An assessment of the effects of prestrain on upper shelf fracture toughness

Abstract

The effects of prestrain on the fracture toughness of steels are examined by using a simple cumulative damage model of microvoid growth and coalescence. First the effects of a shear prestrain on the mode III toughness at a single temperature are calculated in order to obtain guidance on how best to approximate the stress—strain curve after pre-strain. Then the models are used to examine the influence of a uniaxial pre-strain on the values of mode I toughness on the upper shelf. The mode I analyses require crack tip blunting solutions, and it is demonstrated that an approximate blunting solution enables the models to be applied readily. Numerical results for various amounts of pre-strain are calculated by taking material properties typical of an A533B steel. It is found that the effects are generally small for the material properties considered.