【作者】 孙树峰；

【导师】 计时鸣； 谭大鹏；

【作者基本信息】 浙江工业大学 ， 机械电子工程， 2013， 博士

【摘要】 针对模具零件上的微小孔、槽、棱柱、棱锥等结构化表面光整加工技术难题,传统光整加工方法存在很多缺陷很难用于微小结构化表面的光整加工,本文提出采用约束模块调控液-固两相“软性”磨粒流对模具微小结构化表面进行光整加工新方法,通过理论研究、加工模拟仿真和加工试验研究等途径,验证了该方法的可行性和有效性,达到了利用约束模块对磨粒流进行湍流调控实现模具结构化表面光整加工的目的。具体研究摘要如下：本文的研究内容来源于导师主持的国家自然科学基金面上项目和浙江省自然科学基金重点项目,在分析课题研究背景和意义基础上,综合叙述了国内外磨粒流光整加工方法和湍流理论的研究现状及发展趋势,提出本文的研究内容和拟采用的主要方法。通过分析固体磨粒在液体中的受力情况和磨粒流在近壁区的流动特性,揭示了“软性”磨粒流的加工机理：微细固体磨粒与液体混合形成“软性”(低粘度)磨粒流,磨粒流中的微细磨粒对流道粗糙壁面进行撞击和刮削,粗糙壁面在磨粒长时间微力微量切削作用下逐渐被整平,从而达到光整加工提高表面粗糙度的目的。由于“软性”磨粒流的有效光整加工是在湍流状态下进行的,因此介绍了几种充分发展的湍流模型(标准k-ε模型、RNG k-ε模型和Realizable k-ε模型)。对于近壁区和低雷诺数流动,可采用壁面函数法和低雷诺数k-ε模型处理。为了实现“软性”磨粒流的湍流调控,根据结构化表面的结构形状设计约束模块构建磨粒流流道,研究约束模块设计和磨粒流流道构建需要注意的问题,要获得充分发展的湍流,雷诺数必须满足Re≥8000,另外还要考虑磨粒不淤临界速度。设计了一些典型的结构化表面和约束模块设计构建了磨粒流流道。提出广义约束模块的概念和“软性”磨粒流辅助EDM/ECM复合加工微细结构化表面新方法。基于不同结构类型的结构化表面和约束模块构建磨粒流流道,对流道中的磨粒流进行模拟仿真。通过Gambit前处理器对磨粒流模型进行网格划分,利用Fluent软件对磨粒流流动进行仿真研究,分析磨粒流的动压力、湍动能、速度和壁面切应力等分布情况,通过软件仿真验证约束模块调控磨粒流流动的可行性,以期达到提高“软性”磨粒流光整加工质量的目的。为了进行“软性”磨粒流光整加工试验研究,搭建了“软性”磨粒流光整加工试验平台,配置了最佳组分的“软性”磨粒流,进行了约束模块调控下的“软性”磨粒流光整加工试验和“软性”磨粒流辅助EDM/ECM复合加工试验研究,证明了基于“软性”磨粒流的微细结构化表面光整加工的可行性和有效性。更多还原

【Abstract】 In view of the challenging technical problems of structural surface finishing of small/micro hole, slot, prism, pyramid of mould part. Traditional finishing methods can not be used to finish small/micro structural surfaces for having many disadvantages. A new method is provided in this paper that small/micro structural surface of mould is finished by liquid-solid two phases "soft" abrasive flow regulated with constraint module. The feasibility and effectiveness of the method are verified through the research measures of theoretical research, machining simulation and machining experiment, et al. The goal is achieved that mould structural surface finishing is realized by abrasive flow turbulence regulation with constraint module. The specific studies are as follows.The research contents of this paper come from the project of National Natural Science Foundation and key project of Natural Science Fundation of Zhejiang Province. Reseach background and significance of this paper are analyzed. Research status and development trend of domestic and foreign abrasive flow finishing method and turbulence theory are summarized. Research content and the main methods are put forward.The "soft" abrasive flow machining mechanism is revealed through stress analysis of solid particle in liquid and flow characteristics of abrasive flow in near wall region."Soft"(low viscosity) abrasive flow is formed by mixing micro solid particles with liquid. Rough surfaces of flow channel are hit and scraped by micro particles in abrasive flow. Rough surfaces gradually become smooth under the long time function of micro abrasive particles. The goal of improving surface roughness by abrasive flow finishing is achieved. The effective finishing of "soft" abrasive flow is under the condition of turbulence. Several fully developed turbulence models (standard k-ε model, RNG k-ε model and Realizable k-ε model) are introduced. The wall function method and the low Reynolds number k-ε model can be used for near wall region and low Reynolds number flow.In order to realize turbulence regulation of "soft" abrasive flow, constraint module is designed according to the structural surface and abrasive flow channel is constructed. Problems need to be paid attention to are researched during constraint module design and abrasive flow channel construction. To obtain fully developed turbulence, Reynolds number must be Re≥8000. In addition, non silting velocity also needs to be taken into account. Some typical structural surfaces and constraint modules are designed to construct abrasive flow channel. The concept of generalized constraint module and the method of "soft" abrasive flow assisted EDM/ECM combined machining micro structured surfaces are put forward.Abrasive flow channels are constructed based on different structural surfaces and constraint modules. Abrasive flow in the flow channel is simulated. Gambit preprocessor is used to mesh abrasive flow model. Abrasive flow is simulated by the software of Fluent. Distribution of dynamic pressure, turbulent kinetic energy, velocity and wall shear stress of abrasive flow are analyzed. The feasibility of abrasive flow is regulated by constraint module is verified through software simulation. The purpose of improving "soft" abrasive flow finishing quality is expected to be achieved.In order to carry out experimental study of "soft" abrasive flow finishing,"soft" abrasive flow finishing test platform is built and "soft" abrasive flow is mixed with the optimum percentage of components."Soft" abrasive flow finishing experiment is carried out under the regulation of constraint module. Experiment of "soft" abrasive flow assisted EDM/ECM combined machining is carried. Feasibility and effectiveness of small/micro structural surface finishing based on "soft" abrasive flow are verified更多还原