The effect of stress biaxiality on fracture initiation at a blunt flaw

Abstract

From the basis of the cohesive process zone representation of the micro-mechanistic processes that are associated with fracture, the author has, in earlier work, derived a blunt flaw fracture initiation criterion for situations where the process zone size s is small compared with the flaw depth (length) and any other characteristic length, e.g. remaining ligament width, of a configuration, other than the flaw root radius ρ. The criterion gives the critical elastic flaw tip peak stress σ pcr in terms of the process zone material parameters and geometrical parameters, and was derived using a two-extremes procedure, whereby the separate and exact solutions for small and large s/ ρ values are blended together to give an all-embracing relation that is valid for all s/ ρ values. For a wide range of flaw geometry parameters and loading scenarios, it has been demonstrated that σ pcr approximately depends on only one geometrical parameter: ρ. In this paper, we show that in the presence of transverse stresses in the direction of the flaw, i.e. with biaxial stress situations, σ pcr depends, in a coupled manner, on the flaw shape and the degree of stress biaxiality.