A less hypothetical perspective on rate-independent continuum theory of metal plasticity

In the framework of rate-independent theory of metal plasticity the hypothesis of maximum plastic dissipation is commonly applied to derive the associated flow-rule and to prove convexity of the yield surface in stress space. Alternatively, Drucker’s postulate of material stability may be used to prove convexity. Both hypotheses appear reasonable, but it is appealing to derive the basic framework for rate-independent metal plasticity without involving additional hypotheses.In the present article it will be shown that indeed both hypotheses can be dropped and an alternative way is established to derive the associated flow-rule and to prove convexity of the yield surface. It turns out that the associated flow-rule as well as the convexity of the yield surface are intrinsic features of the proposed theoretical framework.