分离-接触特征对钛合金超声振动辅助铣削加工特性影响规律研究

Effect of Separation-contact on the Processing Characteristics of Ultrasonic Vibration-assisted Milling of Titanium Alloy

超声振动铣削中分离-接触特征会影响钛合金的高效高质量加工,为了更深入的认识分离-接触特征对超声振动辅助铣削的影响,建立了接触率、平均切厚比的铣削模型,并提出基于平均切厚比的超声作用判别准则;通过开展铣削实验,讨论了周期性与持续性接触超声铣削中接触率与平均切厚比的作用机理;研究了不同铣削与超声参数对刀具磨损的影响规律。结果表明:在纵向超声振动辅助铣削钛合金时,分离效应与平均切厚效应共同作用使得超声加工相较于传统加工能改善加工质量,在周期性接触铣削中,刀具-工件周期性接触的间歇切削现象引起的分离效应是铣削力与表面质量改善的主要因素,在持续性接触铣削中(接触率为1),单位周期的平均切削厚度降低现象引起的平均切厚效应使得在一定范围内刀具-工件不分离也能降低铣削力,改善表面质量;Ti-6Al-4V钛合金存在临界切入速度值,约为42m/min,合理搭配主轴转速及超声振幅可改变切入速度以防止刀具磨损,这对钛合金的高效高质量加工与工艺控制具有重要的作用。

The separation-contact in ultrasonic vibration milling will affect the high-efficiency and high-quality machining of titanium alloys.To further understand the influence of separation-contact on ultrasonic vibration-assisted milling,the milling models of contact rate and average cut thickness ratio are established,and the discrimination criterion of the ultrasonic action based on the average cut thickness ratio is proposed.By carrying out milling experiments,the mechanism of contact rate and average cut thickness ratio in periodic and continuous contact ultrasonic milling is discussed.The effect of milling and ultrasonic parameters on the tool wear of titanium alloy is investigated.The results show that the separation effect and the average thickness effect can improve the machining quality compared with traditional machining in longitudinal ultrasonic vibration-assisted milling of titanium alloy.In periodic contact milling,the separation effect caused by intermittent cutting of the cutter-workpiece is the main factor in reducing the force and improving the surface quality.In continuous contact milling(contact rate is 1),the average cutting thickness effect caused by the decrease of the average cutting thickness per unit period can reduce the force and improve the surface quality within a certain range.There is a critical cutting speed value of Ti-6Al-4V titanium alloy,which is about 42 m/min.A reasonable combination of spindle speed and ultrasonic amplitude can change the cutting speed to prevent tool wear.This plays an important role in the high-efficiency and high-quality machining and process control of titanium alloys.