FEM and a microstructure based work hardening model used to calculate forming limit curves

ABSTRACT: This work considers representation of the localised necking phenomenon in non-linear finite element simulations and related sensitivity to constitutive modelling approaches and parameter identification methods. Forming Limit Curves of an AA3103 alloy have been predicted based upon non-linear Finite Element (FE) simulations of a patch of shell elements with a random, Gauss-distributed thickness subject to membrane stretching along proportional deformation paths. Results obtained with the microstructure based work hardening model of Nes and co-workers are compared with the use of a phenomenological Voce-type hardening curve, both combined with the yield criterion Yld89 of Barlat and Lian and the associated flow rule. The parameters of the yield criterion have been fitted to crystal plasticity calculations and to experiments. The resulting Forming Limit Curves (FLCs) are compared to experiments as well as to prediction by the classical Marciniak and Kuczynski theory. Key words: forming limit, microstructure, texture, yield locus, work hardening, FEM