Contact conditions at the chip-tool interface in machining.

摘要

An experimental study has been made of the chip-tool interface with the objective of realizing an improved understanding of the contact conditions. Cutting of a range of non-ferrous workpiece materials, both pure metals and alloys, have been performed using transparent sapphire tools. Direct images of the chip-tool interface in both the visible and infra-red (IR) spectral ranges have been obtained at high temporal and spatial resolution. The observations suggest two distinct models for the chip-tool contact conditions along the rake face. The first of these is characterized by a zone of stagnant material in the region adjoining the cutting edge followed by a zone of intimate sliding. Retardation of the chip underside occurs in this zone of intimate sliding. The second model, widely applicable to aluminum alloys, is characterized by an expanding zone of stagnant material beginning from the cutting edge.; The direct observations have been extended to study the action of a cutting fluid along the chip-tool interface. The results show that the fluid reduces the chip-tool contact region, prevents the expansion of the zone of stagnant material beyond the intimate contact region, and eliminates the zone of metal deposit in the intermittent contact region. In modulation-assisted machining, the cutting fluid is shown to be active in the region of the intimate contact adjoining the cutting edge; this is a consequence of the fluid penetrating into this region when the chip-tool contact is broken during each cycle of modulation.; The rake face temperature field, another aspect of the chip-tool contact condition, has been measured using dual-wavelength IR pyrometry. The characteristics of the measured temperature field, its correlation with the chip-tool contact condition and its dependence on cutting conditions are explored. The measurements show that the zone of high temperature coincides with the zone of metal deposits observed on the tool rake face and that the temperature gradient in the chip flow direction depends on the chip-tool contact condition.; The findings of the present study enhance our understanding of the chip-tool contact condition and provide impetus for the development of new and improved models of the contact region.