Eddy Current Characterization of Applied and Residual Stresses

An exploratory investigation was conducted to evaluate the applicability of state-of-the-art eddy current nondestructive evaluation techniques to the characterization of applied and residual stresses in structural steels. Eddy current response versus stress measurements were developed for ASTM Type A533B and A471 steels under tensile, bending and residual stress loading conditions. A “shrink fit” specimen was used to establish applicability to residual stresses. Results show that an eddy current approach can be used to provide an accurate quantitative measure of surface stresses. The technique can also be used to map surface stress contours. Details of the procedure are described along with the test results and proposed applications. Recommendations for further work needed to optimize and expand the technique are included.