Theoretical and experimental investigations on phase difference in ultrasonic elliptical vibration cutting of tungsten alloys

Abstract

Ultrasonic elliptical vibration cutting (UEVC) has been established as a unique method for achieving ultra-precision machining of tungsten alloys. In this paper, a multiple factor UEVC surface creation model using the center of diamond tool edge as the characteristic point is developed. The effects of phase difference between two phase vibrations on the residual height of the machined surface, while the tool-workpiece contact rate and tool mean speed are quantitatively analyzed. Subsequently, FE simulation is conducted to examine the impact of phase difference on the tool-workpiece separation behavior, cutting force, cutting temperature, and strain rate in the cutting zone of UEVC. Furthermore, UEVC experiments are conducted on tungsten alloys with different phase differences using a self-developed UEVC system, and machined surface integrity and chip morphology are measured. The results indicate that an increase in phase difference not only significantly increases the strain rate, allowing for plastic removal mode of tungsten alloys in UEVC, but also reduces the residual heigh, further improving the machined surface quality with a surface roughness Ra reaching to 32 nm. The intensified plastic deformation of the material leads to an increase in the dislocation motion rate, which in turn increases the Pomeron force, dislocation increment, and enhances the surface dislocation density, hardness, and residual compressive stress of tungsten alloys. These findings provide a basis for optimizing UEVC of tungsten alloys.