Modelling of Prestrain Effects on Fracture Using Local Approach Methods

The effects of load history on component fracture behaviour have been studied at length in terms of the generation and resulting influence of residual stresses. Despite this, the effect of plastic strain history, separate from the generation of residual stresses, is still not clearly defined. This work presents an investigation into the effect of accumulated strain on subsequent fracture behaviour. The effects of load history on low temperature cleavage fracture are modelled by means of a number of local approach methods, accounting for variations in stress and strain throughout the component’s load history. Prior strain was found to reduce the mean fracture load of 20mm thick CT specimens, irrespective of the level of room temperature strain applied. Local approach methods, calibrated to low and high constraint fracture data, were able to correctly predict a reduction in fracture load, although the exact magnitude of the reduced loads were not always correctly resolved. Further experimental data and further work on model formulation is needed to confirm the conclusions drawn here.