基于CFD的超声空化对抛光介质运动影响的研究

发布时间：2018-05-24 22:34

本文选题：超声抛光 + 超声空化　；参考：《苏州大学》2015年硕士论文

【摘要】：模具在现代工业的应用日益广泛,激烈的市场竞争和对产品质量要求的不断提升致使对模具表面处理趋向精密化。抛光是模具制造业中一道至关重要的工序,抛光工序直接影响产品的性能。众多材料具有一些特性,如持续高温下的高强度和刚度、极高的硬度、脆性、耐腐蚀性、抗氧化性和化学惰性等,这些特性均需经过包括抛光在内的精密加工才能得以体现。目前国内对模具的抛光,特别是异型的模腔主要依赖于手工,抛光的质量往往取决于操作者的熟练程度,这将直接导致产品质量的不稳定,甚至会降低产品应有的性能;此外,手工抛光还使抛光效率低下。因此,亟需一种有效的自动化的抛光方法能够解决复杂曲面、凹槽、盲孔等异型腔的抛光问题,提高抛光效率,稳定抛光质量。本文针对新型超声抛光方法中的一基础理论问题进行了研究,对由超声换能器高频振荡产生的超声空化进行了理论分析和数值模拟。超声抛光的复杂性和微观性因素,包括声压场和汽含率的分布、微观磨粒的运动机理以及各影响因素对超声空化的影响,都难以采用实验手段直接观测,因此,本文采用了基于CFD的数值仿真方法对上述关键问题进行了研究,主要的内容和创新性成果如下:(1)文中首次采用FLUENT中的湍流模型、空化模型以及动网格模型模拟了超声抛光中的声致空化现象,分析了超声空化产生的能量可加强磨粒对模具异型腔的抛磨,导致更为强烈的材料去除,并给出了具体的验证方法。(2)本文还利用MINITAB中DOE模块对抛光试验进行了正交设计,得到各影响因子之间的交互作用以及影响超声抛光的最主要因素。(3)另外,研究中并未发现空化的选择性,空泡在模具异型腔内的分布相对稳定,集中出现在模具异型腔底面中心附近,而在内壁处和边缘地带相对较少。根据空化在模具异型腔内的分布,磨粒的速度发生相应的变化。(4)为使超声抛光达到更精密的抛光效果,需抑制空化效应对磨粒材料去除率产生的影响,而着重强化磨粒本身对工件表面的研磨作用。(5)可通过改变超声频率、振幅、液体黏度以及工具头深度等改变超声抛光过程中空化作用的强弱,这些参数的合理范围值以及它们之间的交互影响可以依据DOE设计的正交试验而获得。
[Abstract]:The application of mould in modern industry is more and more extensive. The fierce market competition and the continuous improvement of product quality make the surface treatment of mould become more and more precise. Polishing is one of the most important processes in die manufacturing industry, and the polishing process directly affects the performance of products. Many materials have some properties, such as high strength and stiffness, extremely high hardness, brittleness, corrosion resistance, oxidation resistance and chemical inertia. At present, the domestic polishing of mould, especially the special mold cavity, mainly depends on the handwork, and the polishing quality often depends on the operator's proficiency, which will directly lead to the instability of the product quality and even reduce the due performance of the product; in addition, Manual polishing also makes polishing inefficient. Therefore, an effective automatic polishing method is urgently needed to solve the polishing problems of complex curved surfaces, grooves, blind holes and other special-shaped cavities, to improve the polishing efficiency and to stabilize the polishing quality. In this paper, a basic theoretical problem in the new ultrasonic polishing method is studied, and the ultrasonic cavitation caused by the high frequency oscillation of the ultrasonic transducer is analyzed theoretically and numerically simulated. The complexity and microcosmic factors of ultrasonic polishing, including the distribution of sound pressure field and vapor holdup, the motion mechanism of micro-abrasive particles and the influence of various factors on ultrasonic cavitation, are difficult to be observed directly by experimental means. In this paper, the numerical simulation method based on CFD is used to study the key problems mentioned above. The main contents and innovative results are as follows: (1) the turbulence model in FLUENT is used for the first time. The cavitation model and dynamic mesh model are used to simulate the acoustic cavitation phenomenon in ultrasonic polishing. The energy generated by ultrasonic cavitation can enhance the grinding of the mold cavity and lead to stronger material removal. This paper also uses DOE module in MINITAB to carry on the orthogonal design to the polishing experiment, and obtains the interaction between the influencing factors and the most important factor of the ultrasonic polishing. The cavitation selectivity was not found in the study. The distribution of cavitation was relatively stable in the special cavity of the mould, which concentrated near the center of the bottom surface of the die shaped cavity, but relatively few in the inner wall and the edge zone. According to the distribution of cavitation in the die cavity, the velocity of abrasive particles changes correspondingly. In order to achieve more precise polishing effect, the effect of cavitation effect on the removal rate of abrasive material should be restrained. The grinding effect of abrasive particles on the workpiece surface can be enhanced by changing the ultrasonic frequency, amplitude, liquid viscosity and the depth of the tool head. The reasonable range of these parameters and their interaction can be obtained according to the orthogonal test designed by DOE.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG76

【参考文献】