金属材料电火花加工熔池动力学行为及其微观机理与影响规律研究

Lower removal rate of the molten material and thicker molten-resolidified layer are the bottlenecks restricting the development of electrical discharge machining (EDM). The fundamental reason is that the removal force acting on the molten pool is not enough to remove most of the molten material in the discharge process. Thus, studying the dynamic behavior of the molten pool is the key to solve the above bottlenecks. Firstly, a high-speed camera, which can filter out the plasma, is used to observe the movement of the molten pool. Combining theoretical analysis results of the forces acting on the molten pool, the relationship between the forces acting on the molten pool and the molten pool movement is built. Then, this project utilizes the coupled FE/CGMD (Finite Element/Coarse Grained Molecular Dynamics) method to accomplish the trans-scale simulation of EDM process, which can reveal the influential mechanisms of the forces acting on the molten pool on the movement of the molten pool from the micro level. Furthermore, based on the above researches, the influential laws of the external conditions on both the forces acting on the molten pool and the movement of the molten pool are investigated through the observation of the molten pool. Also, the key theory that the external conditions can affect the forces acting on the molten pool and the movement of the molten pool is built. Lastly, based on the above key theory, the research on the regulation of the movement of the molten pool is carried out. The final goal is to improve the removal rate of the molten material by enhancing the removal process of the molten material. We intend to make breakthroughs in the key theory of high removal and low residue of the molten material, which can lay a theoretical foundation for the research of new methods and techniques of EDM. This study is important for promoting further development of EDM technology.

较低的熔融材料蚀除率和较厚的熔融再凝固层是制约电火花加工技术发展的瓶颈，其根本原因是放电过程中作用于熔池上的蚀除力不足以将大部分熔融材料蚀除，因此开展熔池动力学行为的研究是解决上述瓶颈的关键突破口。首先，采用可过滤掉等离子体的高速摄影装置实现对熔池运动的观测，结合熔池受力的理论分析结果揭示熔池运动与熔池受力之间的关系。其次，通过耦合有限元与粗粒化分子动力学的方法实现电火花加工过程的跨尺度模拟，从微观层面揭示熔池所受作用力对熔池运动的作用机理。基于上述研究，通过熔池观测研究外界条件对熔池受力与熔池运动的影响规律，建立可通过外界条件影响熔池受力与熔池运动的关键理论。最后，基于上述关键理论，开展熔池运动的调控研究，通过增强熔融材料蚀除运动来提高熔融材料蚀除率。本研究将在熔融材料高蚀除和低残留的关键理论上产生突破，为电火花加工新方法与新工艺的研究奠定理论基础，对推动电火花加工技术发展具有重要意义。

本项目针对电火花加工较低的熔融材料蚀除率和较厚的熔融再凝固层问题，开展了熔池动力学行为的基础研究。主要工作内容和研究结论如下，（1）搭建了单脉冲放电过程的高速可视化实验装置，对放电过程中放电等离子体的形成过程以及动态行为进行了观测研究，并研究了外界条件对放电等离子体运动的影响规律。对放电过程中熔池的运动以及熔融材料的蚀除过程进行了观测，研究并揭示了熔池的动态行为。（2）建立了单脉冲放电过程的大尺度分子动力学仿真模型，研究了放电过程中熔池的演变过程和熔融材料的蚀除过程以及熔融再凝固层的形成过程，揭示了熔融材料的蚀除驱动力，研究了外界条件对熔池动态行为和熔融材料蚀除过程的影响机理，揭示了熔池运动与熔池受力的关系。（3）建立了单脉冲放电过程的热-流耦合多物理场仿真模型，实现了放电过程中熔池动态行为的模拟，研究了外界条件对熔池运动的影响规律与机理，揭示了熔池运动与熔池受力的关系。（4）提出了基于高低电流复合脉冲放电的高效蚀除方法，搭建了高低电流复合脉冲放电实验装置，开展了单脉冲放电实验，证实了复合电流波形放电的材料去除量比相同放电能量下的方波脉冲提高了70%，并进行了连续脉冲放电铣削加工实验，证实了该方法在提高电火花加工速度方面的有效性。本项目为电火花加工高蚀除和低残留的新方法与新工艺研究奠定理论基础，对推动电火花加工技术发展具有重要意义。