微细复杂曲面电火花加工成形规律及多材质电极损耗机理研究

The machining of micro complex surfaces has always been a problem puzzling the world. Because of its special machining mechanism, micro electrical discharge machining (micro EDM) is considered to be an effective method for micro complex surface machining. However, due to the serious and unavoidable tool wear, the traditional method of laminated removal micro ED milling is very difficult to improve itself in processing efficiency and surface quality. Only by mastering the law of tool wear and rationally using it, can the efficient and precise machining of micro complex surfaces be truly realized. In this proposal, based on the tool wear, a die sinking micro EDM method with multi-material electrode for micro complex surface machining is presented. The discharge point distribution model under skin effect and the plasma thermal-magnetic fluid coupling model are established, to study the electrode material removal mechanism under the effect of super high frequency induction electromagnetic field. The quantitative equation of thermionic field emission with variable barrier width and the micro scale electro thermal effect model of dielectric-electrode multiphase region are proposed, to analyze the discharge removal characteristics of multiphase materials and interphase interface, and then to reveal the tool wear mechanism of multi-material electrode under super high frequency pulses. Based on the electric field-structure coupled governing equation, the tool shape topology evolution model is presented to clarify the shape change law of multi-material electrode under super high frequency pulses. Finally, a design-manufacturing system for multi-material die sinking electrode is established, and a die sinking micro EDM method suitable for efficient and precise machining of micro complex surfaces is developed. The achievements of this project are of great significance to enhance our micro manufacturing technology level.

微细复杂曲面的加工一直是困扰世界各国的难题，电火花加工因其特殊的加工机理，被认为是微细复杂曲面加工的有效方法。但由于电极损耗严重且不可避免，电火花分层铣削法在加工效率和曲面质量上很难再有所提高，只有掌握电极损耗规律并将其合理利用，才能真正实现微细复杂曲面的高效精确加工。本项目提出基于电极损耗的微细复杂曲面电火花多材质电极成形加工方法，研究超高频感应电磁场作用下电极材料蚀除机理，建立集肤效应下放电点分布模型及等离子体热-磁流耦合模型；分析多相材料及相间界面放电损耗特性，建立变宽势垒热场致发射定量方程与介质-电极多相区域微尺度电热效应模型，揭示超高频脉冲下多材质电极损耗机理；建立基于电场-结构耦合控制方程的电极形状拓扑演变模型，阐明超高频脉冲下多材质电极形状变化规律；建立多材质成形电极设计-制备体系，探索适用于微细复杂曲面高效精确加工的电火花成形加工方法，对提升我国微制造技术水平具有重要意义。

针对微细复杂曲面电火花加工中电极损耗严重且不可避免的现实问题，利用加工中不同材料电极损耗及形状变化规律，开展基于电极形状变化的微细电火花复杂曲面多材质电极成形加工方法的研究。在以下4个方面取得了进展：. （1）研究了微细电火花加工纳秒级脉冲放电生成的超高频感应电磁场，对不同材料电极截面放电能量分布与传输规律的影响，建立了集肤效应影响下电极截面放电能量分布模型，得到了超高频脉冲作用下电极截面放电点位置分布规律。分析了超高频脉冲作用下放电通道内带电粒子的运动规律，建立了放电通道磁流体耦合微观模型，获得强磁力箍缩效应影响下放电通道的位形变化情况。提出放电区域电极表面热爆炸力、磁流体力变化规律，揭示超高频脉冲电磁感应影响下电极材料蚀除机理。. （2）从多相材料阴极电子场致发射的微观角度，建立了单次放电和连续放电情况下多相材料对放电击穿影响的对比模型，研究了多材质电极多相材料及界面特性对放电击穿概率的影响规律。建立电极多相界面材料微尺度电热效应有限元模型，分析多相界面材料组织结构对放电热传导的影响机制，揭示了各相材料及界面的放电能量分配、吸收、传导规律，阐明多相材料及相间界面放电损耗特性。. （3）开展了微细电火花加工中多材质电极损耗和形状变化规律的试验研究，仿真研究了多材质电极加工过程形状变化规律，建立多材质电极电场-结构耦合控制方程，通过对放电点位置判断及材料蚀除的反复迭代，模拟连续脉冲电火花加工中多材质电极形状变化演变过程，揭示多材质电极损耗及形状变化规律。. （4）根据电极形状变化规律，提出电极形状预测-反求设计方法，根据曲面形状反求多材质电极各电极组分的组合搭配方案，提出了热镀连接法进行电极组分粘结的多材质电极制备方法，建立了多材质成形电极设计-制备体系，通过典型复杂曲面零件加工试验，实现微细复杂曲面的高效高精度电火花成形加工。. 项目的研究成果对提升我国微制造技术水平具有重要的意义。