Finite element anaysis of out-of-plane deformation in laminated sheet metals based on an anisotropic plasticity model

An anisotropic plastic constitutive model is applied to a three-dimensional finite element method based on the up-dated Lagrangian type formulation, and out-of-plane deformation of the laminated sheet metal which comprises different materials of stainless steel sheet and Al sheet is analyzed. The constitutive model involves a fourth order tensor in its representation, by which not only the initial orthotropy but also the subsequent skewed-anisotropy can be predicted. The variation of anisotropic axis is taken into account with reference to the kinematic relationship of the axis before and after the deformation. The conventional laws of both a power formula for work-hardening and a normality rule for plastic flow are employed in the model. Before the analysis, simple tension tests in various directions are performed to identify the anisotropic material parameters of each component layer. Since the mechanical properties vary in the thickness direction, a fully three-dimensional scheme is adopted in the numerical analysis. Here, we examine the following three kinds of loading patterns; (a) curl in transverse direction under a simple tension, (b) deflection at longitudinal direction in unloaded state following the tension, and (c) strain localization behavior in large deformation regime. The effect of thickness rato is discussed from the viewpoint of the reduction of out-of-plane deformation, and the difference due to lamination angle is also examined to clarify the combination effect of planer anisotropy.