Allowing for the influence of strain hardening in determining the frictional conditions at the tool-chip interface in machining

Abstract In a previous paper it was shown that, when the flow stress of material in the layer of intense plastic deformation in the chip adjacent to the toolchip interface varies with strain rate and temperature, the frictional conditions at the interface can be determined from minimum work considerations, the thickness taken up by this layer being such as to give combinations of strain rate and temperature which minimize the flow stress and hence minimize the rates of both frictional work and total work of chip formation. In this paper it is shown that, when in addition to strain rate and temperature the influence of strain on flow stress is taken into account, then the frictional conditions can still be determined by assuming minimum work. The influence of strain hardening is investigated by comparing results predicted both with and without strain hardening and a comparison is made with experimental results.