Extremal paths in progressive plasticity

A global minimum condition is established for a certain class of quasi-static processes of progressive crushing. The structures considered are thin-walled shells made of rigid/plastic material with a convex yield surface. An appropriate minimum condition is derived by considering energy trajectories for a class of steady-state and quasi steady-state processes. Plane isochoric deformations are subsequently studied in detail in order to demonstrate that actual crushing processes follow the deformation path at which the total expenditure of work is a global minimum. Copyright (C) 1996 Elsevier Science Ltd.