Plastic Deformation

Continuum models for yielding

· Experiments show that hydrostatic stress causes no plastic deformation.
· Plastic deformation results from the shear displacements in the sample under stress.
· The diagram shows an element of an isotropic continuum and the general stresses acting on it. In equilibrium, the element experiences no net force and no net torque.
· The stress tensor describing this state is symmetric about its diagonal and has the form shown:

From: Wyatt and Dew-Hughes,
"Metals, Ceramics, and Polymers,"
Cambridge (1974)