| 引用本文: | 常敬忠,翟文杰.超声辅助抛光流场规律CFD仿真分析[J].哈尔滨工业大学学报,2018,50(7):23.DOI:10.11918/j.issn.0367-6234.201705158 |
| CHANG Jingzhong,ZHAI Wenjie.CFD analysis of flow field of ultrasonic-assisted polishing[J].Journal of Harbin Institute of Technology,2018,50(7):23.DOI:10.11918/j.issn.0367-6234.201705158 |
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| 摘要: |
| 为探究超声辅助抛光的作用机理，利用FLUENT非稳态动网格湍流和离散相模型并结合mixture的空化模块, 仿真分析不同超声振动参数对流场绝对压强、流速和气含率分布的影响以及各参数间存在的相互作用规律.仿真结果表明:超声空化作用主要集中在试件正下方的小范围区域内，即试件的有效加工区域，进而可以确定流场所需最小膜厚；流场绝对压强、速度等参数一个周期内出现两次峰值，周期内气泡长大后受压溃灭过程分为两个阶段，表明超声振动下流场存在二次空化现象，二次空化在抛光过程中强化了空蚀效应；周期变化过程中，流场同一位置的不同参量、同一参量在不同位置与超声的周期性振动间均存在不同程度的滞后现象；超声振动使流体内产生超声纵波，遇到抛光盘发生反射并伴随半波损失；膜厚足够大时，则会形成驻波，试件表面处振幅最大，有利于提高超声辅助的抛光效果；利用有效加工区域和驻波现象可以使试件加工效果达到最优，二次空化和滞后现象有助于揭示超声辅助抛光过程的作用机制和规律.
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| 关键词: 超声辅助抛光 CFD仿真 超声振动 空化 二次空化 |
| DOI：10.11918/j.issn.0367-6234.201705158 |
| 分类号:TH133; TP183 |
| 文献标识码:A |
| 基金项目:国家自然科学基金(51475119) |
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| CFD analysis of flow field of ultrasonic-assisted polishing |
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CHANG Jingzhong,ZHAI Wenjie
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(School of Mechatronic Engineering, Harbin Institute of Technology, Harbin 150001, China)
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| Abstract: |
| To explore the mechanism of ultrasonic vibration assisted polishing, the effects of different ultrasonic vibration parameters on the flow field parameters, e.g., absolute pressure, velocity and vapour volume fraction, have been analyzed by using FLUENT unsteady dynamic grid turbulence and discrete phase model combined with cavitation module of mixture. The inherent rules and relations of these parameters have been investigated to reveal the phenomenon of secondary cavitation. The simulation results show that the effect of ultrasonic cavitation is mainly concentrated on the small area just below the specimen, so there is an effective processing area in the flow field, the minimum film thickness required for polishing effectiveness of the flow field can be determined. There are two peaks of the absolute pressure, velocity, vapour volume fraction within a vibration cycle which is related to the vapour bubble grow and collapse, namely, the secondary flow field cavitation phenomenon, which enhances the erosion effect during polishing process. There are time-lags between these fluid parameters at same position and ultrasonic vibration parameters, as well as for the same flow parameter at different position in the flow domain. The ultrasonic vibration results in transverse wave in the fluid, after meeting the reflected one, mechanical wave interferes and half wave loss occurs, which will affect the effective processing area. When the standing wave appears at condition of large-enough film thickness, the vibration amplitude of the wafer surface is increased and polishing effectiveness can be greatly improved. So the wafer processing can be optimized by determining the effective processing area and utilizing standing wave phenomenon. The secondary cavitation and time-lag phenomena are helpful in revealing the mechanisms of ultrasonic-assisted polishing(UAP).
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| Key words: ultrasonic-assisted polishing(UAP) CFD simulation ultrasonic vibration cavitation secondary cavitation |
