Plastic spin associated with a non-normality theory of plasticity

A plasticity model using a vertex-type plastic flow rule on a smooth yield surface for an anisotropic solid has been proposed recently. This model is here completed by incorporating the effect of plastic spin. Simple shear wi th a large shear strain is one of the hardest tests on finite strain anisot ropic plasticity models, and it is here shown which plastic spin expression is needed to avoid unrealistic oscillatory behavior of the shear stress un der large shear strains. The idea of using non-normality with a smooth yiel d surface originates from a recent proposal of using an abrupt strain path change to determine the subsequent yield surface shape. For this method bot h polycrystal plasticity calculations and experiments have shown a vertex-t ype response on the apparently smooth yield surface. (C) 2001 Editions scie ntifiques et medicales Elsevier SAS.