Kinematical characteristics of two-dimensional vertical ultrasonic vibration-assisted grinding technology

The ultrasonic vibration-assisted machining (UVAM) technology is increasingly attractive for the ultraprecision machining of brittle materials. But the machining mechanism for UVAM is still unknown, especially for the grinding process. In this paper, the kinematical characteristics of two-dimensional vertical ultrasonic vibration-assisted grinding (UVAG) technology are investigated. A consistent physical modeling of the grinding process with ultrasonic vibration assistance is established firstly, which is based on the interaction of individual grinding grains with the workpiece. Then the kinematical equation is deduced, and so does the velocity and acceleration of a single abrasive grit relative to the workpiece in UVAG. The kinematics of a single abrasive grit during 2D UVAG is simulated for the perpendicular vibration mode. The results show that the relation motion of an abrasive grit is altered significantly with the assistance of ultrasonic vibration, and the grinding path is elongated, which will increase the material removal rate per abrasive grit. The most interesting result is that the relative velocity of an abrasive grit in UVAG is changed slightly when compared to that without ultrasonication. While the relative acceleration in UVAG is increasing tremendously, especially for high frequency ratio (a ratio between the vibration frequency to the rotation frequency) condition. This result means that the ultrasonic vibration assistance can introduce a huge acceleration impact on the material in the machining deformation zone by the grinding grit, and may change the material removal mechanism of grinding. Thus it can do a favor to the precision machining of brittle materials. The UVAG experiment of polysilicon shows that the surface roughness is improved and the normal and tangential grinding forces decrease with the increasing of applied voltage, while the axial grinding force increases. The results indicate that the assistance of ultrasonic vibration can result the change of the grinding mechanism of brittle material.