FEM Investigation of Phase Transformation in Vibration Assisted Nano Impact Machining by Loose Abrasives (VANILA)

In this paper, a numerical study of a nanomachining process, Vibration Assisted Nano Impact machining by Loose Abrasives (VANILA), has been conducted. In the VANILA process, an atomic force microscope (AFM) is used as a platform and the nano abrasives (diamond particles) are injected in slurry between the silicon workpiece and the vibrating AFM probe. The vibration of the AFM probe generates kinetic energy for the abrasives to impact the silicon workpiece and result in nanoscale material removal. In addition, silicon usually experiences phase transformation when subject to high pressure at nano-scale. The commercial Finite Element Method (FEM) software package Abaqus is employed to simulate the phase transformation experienced by the silicon workpiece in this VANILA process under different machining parameters such as impact speed, impact angle and coefficient of friction between the nano-abrasive and silicon workpiece. It is found that the machining parameters (impact speed, impact angle, and coefficient of friction) have substantial influence on the phase transformation of silicon workpiece in the nanomachining VANILA. Phase volumes for Si-VII, Si-VIII, and Si-X increase as the impact speed increases from 100 m/s to 200 m/s. Phase volume of Si-X increases as the friction coefficient increases. For Si-VII and Si-VIII, the phase volumes decrease as friction coefficient increases from 0.05, 0.3 and 0.5. In addition, the phase volumes for Si-VII, Si-VIII, and Si-X usually increase as the impact angles increases from 20 degrees to 90 degrees. However, for impact speed of 150 m/s and frictional coefficient of 0.05, the Si-VII phase volume increases first as impact angle increases from 20 degrees to 70 degrees and then decreases as the impact angle increases from 70 degrees to 90 degrees.