Abstract
Recent research results indicate that eddy current conductivity measurements can be exploited for nondestructive evaluation of subsurface residual stresses in surface-treated nickel-base superalloy components. According to this approach, the depth-dependent electric conductivity profile is calculated from the measured frequency-dependent apparent eddy current conductivity spectrum. Then, the residual stress depth profile is calculated from the conductivity profile based on the piezoresistivity coefficient of the material, which is determined separately from calibration measurements using the known external applied stresses. This paper reviews the basic principles, measurement procedures, advantages, and limitations of eddy current residual stress profiling.
Acknowledgments
This work was supported by the Air Force Research Laboratory partly under Contract No. F33615-03-2-5210 with the University of Cincinnati and partly through the Quantitative Inspection Technology for Aging Military Aircraft program with Iowa State University on delivery order number 5007-IOWA-001 of the prime contract F09650-00-D-0018. Additional support was provided through cooperation with the Center for NDE at Iowa State University with funding from the Air Force Research Laboratory on contract FA 8650-04-C-5228. The diffraction measurements reported in this study were made by Lambda Research of Cincinnati. The authors would like to acknowledge valuable discussions and ongoing collaboration with Susanne Hillmann and Norbert Meyendorf of the Fraunhofer Institute for NDT in Dresden, Germany.
Notes
1. General Electric Aviation, Cincinnati, OH 45215, USA.
2. Cessna Aircraft, Wichita, KS 67277, USA.
3. Rolls-Royce Corporation, Indianapolis, IN 46241, USA.