Relationship between Acoustic Emission and Dislocation Kinetics in Crystalline Solids

Abstract

The sounds emitted from single crystals of irradiated LiF, annealed LiF, NaCl, and zinc during constant‐strain‐rate compressive deformation were recorded and analyzed. The acoustic emission consisted of discrete pulses of varying amplitudes, and the rate of pulsing changed with total strain during the continuous deformation experiments. A reasonable correlation between acoustic‐emission pulse rate and the rate of change of mobile dislocation density was found and led to the conclusion that the pulses were generated by dislocation breakaway from pinning points. The measured dislocation densities were used to estimate that several thousand centimeters of dislocation line length had been involved in the generation of an individual acoustic pulse. It was suggested that some 10⁵−10⁶ segments of dislocation line were involved in a cumulative fashion due to the stimulating effect of the moving acoustic wave on bowed dislocation segments. The concept of stimulated dislocation breakaway from pinning points appeared to be a reasonable model to explain the acoustic results of this study and may provide the fundamental basis for explaining discontinuous plastic flow, jerky dislocation motion, slip line broadening, and other features of crystal plasticity.