基于有限元分析的超声椭圆振动切削装置设计

Design of a Device for Ultrasonic Elliptical Vibration Cutting Based on the Finite Element Method

超声椭圆振动切削技术(ultrasonic elliptical vibration cutting,UEVC)是近年来发展起来的一种超精密加工技术,其加工装置的结构设计是当前研究的难点之一。通过分析现有的超声椭圆振动切削装置,设计了一种基于圆弧型柔性铰链结构的超声椭圆振动装置,利用有限元分析工具对该装置进行模态分析,找出了影响其谐振频率的关键结构参数并用全局优化模块优化参数,使装置的某一阶纵振和弯振模态的谐振频率一致,同时,对该装置进行了多场耦合分析以预测不同相位下的刀尖运动轨迹。仿真分析表明,后盖板长度的变化会引起纵振和弯振模态谐振频率的显著改变,而底座厚度的变化对纵振和弯振模态的谐振频率几乎都没有影响,顶端长度的变化仅对弯振模态的谐振频率有一定程度的影响。基于上述仿真分析及优化,制造出UEVC装置的样机并测量其谐振频率和振动特性,测量结果显示该装置的谐振频率测量值与仿真结果吻合较好,所开发的装置能在谐振状态下输出椭圆轨迹,同时,可通过调节施加电压的幅值和相位使得刀尖输出不同的椭圆轨迹,能用于脆性材料微结构曲面的加工。此外,对该超声椭圆振动切削装置施加频率与装置谐振频率一致的交流电时,其纵振和弯振的振幅将随电压幅值的增加而线性增大,其中弯振振幅对电压幅值的变化更为敏感。

Ultrasonic elliptical vibration cutting （UEVC） is a processing technology developed for ultra-precision in recent years.Its structure design is one of difficulties in current research.Based on the analysis of the current UEVC devices,a different UEVC that uses the circular flexure hinge was designed in this paper.Modal analysis of the device was carried out using finite element method （FEM） to identify the key structural parameters that affect the resonant frequencies.Its structure was optimized by the global optimization module to ensure that the resonant frequen- cies of the longitudinal and flexural vibration modal are the same.In addition,multi-field coupled analysis was performed to predict the motion tra- jectory of the tool tip in different phase shift.FEM results indicated that length of the back cylinder greatly affects the resonant frequency of lon- gitudinal and flexural vibration modal,while the thickness of the base had almost no effect on the resonant frequency,and length of the tip slightly affects the resonant frequency.Based on the FEM analysis and optimization,a prototype of UEVC device was fabricated.Its resonant frequency and vibration characteristics were measured by an impedance analyzer.Experimental results showed that the measured resonant frequency correlates well with the simulated one.Therefore,the designed UEVC device can generate elliptical trajectory at the resonant frequency.In addition,the vibra- tion trajectory can be tuned by adjusting the phase shift and the amplitude of the applied voltage,which enables the machining of micro-structured surface on the brittle material.Besides,when alternating current is applied to the UEVC device, and the frequency of the current equals to the res- onant frequency of the device.The amplitude of the longitudinal and flexural vibration linearly increases with the amplitude of the voltage.Never- theless,the flexural vibration is more sensitive to the change of the voltage than the longitudinal vibration.