THEORY OF THERMALLY ACTIVATED PROCESSES IN BRITTLE STRESS-CORROSION CRACKING

The application of reaction kinetics theory to the thermally activated processes of stress corrosion cracking in brittle materials shows that the energy barrier of Region III is in parallel with the consecutive barrier system of Regions I and II. The rate constants, associated with each of the three Regions, are the resultants of several combined mechanisms effecting crack propagation: in Region II surface chemical reactions and in Regions I and III the formation and sideways spreading of double kinks in the crack front. The criteria that control the effectiveness of the dominating mechanism are defined by the interrelations between the activation free energies and the activation volumes. The consideration of backward activation leads to the rigorous description of the threshold effect. © 1979.