ON THE EFFECT OF PERSISTENT SLIP BAND (PSB) PARAMETERS ON FATIGUE LIFE

An examination of PSB data pertaining to the effects of an air-excluding environment and electric current on the fatigue life of polycrystalline Cu and 316 stainless steel in rotating bending reveals that the spacing and width of the PSBs are smaller throughout the fatigue test for those conditions which lead to increased fatigue life. Moreover, the life correlates directly with the square of the product of the surface.area fraction of PSB patches and the density of the PSBs contained therein. These results suggest that in these cases slip-homogenization is responsible for the increased fatigue life and not a consequence of it. A model is proposed for the observed relationship between slip band parameters and fatigue life, which is based on the strain concentration that exists at or near the PSB-matrix interface. The mechanisms by which an air-excluding environment or an electric current can increase slip homogenization are considered.