钨合金高效高表面完整性旋转超声加工基础研究

Due to high hardness, high density, and high strength, tungsten heavy alloy has been used widely in aerospace, military and national defense, which makes it to be an important strategical metal. However, its poor machinability results in low productivity, and poor surface integrity of workpiece, which severely hinders the improvement of cutting-edge weapons and equipments. Rotary ultrasonic machining exhibits excellent characteristics at improving machining efficiency and surface integrity of workpiece, making it may become a new machining method for tungsten heavy alloy with high quality. But the study on rotary ultrasonic machining of tungsten heavy alloy is very deficient to date. So in this project, a two-phase mixed constitutive model under high strain rate, which can reflect dynamic mechanical behaviour of tungsten heavy alloy, is established firstly. Then a molecular dynamics simulation model and an extended finite element simulation model are developed respectively to simulate the process of rotary ultrasonic machining of two-phase tungsten heavy alloy. Using these two models, the microscopic material removal mechanism of tungsten heavy alloy with ultrasonic incentive under ductile and brittle domain will be studied. At the same time, by the models and experiments, the key factors in ultrasonic process are determined and the formation mechanism of surface integrity of tungsten heavy alloy is studied. Finally, according to the built mechanisms of microscopic material removal and surface integrity formation, the parameters in rotary ultrasonic machining will be optimized systematically by both experiments and simulation models to realize high-efficient and high surface integrity of rotary ultrasonic machining of tungsten heavy alloy. The completion of this project would enrich the machining theory of hard-to-machine materials, and may promote the development of manufacturing technology of our country.

钨合金具有高硬度、高密度、高强度等优异特性，广泛用于航空航天、军事国防等领域，是重要战略性材料；但钨合金的难加工特性，导致其加工效率低、工件表面完整性差等问题，严重制约了尖端武器及装备的性能提升。旋转超声加工技术在提高效率和改善工件表面完整性上表现优越，有望成为加工高质量钨合金零件的新方法。然而，目前钨合金旋转超声加工尚不成熟，相关研究十分欠缺。本项目拟通过研究高应变率下钨合金动态力学行为的双相混合本构关系，构建钨合金旋转超声加工的分子动力学和扩展有限元模型；据此模型，系统研究超声能量激励下钨合金塑性域和脆性域的材料微观去除机理，同时辅以试验验证，探寻关键影响因素，并揭示表面完整性的形成机制；基于上述研究，采用仿真和试验互为验证的方法，系统优化钨合金旋转超声加工工艺，实现钨合金高效高表面完整性的旋转超声加工。本研究成果不仅可丰富难加工材料的加工理论，也有望促进我国制造技术水平的提升。

钨合金具有密度高、热膨胀系数小、绝热剪切能力强和吸收射线能力强的特点，使其被广泛应用于飞机惯性元件、导弹弹芯、核反应堆射线屏蔽罩、叶片准直器和精密配重部件等的制造，这些部件在原子能领域、精密医学仪器、航空领域和军工领域均有重要作用。但钨合金的高硬度、高强度等特征使其成为典型难加工材料，加工效率低和工件表面完整性差、刀具磨损严重、加工成本高等问题，严重制约了尖端武器及装备的性能提升。本项目针对钨合金高效高表面完整性旋转超声加工基础问题展开了研究。首先，采用分离式霍普金森压杆建立了高应变率下钨合金动态力学行为的本构模型，基于Abaqus软件和实验获取了双相结构的重要参数，完成了钨合金双相结构模型；在此基础上，结合实验确定了钨合金材料脆塑转变点，并深入探讨了钨合金塑性域和脆性域微观去除行为；进一步地，揭示了旋转超声加工中钨合金表面完整性形成机制并提出了高质量加工方法。此外，还基于第一性原理探索了钨合金旋转超声加工中涂层刀具和金刚石刀具的磨损机理。相关研究成果，在某军工企业得以成功应用，为难加工金属材料复杂零件的极端制造提供了有力保障。