薄壁件加工过程非线性动态特性及表面形貌混沌特征研究

Low efficiency of high-speed machining for aerospace typical workpiece(thin-walled workpiece) is one of the key bottleneck of multiaxial linkage machining efficiency, whose reason is lack of systematic study on the basic theory. High-speed milling on thin-walled structure component is a complex 3D milling process which is easy to produce coupling vibration of tool and hermo-mechanical coupled deformation of workpiece, so as to destroy the surface topography and surface integrity. This project is started with studying nonlinear dynamic characteristics of slowly varying parameters in the milling process,with the supports of heat transfer,thermal elastoplastic theory, nonlinear vibration and numerical techniques for computing, through in-depth theoretical and milling experiments of system,we establish the prediction model of nonlinear chatter of thin-wall workpiece at different processing stages, analyze aurface thermo-mechanical coupled stress field and deformation of thin-walled workpiece, reveal the formation mechanism of chaotic characteristics of processing 3D surface tepography and the relationship with chaotic vibration and deformation of thin-walled workpiece, propose methods of suppressing chaotic vibration. On the basis of considering the space dynamic stiffness of machine-tool-workpiece, synthesized optimize high-speed milling process of thin-walled workpiece, milling conditions and related parameters, targeted at surface topography, which provides theoretical and practical basis for multiaxial high-speed milling of thin-walled workpiece.

高速加工航天航空典型零件（薄壁件）时效率低下是制约多轴联动加工机床效能发挥的关键瓶颈之一，其原因是相关基础理论缺乏深入系统研究。薄壁件的高速铣削是复杂的三维铣削过程，易产生刀具、工件耦合振动和工件热力耦合变形，从而破坏加工表面形貌。本项目从研究铣削过程参数慢变的非线性动力学特性入手，在传热学、热弹塑性理论、非线性振动理论和数值计算技术的支持下，通过深入的理论研究和系统的铣削实验，建立动态铣削力模型、薄壁件不同加工阶段非线性颤振预测模型，分析薄壁件表面热力耦合应力场及变形，揭示加工三维表面形貌混沌特征的形成机理及与混沌振动、薄壁件变形的关系，提出抑制混沌振动产生的措施，在考虑机床-刀具-薄壁工件的空间动刚度场的基础上，以表面形貌、刀具寿命、加工效率为目标进行薄壁件高速铣削过程、铣削条件及非线性动力学敏感参数的综合优化，为多轴联动高速加工薄壁件提供理论和实践依据。

本项目针对高速加工航天航空典型零件（薄壁件）时效率低下的问题，通过深入的理论研究、铣削过程动力学行为仿真和薄壁件铣削试验，从研究铣削过程参数慢变的非线性动力学特性入手，建立了考虑多因素耦合的瞬态铣削力模型，分析了刀具磨损和振动、薄壁件变形和曲面特征、不同润滑量等的影响；基于全离散法和非线性特征判据试验确定了薄板件铣削颤振稳定性条件，建立了薄壁件不同加工阶段非线性颤振预测模型，基于铣削轴向力、陀螺效应、刀具磨损等进行了铣削颤振稳定域修正，在考虑机床-刀具-薄壁工件的综合刚度场的基础上，提出了调整系统动力学参数和切削参数两方面的切削振动抑制措施，试验验证表明预测结果具有较高的精度。. 基于NURBS曲面控制点重构方法对薄壁件表面形貌进行了仿真，在分析铣削振动信号的非线性行为的基础上，揭示了加工表面三维形貌的混沌特征，提出了通过提高系统刚度（控制薄壁件变形）和系统阻尼的方法来抑制混沌振动产生的措施；基于力椭球进行了刀具姿态选定和刀尖点变形误差分析，并通过刀具路径补偿方法进行刀尖点变形补偿，在大量的实验研究基础上，制定了综合考虑薄壁件加工系统刚度场和铣削颤振稳定性的薄壁件加工工艺；基于多目标遗传算法以无颤振稳定铣削、动态加工位置误差、工件变形为约束条件，以加工效率和表面形貌为目标函数，进行了铣削参数综合优化，为实现稳定高效的多轴联动高速加工薄壁件提供了系统的理论支持和实践依据，为工艺推广提供了重要的技术指导。