大型异形件重型高效铣削技术及刀具失效机理研究

The large irregular parts are used more and more widely in the area of aerospace and energy resources and so on. The large irregular parts have complex surface characteristics, the materials of them are special, and when they are machined the large amount of material will be removed. Heavy milling is a primary means for machining the large special-shaped parts, in the milling process, the phenomenon of powerfully impact vibration, thermal deformation and destroy stress will be brought about owing to the huge cutting impact force and high cutting temperature, with the result that the machining quality is poor, the tools are damaged seriously and the machining efficiency is low. The main researching object of this project is on the heavy milling process of large special-shaped parts (The water tight compartment of nuclear reactor). Through doing deep theory research and systematic cutting experiments, the high-efficient milling technology will be studied, and the superposition method of motion amplitude of powerful milling will be also proposed, then the mechanism of powerful mechanical impact will be also revealed. The dynamic characteristics of the milling force and milling temperature were studied and the distribution model of them were build, and the effect principle of the coupled thermo-mechanical field on the cutter properties was analyzed. Yet, both the tool's deformation behavior under the action of alternating heat and the generated mechanism of the devastating stress caused in the process of super-heavy milling will be analyzed, then the model of the tools' service ability will be established, and the measures to restraining the devastating stress will be also proposed, all these will provide a theoretical foundation for super-heavy milling cutters design. All these work will provide the systematic theory support to achieve a stable and efficient target of heavy powerful milling technology for large special-shaped parts of difficult-to-machine materials.

大型异形件在航空、航天及能源等领域应用日益广泛。大型异形件型面特征复杂，材质特殊，加工时材料去除量大。重型铣削作为大型异形件切削加工的一个主要方式,加工过程中切削冲击力大，切削温度高，易产生强冲击振动、热变形以及破坏应力等现象，加工质量差，刀具失效严重，加工效率低下。本项目以高温高强度钢超大型异形件水室封头的超重型铣削过程为研究对象，通过深入的理论研究和系统的切削试验，进行强力高效铣削技术研究，提出强力铣削运动幅叠加方法，揭示强机械冲击振动产生机理；研究重型高效铣削过程力、热动态特性并建立其分布模型，分析热-力耦合场分布对刀具性能的影响规律；分析研究交变热作用下的刀具材料形变特性以及超重型铣削过程破坏性应力产生机理，建立刀具服役能力模型，提出抑制破坏性应力产生的措施，为超重型铣刀设计提供理论依据，为实现稳定高效的难加工材料大型异形件重型铣削加工提供系统的理论支持。

水室封头是核电核岛蒸发器的关键零件，其尺寸与重量比较大，水室封头切削加工时，材料去除量非常大，制造周期长，切削加工过程中，处于极限悬伸状态下的主轴与刀具产生巨大振动，严重降低和影响生产效率与表面加工质量，并且刀具失效严重、使用寿命低。. 针对专用机床(TK6920 型数控落地镗铣床)、刀盘(Φ200R8圆弧刀片刀盘)与主轴系统，通过仿真和实验的方法，进行水室封头铣削机床的刀盘与主轴系统模态分析；分析加工过程中的振动产生的原因，通过测得空转、空转结合空进给以及切削时振动信号并进行分析，最终得到切削过程中的交变切削力所引起的振动为系统振动的主要成分，并对变悬伸量试验振动信号进行分析，进一步获得悬伸改变量对振动的影响，并得到水室封头加工铣削振动为一种复杂的耦合振动；. 在水室封头铣削过程中的强冲击振动特性及振动机理研究的基础上，设计不等齿距刀具降低水室封头加工铣削振动；将水室封头原始尺寸等比例缩小25倍，采用三轴铣床对水室封头外球面进行仿真加工；进行切削层控制原理及理论分析，创建铣削轨迹模型和铣削厚度模型，进行铣刀空间路径分析和铣刀铣削路径优化，提出铣刀运动幅叠加距离的计算方法；. 针对硬质合金刀片的高温失效，进行刀片材料的高温性能研究，设计并进行了硬质合金材料分别在DIL 805A快速相变仪、万能材料实验机等设备上的实验，分析刀片材料的热变形规律、高温力学特性和疲劳断口显微组织及相变行为；建立了刀片前刀面应力分布密度函数模型与温度分布密度函数模型；应用数值分析技术与物理模拟相结合方法，确定刀片材料形变特性与温度的关系；利用ANASYS有限元分析软件，进行切削区域热-力耦合有限元分析，获得了热-力耦合场分布对刀具性能的影响规律；建立刀片材料失稳变形的计算机三维分析模型；. 进行水室封头加工现场和实验室条件下的切削实验，研究刀具的失效机理，进行重型切削条件下刀-屑粘结机理和元素扩散模型研究；对刀具残余应力产生机理和分布状态进行分析，建立残余应力与切削条件的关系模型；对重型铣削刀具服役能力进行研究，进行刀具可靠性分析，并进行分层高效重型铣削刀具的优化设计。. 研究结果可为大型异形零件重型切削加工的生产增效以及重型切削技术的推广提供理论指导和技术支撑。