The influence of finite geometry and material properties on mixed-mode I/II fracture of aluminium

Numerical calculations have been carried out to assess the influence of both finite geometry effects as well as material properties on mixed mode fracture of aluminium. These effects have been studied in close connection to experimental data for two aluminium alloys found in the literature. Interactions between the crack tip and the outer boundary have, for one of these alloys, been quantified in two ways. Firstly, by evaluating a number of non-singular stress terms in the linear elastic stress field expansion and, secondly, by comparative full body analyses. The implications on mixed mode fracture have been examined within the framework of a recently suggested effective plastic strain criterion. The other alloy was addressed in order to furnish a limited investigation concerning the sensitivity of this criterion with respect to material properties. The main conclusions arrived at in this paper are: (i) Boundary induced constraints may relocate the transition between different operative fracture modes and hence be responsible for scatter of experimental achieved under different testing conditions. (ii) The two alloys under consideration were predicted to behave very differently due to variations in the flow behaviour. Different behaviour was also confirmed by the experimental results.