Author:

Keywords:

sheet forming, hierarchical multi-scale modeling, texture evolution, plastic anisotropy, yield criterion

Abstract:

In the last decades, numerical simulation has gradually extended its applicability in the field of sheet metal forming. Constitutive modelling is closely related to the development of numerical simulation tools. The accuracy of the simulation results is given mainly by the accuracy of the material model. The accuracy of the phenomenological yield criteria is considerably influenced by the completeness and reliability of calibration data. In principle, the data should be representative for the stress state expected during the exploitation of the yield locus. Unfortunately, many of these stress states can be hardly investigated in mechanical testing setups. The Virtual Experimental Framework (VEF), which is based on the crystal plasticity ALAMEL model, is able to provide data points for virtually any stress or strain mode, thus the yield criterion can be calibrated in a much more comprehensive way. In this paper we present a new identification procedure of the plane stress BBC2008 yield criterion. We demonstrate that the new identification method is more robust and less sensitive to local minima of the objective function than the method based only on uniaxial and equibiaxial tension testing. This generic feature is particularly useful in case of any yield criteria that contain a large number of adjustable parameters. The BBC2008 yield criterion and its new identification procedure have been incorporated into the hierarchical multi-scale framework (HMS) that allows one to take into account evolution of the plastic anisotropy during sheet forming processes.