Engine Titanium Consortium - Center for Nondestructive Evaluation ...

• 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
Quarterly Report – January 1, 2002 –March 31, 2002
print date/time: 6/6/2002 - 8:39 AM – Page 87