Forming limits prediction of FCC sheet metal adopting crystal plasticity

A rate-dependent crystal plasticity constitutive model together with Marciniak-Kuczynski(M-K) approach is employed to perform numerical simulations of forming limits diagrams(FLDs). An initial imperfection in terms of a narrow band is adopted to initialize the sheet necking. Homogeneous deformations inside and outside the band are assumed and the enforcement of compatibility and equilibrium conditions is required only on the band interface. Constitutive computations are carried out on two aggregates of FCC crystal grains, with each representing one of the two zones, respectively. Taylor homogenization assumption is employed to establish the link of stress between single crystal and polycrystal, and to derive an average response of the aggregates. The same initial texture is imparted to the two aggregates and their evolutions will be traced in the necking process. Factors affecting the FLDs prediction, such as imperfection intensity, initial texture, strain rate sensitivity and crystal elasticity will be taken into account. The above procedure will be applied to an annealed aluminium alloy sheet metal.