超精密铣削加工中的刀具与工件接触分析和动力学模拟

In this proposal, the study will focus on creating a contact/friction model to simulate the contact interface between a milling cutting tool and a workpiece during a ultra precision machining process. The model will be able to represent the transient contact interface occurred during the machining process. By analyzing the surface characteristics of the contact interface between the tool and the workpiece, the contact/friction model will improved to represent multiple contact phenomenon occurred during the machining process. After that, the study will be on developing a fundamental and representative dynamics model for the ultra precision machining system during the process of a particular work piece. By applying a modified contact/friction model to simulate the contact interface, as well as obtained parameters that represents critical system characteristics, the dynamics model will be able to describe the complex dynamic systems with nonlinear and unstable nature. The model will be further analyzed and simplified with reduced order. The model will be further analyzed for its robustness in describing the machining of complex components and complicated processes. An experimental platform with joint in-situ machining and measurement capabilities will be developed during this study. Atomic force microscopy and nano-indentor will be used to characterize the surface property of the machining interface. A combination of measurement equipments, including laser Doppler vibrometer, position sensitive detectors and acoustics emission sensors, will be used to in-situ measure the machining interface for dynamic characteristics. Components functioning as adaptive damping and adaptive stiffness will be used to control the vibration amplitude of the system. Using the feedback from the model and adjustment of functional components, the vibration amplitude of the system during the machining process will be greatly suppressed. Upon completing of this proposed study, the system will be able to adaptively adjust to transition from different conditions. Signals from the measurement system, as well as intrinsic velocity and rotation of the machine system will be used as input for the reduced order dynamics model. The model will then be used to guide the adjustment of the stiffness and damping of the system. With the vibration amplitude of the system been greatly suppressed, the precision of the machining system will be significantly improved.

本项目研究建立接触摩擦力学模型并完善其对超精密铣削加工过程中刀具和工件接触界面的模拟，研究超精密铣削加工过程中刀具和工件的瞬间接触界面，对各自表面特征（几何形貌、粗糙度等）予以单独分析，探索和完善模型对超精密铣削加工中多种接触摩擦现象的模拟。在此基础上，研究并建立多尺度、多自由度动力学模型并检验其对加工过程的模拟，并对其进行降阶求解。实验上，研发建立加工-测量-调节一体化超精密铣削加工软硬件实验平台。应用多普勒干涉仪、位置敏感检测器、加速度传感器、次声波传感器等对刀具和工件进行多自由度实时测量。最终实现以检测的实时参数为变量，应用动力学模型的实时计算结果为指导，控制主动阻尼和主动刚度部件，对系统特征参数（刚性、阻尼、自振频率和模态等）进行调节，以达到提高超精密铣削加工系统的加工精度的目的。

面向超精密加工系统的研究，由于系统的多样性和加工对象的差异性，涉及对加工过程的物理分析和数值模拟、加工方式的分析优化、加工系统整体设计和加工过程的测量等方面。而机械加工过程是刀具对于工件的相对运动致使工件材料发生弹塑性变形和屈服剥离的过程，其中的塑性形变通常是一个非线性的过程，因此建立力学模型对其进行精确模拟十分具有挑战性。刀具和工件的摩擦接触振动和夹持工件的主轴动平衡振动对加工质量有显著影响。基于加工接触力学和机床动力学特性对精密加工过程的影响，本项目研究并建立了刀具-工件接触摩擦力学模型并完善了其对超精密铣削加工过程中刀具和工件接触界面的模拟，研究并建立了基于牛顿动力学方程方程和欧拉动力学方程的多尺度、多自由度耦合的主轴动力学模型。采用matlab完成了动力学仿真检验了其对超精密车削加工过程的模拟，搭建了基于正交激光多普勒干涉仪的超精密主轴振动测量系统，采用改进CEEEMD算法对振动信号进行误差分离，以实测振动信号检验了五自由度耦合主轴动平衡动力学模型的正确性，最后研究了超精密主轴动平衡对表面参数的影响。