Strain changes caused by finite width slots, with particular reference to residual stress measurement

Abstract

This paper describes the use of the distributed dislocation (or displacement discontinuity) method for the analysis of strains in the neighbourhood of a slot of finite width. The results are of particular significance for the ‘crack compliance’ method of residual stress measurement which calculates residual stresses in a component from measured strain changes during the introduction of a slot. Two cases are analysed here: a flat-bottomed slot and a slot with a semi-circular bottom. Both cases are compared with a thin slot approximation (i.e. a crack). It is shown that the effect of the slot width is quite small for practical strain gauge locations, provided that the slot has a flat bottom. The effect of bottom profile is more significant and it is demonstrated that previous empirical results reported in the literature do not appear to account correctly for the effect of the bottom profile.