时变因素作用下薄壁筒类工件车削振动特性与抑制方法研究

Chatter vibrations are frequently encountered during machining operations of thin-walled workpieces, reducing the product quality and production efficiency. In this proposal, through the methods of theoretical modeling, numerical simulation and experimental tests, a comprehensive tool-workpiece compliance chatter model considering the effect of the varying work diameter and cutting position is introduced. Based on this proposed, the chatter behavior and control method chatter model are to be investigated theoretically and experimentally. The matching method for the modal parameters of the tool and the workpiece is proposed to improve the stability of the machining system. The influence of the time-variant factors on the vibration response are studied. The entire 3-D stability chart for a single cutting pass is constructed. By using this stability chart, the chatter onset location along the length of the workpiece and the subsequent development can be predicted. In addition, the vibration features of the chatter model are analyzed. Based on the stability analysis, a dynamic optimization method is proposed for determining the optimal sequence of cutting passes and machining parameters in multipass turning of a flexible tube, which is more effective in comparison with the empirical approaches or the prior works. This optimization method could help to suppress chatter vibrations in the minimum possible time or at the lowest possible cost. The achievements of this study could enrich the approaches for chatter control in machining processes, and also provide theoretical basis for on-line chatter monitoring, intelligent selection of machining parameters in turning of thin-walled workpieces.

切削颤振是影响薄壁筒类工件加工质量和效率的主要问题之一。项目采用理论建模、数值仿真和试验测试三种手段相结合的方法，建立考虑切削过程中时变的切削位置和工件尺寸影响的刀具-工件柔性耦合车削颤振动力学模型，分析切削系统的稳定性与动力学参数的内在关系，提出通过研究刀具与工件动力学参数匹配方法来提高加工稳定性。采用模态分析结合实际切削振动测试，研究时变因素对切削系统振动响应特征的影响，构建在整个切削路径上的三维切削稳定域，定量预测给定切削条件下走刀路径上颤振的起始位置与演化规律。基于稳定性预测图，研究时变因素影响下多次走刀切削参数的动态规划方法，优选走刀次数、次序、切削用量等参数，突破传统依靠减小切削用量避振或多次走刀均采用相同切削用量的简化处理方法的不足，保证切削过程的稳定和高效。研究成果为柔性工件车削颤振的抑制提供一种新思路，在实践方面为薄壁筒件的切削颤振监测、切削参数优选等技术提供理论支撑。

薄壁筒类零件具有重量轻、结构紧凑等优点，广泛用于航天航空、船舶、石油化工等领域，切削颤振是影响此类零件加工质量和效率的主要问题之一。本项目从动力学建模角度出发，深入研究了薄壁筒类工件车削振动特性及其抑制方法，主要研究内容及重要结果包括：1）时变因素对薄壁筒工件车削振动特性影响分析。建立主轴-卡盘-薄壁筒工件工艺系统有限元模型，获得时变的工件壁厚、切削位置对切削系统模态、频率响应函数的影响规律；得出机床主轴、卡盘部件对于薄壁筒工件梁模态影响较大，而对其周向壳体模态的影响较小，壳体模态对于壁厚的变化更为敏感；沿工件轴向不同切削位置处切削系统的振动响应及其主振模态不同，靠近卡盘端时，工件系统的振动以梁振型占主导，而靠近自由端时，振动以壳体模态为主。2）薄壁筒工件切削颤振稳定性分析。建立了刀具-工件柔性耦合2DOF颤振模型，获得刀具与工件动态相互作用及其对切削稳定性的影响规律，构建由切削路径和切削用量组成的三维颤振稳定域，定量预测走刀路径上颤振的起始位置与演化规律；针对传统的颤振监测方法在早期颤振的快速识别方面存在不足，利用声压传感器安装的便捷性，建立一种基于声压信号的小波包能量峭度指标的早期切削颤振预警方法；试验发现当薄壁筒工件车削颤振时，其振动信号频率及表面振纹还可能会出现“跳跃”、“混叠”等现象。3）薄壁筒工件切削颤振抑制方法。获得刀具-工件动力学参数匹配与临界切削深度的映射关系，得出适当降低刀具的刚度反而有益于柔性工件的切削稳定；当刀具与工件具有相同的动力学参数时，相比于单自由度颤振系统，系统临界切削深度减半；相比于提高刀具阻尼，增加柔性工件的阻尼更有效提高加工稳定性；通过刀具与工件动力学参数优化匹配，建立了刀具动力学参数自适应（TDA）抑振方法。研究成果进一步丰富和发展了薄壁筒、细长轴等零件的车削颤振在线监控方法，也为智能制造中机器人切削加工的颤振控制提供一种新的解决思路。