Simplified estimate of elastic–plastic J-integral of cracked components subjected to secondary stresses by the enhanced reference stress method and elastic follow-up factors

Abstract

This paper describes simplified methods to estimate the elastic–plastic J-integral, J, related to the crack growth rate in elastic–plastic situations. Estimating this parameter under general conditions entails costly detailed elastic–plastic FEA modelling of the cracked component concerned, and thus, some simplified methods that do not involve complex numerical calculations are required, particularly, for use in situations where plastic strains are produced by secondary stresses. For mechanical primary stresses, the reference stress method may provide reasonable estimates of J. The direct use of the reference stress method for secondary stresses, however, has not yet been fully established. The method presented in this paper is based on the enhanced reference stress method, which leads to more accurate estimates of J than the original method, and elastic follow-up factors for approximating the inelastic response of the component from the elastic FEA. The present method has been validated by performing detailed elastic–plastic FEA of cracked plates subjected to displacement-controlled loading and of a circumferentially cracked cylinder subjected to thermal loads.