The Appropriateness of Residual Stress Length Scales in Structural Integrity

Abstract

Residual stresses exist in most engineering components as a consequence of material processing and service history. It is well documented that such stresses can vary across a range of length scales and that different measurement techniques are sensitive to different components of the stress. Needless to say for reliable structural integrity assessment the residual stress field must be accurately quantified over the appropriate length scales. A classification system for sub-dividing residual macrostresses into long-, medium- and short-length scales is proposed to aid this process. A series of examples are presented that illustrate how the length scale for residual stress measurement and modelling studies should be determined in terms of the nature and size scale of the specific structural performance concern. The examples are related mainly to the residual stress field induced by a weld repair in a pipe that has been analysed by 3D finite element simulation techniques and measured by neutron diffraction.