TEMPORAL DISSIPATIVE STRUCTURES IN CYCLICALLY DEFORMED METALLIC ALLOYS

We have employed the modified Ananthakrishna non-linear dynamical mode l (proposed originally for the description of the Protevin-Le Chatelie r effect in monotonically deformed metals [1]) in order to understand the nature of temporal instabilities in cyclically deformed metallic a lloys. The model employs quasi-chemical reactions of multiplication, a nnihilation and positive feedback among the populations of mobile, imm obile, and Cottrell-type dislocations [1]. Three major types of loadin g have been simulated, namely, pure sinusoidal, ''creep fatigue'', and ramp loading. Computer movies of the temporal evolution of stress ser rations and dislocation densities have been produced as an aide for an alysis and illustration. It has been demonstrated that the model succe ssfully reproduces strain bursts and stress serrations in fatigued met allic alloys in terms of the underlying dislocations mechanisms, thus establishing the fundamental connection between micro- and macromechan ics of cyclic deformation.