ABSTRACT
Since the plastic component of deformation occurs at constant volume, the plastic equivalent of Poisson's ratio (called the plastic contraction ratio) is numerically equal to 0·5. The actual contraction is the sum of an elastic component (with Poisson's ratio retaining its elastic value) plus the plastic component, so that for large plastic strains the effective ratio approaches 0.5 closely. Nevertheless, an elastic component always remains, associated, as noted previously, with the hydrostatic stress and (elastic) volumetric strain.
