Process Study Of Ultrasonic Assisted Vibration Drilling Aluminum And Titanium Alloys

In aviation industry, Aluminum and titanium alloys are widely used in making aircraft skins, structural parts, connectors of fuselage, engine disks because of high specific strength, strong chemical resistance and other advantages. Many aircraft components are connected by rivet and bolt, therefore a large number of connecting holes are necessary. Traditional drilling process with twist drill has problems such as high thrust force, tool wear, burr formation, low surface quality. It will be even more serious when drilling titanium alloy. Ultrasonic assisted drilling is proposed to solve these problems. In this paper, experiments were carried out in ultrasonic assisted drilling aluminum and titanium alloys. The change rule of thrust force, tool wear surface quality and burr were analyzed. The research content mainly includes:(1) The movement characteristic of ultrasonic-assisted drilling is discussed including the trajectory cutting edge, dynamic uncut chip thickness, dynamic cutting angle and cutting speed. Based on the characters of ultrasonic-assisted drilling, a drilling platform was set up including a 3-axis drilling-milling machine center, power transmission unit and ultrasonic vibration unit.(2) The amplitude and resonant frequency of twist drill in different material, with different diameter, extended length and power transfer mode were tested. The results show that the amplitude of HSS twist drill is 1.5-3 times of that of solid carbide twist drill. The resonant frequency of twist drill decreases with larger extended length. Under the same input current, the amplitude of drilling bit in the non-contact type power transmission unit is larger than the contact type. Among the machining parameters, spindle speed has the least influence on resonant frequency. Larger federate or smaller vibration amplitude in machining state results in a higher resonant frequency.(3) Experiments on thrust force in conventional and ultrasonic assisted drilling were conducted. The results show that thrust force in ultrasonic-assisted drilling is much lower than that in conventional drilling, and the influence of machining parameters on thrust force of the cutting lips and chisel edge is different. In conventional drilling, machining parameters have little influence on the thrust force distribution. In ultrasonic assisted drilling, increasing spindle speed will increase the thrust force of the cutting lips but has little influence on the thrust force of the chisel edge. Feed rate affects the thrust force of the chisel edge more significant than that of the cutting lips. Larger vibration amplitude results in smaller thrust force of the cutting edge. In orthogonal experiments of ultrasonic-assisted drilling aluminum and titanium alloys, feed rate influences trust force most, then amplitude, and spindle speed influences the least. Thrust force increases a little in a higher spindle speed when drilling aluminum alloy but decreases when drilling titanium alloy. Furthermore, ultrasonic-assisted drilling has less tool wear than conventional drilling.(4) In single factor experiments on amplitude in drilling aluminum and titanium alloys, better hole surface quality was obtained when amplitude increased. But scraping occurred when amplitude exceeded 10?m in drilling aluminum alloy. Separate cutting chip was observed in higher amplitude when drilling both aluminum and titanium alloys. Burr height decreased in ultrasonic-assisted drilling aluminum alloy. But amplitude had less influence in drilling titanium alloy. Higher burr height was noticed when amplitude exceeded 4?m. Ultrasonic-assisted drilling had a higher precision grade of pore diameter size than conventional drilling.