OVERVIEW NO-89 - MECHANISM MAPS FOR CYCLIC PLASTICITY AND FATIGUE OF SINGLE-PHASE MATERIALS

Mechanism maps for strain-hardening and fatigue in single phase materials are introduced for isothermal cyclic deformation at constant amplitudes of plastic strain in tension-compression. The maps are drawn for single crystals and polycrystals in diagrams of plastic strain vs cycle number. The successive stages of structural evolution and cracking appear as two-dimensional fields. The dominant micro-mechanicals characeristics of each field can be described by modifications of the theory of two-phase materials. A more complete theory of the maps remains to be developed; but a partial prediction of the effects of temperature, strain-rate and crystal structure on the field pattern is already possible, of the lattice friction and cross-slip of screw dislocations are invoked. The maps give a unified view of the basic mechanisms of work-hardening and fatigue, and they provide useful criteria for design against fatigue. © 1990.