Experimental and simulation studies of abrasive particles impacting monocrystalline silicon in suspension thin film flow field of ultrasonic polishing

Abstract

In ultrasonic polishing (USP), when the gap between the polishing tool and workpiece is small enough, the suspension seeped into it can be considered as suspension thin film (STF). STF flow field provides a periodic oscillation condition for abrasive particles, which can improve abrasive particle cutting performance by changing its behavior. It is very effective for improving the polishing efficiency and surface quality of hard-to-machine materials. However, the interaction behavior of target material, STF flow field, and abrasive particle in USP has rarely been studied. In this paper, to fulfill a fundamental understanding of this field, the behavior of abrasive particles impacting monocrystalline silicon in STF flow field is investigated by experimental and simulation methods. At macro-level, through the study of ultrasonic amplitude, abrasive particle size, and polishing tool rotational speed in USP experiments, the positive role of STF flow field has been revealed, and the change characteristic of surface roughness is obtained. The computational fluid dynamics (CFD) simulation results show that strong transverse shear flow is formed in STF, which plays a major role in material removal. At micro-level, novel mathematical models of plastic deformation and brittleness removal and material removal mechanism of STF flow field are proposed. Comprehensive analysis of blunt and sharp abrasive particles impacting monocrystalline silicon is implemented through finite element method (FEM), which includes the effect of abrasive particle size on material removal rate (MRR), kinetic energy change of abrasive particle, force analysis of impact, the effect of impact angle, and polishing tool rotation on MRR. The final results show FEM simulation results are consistent with that of CFD simulation and experiments, which is of great significance to reveal the behavior principle of abrasive particles in STF and guide the actual production.