钛合金活塞加工表面完整性的多步工艺递进演变机制与分步调控策略

Piston, as the "heart" of diesel engine, is subjected to alternating cyclic thermo-mechanical loads in the adverse working conditions when the engine is in operation. Piston’s manufacturing process, during which it is a multi-step loading and relaxation process, incorporates casting, rough machining, semi-finish machining, and finishing machining. The performance or life of piston depends on evolution history of the machined surface integrity in the multi-step process. With regard to the high efficiency and high quality machining of new titanium piston, a combination of simulation and experimental methods are adopted in this project. The varying-parameter constitutive model in the multi-step cutting of titanium alloy will be established considering machined hardness in the multi-step process of rough machining, semi-fine machining, and fine machining. Numerical simulation of the multi-step process will be conducted to investigate the influence of machined surface material properties of each step on the multi-physics evolution during the process. The variations of surface integrity and fatigue properties under different process combinations can be discussed by means of testing and characterization of the machined surface integrity in multi-step process machining piston. Then the step-wise control of the multi-step process parameters can be realized after the achievement of the established relationship between machined surface integrity and the performance of piston. Finally, the cutting parameters can be optimized with the target of high integrity and high life of piston. This will improve processing efficiency and machining quality of titanium piston, and enhance the piston’s capability of resistance to thermo-mechanical fatigue, which is of great theoretical and practical significance.

活塞是发动机的“心脏”，在发动机工作时承受交变热-机械载荷，工作条件十分恶劣，其制造过程中经历铸造、粗加工、半精加工和精加工等工艺，是一个多步受载和弛豫过程，活塞的使役性能（寿命）取决于多工步加工表面完整性的整个演变历史。本项目针对柴油机钛合金活塞的高效高品质加工，采用仿真和实验相结合的方法，通过建立粗-半精-精多步加工工艺过程中的考虑表面硬度的钛合金多步工艺切削变参数本构模型，进行多步工艺加工过程数值模拟，研究每步工艺待加工表面材料性能对加工过程多物理场的影响规律；通过活塞多步加工过程的加工表面完整性的测试与表征，研究不同工艺组合下最终加工表面完整性和疲劳性能的变化规律；通过建立的加工表面完整性与活塞使役性能的关系，对加工工艺进行分步调控，以高完整性和高寿命为目标进行活塞加工切削参数优化。这对提高钛合金活塞加工效率和加工品质，增强活塞抵抗热-机械疲劳的能力，具有重要理论和应用价值。

活塞是发动机的“心脏”，在发动机启动时承受交变热—机械载荷，工作条件十分恶劣。活塞制造过程中经历铸造、粗加工、半精加工和精加工等，是一个多步受载和弛豫过程，活塞的使役性能（寿命）取决于多步工艺过程的加工表面完整性的演变历史。.本项目针对柴油机钛合金活塞的高效高品质加工过程，采用仿真和实验相结合的方法，通过粗-半精-精多步加工工艺过程中钛合金多步工艺切削变参数本构模型的建立和实验验证，构建活塞关键工序多工步加工多物理场，进行钛合金活塞多步工艺加工过程的有限元模拟，研究了每步工艺待加工表面材料性能对加工过程多物理场的影响规律；通过用户子程序嵌入到Abaqus软件中进行有限元仿真，研究了粗加工和半精加工材料性能对最终精加工过程多物理场的影响规律，揭示了多步加工过程中热-力耦合作用机理、应力弛豫作用和织构演变机理。通过钛合金活塞多步工艺加工表面完整性的表征与检测，探究不同“工艺组合”对最终加工表面完整性和试件疲劳性能的影响规律；结合实验和仿真，进行加工表面性能评估，分析上一工艺对下一工艺表面完整性的影响。通过热疲劳和机械疲劳试验，分析加工表面完整性对疲劳性能的影响规律；建立了钛合金活塞加工中刀具切削参数、表面完整性和疲劳性能的关系和控制模型，以高表面完整性和疲劳寿命设计为目标，进行了切削参数多目标优化，对加工工艺进行了分步调控，分析最优了活塞加工切削工艺参数，从而控制最终精加工表面完整性。.这将提高钛合金活塞加工效率和加工表面完整性，为活塞切削加工工艺参数的制定提供理论和技术支撑，增强活塞抵抗热-机械疲劳的能力，这对具有重要理论和应用价值。这将有助于提高我国装备自主研发能力、提供基础性理论支持、掌握核心技术、增强国防核心竞争力具有重要推动作用和重要理论意义及实用价值。