On the duration of shock loading and yield strength

Abstract

Thermal atomic motion in a crystal is interpreted as a certain rapidly oscillating stress field called a fluctuation field. A fluctuation field theory is developed in the context of solid state physics and statistical physics. The theory is applied to the description of dislocation motion in a crystal at external stress lower than the threshold required for dislocation motion. The dislocation motion is thus due to the joint action of external and fluctuation stresses. The shock pulse duration at which stress fluctuations have no chance (with 0.99 probability) to reach the level required for dislocation motion is calculated. With this pulse duration, the material does not experience plastic deformation, whereas with a longer loading pulse at the same stress it does. The effect, i.e., the absence of plastic deformation with a short loading pulse, can be eliminated by increasing the stress in the pulse. This suggests that the material yield strength increases with decreasing the duration of shock loading.