ANISOTROPIC YIELD SURFACES BASED ON ELASTIC PROJECTION OPERATORS

Although most materials are anisotropic to some extent, most yield sur faces are either chosen to be isotropic or to be a smooth anisotropic surface with no connection to the elastic anisotropic features. Here, the elastic projection operators obtained from the spectral decomposit ion of the elasticity tensor are used to define anisotropic yield surf aces with a yield surface defined for each of the projection operators . The advantages of the approach are (1) plastic deformation modes are associated with the elastic anisotropic behavior, (2) the spectral de composition of the tangent tensor is readily available for a bifurcati on analysis, (3) the composite yield surface has vertices which are th ought to be important for predicting plastic buckling, and (4) the con tributions to plastic deformations from each yield surface are uncoupl ed. The result is a theory that is actually quite simple but yet refle cts some of the observed features for materials to yield in specific m odes.