Material behaviour in conditions similar to metal cutting: flow stress in the primary shear zone

This paper is aimed at determining the flow stress in metal cutting. A major problem in finding the flow stress is the intense circumstances under which deformation takes place in the chip root. Large deformations are imposed on the workpiece material at high speed in a very small area. This results in mechanical material behaviour far removed from that encountered in conventional material tests. Therefore, to determine the flow stress in cutting, it is necessary to determine the conditions under which the material is being deformed firstly. Hereafter, a material test has been developed that can be used in conditions similar to those found in cutting. Based on the obtained information on the deformation conditions in cutting as found in previous work [J. Mater. Process. Technol, in press], a split Hopkinson pressure bar (SHPB) facility could be constructed for mechanical testing of materials at high strain rates and elevated temperatures. From measurements with this SHPB facility, it appeared that both strain rate and temperature have a considerable influence on the flow stress of metals. Combining the information on the deformation conditions in the primary shear zone with the measured constitutive behaviour, the flow stress of the metals in the primary shear zone is found.