Experimental investigation of the biaxial behaviour of an aluminum sheet

A biaxial testing apparatus was used to investigate the elastic-plastic behaviour of an 1145 aluminum sheet alloy. Flat cruciform specimens were deformed up to effective strains of approximately 0.15 in biaxial stretching, along seven different proportional strain paths. A finite element analysis of each test was carried out using four different phenomenological models of anisotropic plasticity. An iterative procedure was coupled with the numerical analyses in order to determine the anisotropic parameters in the various yield functions and thus obtain best fits to these functions. This method of numerically analyzing cruciform specimens leads to fairly accurate biaxial flow curves, as well as plastic work contours. The results are also compared with crystal plasticity simulations using a Taylor-type model.