That is, perhaps a chemical cleaning 

method is more effective at removal of soot on a large, open crack than on a small, tight crack or 



aluminum oxide blasting is concealing the tighter cracks more so than the open cracks. Therefore 

the crack morphology is being considered in interpretation of the results. 

Some of the preliminary observations or conclusions include: 

• Vapor degreasing and aqueous cleaning both appear to be effective for removing oil. 

• Alkaline derust is not effective on oxidation/scale, or soot on Ti-6-4. Short soak, high or low 

concentrations do not effectively remove penetrating oil in Ti-6-4. Alkaline residue may reduce 

fluorescent penetrant brightness. 

• Alkaline gel was not an effective cleaning on either Ti-6-4 or INCO 718. 

• Wet glass-beading lead to loss of 4 of 6 cracks and significant brightness reductions in the 

other two cracks. 

• Aluminum oxide 500 mesh grit may be more suitable for critical rotating parts. Surface damage 

appears to occur for 240 and 320 mesh grit sizes. 

UVA 

Oct 

BL 

00-067 

UVA 

Oxidat. 

& scale 

An example of the data summaries that are being generated is shown above for sample 01-037. 

The information includes the original optical micrograph for the sample, three UVA indications taken 

at different times and under different conditions at Delta and the optical micrograph after 

processing. This particular sample underwent walnut shell media blast which has been coded as 

the “B6” method. The BT values are brightness readings. Note that for this sample the brightness 

decreased from the baseline run after use of the walnut shell blast. However, subsequent 

processing through ultrasonic agitation in an acetone bath returned the brightness to levels near the 

original baseline. This indicates that some media may have remained in the crack immediately 

after blasting which was removed by the subsequent “fluid processing”. Consideration is being 

given to recommending that a water wash step be added after all mechanical blasting operations 

used to clean parts. 



The etch study was repeated during this visit at Delta for both Ti-6-4 and INCO 718. There were 

difficulties in blending the Ti-6-4 and the INCO 178 etch specimens to acceptable conditions for 

processing through the etchant procedures. It may be somewhat reassuring to note that the cracks 

were difficult to smear. It was also difficult to determine visually if smearing was sufficient to close 

the cracks as FPI revealed. The etching of Ti-6-4 had a better effect than etching of INCO718, 

however crack detectability was significantly lower than the baseline for all samples. The report 

summarizing this study is being prepared. 

A considerable volume of data has been generated on this program with analysis underway. A 

meeting to review the data and conclusions is planned for early April. Final report sections were 

assigned and drafts have been or are being completed. 


Complete accounting of all results including crack length measurements from the UV photos, 

organizing UV images, verification of brightness results and crack lengths and spreadsheet results 

by cleaning method. 

A two-day wrap up meeting is scheduled for April 7-8 in Phoenix. This will provide an opportunity to 

evaluate all cleaning results and document conclusions and recommendations for follow-on work. 

Further evaluation of some selected specimens with diminished/no brightness will include scanning 

electron microscopy, a hot water rinse study, and additional fatigue of several specimens to break 

open closed or smeared cracks followed by penetrant testing. 

Report preparation is underway with a draft to be provided in the next quarter. 

Milestones: 

Original 

Date 

Revised 

Date 

Description 

4/00 Complete literature survey. Complete industry 

survey of common practices used in cleaning and 

drying. (All) 

5/00 Identify cleaning and drying methods and typical 

contaminants of concern for study in the problem. 

6/00 Establish experimental parameters for engineering 

studies. 

6/00 Define necessary crack samples and determine 

need for fabrication 

6/00 Establish partnerships with airlines to perform onsite 

evaluation of cleaning methods. 

8/00 Initiate study to define optimal local etching 

practices. 

9/00 Present status update at ATA September NDT 

meeting in San Francisco. (This along with 

telephone survey replaces proposal milestone for 

month 3. Industry workshop to identify cleaning 

and drying methods and typical contaminants of 

concern for study in the program.) 

12/00 Initiate combined Effects of Cleanliness Study and 

Cleanability & Drying Studies. 

12/00 Complete local etching practices study and 

generate guidance document. 

Status 

Completed 4/28/00 





Etch study initiated with OEM etch 

solution comparison 8/16/00 

Complete 9/28/00 at 44 th Annual 

ATA NDT Forum 

Specimen completion 2/01; Delta 

overhaul study 6/01 

Etching study completed 2/02; report 

to be completed 7/02 



Original 

Date 

Revised 

Date 

Description 

12/01 Complete combine Effects of Cleanliness Study 

and Cleanability & Drying Studies and generate 

matrix. 

Status 

Drying studies completed 6/01; 

cleaning study complete 2/02 

12/01 Initiate best practices document. Final report in progress. Draft to 

FAA 7/02. 

2/02 Complete best practices document and provide 

recommendations for further study. 

Final report to FAA in 7/02. 

Milestone change summary from the Phase II Technical Proposal – Volume I, Task 2.2.3 dated July 

10, 1998. 

1.) The industry workshop, month 3 (May 2000) milestone was changed in the February 8 kick-off 

meeting to a status update to the ATA September 12 meeting in San Francisco. It was felt that 

a month 3 milestone could not provide any input that the OEM experts were not already aware 

of and also that the subtask had nothing to communicate to the engine overhaul shops at the 

time. 

2.) The experimental design, month 3 (May 2000) milestone was set back one month to June to 

review contaminates, determine cleaning methods and decide what cleaning methods would be 

performed on which contaminate type. Until this was determined, the necessary crack samples 

could not be determined and so this also was set back one month. 

3.) The team decided that since the “Effect of Cleanliness Study” was very similar to the 

Cleanability and Drying Studies, and would at least require crack samples called for in this 

second study, that the studies be combined. The determination of how clean is clean must 

include not just surface cleaning, but crack cleanliness also. 

4.) Etching practices study will now be completed at the same time as the cleanability and drying 

studies since the sample rendered unusable in the cleanliness study can be and will be used for 

the etching practice study. 

Deliverables: 

Guidance on an optimal process for local etching practices. 

Specimen sets as required. 

Matrices which define the cleaning effectivity vs. typical engine run hardware contaminants, 

detectability for various cleaning methods, and detectability for various drying methods. 

Best Practices Document that provides guidance to the OEMs and airlines and will allow for any 

necessary specification changes. 

Recommendations for further work such as a formal POD study. 

Metrics: 

Improved cleaning and drying processes clearly defined for implementation by the industry as part 

of FPI used in inspection of critical rotating hardware. 




Date 

Feb. 7-8, 2000 

April 2000 

May 2000 

June 2000 

July 2000 

August 2000 

September 

2000 

December 

2000 

February 2001 

June 2001 

October 2001 

December 

2001 

February 2002 

April 2002 

Description 

Technical Kick-off meeting. 

Completion of literature search and industry survey. 

Cleaning and drying methods, and typical contaminants of concern for study were identified and 

listed. 

Experimental parameters were established for engineering studies. The matrix of these 

parameters are being finalized by the sub-team. Necessary crack samples and need for 

fabrication were defined. A list of these samples are being generated. Established partnerships 

with airlines to perform onsite evaluation of cleaning. 

Definitions for typical titanium and nickel based engine hardware contaminates. 

OEM etch solutions compared. 

Experimental parameter write-up completed. 

Detailed procedure for etch study completed. 

Sample fabrication complete. 

Drying study performed at airline overhaul facility. 

Initial cleaning study performed at airline overhaul facility. 

“Baked on” contamination of samples completed. 

Cleaning study performed at airline overhaul facility. Completed cleaning study data generation. 

Team meeting to analyze results and arrive at preliminary conclusions. 


Date 

Sept. 28, 2000 

Description 

Status Update to 44 th Annual Air Transport Association NDT Forum 



Project 3: 

Task 3.1: 


Inspection Systems Capability 

Assessment and Validation 

POD Methodology Applications 

POD of Ultrasonic Inspection of 

Billets 

Team Members: 

HW: Tim Duffy, Andy Kinney, Waled 

Hassan 

ISU: Thomas Chiou, Bill Meeker, Bruce 

Thompson, Frank Margetan, Tim Gray, Ron 

Roberts, Lisa Brasche 

GE: Dick Burkel, Bob Gilmore, Jon Bartos, 

Mike Keller, Dave Copley, Ed Nieters, Walt 

Bantz 

PW: Jeff Umbach, Kevin Smith, Taher 

Aljundi, Andrei Degtyar 

Students: V. Chan 

Program initiation date: June 15, 1999; All effort unrelated to the RDB was stopped on March 17, 

2000. On March 14, 2001, guidance was received regarding resumption of the technical work on 

subtask 3.1.1 with the initial activity being the revision of program schedules and technical path to 

account for the RDB results. 

Objectives: 

• To enhance the ability to estimate the POD of naturally-occurring defects, such as hard-alpha 

inclusions in titanium billet, under a variety of inspection scenarios, through identification of a 

standard recommended approach for adjusting the parameters of the flaw response model to 

match the properties of natural-flaw populations. 

• To verify that the new POD methodology improves on the accuracy of existent techniques, 

provides more information such as PFA, and can be reliably applied to circumstances other 

than those of the actual experimental measurements as influenced by changing individual 

inspection parameters such scan index, transducer properties, etc. 

• To verify that the new POD methodology provides sensible predictions using more limited data 

than is possible with existent techniques. 

• To provide the OEM’s with tools to allow implementation of the new methodology in internal 

damage tolerance analyses by increasing the user-friendliness of methodology software and 

associated flaw and noise response models. 

• To provide the best available estimates of titanium billet POD by means of periodical updates to 

existing estimates based on new information such as new flaw data and extension of the POD 

estimates to a wider range of typical billet diameters. 

• To provide to the aircraft engine industry the first estimates and a capability for further 

estimating POD for ultrasonic inspection of nickel billet that is comparable to that provided by 

the new SNR-based POD methodology for titanium billet. 



• To provide the aircraft engine industry with meaningful assessments of the improvements in 

flaw detectability afforded by the ETC inspection developments. 

Approach: 

The proposed program consists of six major elements, which have been selected in response to the 

issues identified above. 

Method to Tune Flaw Response Model to the Behavior of Naturally Occurring Flaws: A standard 

approach for readjusting parameters of the ultrasonic response model to incorporate information 

about distributions of properties of naturally-occurring flaws will be developed. The advanced flaw 

response models that have been developed as a part of ETC-Phase I treat the case of flaws large 

with respect to the ultrasonic beam which may not be centered on the beam axis. Procedures to 

“tune” the model are now needed, in a fashion analogous to that employed in the R e technique, but 

taking advantage of the much greater capabilities of the ISU flaw response models to treat realistic 

flaw geometries. During the first four months of the program, team members will jointly develop a 

recommended approach to this end. One candidate approach will be to modify the R e method by 

replacing the assumed FBH reflector with a cylindrical reflector viewed from the side. The response 

of such reflectors is readily treated by the new ISU models and it more closely mimics the overall 

shape of naturally occurring hard-alpha inclusions. 

Assessment of Success of the new POD/PFA Methodology: The capability of the new 

methodology, incorporating ISU flaw response models for generating POD and PFA estimates, and 

for predicting the effects on POD and PFA of many individual inspection parameters, has already 

been established qualitatively and quantitatively, using synthetic flaws in test blocks of simple 

shape. The Random Defect Block (RDB) will provide a similar test. It was designed to ensure an 

adequate distribution of SHA properties to provide meaningful tests of the capability of both 

conventional and Multizone inspection systems, while allowing for sufficient randomization of the 

final choice of SHA parameters (such as length, diameter, percentage nitrogen, skew relative to the 

billet axis, and depth below the inspection surface) to avoid an inspector discerning any pattern to 

the design. Inspection results (e.g., amplitude, SNR) will be compared with response ranges 

predicted from the ISU model to validate the adequacy of the flaw and noise response models to 

predict actual experimental data and hence, drive the methodology. A final stage in the validation 

process will be a test of the ability of the ISU model to predict the ultrasonic response from the 

complex-shaped natural flaws found during the CBS. The results will be analyzed by the team as a 

final validation of the Phase I methodology and any necessary modifications will be made. Efforts 

to assess the success of the new methodology will continue through its direct application in other 

Phase II work elements. 

Improvements and Transfer to the OEMs of the POD/PFA Methodology and Software: For the new 

methodology to have full impact on damage tolerant design and management of rotating 

components, it is necessary that the tools, i.e., software be in a form readily usable by the OEMs. 

These tools will be provided in Phase II. The methodology will be revised as needed based on 

results obtained in its application and software will be delivered to the OEMs incorporating those 

modifications. As dictated by the results of the RDB and CBS studies, any necessary refinements 

will be made in the flaw and noise response models. Included will be the development of numerical 

approximations to the predictions of the ultrasonic response models suitable for incorporation into 



the methodology. These may be thought of as approximations to the response surfaces which 

avoid executing the full flaw response calculation each time the methodology needs to examine a 

new case, thereby greatly speeding up the POD calculation process so that it will proceed at a rate 

which will be convenient for a user operating in an interactive mode. Selected improvements will 

also be made in the flaw and noise response models, supported by data generated in Fundamental 

Studies effort and that has the potential to significantly effect POD. Included will be the effects of 

microstructure on the ultrasonic beam profile, and hence, on the distributions of flaw responses; 

and the effects of tightly focusing the beam on the distribution of noise. In this latter case, it has 

been shown that, when the focal spot size approaches the dimensions of the macrostructure, the 

noise distribution is significantly modified. Models were developed in Phase I which described 

microstructural effects on noise, but a good means of determining the parameters that are inputs to 

the models, i.e., of characterizing the material, have yet to be developed. These procedures will be 

developed in Phase II. The laws governing the combinations of signal and noise distributions will 

be developed. Once known, these promise to greatly reduce the need for experimental 

measurements of flaw response to exercise the methodology and hence, should significantly 

increase its portability. Finally, the effects of variations in calibration response and uncertainties in 

the determination of flaw size on the accuracy of POD determination will be investigated, and the 

methodology will be modified as needed to accept these results. Results of all of these software 

and procedural advances will be integrated and provided to the OEMs for their internal use. 

POD for Titanium Billet - Existent/New Data Analysis, and Use of the CBS: Additional information 

about the properties of flaws in titanium alloys will be collected and reviewed as it becomes 

available. Here, particular attention will be placed on the results for large diameter billets. This 

information will be reviewed and used to update POD estimates for ultrasonic inspection of titanium 

billet and to extend the POD estimates to cover billets up to 14″ diameter. Included will be a review 

of the revised inspection approaches for larger diameter billets, the development of any model 

modifications required to predict the flaw response for those approaches, validation of those models 

using calibration standards and chord blocks, and prediction of POD. These predictions will be 

compared to those of existent methodologies where the data is sufficient to allow existent 

methodologies to be used. 

Information from the responses of the CBS defects will be used with the new methodology to 

update POD estimates and provide them to RISC and TRMD. New flaw detection data will be 

incorporated into revised estimates of titanium billet POD as they occur, and will provide a basis for 

revising the “default” POD estimates that have been supplied to the AIA Rotor Integrity 

Subcommittee (RISC). 

Information from the responses of the CBS defects will be used in three ways. Ten of these defects 

will have undergone careful metallographic analysis in Phase I. As noted previously, this 

information will be a part of the detailed validation of the flaw response models. It will provide input 

to tuning the model for the response of naturally occurring flaws. Finally, methods will be sought 

and implemented to utilize the information in the remaining 50 flaws which were not the subject of 

destructive metallographic characterization. Here, the approach will be to seek a correlation 

between the C-scan image size (available for all 60 flaws) and actual defect size available for the 

ten which have been sectioned. If such a correlation is successful on these 10 defects, it will be 



used to estimate the size of all defects found in the contaminated heat. From this size estimate and 

the measured response, an enhanced data base for fine tuning the model for the response of 

naturally occurring flaws will be available. In addition, information about billet flaws gained from the 

related forging studies (i.e., from TRMD); and from direct comparison of multizone and conventional 

ultrasonic inspection system performance, will be considered. Based on this information, integrated 

in the context of the new methodology, updated POD estimates will be made and provided to RISC 

and TRMD. 

POD for Nickel Billet: The new methodology will be implemented on ultrasonic inspection of nickel 

billet analogous to that used for titanium alloys in Phase I. This will draw heavily on the modeling 

work of Phase I, and on results of fundamental studies and model developments planned for Phase 

II. Based on those fundamental studies, flaw response models will be developed for white spots 

and other defects from the critical flaw list. Flaw response data and noise data will be gathered, 

including any pertinent results from the pilot lot inspection in Subtask 1.1.2 as well as 

measurements on synthetic white spots in Subtask 1.1.1. These data will be used as the basis for 

initial estimates of nickel billet POD analogous to that employed for Ti-billet in Phase I, extended 

where possible by subsequent improvements in the methodology, as developed in Phase II. 

Measurements of calibration standards and chord blocks will be used for validation as appropriate. 

A study will be conducted of the effects of calibration response variability and determination of flaw 

size on the accuracy of POD predictions. 

Comparison of Inspection Systems - Use of the Random Defect Block: This section will be updated 

in the next quarter to reflect all changes currently being made. 

Objective/Approach Amendments: 

The objective and general approach remain as originally proposed in July 1998 with the exception 

of work related to the Random Defect Block. A proposal for new work was submitted to the FAA in 

February 2000. Per FAA technical redirection, on March 17, 2000, all effort other than that related 

to the RDB was suspended. The RDB recovery program was initiated in May 2000. On March 

14, 2001, guidance was received regarding resumption of the technical work on subtask 3.1.1 with 

the initial activity being the revision of program schedules and technical path to account for the RDB 

results. 


In this period, our CBS reconstruction work was focused on defect B1AW2-B (POD 9). Because 

this defect is very close to the surface of the billet, side 1 of the cube block retained the original 

billet surface to prevent the defect from being accidentally cut-off. The curved surface geometry, 

however, had caused some degree of accessibility problem in carrying out ultrasonic scans from 

neighboring sides 2, 4, 5 and 6 (Fig. 1). The footprint of the 5 MHz insonifying transducer beam 

might be partially off the edges of one or more of these sides, resulting in signal loss. Furthermore, 

other than vertical edges of the cube block, there were no fiducial marks available in the 

micrographs to help align the successive cross-sections of the defect. This has made the 

micrograph re-alignment in the vertical direction quite difficult and uncertain. Nevertheless, both 

geometric and ultrasonic models of this defect have been completed to the best our capacity. The 

geometric model consists of one flat void part with four branches, and was built using 6 geometric 



model parts across 17 micrograph planes (including 4 patches) with 30 boundary traces. The 

physical dimension of the minimal “bounding box” in the original orientation of micrographs (also 

shown in Figure 1) is 135 (X) x 31 (Y) x 64 (Z) mils. Figs. 2-4 depict the three-dimensional 

geometric surface model of the defect. Based on the geometric model results, the corresponding 

UT model was utilized to produce the simulated C-scan images as shown in Fig. 5. The overall 

agreement between the experiment and model predictions is not as good as for previous cases. As 

viewed through sides 5 and 6, the model predictions are low by 5.8 dB and 6.1 dB respectively, 

Through side 2, the predictions are high by 8.1 dB. For the CBS, our target agreement is 6 dB, 

although we have often obtained agreements on the order of 3 dB. We believe that the differences 

observed for this defect are on the high side of the target agreement because of the 

aforementioned absence of fiducial marks which made the construction of the solid model less 

accurate. As viewed through side 4, the model predictions are high by an unacceptable 15.2 dB. 

We believe that this is caused by the aforementioned possibility that part of the beam was “cut-off” 

by the curved exterior surface of the sample. Examination of Figure 1 shows that this would have 

been most likely to occur for side 4. 

Flaw (inside) 

Side 1 (top) 

Side 2 (back) 

Side 5 (right) 

Side 6 (left) 

Side 4 (front) 

Z 

Side 3 

X 

Side 6 

Side 2 Side 5 

Y 

Side 1 

Figure 1 



Z 

Y 

X 

Figure 2. Angle View of Void Model for B1AW2-B (I) 

Z 

Y 

X 

Figure 3. Angle View of Void Model for B1AW2-B (II) 



Z 

Y 

X 

Figure 4. Angle View of Void Model for B1AW2-B (III) 



5 MHz C-scan Image Comparisons: B1AW2-B 

Side 2 

Model Experiment Model 

Side 4 

Experiment 

31(H) x 31(V) @10 mils, 2dB 

peak amplitude @2dB=573 mv 

deviation=155% or 8.1 dB 

60(H) x 30(V) @10 mils, 2dB 


51(H) x 31(V) @10 mils, 0dB 


deviation=474% or 15.2 dB 

60(H) x 30(V) @10 mils, 0dB 


Model 

Side 5 

Experiment 

Model 

Side 6 

Experiment 

31(H) x 31(V) @10 mils, 2dB 


deviation=-49% or -5.8 dB 

60(H) x 30(V) @10 mils, 2dB 


31(H) x 31(V) @10 mils, 0dB 


deviation=-51% or -6.1 dB 

60(H) x 30(V) @10 mils, 0dB 


Multizone Color Code 

0 128 255 

Experiment 255 = 500mv for sides 2, 5 and 6 

= 250mv for side 4 


Figure 5. 5 MHz C-scan Image Comparisons: B1AW2-B 

Primary plans for this period are to complete the analysis of the CBS data. Assuming approval of 

the restart technical plan by the FAA, technical work will resume as directed by the agency. 

Milestones: 

Revised dates of TBD are shown for most of the tasks, given that work has been stopped while the 

problems with the random defect block are being addressed. Revised dates to be provided in next 

report. 

Original 

Revised 

Description 

Status 

Date 

Date 

Approach to tune flaw response model to the 

behavior of naturally occurring flaws 

4 months TBD Provide a written description of the recommended 

method (GE, ISU) 

6 months TBD A report defining a method for relating properties of 

naturally-occurring flaws to the parameters of the 

ISU model. 

12 month deliverable of 3.1.2 is 

serving as a common basis for 3.1.1, 

3.1.2. General procedure for tuning 

flaw response model is included in 

the 3.1.2 white-paper. 

Completion of full report delayed by 

redirection of work. 

Improvements and assessment of POD/PFA 



Original 

Date 

Revised 

Date 

Description 

Status 

methodology 

12 months TBD Report results from applying RDB and CBS data to 

validate the ISU models developed in Phase I. 

(ISU, with support from AE, GE, PW) 

12 months TBD A report assessing success of the Phase I 

development of a new POD methodology. 

Ongoing 

Modify the modeling software if and when 

necessitated by experimental data. (ISU) 

30 months Review and report on effects on POD of calibration 

response variability, and uncertainty in determining 

flaw size, conducted on Nickel only. (GE, with 

support from ISU) Provide OEMs with integrated 

software containing flaw response and noise 

models. (ISU) 

30 months Report documenting the software and material 

characterization procedures with which the OEMs 

can implement the new methodology. 

48 months Complete development and validation of models for 

the effects of microstructure on beam profiles and 

apparent attenuation. (ISU, PW with support from 

GE, AE) 

60 months 

TBD 

Provide OEMs with final software and procedure 

packages. (ISU) 





POD for titanium billet – existent/new data analysis, 

and use of the CBS 

12 months TBD Complete report of analysis of CBS data. (ISU, 

with support from AE, GE, PW) 

Ongoing 

Updated POD estimates for naturally occurring 

flaws in titanium alloys as new field-find data 

become available. (GE, ISU, with support from AE, 

ISU) 

42 months 

Initiate POD assessment of revised inspection 

approaches for large diameter billet (10″ to 14″). 

(PW with support from ISU, GE) Characterize 

transducers to be used in inspection of large 

diameter billets. (Utilize results from 1.2.1) 

42 months Report documenting the revised estimates of POD 

for larger diameter titanium billet 

51 months Predict response for large diameter billets. Use 

calibration standards, RDB, and chord blocks for 

validation as appropriate. (ISU with support from 

PW, GE) 

Provide POD estimate for larger diameter billet. 

(ISU, with support from AE, GE, PW) Compare 

results with those from alternative POD 

methodologies. (GE, with support from ISU) 

51 months Report documenting the estimates of POD and 

PFA for titanium billet based on use of the random 

defect block, CBS data, and data reported to 

JETQC, including comparison with POD results 

from existent methodologies. 





Original 

Revised 

Description 

Status 

Date 

Date 

POD for nickel billet 

24 months Initiate nickel billet POD program utilizing results 

from Production Inspection Task. (ISU, with 

support from AE, GE, PW) 

30 months Characterize transducers to be used in inspection 

of nickel billets. (Utilize results from 1.1.2) 

58 months Predict response for nickel billets. Use calibration 

standards and chord blocks for validation as 

appropriate. (ISU with support from AE, GE, PW) 

60 months Provide report of POD estimates for nickel billet. 

(ISU with support from AE, GE, PW) 

Compare results with those from alternative POD 

methodologies. (GE, with support from ISU) 

60 months Report documenting the POD and PFA estimates 

for nickel billet, including comparison with POD 

results from existent methodologies. 

(8/97 - 

Phase I 

(12/97 - 

Phase I) 

(4/98 - 

Phase I) 

(8/98 - 

Phase I) 

Program 

start 

6/15/99 

Comparison of inspection systems - Use of the 

Random Defect Block 

Random defect block fabrication completed. 

ISU predictions of accuracy of model completed. 

Initiate ETC measurements using zoned and 

conventional inspection (on commercial systems. 

Complete measurements on RDB. (GE) 

Begin data analysis of ETC measurements on 

random defect block. (All) 

5/8/00 

1/8/01 

Begin random defect block recovery program. 

Complete random defect block recovery program. 

6 months TBD Incorporate interim results into provision of 

improved default POD curves to RISC and TRMD. 

(GE, PW, with support of AE) 

38 months Provide report comparing conventional and zoned 

inspection systems in use by billet suppliers, based 

on data from the Random Defect Block. (All) 

40 months A report documenting the relative effectiveness of 

conventional and Multizone systems for the 

ultrasonic inspection of billet. 

Completed. Effort initiated at 

program start in June 1999 

Completed 

Expect delay resulting from RDB 

issues. 

Deliverables: 

A report defining a method for relating properties of naturally-occurring flaws to the parameters of 

the ISU model. 

A report assessing success of the Phase I development of a new POD methodology. 

Software and material characterization procedures with which the OEMs can implement the new 

methodology. 



A report documenting the relative effectiveness of conventional and Multizone systems for the 

ultrasonic inspection of billet. 

Revised estimates of POD for larger diameter titanium billet (10″ to 14″). 

POD and PFA estimates for nickel billet, including comparison with POD results from existent 

methodologies. 

Estimates of POD and PFA for titanium billet based on use of the random defect block, CBS data, 

and data reported to JETQC, including comparison with POD results from existent methodologies. 

Metrics: 

A procedure for incorporating the properties of naturally-occurring defects into a model-based POD 

methodology will have been defined in a formal report which becomes the basis for industrial 

practice, providing a consistent basis for future implementation of the POD methodology. 

The success of the new POD methodology developed in Phase I will be critically reviewed in terms 

of attainment of the original goals, using the following criteria: 

• POD results are more accurate than those of existing methodologies. They should be close 

(e.g., flaw size for a given probability within ±40%) to those from existing (R e and â-versus-a) 

methods when the requirements of those methods are satisfied and provide sensible 

predictions in cases in which the existing methods cannot produce answers. 

• PFA results are estimated as a function of threshold and these estimates are validated by 

independent experiments. 

• The method provides a means to predict the effect on POD and PFA of changing (as a 

minimum) transducer beam properties (diameter, focal length, water path, beam orientation); 

transducer frequency; scan index; flaw properties (location, dimensions, acoustic impedance, 

orientation relative to the sound beam); material properties (acoustic impedance, 

grain-boundary noise), with experimental validation that the response agrees with that predicted 

by the model, as a result of changing any one of these parameters, within accuracies typical of 

ultrasonic measurement, i.e., about ±3 dB (or ±40%). 

Modifications will be developed that will enhance the speed, simplicity of use, and range of 

applicability of the POD software developed in Phase I; the ease of operation will be demonstrated 

by successful transfer of the software to one or more OEMs. 

Estimates of the POD of hard-alpha defects in titanium billets will be extended to cover billet 

diameters up to 14″. Success of this enhanced capability for assessing the quality of one of the 

materials used in manufacture of aircraft engines will be indicated by incorporation of these 

estimates in life management calculations by the FAA, members of ETC and the Rotor Integrity 

Subcommittee of AIA. 

Estimates of the POD of hard-alpha defects in titanium billets, and of white spots in nickel billets, 

will be updated periodically. Success will be indicated by incorporation of these estimates in life 

management calculations by the FAA, members of ETC, and the Rotor Integrity Subcommittee of 

AIA. 



Improvements in detectability attainable through use of zoned ultrasonic inspection will be 

quantified and documented, permitting subsequent assessments by the OEMs of the effectiveness 

of such systems in improving the quality of titanium billet used for aircraft engine applications. 


Date 

June 14-15, 1999 

September 15, 

1999 

June 8-12, 2000 

August 15, 2000 

October 6, 2000 

November 15, 

2000 

February 8, 2001 

February 22, 2001 

May 7-8, 2001 

August 14, 2001 

Description 


Workshop in Ames to discuss the random defect block and other 3.1.1 planning issues. 

Inspection of the Random Defect Block by RMI in Niles, OH before and after modification of 

the surface condition, as observed by entire team. 

Presentation of preliminary results of the RDB recovery program to the FAA at the Semi- 

Annual Review Meeting in Evendale, OH.. 

Team discussion, with FAA, of RDB recovery program. 

Presentation of status of RDB recovery program at AACE Annual Symposium in Seattle, WA. 

Presentation of status of the RDB recovery program at the ETC Semi-Annual Review in 

Atlantic City, NJ. 

Presentation of results of the RDB recovery program and proposed future plans at ANE, 

Burlington, MA. 

Team meeting to lay out plan for restart of subtask 

Presentation of current status at the FAA R E&D Technical Review in Atlantic City 


Date 

December 8, 1999 

March 28, 2000 

July 19, 2000 

July 19, 2000 

Description 

“Probability of Detection Determination for Internal Inclusions in Gas Turbine Engine Rotating 

Components”, presented by Bruce Thompson at the 4 th Annual FAA/Air Force Workshop on 

the Application of Probabilistic Methods to Gas Turbine Engines, Jacksonville, Florida. 

“Overview of S/N Based POD Methodologies”, presented by Bruce Thompson at the ASNT 

Spring Conference and 9 th Annual Research Symposium, Birmingham, Alabama 

“A Methodology for Predicting the Probability of Detection for Ultrasonic Testing”, presented 

by W. Q. Meeker at the Review of Progress in Quantitative Nondestructive Evaluation, Ames, 

Iowa. 

“Ultrasonic and Statistical Analyses of Hard-Alpha Defects in Titanium Alloys”, presented by 

C.-P. Chiou at the Review of Progress in Quantitative Nondestructive Evaluation, Ames, Iowa. 

October 16, 2000 “The Use of Physical Models of the Inspection in the Determination of POD”, presented by R. 

B. Thompson at the workshop, “POD Methodologies: New Horizons,” organized by The 

Technological Cooperation Program (TTCP), an international collaboration of the defense 

departments of English-speaking countries, in Patuxent River, Maryland. 

March 28, 2001 

July, 2001 

“Use of Physical Models of the Inspection Process in the Determination of Probability of 

Detection,” presented by R. B. Thompson at the ASNT Spring Conference and 10 th Annual 

Research Symposium, Denver, Colorado. 

“Use of Physical Models of the Inspection Process in the Determination of Probability of 

Detection,” R. B. Thompson, published in Materials Evaluation, Volume 59, Number 7, 

pp.861-865 (2001) 



Project 3: 

Task 3.1: 





POD of Ultrasonic Inspection of 

Titanium Forgings 

Team Members: 

HW: Tim Duffy, Andy Kinney, Waled 

Hassan 

GE: Dick Burkel, Bob Gilmore, Jon Bartos, 

Dave Copley, Walt Bantz, Ed Nieters 

ISU: Thomas Chiou, Bill Meeker, Bruce 

Thompson, Lisa Brasche 

PW: Jeff Umbach, Kevin Smith, Taher 

Aljundi 


Program initiation date: June 15, 1999. All effort was stopped on March 17, 2000; On March 14, 

2001, guidance was received regarding resumption of the technical work on subtask 3.1.2 with the 

initial activity being the revision of program schedules and technical path to account for the RDB 

results. 

Objectives: 

• To extend the SNR-based methodology developed in Phase I to predict the POD of naturally 

occurring defects in titanium, sonic-shaped forgings for commonly used ultrasonic procedures 

and geometries. 

• To further extend the POD methodology to forgings of final shape, including the prediction of 

POD as a function of position within the part. 

• To provide the OEM’s with a set of tools which they can use to implement the new methodology 

in internal analysis of POD of forgings by increasing the user-friendliness of the methodology 

software and flaw and noise response models for forging conditions. Included are 

improvements in speed, accuracy, range of cases treated and reduction in the amount of 

experimental data required. 

• To improve the reliability of experimental methods for detecting flaws in sonic-shaped forgings 

and final-shaped, machined parts by developing and validating tools which allow evaluation of 

the likely effect on POD of proposed changes in inspections systems and procedures such as 

scan plans, transducer properties, gate widths, etc. 

• To verify that the new methodology produces POD results which are comparable with results 

from existent methodologies in cases when sufficient data is available that the existent 

methodologies can be successfully applied and which are consistent with reasonable 

expectations when such data is not available. 

• To provide the best available estimates of titanium forging POD to the aircraft engine industry, 

by means of periodically updating existing estimates based on new information, as it becomes 

available. This will include incorporating new flaw data, and extending the POD estimates to a 

wider range of typical forgings geometries through use of the ISU physical models. 



• To use this methodology to assess the improvements in POD afforded by the Production 

Inspection Task 1.3.2. 

Approach: 

This task will extend and apply the approach used in Phase I for billets to develop a method for 

estimating POD of naturally occurring flaws in forgings. The methodology developed in Phase I is 

based on detection theory concepts involving distributions of noise and of flaw response in the 

presence of noise. In this subtask, that methodology will be applied to the case of forgings, with a 

major extension being related to predicting the POD as a function of position within the forging. 

The proposed program consists of four major elements, which have been selected in response to 

the issues identified above. 

Application of the Methodology to Sonic-Shaped Forgings: Initial work in Phase II will use designed 

experiments to specify distributions of noise and signal response in existing blocks of forged 

material containing FBHs and/or SHAs. The initial focus will be on the effect of material anisotropy 

that results from flow lines created by the forging process on POD. The first step will be 

determination of the magnitude of anisotropy, which will be determined in subtask 1.3.1, 

Fundamental Studies. Given that information, the flaw response and noise models will be modified 

to take into account this anisotropy. Appropriate statistical distributions will then be developed, 

based on a combination of these models and experimental data to describe the distributions of 

signal and noise response for a simple forging geometry. Any further modifications to the 

methodology needed to take into account anisotropy will be made. 

When samples become available from Task 1.3.2, similar, but more extensive, experimental studies 

will be conducted on sonic-shaped forgings. These experiments will be conducted with samples 

containing flat bottom holes placed at some number n (to be determined later) positions in the 

sample. The positions will be chosen to provide a range of inspection geometries, surface 

curvatures, flaw depths, etc. Because of the symmetry of sonic-shaped samples, it will be possible 

to replicate these synthetic flaws systematically around the sample unit to allow a study of the 

variability of the responses of nominally identical flaws (providing important information needed to 

quantify sources of variability in signal response). Initial scanning, analysis, and modeling will be 

done on a representative sample of n/2 of the seeded flaw positions. The experimental data will be 

important for developing a methodology that will account for the strong effect that flaw location will 

have on POD with complicated geometries. The data will be analyzed to check and tune the 

deterministic signal-response model and to develop appropriate statistical models for the variability 

in the signal response measurements, the important components of the POD prediction model. 

The resulting POD prediction methodology will then be used to predict POD at the other n/2 

positions, to validate the results. The data generated during these scans will also be used to 

provide a database which will be used in the development of noise distributions, as influenced by 

surface curvature. 

Because a significant amount of the data will be generated in the above study, it should be possible 

to compare POD predictions from the new methodology with predictions of existing methods such 

as the ahat vs. a and the R e methods. Such comparisons will be made to provide an important 

check on the different aspects of the methodology over the required wide range of inspection 

conditions encountered in forgings. Efforts will be initiated to take into account the morphology of 



naturally occurring flaws in forgings. It is recognized that this morphology will be somewhat 

different from that in billets due to the deformations that occur in the forging process. Close 

contacts will be maintained with the TRMD program to obtain the necessary morphology 

information. 

Development of the Capability to Make Predictions of the Local POD in Final Forging Shapes: 

Because of the complexity of the geometry of final part shape and of the effects of anisotropy 

associated with flow lines, the POD will depend strongly on position in final forging shapes. The 

new methodology is designed to take these effects into account, and this capability will be 

developed and applied. The essential steps that are required will be determinating, on a 

point-by-point basis, the following: 

• Effect of forged material on the flaw response and noise distributions, building on the results of 

the sonic-shaped studies 

• Effect of surface curvature and other geometrical parameters on the beam shape and there by 

on the flaw response and noise distributions 

In parallel, an implementation plan for including these point-by-point variations in the methodology 

will be developed, so that the result can be efficiently integrated with the life prediction code, 

DARWIN. 

Experimental validation will then be undertaken. The ultrasonic response model will be used to 

predict the signal response from flaws which are insonified through representative surface 

geometries using the samples being developed in Task 1.3.1. Samples will be designed in 

cooperation with 1.3.1 to evaluate the full range of surface curvatures typical in final and sonic 

shape forgings. Consideration will also be given to evaluation beyond typical curvatures to 

determine the limits of the model applicability. The flaw response model will be verified by scanning 

these specimens and comparing these observations to the model predictions. Checks on the 

resulting POD predictions will be made for certain testing situations for which POD curves have 

been estimated by other means (e.g., the ahat vs. a and the R e methods). Upon completion of 

these tests, an updated version of the methodology will be prepared. 

Improvements/Transfer of the POD/PFA Methodology Software to OEMs: For the new 

methodology to have full impact on damage tolerant design and management of rotating 

components of aircraft engines, it is necessary that the tools, i.e., software for implementing the 

methodology, the associated modules for predicting flaw and noise response as influenced by 

anisotropy and geometry, and materials characterization procedures to efficiently use them, be in a 

form that can be readily used by the OEMs. These tools will be developed, incorporating the results 

of the previously described major work elements. Included will be the methodology software, flaw 

and noise response modeling modules (as influenced by anisotropy and part geometry), and 

characterization procedures to provide the necessary inputs. As in 3.1.1, numerical approximations 

to the predictions of the ultrasonic response models will be developed which are suitable for being 

called by the methodology to speed the calculation process to a rate which will be convenient for a 

user operating in an interactive mode. Also building on the experiences gained in the Task 3.1.1, 

the flaw response models and noise models will be designed to incorporate the effects of 

microstructure on beam profile, and hence, on the distribution of flaw response, the effects of tight 



focusing with respect to the scale of the microstructure on the form of the signal and noise 

distributions, and the rules required to determine the distribution of signal-in-the-presence-of-noise 

from the noise distribution and the flaw free noise response. All of these will be considered as 

influenced by the presence of anisotropy and beam modification by the part geometry. Results of 

these software and procedural advances will be integrated and provided to the OEMs for their 

internal use. These uses are anticipated to include life management calculations, such as 

consideration of the likely effects on POD of proposed changes in inspection systems and 

procedures such as scan plans, transducer properties, gate widths, etc. 

POD for Titanium Forgings: Efforts to acquire naturally occurring hard alpha inclusion data will be 

continuously made. Possible sources include field and manufacturing finds, the utility of which will 

depend on the degree to which appropriate procedures are utilized to fully characterize the 3-D 

shapes of these finds. Information gained during the forging studies of the TRMD program will also 

be used. This information will be used, as appropriate, to provide POD estimates. The 

methodology will be used to evaluate the improvements in POD afforded by developments of the 

Production Inspection Task 1.3.2. 


1998. 


On March 16, 2000 the FAA issued instructions to end all expenditures on Task 3, other than those 

associated with the RDB technical plan, with a restart to be considered once the sources of the 

discrepancy had been resolved. Hence the vast majority of the work on this task was terminated. 

A low level of effort has continued with the objective of coordinating with the Production tasks the 

work that is needed to support the POD effort. This had the objectives of ensuring that the 

fundamental studies measurements would produce the information needed by the POD group and 

that forging samples being produced would support the POD methodology. To these ends, the 

progress of the fundamental studies and forgings tasks have been monitored in terms of findings 

such as the degree of anisotropy and inhomogeneity of noise that has been observed in billet and 

forging materials and plans to prepare samples that will provide information to be used in POD 

assessment. In the latter context, particular attention has been paid to the fabrication of a forging 

containing synthetic hard-alpha inclusions and flat bottom holes. On March 14, 2001, the FAA 

indicated that work is to be resumed on sub-tasks 3.1.1 and 3.1.2, and planning for that restart 

initiated. 


Planning of the restart of subtask 3.1.2 will take place after the completion of the planning for 

restart of subtask 3.1.1. In the meantime, continued interactions with the Fundamental Studies and 

Production Tasks will occur, with the initial effort focused on the design of the forging POD sample. 



Milestones: 


problems with the random defect block are being addressed. 

Original 

Date 

Revised 

Date 

Description 

Status 

Application of the Methodology to Sonic-Shaped 

Forgings: 

12 months TBD White-paper defining a method for predicting POD 

for sonic-shaped forged parts. 

18 months Complete scanning and analysis of blocks of forged 

material with FBH and SHA flaws. (ISU with 

support of AS) 

22 months Investigate the application of Phase I methodology 

to the scan data on forged material with FBH and 

SHA flaws. (ISU) 

24 months Initiate generalization of the POD methodology to 

apply to sonic-shaped forgings. (ISU with support 

from GE) 

27 months Define experimental plan for use of FBH and SHA 

sonic-shaped forged samples available from TRMD 

and Phase II Production Inspection Task. (All) 

27 months Report documenting a method for predicting POD 

for sonic-shaped forged parts. 

30 months Acquire data from available FBH and SHA 

sonic-shaped forged samples to generate 

noise and signal plus noise distributions. 

(PW, AS, GE) 

32 months Complete necessary modeling and supply 

model predictions corresponding to data 

available from sonic-shaped forged samples. 

(ISU with support from AS) 

Utilize sonic-shaped forging scan data to 

define noise distribution. (GE, PW with 

support from ISU) 

32 months Report documenting the revisions to the noise 

and flaw modeling developed in this subtask 

and supply the modified model predictions. 

36 months Utilize sonic-shaped forging scan data to 

estimate the flaw-signal distribution and to 

compare with model prediction to define the 

deviation distribution. Apply the generalized 

methodology to estimate POD of synthetic 

hard alpha inclusions. (ISU with support from 

GE, PW) 

Compare with ahat vs. a and the R e methods. 

(GE with support from PW) 

36 months Report assessing the adequacy of POD predictions 

of the physical/statistical model-based methodology 

developed in this program, based on comparison 



Original 

Date 

Revised 

Date 

Description 

Status 

with the ahat vs. a and the Re methods, and 

describing and illustrating the advantages of the 

new methodology. 

Development of the Capability to Make Predictions 

of the Local POD in a Final Forging Geometry 

24 months Analyze results (anisotropy, geometry effects) of 

Production and Inservice Inspection Tasks for 

implications to POD as a function of position in 

typical forging geometries. (ISU with support from 

AS, PW) 

27 months Define implementation plan for POD as function of 

position. (GE with support from ISU, PW, and AS) 

30 months Report providing default POD curves for titanium 

forgings, for both production and in-service 

inspections, for use by the OEMs and FAA in life 

management/risk assessment studies. 

30 months Initial estimates of POD and PFA for sonic-shaped 

titanium forgings based on use of the FBH, SHA, 

CBS data, and field finds. 

36 months Complete modeling tools for the effects of 

geometry on flaw response and noise distributions. 

(ISU with support from PW) 

36 months Revised estimates of POD as a function of forging 

geometry, including effects of anisotropy, 

curvature, and position within the forging. 

38 months Complete experimental validation of modeling 

tools. (PW with support from GE, AS) Complete 

the development of the methodology needed to 

account for positional effects on POD. (ISU with 

support from GE, PW, and AS) 

40 months Compare with ahat vs. a and the R e methods. (GE 

with support from ISU and PW) 

42 months Provide updated methodology with POD as 

function of position as an output. (ISU) 

ongoing 

Improvements/Transfer of the POD/PFA 

Methodology Software to OEMs 

Modify the modeling software if and when 

necessitated by experimental data. (ISU) 

40 months Provide OEMs with integrated software containing 

flaw response and noise models as influenced by 

anisotropy and geometry. (ISU) 

48 months Review results for effects of introducing numerical 

approximation methods to the flaw response 

surface to speed the operation of the new 

methodology. (ISU, with support of AS, GE, PW) 

52 months Complete development and integrate validated 

methods to add noise to flaw response in c-scan 

images in the presence of anisotropy. (ISU with 

support from PW) 

60 months Provide OEMs with final software and procedure 

packages. (ISU) 

60 months Report describing the technical details of the POD 

prediction methodology for sonic-shaped and final 



Original 

Date 

Revised 

Date 

Description 

Status 

geometry forgings. 

POD for Titanium Forgings 

48 months Apply the generalized methodology to estimate 

improvements in POD afforded by developments of 

Task 1.3. (ISU with support from GE) 

ongoing 

Deliverables: 

Update POD estimates for naturally occurring flaws 

in Ti alloys as field find data become available. 

(ISU with support of GE, PW, and HW) 

White-paper defining a method for predicting POD for sonic-shaped forged parts. 

Initial estimates of POD and PFA for sonic-shaped titanium forgings based on use of the FBH, 

SHA, CBS data, and field finds. 

Revised estimates of POD as a function of forging geometry, including effects of anisotropy, 

curvature, and position within the forging. 

Report providing default POD curves for titanium forgings, for both production and inservice 

inspections, for use by the OEMs and FAA in life management/risk assessment studies. 

Report assessing the adequacy of POD predictions of the physical/statistical model-based 

methodology developed in this program, based on comparison with the ahat vs. a and the R e 

methods, and describing and illustrating the advantages of the new methodology. 

Report describing the technical details of the POD prediction methodology for sonic-shaped and 

final geometry forgings. 

Prototype software implementing the methodology and associated flaw and noise response models 

for POD prediction as a function of inspection parameters, position in forging, and flaw 

characteristics. 

Metrics: 

Procedures will be developed for estimating the POD of sonic shaped forgings and of final forging 

geometries as a function of position. Success will be indicated by the incorporation of these 

procedures by the OEMs in their life management programs. 

The ability of response models to predict flaw signals will be measured against the goal of having 

the predicted ultrasonic flaw response be within 3dB of experimental values at least 95% of the time 

when considered over typical inspection modalities. 

The ability to predict noise distributions will be measured against the goal of having predicted 

ultrasonic noise response within 3dB of experimental values at least 95% of the time when 

considered over typical inspection modalities. 



The development and transfer of the software for POD/PFA curve generation will be considered 

successful if it is utilized by the members of ETC and the Rotor Integrity Subcommittee of AIA in life 

management decisions. 

Estimates of the POD of hard-alpha defects in sonic-shaped and final forging geometries will be 

provided to the FAA and members of the ETC and Rotor Integrity Subcommittee. These estimates 

will be judged adequate if they compare favorably with predictions of existing POD methodologies 

for inspection situations in which such POD values can be obtained and if they provide sensible 

predictions in cases in which the existing methodologies cannot do so. 


Date 

June 14-15, 

1999 

September 16, 

1999 

Description 


Workshop to detail the approach for POD for Forgings. Included review of first draft of white paper 

and assignment for preparation of chapters of the document. 


Date 

Description 



Project 3: 

Task 3.1: 





POD of Eddy Current 

Inspections in the Field 

Team Members: 

HW: 

GE: Dick Burkel, Jon Bartos, Shridhar 

Nath, Walt Bantz 

ISU: Bill Meeker, Norio Nakagawa, Bruce 

Thompson 

PW: Kevin Smith, Dave Raulerson, Taher 

Aljundi 


Program initiation date: June 15, 1999. All effort was stopped on March 17, 2000. 

Objectives: 

• To develop a new methodology for estimating the POD and PFA of eddy current (ET) 

inspections in the field which facilitates prediction of POD and PFA for specific changes in test 

parameters, surface conditions, material noise characteristics and feature geometries in a rapid 

fashion without the need to construct extensive specimen sets. 

• To validate that methodology by comparing its POD results to corresponding predictions of 

existing methodologies, such as the a-hat versus a model, when sufficient data exists to 

support that comparison. 

• To apply the methodology to the estimation of POD/PFA of inservice inspections of flat plates and 

slots. 

• To transfer the resulting software and procedures to the OEM’s for their use in life management 

calculations. 

Approach: 

As in the previous work on UT, the methodology will be based on the determination of the 

distributions of signal and of noise, with physical models of the measurement process being used to 

allow the maximum information to be obtained from limited experimental data. Special emphasis 

will be placed on the needs imposed by the development of field durability issues. 

The incorporation of physical models of the inspection adds flexibility and extensibility to the 

methodology, while reducing the cost. In general, physical models make parametric studies 

inexpensive, by repeated computations of output signals for a wide range of inspection parameters. 

The specific benefits of the models used in POD/PFA analyses are twofold: 

• The model-assisted POD/PFA estimation significantly reduces the specimen preparation, 

compared to a purely experiment-based POD estimate. The economic benefit is substantial for 

flat-surface geometry since only a handful of crack specimens are sufficient to provide 

normalization and model predictions can then cover a wide range of parameters. The benefit is 

even more substantial when complex geometries are considered because, without models, one 



must prepare a large number of specimens of varying defect sizes and conditions to perform 

POD analyses for each new inspection geometry. The expense of this approach often leads to 

a best effort approach rather than a rigorous statistical study of the required number of 

samples. 

• Models make POD/PFA results transferable. For instance, suppose that the distributions have 

been determined for a given probe and the POD/PFA estimated. The model can then be used 

to transfer this POD/PFA result to another probe, with appropriate correction factors, because 

of the model’s ability to reliably predict relative signal strengths between one probe and 

another. Also, the model allows results to be transferred from one geometry [e.g., straight 

edges] to another geometry [e.g., slot edges]. Collectively, the use of models can reduce the 

cost and time requirements of POD/PFA analyses to more manageable levels in an 

environment where both inspection demands and opportunities are increasing. This results not 

only in cost savings, but more importantly, increases the likelihood that formal POD/PFA 

estimates will be made with enhancement to safety and quantification of the benefits now 

possible. 

Figures 4 and 5 present flow diagrams of the work plan that has been developed to accomplish 

these goals, as is discussed in detail in the following text. 

a 

Notch 

& crack 

specimens 

h 

ET measurement 

b 

1D line/ 

2D raster 

scan data 

g 

Physical probe 

response 

model 

(flaw & geometry) 

c 

Data 

analysis 

Validation 

Noise 

component 

Flaw 

signal 

Geometry 

signal 

d 

e 

Monte Carlo 

(Scan index,etc) 

f 

i 

Stat. model of 

noise 

distribution 

j 

Stat. model of 

signal 

distribution 

l 

Crack 

morphology 

database 

k 

POD, PFA, 

ROC 

Figure 4. Detailed experimental and validation plan for EC methodology. 



7a-7l 

6 

8 

9 

10 

Key 

additional 

ingredients 

Bolt hole 

or 

slot demonstr. 

Second 

generation 

methodology 

Validation 

Third 

generation 

methodology 

2 

Workshop 

& 

Implementation plan 

3a-3l 4 5 

First 

Flat plate 

generation 

demonstration 

Validation 

methodology 

Figure 5. Overall framework for development and validation of the EC methodology. 

Workshop and Implementation Plan: A kickoff meeting will be held to finalize a number of aspects 

of the program. 

Development of Key Additional Ingredients for POD Modeling: The basic tools for the flaw 

response models are already in place and formed the basis for feasibility demonstrations. In this 

element a number of required extensions will be made. The primary model software is the 

BEM-based code, the development of which was initiated in the ETC Phase I, novel probe design 

program. The code has progressed recently to the point that it can deal with complex part 

geometries as well as general probe geometries and constructions. Of particular importance for 

this proposed effort is its capability to deal with two types of probes of high current interest, i.e., 

differential reflection and wide-field probes, and with complex geometries such as the edges of a 

slot. The code has been validated against experimental data from edge crack inspections with 

air-core coil probes. It is therefore a crucial component of the project to validate the BEM code 

experimentally against data from the project-specific inspection conditions, namely cracks in flat 

plate and slot geometries, with differential-reflection and wide-field probes. Such experimental 

validations will be performed, as discussed below. In this work element, the theoretical 

comparisons will be made and model modifications made as needed. FEM-based models will also 

be used as a tool for cross-checking on the accuracy and validity of the BEM-based code. Practical 

inspection methods for complicated geometry often include methods for edge signal suppression. 

These will be reviewed and extended as needed, and methods will be developed for the 

characterization of their capability to reduce this component of noise. 

Application to a Simple Geometry: Flat Plates: The elements of the new methodology will be 

demonstrated by predicting the POD of notches and fatigue cracks in flat plates. Both differential 

reflection and wide field probes will be considered. A set of samples containing representative 

notches and cracks will first be obtained. These will be scanned to develop a data base, from 

which smaller data bases of noise and flaw response signals can be extracted. The noise data will 

be analyzed to yield a statistical model of the noise distribution, including its functional form and 

procedures for determining its parameters. The data will also be analyzed to determine the extent 

to which the noise is controlled by surface finish, microstructure, or other effects. The flaw signals 



will be used to validate the physical models for flaw response. These, as well as the noise 

distribution, will form the basis for the formulation of a physical model for the signal distribution. In 

the formulation of this model, attention will be paid to providing “hooks” which will allow a crack 

morphology database to be introduced at a later time (the development of such a database is not 

priced in this proposal). From the statistical models of noise and signal, POD, PFA and ROC 

curves will be determined. 

Based on the flat-plate demonstration, a first generation methodology will be specified. This will 

include procedures for each of the steps mentioned above. The methodology will be validated by 

exercising it on a set of existent samples and comparing the results to those of existent 

methodologies such as a-hat versus a. The conditions under which one or the other breaks down 

and the degree of agreement between their predictions will be noted and interpreted. Particular 

attention will be paid to the sparseness of data that can be accommodated by the new 

methodology, and the time that would be required for its implementation in the field. The new 

methodology will be used to make predictions of POD, as influenced by a variety of parameters, for 

use by the lifting community. 

Application to a Complex Geometry: Blade Slots: A demonstration will then be conducted on a 

blade slot, using a differential reflection probe. The same steps will be followed as in the flat plate 

demonstration, modified by insights gained in the formulation of the first generation methodology, 

and considering the edge geometry signals as sources of noise in the analysis of the data. Poorly 

managed edge responses can easily mask defect responses. One must assume that the 

inspection procedure incorporates appropriate mechanisms (e.g., by correct choices of probes and 

scans, and/or by signal processing) so that the edge contamination is suppressed. This is the 

reason for the consideration of the differential reflection probe, which is frequently used to suppress 

edge responses in the field. The edge signal remaining is effectively a source of noise. Our new 

POD/PFA methodology will be designed to quantify the edge-suppression capabilities as well as 

the other sources of noise. Once the signal and noise distributions are determined, following 

procedures already discussed, predictions will be made of the POD, PFA and ROC. 

Based on the experiences gained in the blade slot demonstration, a second generation 

methodology will be formulated. The second generation methodology will be validated by 

exercising it on an independent set of blade slot samples and comparing the results to those of 

existent methodologies such as a-hat versus a. The conditions under which one or the other 

breaks down and the degree of agreement between their predictions will be noted and interpreted. 

Particular attention will be paid to the sparseness of data that can be accommodated by the new 

methodology, and the time that would be required for its implementation in the field. After 

validation, the new methodology will be used to make predictions of POD, as influenced by a 

variety of parameters, for use by the lifing community. 

Improvement/Transfer of the POD/PFA Methodology Software to the OEMs: In order for the new 

methodology to have full impact on the damage tolerant design and management of rotating 

components of aircraft engines, it is essential that the necessary tools, i.e., software for 

implementing the methodology, the associated modules for predicting flaw and noise response as 

influenced by geometry, and materials characterization procedures to efficiently provide input to 

them, be in a form that can be readily used by the OEMs. These tools will be developed, 



incorporating the results of the previously described major work elements. For example, 

procedures will be specified for the determination of the signal and noise distributions, defining the 

relative roles of empirical data and physical models. A final form of the methodology will be 

produced, including software incorporating all experiences gained in the execution of the subtask. 

This will be transferred to the OEMs and documented in a final report. 


1998. 


On March 16, 2000 the FAA issued instructions to end all expenditures on Task 3, other than those 

associated with the RDB technical plan, with a restart to be considered once the sources of the 

discrepancy had been resolved. On March 14, 2001, the FAA has indicated that work is to be 

resumed on sub-tasks 3.1.1 and 3.1.2, but discussions have not yet been held regarding the restart 

of Task 3.1.3. 


At the present time, no activity is planned for this period. 

Milestones: 


problems with the random defect block are being addressed. 

Original 

Date 

Revised 

Date 

Description 

Status 

Workshop and Implementation Plan 

6 months TBD Establish implementation plan for adaptation of the 

methodology to eddy current inspection. Define 

data needed by Inspection Systems Capability 

Working Group to generate POD/PFA estimates 

and provide guidance to Inservice Inspection 

working group. (All) 

18 months TBD Application to a Simple Geometry: Flat Plates 

24 months TBD Development of Key Additional Ingredients for POD 

Modeling 

Application to a Complex Geometry: Blade Slots 

Improvement/Transfer of the POD/PFA 

Methodology Software to the OEMs 

Deliverables: 

Validated POD/PFA methodology for ET inspection based on signal and noise distributions which 

incorporates false call considerations, can be applied to sparse data and can predict the results of 

similar inspections for which no data is available. 



Estimates of POD/PFA for ET inspection Milestones: improvements made with ETC tools. 

Updates to default POD curves for RISC documents. 

Prototype software suitable for implementation of the methodology by the OEMs. 

Metrics: 

The methodology developed for estimating POD of eddy current inspections will be judged 

successful if three conditions are met. For data sets such as those used by existent 

methodologies, the new methodology should make comparable POD predictions. For sparse data 

sets, the new methodology should make sensible predictions when none are made by existents 

empirical methodologies. In either case these predictions should be able to be obtained with less 

expense and more rapidly than with existent methodologies. 

The updates to the POD curves will be judged successful if they are incorporated by RISC in life 

management guideline materials. 

The software produced to implement the methodology will be judged successful if it is utilized by 

the members of ETC and the Rotor Integrity Subcommittee of AIA in life management decisions. 

The estimates of improvements afforded by the advances in the ETC will be judged successful if 

they impact the acceptance of these technologies by the OEMs. 


Date 

June 14-15, 

1999 

September 17, 

1999 

Description 


Workshop to detail the approach for POD for EC. Included review of first draft of white paper and 

approach to the methodology. 


Date 

Description

Engine Titanium Consortium - Center for Nondestructive Evaluation ...

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