Engine Titanium Consortium - Center for Nondestructive Evaluation ...

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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, Quarterly Report – January 1, 2002 –March 31, 2002 print date/time: 6/6/2002 - 8:39 AM – Page 109
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. Objective/Approach Amendments: Objective and approach remain as originally proposed in July 1998. Progress (January 1, 2002 – March 31, 2002): 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. Plans (April 1, 2002 – June 30, 2002): At the present time, no activity is planned for this period. 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. 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. Quarterly Report – January 1, 2002 –March 31, 2002 print date/time: 6/6/2002 - 8:39 AM – Page 110
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Engine Titanium Consortium Quarterl
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Project 1: Task 1.1: Subtask 1.1.1:
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findings for the first billet studi
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measured P(L) curve, and tabulate t
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1.2 1.0 0.8 V-DIE-A coupon "D" (axi
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Attenuation (dB/in) . Waspalloy Att
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Small Diameter Billet Assessment: A
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Under normal circumstances one woul
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Plans (April 1, 2002 - June 30, 200
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system will be at GE, and evaluatio
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fixed-focus transducers that were n
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Back-Wall Scan FBH scan 20% 57% 49%
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63% Back-Wall Scan 74% FBH scan 58%
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Figure 6. Noise and target amplitud
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Original Date Revised Date Descript
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Objective/Approach Amendments: Obje
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(a) Transducer is: 15 MHz 0.5”-Di
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Peak> Range of Ave. Range of Peak G
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The average noise characteristics,
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% FSH Noise Measurements from flat
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possible candidates. Development wo
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