Abstract
Based upon a measured distribution of tool-chip interface temperature in continuous turning, the transient distributions of temperature and thermal stress within the cutting edge, which may appear during the heating and cooling in interrupted turning operation, are obtained through the three dimensional finite element calculation. The calculated transient temperature is verified to be in good agreement with the temperature obtained experimentally. On the contrary to the common consent, it is found for tungsten carbide tool that the surface layer of the tool-chip contact zone is not cooled down lower than the interior even by water cooling, due to the higher rate of heat conduction within the cutting edge. Two fields of tensile thermal stress, which is almost uniaxial and parallel to the cutting edge, are found to be induced along the side and front cutting edges respectively. The tensile stress is caused mainly by the temperature distribution in planes parallel to the rake face, but not caused by the simple surface cooling as mentioned before. The magnitude of the calculated stress is also proved experimentally to be true and so small (about 300 MPa) compared with the fracture strength of tungsten carbide and the induced impact stress as well that it may not have a direct concern with the initiation of the thermal crack and the edge chipping.
