Investigation of the role of dislocation motion in the generation of acoustic emission from metal cutting

Abstract Due to the very high strain rates and temperatures encountered in metal cutting, opposing viscous damping forces are the dominant mechanism governing dislocation movement, which is the main mechanism for plastic deformation in metals. However, although viscous damping governs the physics of metal deformation, it is concluded that the detected high frequency acoustic emission (AE) signals arising from metal cutting can only be generated owing to the interaction between moving dislocations and obstacles. This would appear to be the reason why the amplitude of the AE signal cannot be directly related to the cutting power, since it arises from a different generation mechanism. As a result, a qualitative model relating the AE to basic deformation parameters was derived, in which the power of the AE is expected to increase with strain and strain rate, but to decrease with temperature. In addition, the frequency content of the AE is expected to increase with strain rate, to decrease with temperature, and to remain unchanged with strain. These results were validated against data from experimental cutting tests and seem to suggest that the generation of the AE during metal cutting is very heavily dependent on dislocation motion.