The Monkman-Grant relationship

Abstract

The interrelationships between the steady creep rate e^·_s, time t_f to fracture and strain e_f to fracture are usually characterized in terms of Monkman-Grant relationships or their modifications. The objective of the present paper is to rationalized the modified Monkman-Grant relationship (e^·_st_f/e_f=constant) on the basis of the intergranular creep fracture model. A generalized intergranular cavity growth model which allows for varying degrees of matrix constraint on cavity growth has been developed for this purpose. The variation of the modified Monkman-Grant constant C_MMG with applied stress predicted by such a model corresponds extremely well with the variation of C_MMG with stress observed in the literature. The model also explains why C_MMG correlates the data better than the originally proposed Monkman-Grant constant.