Application of minature ring-core and interferometric strain/slope rosette to determine residual stress distribution with depth - part I: Theories

The principle of an interferometric strain/slope rosette (ISSR) is based on interference of laser beams reflected from three microindentations on a specimen surface. The ISSR can simultaneously measure the in-plane strains and the out-of-plane slopes. Ring-core cutting is a mechanical stress relief method. When used with the ISSR technique for residual stress measurement, the ring core can be made much smaller than used with the resistance strain rosette. Thus, more localized residual stresses can be measured. The theories of the ISSR/ring-core cutting method are described in this paper Both mechanical and finite element models are developed,for the incremental ring-core cutting process with the application of the ISSR technique. The stress-strain coefficients of the ISSR/ring-core method are calculated and nondimensionalized for general applications. A test example is given to demonstrate how residual stress distribution is determined by using the stress-strain coefficients and the ISSR data.