Font Size: 

The rate and direction in which cracks grow during ductile fracture is influenced by both stress state and material properties, particularly plasticity and anisotropy. Previous work has shown that compressive surface residual stress fields such as those caused by shot-peening or burnishing can be used to modify the behaviour of a propagating crack. To exploit the controlling behaviour of residual stresses it is necessary to understand the interaction between secondary applied residual stresses and the crack tip stress field. Controlled plasticity burnishing has been used to create near 1-dimensional compressive residual stress fields in the surface of AA2024 in attempts to modify cracking behaviour. A direct optical method (Digital Image Correlation) has been used to characterise the crack tip displacement fields and subsequently calculate values of CTOA. A series of tests on specimens with continuous and intermittent compressive stress zones was used to explore the relationship between the crack tip and the applied residual stress.