A Molecular Dynamics Simulation Study of Material Removal Mechanisms in Vibration Assisted Nano Impact-Machining by Loose Abrasives

摘要

Vibration assisted nano impact-machining by loose abrasives (VANILA) is a novel nanomachining process to perform target-specific nano abrasive machining of hard and brittle materials. In this study, molecular dynamic (MD) simulations are performed to understand the nanoscale material removal mechanisms involved in the VANILA process. The simulation results revealed that the material removal for the given impact conditions happens primarily in ductile mode through three distinct mechanisms, which are nanocutting, nanoplowing, and nanocracking. It was found that domination by any of these mechanisms over the other mechanisms during the material removal process depends on the impact conditions, such as angle of impact and the initial kinetic energy of the abrasive grain. The transition zone from nanocutting to nanoplowing is observed at angle of impact of near 60 deg, while the transition from the nanocutting and nanoplowing mechanisms to nanocracking mechanism is observed for initial abrasive kinetic energies of about 600-700 eV. In addition, occasional lip formation and material pile-up are observed in the impact zone along with amorphous phase transformation. A material removal mechanism map is constructed to illustrate the effects of the impacts conditions on the material removal mechanism. Confirmatory experimentation on silicon and borosilicate glass substrates showed that all the three nanoscale mechanisms are possible, and the nanoplowing is the most common mechanism. It was also found that the material removal rate (MRR) values are found to be highest when the material is removed through nanocracking mechanism and is found to be lowest when the material removal happens through nanocutting mechanism.