| 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... |
PDF Full Text Request