Papers by Author: Toshiyuki Obikawa

Abstract: The finite difference method was applied to simulate temperature distribution in the workpiece, cutting zone and tool in the orthogonal cutting process with multilayer coated sintered alumina tools. The analysis was conducted under different cutting speeds, while experiments were carried out to measure temperatures in different positions of the tool rake face using tools with built-in thin film thermocouples developed by the authors. The temperature distribution calculated along the rake face was consistent with experimental data. This proved that the finite difference modeling developed can be applied to the prediction of cutting temperatures of aluminum alloys for a range of ultra high cutting speeds.

Abstract: FEM cutting simulation predicts that the plastic shock waves are generated that develop the high levels of hydrostatic stress in the shear zone when cutting speed exceeds the plastic wave speeds of the workpiece material. The orthogonal impact cutting testing machine was developed to confirm this phenomenon experimentally. In the testing machine, two guide rails are set up in parallel. The cutting tool and the workpiece are installed on the blocks that slide on the rail. Each block connected with the piston in the air tube by the pushrod is launched by the expansion of compressed air, and is accelerated rapidly. When the two blocks passes each other, cutting is done. This paper describes the details of the developed impact cutting testing machine and experimental results of cutting a pure lead at cutting speed up to 65m/s.

Abstract: MQL (Minimum Quantity Lubrication) technology was applied to finish-turning of a nickel base superalloy, Inconel 718, with a PVD coated carbide tool with a super lattice coating of TiN/AlN. Cutting lubricant used for MQL was a biodegradable synthesis ester, which was supplied to the cutting point with compressed air from the both sides of flank and rake faces of the tool. At a cutting speed of 1.0 m/s and an air supply pressure of 0.4 MPa, MQL cutting showed longer tool life and better surface finish than both the dry cutting and wet cutting. When increasing the pressure of the air supply from 0.40 MPa to 0.60 MPa, however, the corner wear, the most predominant wear in all the cutting conditions in this study, increased. When the cutting speed was increased to 1.5 m/s, the tool life in MQL decreased drastically. These results suggested that when finishing Inconel 718, the special care must be taken for choosing the pressure of air supply and cutting speed. The obtained results provided a useful understanding of the complicated influence of MQL on the cutting performance of Inconel 718.

Abstract: Grinding temperature was analyzed considering heat generation by cutting with each abrasive on the wheel working periphery. A geometrical analysis of interference between the abrasives and workpiece gave the instantaneous cutting cross section, and visualized the surface topography generated by the time. Using the specific grinding energy and the instantaneous cutting cross sections, the instantaneous distribution of heat generation on the wheel-workpiece contact area was obtained. Then grinding temperature was calculated for a given heat partition into the workpiece. Since a cutting with an abrasive generated an impulse of heat flux, temperature distribution calculated for grinding carbon tool steel varied drastically, and very high local temperature or temperature spikes appeared.