Methodology for Studying Residual Stress Distributions in Sheet Metal Samples

Abstract

A methodology for studying the distribution of residual stresses across the thickness of thin-sheet rolled materials is presented. The tested specimens were narrow strips cut from the blank along and across the rolling direction. Stresses in the specimen were determined using a gradually deepening transverse notch-groove method (slotting method). The recorded response was the angle of the resulting mutual rotation of the specimen ends. For reliable recording, the non-contact optical methods such as electron speckle interferometry or digital image correlation are considered optimal. The choice of one of these methods is determined based on the test conditions. The procedure for interpreting primary experimental data in terms of residual stresses is formulated as an inverse problem of solid mechanics. Two possible mathematical approaches to data processing are considered, taking into account the problem’ ill-posedness. Stabilization of solution is achieved, in part, through the use of a regularization algorithm. The developed method effectiveness is demonstrated using a study of stress distributions in thin-sheet steel samples produced by the Novolipetsk Steel Plant (Industrial complex). It is shown that different approaches to mathematical processing yield virtually identical results.