磁场辅助微细磨料水射流精抛复杂型面陶瓷零件关键技术研究

Nowadays, the complex profile ceramic part with many excellent properties such as high temperature and pressure resistance etc., has been widely used. The surface quality including shape accuracy and surface defect such as microcrack and residual stress,are the key factors for its performance. Micro-abrasive waterjet (MAWJ) technology, due to its various distinct advantages over the other technologies such as no thermal distortion, high machining versatility, high flexibility and small cutting forces, has been considered as one of the most appropriate micro-machining technologies for hard and brittle materials, such as ceramics and semiconductors.With a aim to improve the surface quality of ceramic complex profile parts, this project will carry out the following research. The magnet abrasive is mixed with the micro abrasive water jet, and then the micro magnetorheological jet is formed, which has the characters of micro, collimating, cooling etc. and it is used to polish the complex profile ceramic parts to obtain the high surface quality. Its key technology is including the following. The research of the field distribution of the abrasive water jet flow is carried out by help of the computational fluid dynamics (CFD)softwares and ansys multi-physics TM model,and the moving state of the abrasive in the flow coupled with the magnet field, flow field and gravity field is obtained. The research of the process of the jet impacting the ceramics is carried out by help of fluent and ansys ls-dyna model; the method of getting micro abrasive water jet machining equipment is studied by designing field coil and the shape of the magnetic pole, which are connected with the micro abrasive waterjet equipment and robot. The experimental research of the parameters of the finishing process effect on quality surface of the ceramic parts is carried out. The surface is measured by high precision measuring instruments, and then the brittle material removal mechanism of the micro abrasive water jet machining is studied by help of theory of geometric topology, and the optimize and predict model of the process parameters are set up to gain the high integrity and quality surface by the help of the artificial neural network and Matlab software.

当前具有诸多优良性能的复杂型面陶瓷零件应用愈加广泛，而表面质量如面形精度、微裂纹、残余应力等对其使用性能影响很大。微细磨料水射流加工因对材料无选择性、效率高、无明显热变形等优点而被认为是理想的陶瓷材料抛光加工工艺。为提高复杂型面陶瓷零件表面质量，本项目拟将磁性磨料混入微细磨料水射流中，在外加辅助磁场作用下，产生微细，准直、冷态等射流并开展工程陶瓷抛光加工技术研究。研究重点包括：研究输送管道内、喷嘴内外的微细磨料水射流在磁场-流场-重力场等多物理场耦合作用下的流场特征规律和微细磨料运动控制技术；研究磁场作用下获得微细磁射流的新方法；实验研究复杂型面陶瓷零件抛光工艺，利用高精度测量仪器测量陶瓷表面形貌，借助几何拓扑学等理论，分析陶瓷材料表面形成机理，利用人工神经网络等相关理论，分析磁场辅助微细磨料水射流加工工艺参数对陶瓷材料表面质量的影响规律，建立基于表面完整性的工艺参数优化和预测模型。

微细磨料水射流加工由于对材料无选择性、效率高、无明显热变形等优点成为复杂型面陶瓷零件表面的抛光加工主要方法。磁性磨料作为一种新型合成磨粒被广泛应用于光整加工技术中。本项目用磁性磨料代替普通磨料，施加轴向分布磁场开展异型陶瓷零件的微细磨料水射流抛光技术研究。首先，借助COMSOL和Fluent软件模拟了磁场作用下磨料水射流射流流动规律，结果表明施加磁场后射流的集束效果增强，磨料的运动速度明显增加。模拟磁性磨料在射流中的运动轨迹发现，轴向磁场作用促使磁粒分布有序，方向一致性增强，集中分布于射流轴线附近。其次，研制了多自由度磁场辅助微细磨料水射流抛光机械手，可实现喷头在空间内灵活运动。研制了并联双作用气液增压装置，可实现高压水的连续稳定供给。开发了基于电磁技术和脉冲技术的微细磨料水射流供料装置。开发了基于西门子PLC的水射流抛光加工装置的控制系统和基于WinCC技术的人机交互界面，实现对抛光加工过程的实时控制与监控。研究了异型陶瓷工件表面抛光时喷嘴的运动路径规划，构建了由直线、圆弧和三次样条曲线等组成的抛光运动路径。再次，利用流固耦合理论研究了磨料水射流冲蚀陶瓷材料表面的应力应变分布规律，分析了磨料形状、数量、排列方式，冲蚀角度对陶瓷材料去除的影响规律。最后，开展了磨料水射流抛光陶瓷材料实验研究，建立了基于材料体积去除量和冲蚀深度的抛光工艺参数实验预测模型。陶瓷材料去除机理的分析结果表明磨粒对表面存在抛磨、滑擦、耕犁和微切削等行为，其加工表面形貌表现为冲蚀坑边沿有微隆起，存在出明显的塑性行为，而在大变形情形下材料去除表现为晶粒断裂脱落。陶瓷表面微观几何形貌的创成是伴随着材料去除过程完成的，磨料喷射形成表面呈现为“波浪形”。表面微观凸起随喷射时间增加而衰减,形成均匀一致的表面形貌，新创成的表面纹理方向几乎一致，因此需要改变喷射方向并采取合理匹配加工参数才能获得精密光整加工表面。