Ductility Transition and Cold Brittleness

Abstract

The occurrence of the change of fracture from ductile type to brittle one which is often called ‘cold brittleness’ is studied from the standpoint of the stochastic theory. In the present paper failure and fracture processes were treated as reaction rate process. The relation between deformation velocity, V_B, and the absolute temperature for brittle fracture was obtained as the form:
logV_B=−\fracQRT+c₀.
The effect of radius of notch on the transition, the size effect, and the scatter of the brittle strength were also interpreted from the same standpoint. In the case in which the Cottrell-Bilby mechanism for yielding, and nucleation process for brittle fracture, respectively, are regarded as rate-determining, similar results can also be obtained.