Minimum work as a possible criterion for determining the frictional conditions at the tool/chip interface in machining

An approximate theory of machining is described in which the average shear flow stress in the plastic zone in the chip adjacent to the tool/chip interface, which is allowed to vary with strain rate and temperature, is used as the friction parameter and this is shown to be far more effective than the normally used average coefficient (or angle) of friction. It is proposed that the average thickness of the tool/chip interface plastic zone is determined by a minimum work criterion, its value being such that for given cutting conditions the average shear flow stress within the plastic zone will be minimized, thus minimizing both the frictional and total work done in chip formation. A comparison is made between results predicted by assuming minimum work and experimental results.