Large strain deformation field in machining

Measurement of strain field in the primary deformation zone is of major interest for development of machining as an experimental technique for studying phenomena associated with large strain deformation. A study has been made of the primary deformation zone and tool-chip interface in planestrain (two-dimensional) machining of metals. The use of a high-speed, charge-coupled device (CCD) imaging system in conjunction with an optically transparent, sapphire cutting tool has enabled characteristics of the deformation field such as velocity, strain, and material flow, to be obtained at high spatial and temporal resolution. The velocity distributions in the primary deformation zone and along the tool rake face have been obtained by applying a particle image velocimetry (PIV) technique to sequences of high-speed images of the chip-tool interface taken through the transparent tool, and of the primary deformation zone recorded from a side of the workpiece. A procedure is presented and demonstrated for determining the strain and strain rate distributions in the primary deformation zone. The measurements have provided data about the variations of velocity, strain rate, and strain, in and around the cutting edge and primary deformation zone; confirmed the existence of a region of retarded sliding in the region of intimate contact between tool and chip; and highlighted the occurrence of a region of dead metal ahead of the cutting edge when cutting with a negative rake angle tool.