YIELD STRESS OF RANDOMLY PERFORATED SHEETS AND ANISOTROPIC YIELD FUNCTION

The influence of the distribution of voids on macroscopic mechanical p roperties is an important problem in plastic deformation of damaged ma terials. Since the distribution of voids in actual damaged materials i s heterogeneous, we have to evaluate the heterogeneous distribution of voids quantitatively We propose a new method using the voronoi tessel lation and the stereology to evaluate the heterogeneous distribution o f voids in this paper. In order to verify the availability of the new method, perforated sheets with randomly distributed holes are set up a s plane models of damaged materials and are examined under uniaxial te nsion. Mechanical properties of perforated sheets are estimated by ani sotropic yield function and the relationship between distiribution of holes and macroscopic yield stress is investigated quantitatively. It is shown that the method is valid for evaluating the heterogeneous dis tribution of holes.