Opportunities and Challenges for Nondestructive Residual Stress Assessment

For a long time, nondestructive residual stress assessment has been one of the greatest opportunities as well as one of the greatest challenges for the NDE community, and probably it will remain so in the foreseeable future. The most critical issue associated with nondestructive residual stress assessment seems to be that of selectivity. Numerous NDE methods have been found to be sufficiently sensitive to the presence of residual stress, but unfortunately also rather sensitive to other spurious variations that usually accompany residual stresses, such as anisotropic texture, microstructural inhomogeneity, plastic deformation, etc., which could interfere with, or even overshadow, the elastic strain caused by the sought residual stress. The only sufficiently selective NDE method that is more or less immune from these spurious effects is X‐ray diffraction measurement, which however does not have the required penetration depth in most applications unless high‐energy neutron radiation is used. It is timely for the community to sit back and ask where we are in this important area. This paper presents an overview of the various indirect techniques that have been used to measure residual stress in the past. It is shown that traditional techniques have a number of limitations, which have spurred several recent research programs. Some of the new techniques that are presently being examined in the NDE community are reviewed and the current status of these research efforts is assessed.