THE EFFECT OF DISLOCATION DRAG ON THE STRESS-STRAIN BEHAVIOR OF FCC METALS

The introduction of viscous drag into a simple thermally activated dislocation model for the low temperature plastic deformation of fc.c. metals leads to some surprising predictions about their stress strain behavior. One effect of dislocation drag is to produce a region of tensile instability at small strains for any strain rate. At sufficiently high strain rates there is no region of tensile stability. However, computation of a decreased strain for tensile instability at strain rates greater than 10(3) s-1, in opposition to experimental measurements, provides evidence that the strong upturn reported for the flow stress of copper is not caused by dislocation drag. The likely explanation is an enhanced rate of dislocation generation.