Engine Titanium Consortium - Center for Nondestructive Evaluation ...

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
Quarterly Report – January 1, 2002 –March 31, 2002
print date/time: 6/6/2002 - 8:39 AM – Page 88