Stress dependences of dislocation velocities

Abstract

Motion of a dislocation through a crystal is treated as comprising jumps past relatively disperse obstacles and viscous glide through the clear lattice between obstacles. Well-known expressions for dislocation velocity dependence upon stress for these two types of motion are combined in series to obtain an expression for overall velocity. This expression is investigated in terms of three parameters: stress, drag ratio and limiting velocity ratio. It is shown that under some circumstances no relationship exists between average velocity and parameters determinable from ultrasonic attenuation. Furthermore, this treatment qualitatively reconciles some apparently anomalous dislocation velocity observations with a fairly simple theory of dislocation motion.