超声辅助抛光过程中流体性能仿真分析

Simulation and analysis on the fluid characteristics in sono-assisted polishing

为探究超声辅助抛光过程中流体特性对抛光性能的影响,分析超声辅助对试件表面材料去除率的影响机理,分别对光滑及多孔抛光垫建立不同膜厚尺度下超声振动抛光过程的FLUENT仿真模型,分析不同变量对流体的压力分布、速度分布、气相分布等特性的影响规律.仿真结果表明:超声振动会使试件表面的流体剧烈变化,在横向产生高速流动;工具与研抛表面之间的液膜越薄,在试件表面产生的压力越大,流体横向流动越强,加工效率越高;抛光垫上的小孔会使液膜中的压力分布出现阶跃变化,产生更多有利于提高材料去除率的超声空化.

To investigate the influence of fluid characteristics on the polishing properties during sono-assisted polishing and analyze the affecting pattern of ultrasonic wave on the material removal rate（ MRR） at the workpiece surface, for smooth polishing pad and pad with small holes, simulation models for ultrasonic vibration assisted polishing under different film-thickness are built and analyzed with FLUENT software. The influence of different process parameter on the value and distribution pattern of pressure, velocity and air phase are obtained. Simulation results show that the ultrasonic wave can cause strong shear flow and high pressure at the workpiece surface, and the shear flow and pressure grow stronger with the decrease of film thickness. Pores at the pad break the continuous fluid flow under workpiece, which makes velocity and pressure of fluid change abruptly and creates more ultrasonic cavitation, which increases the MRR.