A New Method of Introducing Long Range Residual Stresses to Study Creep Crack Initiation

摘要

One of the many challenges in the behaviour of structures is to understand if the presence of residual stress plays an important role in contributing to failure of a structure operating at high temperature. A typical example is the reheat cracking, associated with the austenitic stainless steel welded components, where the presence of residual stress is seen as a major factor. A review of previous methods that introduce residual stresses into specimen indicated that a method that doesn't introduce microstructural changes during the generation of residual stresses should be sought. The purpose of this paper is to describe a new method of introducing long range residual stresses at high temperature. The method uses a three bar structure with an initial misfit introduced into the central bar to represent a long range residual stress. The rig was designed so that the induced residual stresses could be characterised easily without using time consuming residual stress measurement techniques. Initial results demonstrated that the magnitude and the interaction of the residual stress with the applied loading is a function of the initial misfit displacements and the relative stiffness of the components of the system. Additionally, the subsequent behaviour of the system, with and without the application of additional loading, is governed by (a) the degree to which the misfit is accommodated by plastic and creep strain and (b) the elastic follow-up provided by the system. The paper describes the design of a test rig and laboratory tests conducted to validate the method.