Intralaboratory Repeatability of Residual Stress Determined by the Slitting Method

Abstract

This paper presents repeated slitting method measurements of the residual stress versus depth profile through the thickness of identically prepared samples, which were made to assess repeatability of the method. Measurements were made in five 17.8 mm thick blocks cut from a single plate of 316L stainless steel which had been uniformly laser peened to induce a deep residual stress field. Typical slitting method techniques were employed with a single metallic foil strain gage on the back face of the coupon and incremental cutting by wire EDM. Measured residual stress profiles were analyzed to assess variability of residual stress as a function of depth from the surface. The average depth profile had a maximum magnitude of −668 MPa at the peened surface. The maximum variability also occurred at the surface and had a standard deviation of 15 MPa and an absolute maximum deviation of 26 MPa. Since measured residual stress exceeded yield strength of the untreated plate, microhardness versus depth profiling and elastic–plastic finite element analysis were combined to bound measurement error from inelastic deformation.