THE RESEARCH OF A TEMPERATURE FIELD WHEN TURNING WITH VIBRATIONS SUPERPOSITION

The temperature of a cutting process influences significantly the quality of the treated surface and the performance of a tool. The rational use of vibrations, including the ultrasonic frequency vibrations is one of the means to improve the efficiency of a cutting process. However, there are no analytical studies of the temperature of turning with vibration superposition. It was accepted that the total heat output power when turning was equal to the sum of heat output powers of sources aroused as the result of the transition to the heat of work of deformation and work of friction forces on the leading and flank surfaces of a tool. The paper presents the mathematical dependences for calculation of the components of the total power of heat release. The authors took into account that the yield stress, which determines the cutting and frictional forces on the contact surfaces of a cutter, workpiece, and chip, depends on the temperature in the plastic deformation area. The law of distribution of thermal power density on the shear plane was taken as uniform; the combined law was adopted on the surface of the contact of a chip with the front surface of a cutter; the asymmetric normal law was adopted on the surface of the contact of a cutter with a workpiece. The authors gave the dependence for the calculation of the cutting depth when applying vibrations in the direction perpendicular to the treated surface. Heat exchange at the boundaries of the objects contacting with the process liquid or air is given in the form of the Newton-Richman law. The thermal conductivity equations of the contacting objects were solved in combination with the general boundary conditions in the contact zone using the finite element method. The method of calculation based on the discrete analogs of the heat conduction equations is implemented in the original programs. The authors compared the results of calculation of temperatures when turning without the vibrations superposition with the experimentally obtained results, in this case, the discrepancy between the calculated and experimental values does not exceed 10 %. The simulation of the turning process with the superposition of ultrasonic vibrations showed that the main component of the cutting force Pz reduced by a mean of 11 %, the maximum temperature in the zone of contact of the back surface of a cutter with a workpiece reduced by 20 %, and the maximum temperature in the zone of contact of the front surface of a cutter with a chip reduced by 26 %.