High-Strain-Rate Investigations,with Particular Reference to Stress/Strain Characteristics

Abstract

Cottrell has suggested that a given value of strain rate may be termed ‘high’ or ‘low’ in relation to some molecular process of deformation such as the vibration of an atom or a molecule in a cell bounded by its neighbouring atoms or molecules. Thus, when considering strain rates at microscopic levels a strain rate of 10⁶ S^-l at a plastic wave front may be considered as low, whereas at an elastic wave front, where the stress intensity may be of the same order of magnitude, a strain rate of 10¹² S^-l is considered as high. At a shock-wave front, where the stress intensity is very high in comparison with the yield point, the strain rate may approach or even exceed this latter value. The strain rate of 10¹² S^-l has been shown to be the upper limit attainable in tension when the interatomic bonds are strained to breaking point during the period of one atomic vibration. However, the strain rates considered here are those taken on a macroscopic level.