# Research on a Composite Power-Superimposed Ultrasonic Vibrator for Wire Drawing
## 1 Introduction  
Titanium and its alloys are used in aircraft, armor plating, naval ships, spacecraft, and missiles due to their high tensile strength to density ratio [1], high corrosion resistance [2], fatigue resistance, high crack resistance [3], and ability to withstand moderately high temperatures without creeping. However, they are also of high resistance, which make them difficult to machine, especially for the wire-drawing process. Conventional processing methods are involved, with complicated heat preparation, surface treatment and multiple vacuum annealing [4; 5; 6], which is neither energy-saving nor environmental friendly. In addition, they involve high wire breakage ratio, large contact or friction force, and poor surface quality [7]. Ultrasonic-vibration drawing, which applies ultrasonic vibration to the die axially or radially, contributes to the improvement of lubricant conditions, the softening of metals and the reduction of drawing force [8; 9; 10]. Therefore, it is promising to superimpose ultrasonic vibration in the process of titanium wire drawing. In the previous studies, [PERSON] and [PERSON] [11] firstly observed the \"volume effect\" of ultrasonic vibration during a static tensile test of zinc monocrystal. The phenomenon was similar to that of the thermal softening effect, with decreased yield stress and flow stress, and was more efficient [12]. [PERSON] and [PERSON] [13] carried out the study to fabricate fine wires using the longitudinalultrasonic-vibration drawing method. [PERSON] _et al._[PERSON] _et al._ (2014) carried out chlorine-free skin-pass drawing of stainless steel wires through the application of the radial direction ultrasonic-vibration drawing method. [PERSON] _et al._[PERSON] _et al._ (2015) carried out an oxygen-free brass wire drawing experiment on the LH-200/17 drawing machine at the approximate speed of practical production using an ultrasonic vibrator which can achieve a maximum amplitude of about 20 \(\upmu\)m. The ultrasonic vibration reduced the drawing force by 7% and greatly improved the surface quality of the wire. He also developed a orthogonal composite ultrasonic-vibration system for titanium and titanium alloy wire drawing ([PERSON] _et al._, 2016), but the surface quality was poor. [PERSON] _et al._[PERSON] _et al._ (2016) developed a new piezoelectric ceramic longitudinal-torsional composite ultrasonic vibrator with four uniform slant slits cut off at the end of the ultrasonic amplitude horn to transform the longitudinal ultrasonic vibration into a L & T composite motion. The torsional and longitudinal amplitude of the vibrator could reach 0.25\({}^{\circ}\) and 25 \(\upmu\)m, respectively. He then applied it to titanium wire drawing, and it was proven that the new system could apparently reduce the drawing force, though at the sacrifice of surface quality due to its higher friction force within the contact area. We attribute the cause of the difficulties in titanium wire drawing to the inadequate power intensity of ultrasonic vibration, considering the relatively high resistance of titanium and titanium alloy wires. Therefore, we intend to develop an ultrasonic system which can produce much greater longitudinal amplitude. However, it is impractical to develop an ultrasonic vibration system with a single ultrasonic transducer that can provide enough power for both the limitation of structural parameters and for that of the piezoceramic's property. Thus, a power-superimposed vibration system was proposed with three ultrasonic transducers uniformly distributed along the disc, which acts as a component of the amplitude horn. The piezoceramic stacks were poled axially to transfer vibrational energy radially to the center of the disc. The disc will transform the radial vibration into longitudinal vibration due to the Poisson effect. In order to study the characteristics of the ultrasonic vibrator, the frequency equation of the system was established using the four-terminal network method, and the finite element model was built in ANSYS.