A constitutive model for elastic-plastic deformation under cyclic multiaxial straining

The yield criterion is interpreted as defining the metric of the stress space. Hydrostatic stresses correspond to null geodesics. The plastic strain increment represents a normal projection of the increment undergone by a certain scalar function (hardening function) which depends only on the distance between stress points. This establishes a how rule formally equivalent to the Prandtl-Reuss equations. Consideration of un-loading processes leads to the analysis of equivalent paths and to the definition of a generalized length or separation which provides a new representation of kinematic hardening.