Elastoplastic Constitutive Analysis with the Yield Surface in Strain Space

A COMMON APPROACH used in formulating elastoplastic constitutive equations is to partition the total strain rate into its elastic and plastic parts, and then develop the constitutive expression for the plastic strain rate using the concept of the yield surFace in stress space. An alternative approach is to partition the stress rate into its elastic and plastic parts, and then develop the constitutive expression for the plastic stress rate using the concept of the yield surface in strain space. Both of these approaches are used in this paper to derive and compare the final structures of the corresponding constitutive equations. It is shown that the preferable choice of the yield surface may be in either stress or strain space depending on the selected strain and conjugate stress measures utilized to construct the constitutive formulation.