A new anisotropic constitutive model was proposed. It was further implemented in FEM with NICE scheme and overviewed its flexibility sheet behaviour during forming.
The paper deals with constitutive modeling of highly anisotropic sheet metals and presents FEM based earing predictions in a round cup drawing simulation of highly anisotropic aluminum alloys where more than four ears occur. For that purpose the BBC2008 yield criterion, which is a plane-stress yield criterion formulated in the form of a finite series, is used. Thus defined criterion can be expanded to retain more or less terms, depending on the amount of given experimental data. To be used in sheet metal forming simulations the constitutive model, derived in accordance with the associated flow theory of plasticity, has been implemented in a general purpose finite element code ABAQUS/Explicit via VUMAT subroutine, considering alternatively different number of parameters in the BBC2008 yield criterion, where possible number of parameters are any multiple of number 8. For the integration of the constitutive model the explicit NICE (Next Increment Corrects Error) integration scheme has been used. The CPU time consumption for an explicit deep drawing simulation, which is based on the developed constitutive model, has been proven to be, due to effectiveness of the used integration scheme, fully comparable to the performance experienced when the simulation is performed with ABAQUS built-in constitutive models and implicit integration schemes. Two aluminum alloys, namely AA5042-H2 and AA2090-T3, have been considered for a validation of the constitutive model. The respective BBC2008 model parameters have been identified for both alloys with a developed numerical procedure, based on a minimization of the specified cost function. For both materials, the simulation predictions based on the BBC2008 model prove to be in very good agreement with the experimental results. Further, in order to show the flexibility of the BBC2008 model in modeling of highly anisotropic sheet metal response, we have introduced a highly anisotropic fictitious material which yields, according to the theory, twelve ears in cup drawing. As it is shown in the paper the BBC2008 model is able to predict twelve ears in cup drawing simulation with the formulation containing 16 parameters for anisotropy description only. The flexibility and accuracy of the constitutive model together with the robust identification and integration procedure guarantee the applicability of the BBC2008 yield criterion in industrial applications.
VRH, Marko, HALILOVIČ, Miroslav, STARMAN, Bojan, ŠTOK, Boris, COMSA, Dan-Sorin, BANABIC, Dorel. Capability of the BBC2008 yield criterion in predicting the earing profile in cup deep drawing simulations, European Journal of Mechanics - A/Solids, 2013