The Effect of Hydrostatic Pressure on the Cleavage Fracture of Polycrystalline Materials

Abstract

The dislocation pileup model of Stroh and the wall splitting model of Stroh and Friedel have been used to calculate the effects of hydrostatic pressure on the fracture stress of polycrystalline metals. For each model, the three critical stages of fracture, nucleation, propagation through a grain, and the propagation across a grain boundary have been considered in turn. The variation of the critical cleavage‐crack orientation with respect to the tensile axis has been shown to be a function of the hydrostatic pressure. The fracture stress depends upon the grain size and at high pressures where grain boundary propagation is the critical stage, a d^−1/2 dependence was found. This analysis both predicts and provides a physical interpretation of the ductility‐transition curve.