介观尺度薄壁特征微铣加工理论与技术研究

To solve the difficult problems of machining deformation control, chatter state recognition and suppression, surface integrity prediction of micro-milling thin-wall structures, starting from the building of micro-milling force model considering the processing deformation and micro-milling cutter wear, the effective control of the machining deformation is realized. A kinetic model of the micro-milling system is established, which considers the centrifugal force and gyroscopic effect caused by the high-speed rotation of the spindle. Aiming at the small stiffness and dynamic changes of frequency response of micro-milling system for meso-scale thin-wall structures, the prediction theory of chatter stability is studied, and a prediction method by tracking the dynamic characteristics of thin-wall structures in different processing stages is proposed, which provides reference for the stable micro-milling of thin-wall structures. Thermal-mechanical coupling analyses of micro-milling thin-wall structures are performed. Based on ABAQUS platform, a 3D thermo-mechanical coupling finite element simulation model is established, the influence of cutting edge radius and cutting parameters on residual stress and surface hardness of micro-milled thin-wall parts is analyzed, the formation mechanism of residual stress is studied, and the prediction of residual stress and surface hardness is achieved. Based on the truth that the machined surface is generated by duplicating the tool profile on the workpiece surface, a simulation model of sidewall surface topography is established, which provides the basis for the control of forming quality. Finally, relying on the method of tool setting, tool path planning and multi-objective optimization of cutting parameters, stable, high-quality and high-efficiency micro-milling of high-aspect-ratio meso-scale thin-wall structures is achieved. The research forms the control theory, technique and method of micro-milling meso-scale thin-wall structures.

针对薄壁件微铣加工变形控制、颤振识别与抑制及表面完整性预测难题，从考虑加工变形和微铣刀磨损的微铣削力模型研究入手，实现加工变形的有效控制。建立考虑高速旋转主轴引起的离心力和陀螺效应的微铣削系统动力学模型。针对薄壁件微铣加工系统小刚度、动态变化的频响特点，研究无颤振稳定铣削预测理论，提出通过跟踪工件不同加工阶段的动态特性进行稳定性预测的方法，为实现微铣稳定切削奠定基础。进行薄壁件微铣加工热力耦合作用分析，基于ABAQUS建立薄壁微铣三维有限元仿真模型，研究切削刃圆弧半径和切削参数对残余应力和加工硬化的影响规律，探究残余应力的生成机理，实现残余应力和加工硬化的预测，建立基于刀具轮廓复映原理的侧壁表面形貌仿真模型，为薄壁件成形质量控制提供依据。依托对刀方法、刀具路径规划和切削参数多目标优化工艺研究，实现大高厚比介观尺度薄壁特征稳定、高质、高效微铣加工，形成薄壁件微铣削加工的控制理论、技术与方法。

针对薄壁件微铣削加工变形控制、颤振识别与抑制及表面完整性预测难题，开展了介观尺度薄壁件微铣削加工基础理论与技术研究。建立了薄壁微铣削瞬时切削厚度模型，以最小切削厚度为分界点，分别建立剪切效应和耕犁效应为主导的薄壁微铣削力模型。基于ABAQUS建立了Inconel718薄壁微铣削加工过程仿真模型，实现了热力耦合分析和微铣削力的准确预测。基于单元编码和生死单元技术，建立了薄壁微铣削加工变形预测模型，实现了变形预测。利用旋转Timoshenko梁理论和子结构响应耦合法求解主轴系统频响函数。结合结构修改法，考虑与转速有关的主轴轴承特性，获得考虑离心力和陀螺效应的微铣削刀尖频响函数。基于克希霍夫板理论，通过罚函数法对薄壁件边界约束简化，利用瑞利—里兹法得到薄壁件在微铣削过程中的横向振动位移，通过拉格朗日方程获得与刀具切削位置有关的薄壁件微铣削运动方程。基于切削力与振动的相互作用关系，求得频域范围内的相对传递函数，进而将刀具与薄壁件的动态特性共同纳入到薄壁件微铣削系统中。建立了薄壁微铣削系统动力学模型，实现了薄壁件微铣削过程仿真，得到与切削位置有关的薄壁微铣削稳定性叶瓣图，开展了薄壁件微铣削实验，通过对铣削力频率成分及薄壁件切削表面形貌的综合分析，证明了薄壁微铣削稳定性叶瓣图是效的。基于次摆线理论轨迹，考虑刀具磨损、跳动、变形、振动等因素的影响，建立铝合金LF 21微铣削加工切削轨迹模型。基于刃形复映原理，实现侧壁表面形貌仿真和表面粗糙度预测。提出基于薄壁微铣削过程仿真的残余应力预测方法。建立了工件材料应力、应变和硬度之间的关系，实现了微铣削加工硬化程度的预测。最终，依托对刀方法、刀具路径规划和切削参数多目标优化工艺研究，实现介观尺度薄壁特征稳定、高质、高效微铣加工，形成薄壁微铣削加工的控制理论、技术与方法。