A Dislocation-Model of Limit Strain Prediction in Aluminium Sheet Metals under Biaxial Deformation

The development of strain inhomogeneity and fracture events are influenced to a great extent by the local properties of the microstructures. The effect of dislocation hardening is incorporated into a rate sensitive crystal plasticity model for the prediction of limit strain in biaxial deformation. The assumption of a pre-existing surface groove defect in the Marciniak-Kuczynski method of limit strain prediction is relaxed, and the surface defect is seen to arise from the differential deformation between two colonies of grains with different crystallographic orientations. With the use of a modified localized necking criterion which incorporates the changes in the dislocation density, the limit strain of a sheet metal with two ideal orientations is predicted.