The Facet Method for the Description of Yield Loci of Textured Materials

Abstract

A new approach, the Facet method, to describe the yield loci of textured materials is proposed. It is based on an analytical expression of plastic potentials in strain rate space of which the parameters are identified by fitting to the predictions of multilevel micromechanical models. The chief advantage of this new formulation is that it automatically ensures convexity of the anisotropic yield loci. Furthermore, the approach can be easily extended to formulate stress-space based plastic potentials. This is quite an efficient property especially for the implementation in finite element codes that are used for simulation of industrial metal forming processes because it offers a significant reduction in computation time needed for yield checks compared to that of strain rate space based plastic potential expression. In our work, the Facet method is applied in combination with the Taylor-Bishop-Hill micromechanical model, with both strain rate as well as stress space formulations, to various model textures and industrial materials. In this paper, the equipotential surfaces and the corresponding yield loci will be presented for a sharp rotated-cube model texture and a moderately sharp industrial grade IF steel sheet texture. A brief quantitative assessment of the new method with respect to the original model data will be presented.