Upper Bound Estimates of the Contribution of an Unknown Residual Stress Field to Stress Intensity Factor

Abstract

When assessing the effect of residual stresses on the driving force for fracture of a structure containing a defect, it is necessary to determine the residual stress field either via measurement or process simulation (e.g. weld modelling). However, residual stresses can be difficult and time-consuming to measure and model, especially in welded components which are subject to complex patterns of deformation during manufacture in addition to material inhomogeneity. To avoid this, many assessment procedures provide compendia of conservative estimates of the residual stress distribution for a limited set of welded joints. Unfortunately the use of these conservative estimates can lead to unrealistic results. In this article we propose alternative methods to account for the effect of residual stress on linear elastic defect assessments. We determine the maximum possible stress intensity factor that can be generated in a cracked component by any unknown self-equilibrating residual stress field. The limiting value of stress intensity factor can then be used to assess the acceptability of defects without the need for any residual stress data.