Material Removal Mechanism of Three-Phase Flow in Sapphire Ultrasonic Polishing: Insights from the Dense Discrete Phase Model and Polishing Experiments

Ultrasonic vibration affects three-phase flow behavior under the hydrodynamic contact mode in sapphire ultrasonic vibration chemical mechanical polishing (UVCMP). Nevertheless, the effects of slurry dynamics on material removal remain unclear due to challenges in experimental characterization. In this paper, the influences of key factors on the material removal of three-phase flow were investigated via the dense discrete phase model. The simulation results reveal that concentration and particle size present insignificant impacts on the multiphysical fields. However, the shear stress and material removal rate (MRR) increase with the concentration. While shear stress increases by 6 orders of magnitude as abrasive diameter grows from 20 to 5000 nm, the MRR only triples. As the ultrasonic amplitude and frequency rise, the multiphysical fields and shear stress are enhanced. The numerical MRR increases by 59% when the amplitude rises from 1 to 3 μm. The ultrasonic frequency is found to markedly affect the mechanical removal capability of sapphire UVCMP. The gray relational analysis reveals that frequency has the most significant effects on the simulation MRR ( χ nm = 0.8608). The influences of various factors on simulation MRR are experimentally validated. This paper establishes a theoretical foundation and provides novel insights for the optimization of sapphire UVCMP.