Abstract

We present an application on springback of an anisotropic elastoplastic finite strain model. The computational procedure allows the sole use of internal elastic variables as it is fully hyperelastic. Based on the Lee-type multiplicative decomposition, which permits an additive solution in a logarithmic strain approach, it resolves the 'rate issue' by the employment of a corrector rate of elastic strains and its algorithmic implementation [1]. The associative nature and Clausius-Duhem inequality recover the formulation of Simo's isotropic strain-hardening particular case. Its application to metal and soft materials has been corroborated as it is also valid for anisotropic yield functions and for any anisotropic stored energy (linear and nonlinear in logarithmic strains) [2]. The computation of the stress-point algorithm is done using a simple backward-Euler scheme. Its validation has been performed by the implementation of the procedure into a subroutine which allows the user to compute benchmark models in the commercial program ADINA [3]. This permits to explore its usefulness in application for the numerical prediction of springback in thin sheet metal forming processes. The results are compared with both experimental and other authors' results. Moreover, many simulations were performed such as the draw-bending test, the unconstrained bending problem, the square cup or the 3DS warping benchmark.

Abstract

This publication is focused on comparing three different material hardening models i.e. purely isotropic, mixed hardening and purely kinematic hardening model for the simulation of forming operations. The influence of nonlinear strain paths is investigated using deep drawing and strip tensile bending experiments and their comparison with numerical simulations. This comparison enables us to determine which of the three material models is more accurate for forming operations. Subsequently, the complex nonlinear strain paths are analyzed using an analytical indicator developed at the Chair of Forming and Machining Process, TU Dresden [3], to predict the influence of kinematic hardening by comparing the experimental results with a combined material hardening model as well as a purely isotropic and kinematic material model. The analytical indicator illustrates the regions in deformed samples that are most affected by kinematic hardening and shows the difference in target values as a result of mixed and purely isotropic hardening law