Void Nucleation and Growth during Plane Strain Extrusion

A unit cell approach is pursued to investigate the effects of defects such as voids or rigid particles leading to voids on deformation and stress histories during plane strain extrusion processes. Particular attention is paid to the phenomenon of void nuclea tion from a rigid particle and the subsequent evolution of the void during an extrusion pro cess. Contact between the void surface and its nucleating particle is taken into account and is found to be important for such forming processes. It is observed that the aspect ratio of the void can change drastically. The stress and strain fields in the vicinity of such defects are significantly influenced by these distortions. Accordingly, the distortions play impor tant roles in determining the development of stress and strain fields and the possibility for coalescence of microvoids. In plane strain extrusions with voids present from the begin ning, concentrations of stress and strain fields due to distortions of void are observed to develop strongly while the void volume fraction decreases under the highly compressive loading.