A Statistical Model ofMicrovoids Evolution in Rate Sensitive Ductile Materials-Solution for High Stress Triaxiality Cases

Statistical behavior of the microvoidsʹ evolution process in ductile materials is investigated in this article with the emphasis on the discussion about the effect of strain rate-sensitivity of the matrix material. The viscoplastic constitutive relation of the matrix material is assumed to have the overstress form proposed by Perzyna. In the case of high stress triaxiality, the nucleation rate and the growth rate of microvoids are discussed. Then, based on the balance law of microvoidsʹ number density, differential equations governing the evolution of microvoids are obtained and solved with the help of the two kinetic equations describing the nucleation rate and the void growth rate. Thus, the size distribution functions of microvoids are found from the theoretical analysis, and the effect of strain rate-sensitivity of the matrix on the evolution of microvoids is examined. The present theoretical prediction provides a reasonable explanation of the experimental phenomena observed by previous researchers.