Corners in plasticity—Koiterʹs theory revisited

A general theory for plastic loading at corners is presented that includes Koiter’s theory as a special case. This theory is derived within a thermodynamic framework and includes nonassociated as well as associated theory. The non-associated theory even allows the number of potential functions to differ from the number of yield functions. The properties of the matrix of plastic moduli as well as of another important matrix are discussed in detail and hardening, perfect and softening plasticity are concisely defined. The existence of limit points is also discussed. The strain driven format turns out to be the most general. Moreover, consistent loading and unloading criteria are established for general non-associated plasticity. An explicit criterion for uniqueness is derived, and finally, some of the general findings are illustrated by means of specific plasticity formulations often encountered in practice. Copyright 0 1996 Elsevier Science Ltd