Application of Theory of Wedge-Crack Growth to Rupture Times in Hot Torsion

Abstract

The wedge-crack growth model proposed by Williams for creep rupture has been modified by inclusion of the Cottrell criterion for crack instability. By combining this model with empirical relationships between strain rate, grain-boundary sliding rate, stress, and grain size, it can be applied to conditions of high-strain-rate deformation where the grain size may be established by dynamic recrystallization. Comparison of predicted rupture times with experimental results obtained in torsion indicates that control of ductility by wedge-crack growth is reasonable under these conditions and that the occurrence of dynamic recrystallization significantly decreases crack growth rates.