EFFECTIVE STRESSES IN CYCLIC DEFORMATION

Stress relaxation measurements showed that the relative magnitude of the effective stresses increases with cycling. For the explanation of these results, the mechanism associated with edge dislocation exhaustion and increasing screw dislocation activity is suggested. Stress relaxation measurements around various points of the hysteresis loop showed that the effective stresses are completely absent during the plastic deformation immediately after stress reversal. This is taken as an indication that dislocation gliding is strongly assisted by the back stresses. As the applied load increases after stress reversal, the effective stresses increase in absolute value as well as relative to the applied load. The suggested explanation of this is that plastic strain along the hysteresis loop is derived from mobile dislocations which change in number and also in character with increasing stresses. © 1979.