Effect of cyclic deformation on the resistance of a material to brittle failure

A physicomechanical model is suggested for determining the critical brittle failure stress S_c in statically and cyclically deformed material. The model is based on ideas about retardation of microcracks in a deformed substructure which changes during material loading. The effect is determined by experiment of prior cyclic material deformation on resistance to cleavage. The calculated dependence of S_c on the Odquist parameter is compared with the experimental results obtained. Model ideas about the effect of material substructure on brittle failure are confirmed by fractographic studies. Unstable fatigue crack growth is studied on the basis of models for brittle and fatigue failure of BCC-metals.Translated from Problemy Prochnosti, No. 1, pp. 14–21, January, 1991.