Effect of Strain Rate Sensitivity and Strain Hardening Exponent of Materials on Plastic Strain Distribution and Damage Accumulation During Equal Channel Angular Pressing

摘要

Flow pattern and plastic strain distribution inside deformed sample are two important factors governing the microstructural uniformity of equal channel angular pressing (ECAP) processed materials. In the present study, the effects of strain hardening exponent (n) and strain rate sensitivity (m) on the characteristics of the ECAP process were investigated by the aid of finite element simulation. Investigated parameters are plastic strain distribution and accumulated damage. In addition, contour maps were generated to demonstrate mutual effects of n and m coefficients on the uniformity of plastic strain and maximum damage developed on ECAPed samples. Results showed that the effect of m and n values on plastic strain is more pronounced at downside regions of sample compared with upper regions. Also, at a constant strain rate sensitivity, the plastic strain is increased with decreasing strain hardening exponent due to the small corner gap formed in outer region of the intersecting area of two channels. Increasing strain rate sensitivity at constant strain hardening rate is accompanied by the formation of severely deformed area near downside of sample which leads to non-uniform strain distribution.