On the Uniqueness and Stability of Endochronic Theories of Material Behavior

Abstract : Endochronic models represent the difference between the loading and unloading behavior of materials without employing the classical plasticity concept of a yield condition. In this report such models are shown to violate Drucker's stability postulate in the small for a cycle, and the implications of this violation are discussed. In particular, some simple problems involving endochronic models are analyzed, illustrating the difficulties which can arise when such models are used, and leading to the conclusion that they are unsuitable for the numerical solution of mechanical problems. (Author)