Engine Titanium Consortium - Center for Nondestructive Evaluation ...

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.
Progress (January 1, 2002 – March 31, 2002):
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
Quarterly Report – January 1, 2002 –March 31, 2002
print date/time: 6/6/2002 - 8:39 AM – Page 89