On the Theory of Stage-by-Stage Fatigue Failure of Metals upon a Complex Stress State

Resumo

This article presents a phenomenological model of brittle fatigue failure of metals and alloys upon proportional (simple) loading. The model is developed in the frames of physicomechanical approach as a set of hypotheses on the gradual development of defects in metals at various scale and structural levels (such as brittle micro- and macrocracks). On its basis, defining relationships are formulated for probability of failure with regard to defects of each level. Fatigue curves are obtained for various ultimate metal states as a consequence of the evolution of micro- and mesodefects, and the lifetime is determined with regard to a predefined level of accumulated defects. The results for structural steels are given as an example.