Modelling and simulation of ductile fracture in aluminium alloys

Abstract

Reversed loading test were conducted on diablo specimens. The samples were first run in compression, before loaded in tension until fracture. The compression ranged from 0 to 40% pre-compression, in 10% increments. The specimens for the tests were machined from three different alloys; AA6060, AA6082.25 and AA6082.50 alloys, and samples from each tempered to three different tempers. These three tempers were the peak strength (T6), overaged (T7) and annealed (O).

Two materials AA6060-T6 and AA6060-T7 displayed a behavior which may be described as clustering of the material failure strains. Both AA6060 and AA6082.25 increases in ductility with increasing pre-compression, while AA6082.50 remains fairly constant. The AA6082.50 samples showed indications of a highly detrimental effect, presumably caused by the alloys large grain size.

Numerical tools were utilized in an attempt to simulate the trends observed in the experiments. These tools were the Gurson-Tvergaard porous plasticity model, with and without a modification upon the void development. Simulations were conducted with a modified representative volume element model, which can impose non-proportional loads and change the load direction during loading.

The simulations managed to fairly recreate the observed trends of AA6060 and AA6082.25, while the trends observed for AA6082.50 was not captured by the simulations.