CAJ | 학술논문

软性磨粒流超精密加工方法已被应用于模具细微结构化表面的光整加工中，湍流形态下的软性磨粒流具有最佳加工效果，所以需要对软性磨粒流的流场形态进行判断。以汽车模具中的结构化表面为研究对象，采用可实现k-ε模型对软性磨粒流进行数学描述，对软性磨粒流流场内的压力、速度、湍流耗散率以及不同阶段的运动轨迹进行数值模拟研究；基于粒子图像测速（particles image velocimetry，PIV）技术，搭建软性磨粒流流场测量试验平台，得到了流场内的颗粒分布、速度矢量以及流场涡量，并将观测结果与数值模拟结果进行对比分析。结果表明，数值模拟与流场观测结果一致，软性磨粒流流场符合湍流特征，利用该状态下的软性磨粒流对模具结构化表面进行超精密光整加工，加工后模具工件表面粗糙度达到27μm。
연성마립류초정밀가공방법이피응용우모구세미결구화표면적광정가공중，단류형태하적연성마립류구유최가가공효과，소이수요대연성마립류적류장형태진행판단。이기차모구중적결구화표면위연구대상，채용가실현k-ε모형대연성마립류진행수학묘술，대연성마립류류장내적압력、속도、단류모산솔이급불동계단적운동궤적진행수치모의연구；기우입자도상측속（particles image velocimetry，PIV）기술，탑건연성마립류류장측량시험평태，득도료류장내적과립분포、속도시량이급류장와량，병장관측결과여수치모의결과진행대비분석。결과표명，수치모의여류장관측결과일치，연성마립류류장부합단류특정，이용해상태하적연성마립류대모구결구화표면진행초정밀광정가공，가공후모구공건표면조조도체도27μm。
During the course of mold manufacture, lots of structural surfaces are involved, which are of complicated structure and tiny scale. Owing to the special profile of a structural surface, its finishing cannot be realized by the traditional method; so a softness abrasive flow ultraprecision machining method is proposed for mold structural surface finishing. Because of the weak viscosity of softness abrasive flow, it could develop turbulent flow easier than viscous fluids. The best finishing result can be obtained with the turbulent softness abrasive flow, so the flow pattern recognition of softness abrasive flow is necessary. Taking the structural surface of vehicle mold as the study object, a realizablek-ε double-equation turbulent model is used to describe a softness abrasive flow field. Based on the finite element analysis method, computational fluid dynamics (CFD) software was used to simulate the softness abrasive flow field. With the numerical simulation, distributions of dynamic pressure, velocity vector, and turbulent dissipation rate of the softness abrasive flow field were obtained; and the evolutionary process of the softness abrasive flow was showed by simulating different moments of particle motion trails, and the feasibility of a softness abrasive flow finishing method has been proved by these simulation results. Based on the similarity theory, a model of flow passage which was made of plexiglass was designed, three typical areas of the flow passage were selected for measuring the characteristics of the flow field, and the measurement platform of the softness abrasive flow field was constructed by using particle image velocimetry (PIV) technology. With the measurement platform, distribution of particle motion, velocity vector, and flow field vorticity were derived. From the particle motions, it was shown that the particles in the flow field were moving irregularly, particles can collide with the surface randomly, and the removal finishing can be realized; particle motion trails are observed from the velocity vector distribution, it was shown that particle trails in the flow field were votex, which was according to the features of turbulence, and this was conducive to the mold structural surface finishing. The vorticity distribution of the flow field illustrates that the softness abrasive flow has high vorticity energy, and it was helpful for increasing materials removal. Contrasting with simulation and measurement results, the softness abrasive flow field in this situation is turbulent, and the ultraprecision machining of mold structural surface can be realized by the softness abrasive flow in this state. A finishing platform which oriented to mold the structural surface was constructed, with the turbulent softness abrasive flow, the finishing experiment which was designed to mold the structural surface was carried out. The experiment results showed that SAF method can improve the surface quality of a mold structural surface without changing the morphology, and the machined roughness of a mold structural surface can be reduced to 27μm.Experimental results have demonstrated the effectiveness of a softness abrasive flow finishing method.