三相磨粒流文丘里管结构空化辅助抛光机理与试验

Mechanism and experiment of three-phase abrasive flow venturi tube structure cavitation assisted polishing

为解决传统流体抛光效率低等问题,该文提出三相磨粒流文丘里管结构空化辅助抛光方法,进行了理论分析和试验研究。利用计算流体力学对三相磨粒流有无文丘里管结构空化2种情况分别进行数值模拟,分析和对比流场内的速度矢量、动压力和湍动能等参数。为了验证数值模拟的正确性和所提出方法的有效性,一方面进行了PIV(Particle image velocimetry)观测试验,观察和分析流场内空化云团的演化,进一步分析空化辅助抛光机理;另一方面进行了三相磨粒流空化抛光试验,对工件的表面粗糙度和表面形貌进行测量和分析。理论和试验结果表明:空化辅助下的流场速度、动压力、湍动能和有效加工区域明显增大,数值分析与PIV观测试验、抛光试验结果具有很好的一致性,三相磨粒流文丘里管结构空化辅助抛光方法显著提高了抛光效率。加工对比试验显示,空化辅助磨粒流抛光相比同参数的传统流体抛光效率大幅提高,经12 h抛光后工件表面粗糙度Ra从160 nm最低下降到4.95 nm。

The ultra-precision processing of electronic information materials is of great significance for the development of modern agricultural equipment from mechanization to automation,digitization and intelligence.To improve the efficiency of traditional fluid polishing which has a wide range of adaptability,a three-phase abrasive flow based on venturi structure cavitation-assiste polishing method was proposed,and the theoretical analysis and experimental research were conducted at the same time.The 2 different cases,with and without cavitation in three-phased abrasive flow,were numerically analyzed by computational fluid dynamics.Firstly,the three-phase abrasive flow machining model and machining mechanism based on cavitation-assisted were introduced.Then the flow field based multi-phased flow mixing model and the Realizable k-εturbulence model was applied to couple the cavitation and the flow field model.The analysis and comparison of the key parameters,like velocity vector,dynamic pressure,and turbulent kinetic energy in the flow field were completed.In order to validate the numerical simulation and the proposed method,on the one hand,the PIV(particle image velocimetry)observation experiment was conducted to observe and analyze the evolution of cavitation clouds in the flow field,and the cavitation-assisted polishing mechanism was further analyzed.On the other hand,the surface roughness and surface topography of the workpiece were measured and analyzed through a three-phased abrasive flow cavitation polishing experiment.The theoretical and experimental results showed that the flow velocity,dynamic pressure,turbulent kinetic energy and effective machining area under the assistance of cavitation were obviously increased.The numerical analysis results were aligned with the PIV observation and the polishing experiment results.The processing mechanism of the cavitation assisted polishing method for gas-liquid-solid three-phase abrasive is that the cavitation impact caused by cavitation bubbles collapse increase the effective impact of abrasive particles on the surface of the workpiece in the flow field.Further,the movement of the abrasive particles tends to be disordered state,thus achieving the goal of improving the processing efficiency and ensuring the processing quality significantly.The processing comparison experiments showed that the polishing time of cavitation-assisted abrasive flow could be obviously shortened,and the workpiece surface roughness could be reduced from 160 nm to 4.95 nm after 12 h polishing,whereas the non-cavitation assisted abrasive flow polishing can only be reduced to 7.23 nm.In addition,the surface morphology of cavitation-assisted abrasive flow machining is better.