Elastic and elastic-plastic stress release due to material removal in measurement of in-depth residual stresses

Abstract

Elastic stress release is mostly considered during material removal while measuring in-depth residual stresses inside a structure. It can give rise to large measurement errors in the case of high residual stress where plasticity effect is involved. This paper focuses on analysis of elastic-plastic stress release due to material removal and the induced error in measurement of residual stress. Simulation of electropolishing prepared for XRD analysis and contour method process is performed on a shot peened 316L cylindrical specimen by accounting for the work hardening effect. Results show that elastic-plastic stress release can occur in iterative electropolishing when the initial yielding relation is broken. However, the induced error is acceptable with a maximum error of 1.67%. In comparison, significant release of residual stress after cutting in contour method activates obvious plastic flow, and induces a much larger deviation of the measured axial residual stress. Influence of the initial work hardening is discussed by analysing the plastic flow mechanism in the two material removals. It is concluded that occurrence and the influence extent of plastic flow rely on the stress release amount and the initial state of yielding relation which is defined by residual stress, work hardening, and material behaviour.