FATIGUE FRACTURE AT NORMAL TEMPERATURE OF PREVIOUSLY DEFORMED ALLOYS

1. The character of the changes of the current bending of specimens indicate definite stages in the development of the fatigue process in metals. Here an increase of the bending of specimens after the stabilization stage corresponds to the formation of an about. 1.0 mm long crack on its surface. At a ratio ℓcr/d = 0.15 bending of specimens increases sharply in all investigated materials. 2. The effect of preliminary strain of specimens on the kinetics of their fatigue failure depends on the type of material, its initial conditions, and the amplitude of the stress applied. 3. Preliminary hardening of annealed M1 copper specimens retards the development on the fatigue process (increases the time preceding crack initiation, reduces the rate of its propagation) and increases the cyclic life. 4. The dependence of cyclic life on preliminary stretching of M1 hard copper (from 0 to 13%) and of half-hard L63 brass (from 0 to 25%) is nonmonotonic and has a maximum, shifting into the low degrees of strain with decreasing amplitude of the stress applied. © 1991 Plenum Publishing Corporation.