The Combined Effects of Residual Stress and Warm Prestressing on Cleavage Fracture in Steels

Residual stresses (RS) appear in most engineering structures, either because they have been deliberately introduced or they are a by-product of the manufacturing process. Since RS play an important role in increasing and decreasing the possibility of failure, it is necessary that their effect on the integrity of the structure is understood. In the presence of RS, many components are subjected to a variety of prior loading histories. One such case is often associated with warm prestressing (WPS), where the component is subjected to some form of preloading at a temperature higher than operating conditions. The aim here was to explore how WPS, together with RS, might influence the subsequent fracture conditions for cleavage fracture. First, a model for WPS is reconsidered so that it could be used for Monte Carlo (MC) simulations of WPS. Results are compared with experimental data. The model is then adopted to consider the effects of long range residual stress created in fracture samples through an initial misfit. This is done by fitting the sample into a structure, with the new system subsequently being subjected to WPS conditions. The advantage of the system model is that it facilitates the systematic prediction of the interrelationship and interaction between the applied loads and the misfit (or residual) stresses. The results show that tensile RS act to enhance the effects of WPS, and the WPS cycle, in itself, can act to relax the initial residual stress.