Plastic anisotropy and the geometry of yield surfaces in stress space

In the context of classical anisotropic plasticity a general theorem is proved in relation to the pure geometry of convex yield surfaces in a six-dimensional Cauchy stress-space. The analysis subsequently focuses on particular yieldpoints where the local radius vector and surface normal represent coaxial tensors. Further detail is presented for a standard family of yield functions associated with states of generalized plane stress produced in sheet-forming operations. The overall objective is a comprehensive theoretical framework for the improved modelling of anisotropic plastic behaviour. (C) 2000 Elsevier Science Ltd. All rights reserved.