Technology Research On Ultrasonic Welding Of Titanium Alloy And The Preparation Of Titanium Alloy Smart Structure

Compared to polymer-matrix smart composite materials, metal matrix smart composite materials with higher strength, long durability, high working temperature, no aging, no degradability, better adaptability to bad condition, etc. Ultrasonic welding technology and preparing technology for smart structure of titanium alloy were studied in this paper. Massive experiments on welding titanium alloy were performed to obtain the best welding process parameters and smart structure of titanium alloy were prepared by ultrasonic welding.Tensile test, stripping test and microhardness test for sample of titanium alloy were performed to analysis the mechanical property of welded joints, when welding press and welding time are1144.53N and125ms respectively, the resistance to shear, stretching shear strength, stripping resistance and peel strength of titanium alloy are going to be maximum respectively and the values are1940N,121.25Mp,170N and42.5KN/m respectively. With the welding time increased, the influence of the processing for surface oxidation film of sample on shear strength is weakened. In the best welding time, the shear strength for sample with oxidation film removed has little change. When the welding time is135ms, the hardness on the interface is going to be maximum.Infrared radiation thermometer, metallographic microscope, energy spectrum analyzer(EDS) and scanning electron microscopy(SEM) were applied in this paper to analysis the microstructure and mechanism of ultrasonic welding for titanium alloy. The results show that the temperature of ultrasonic welding for titanium alloy range from37%to70%times of the melting point. Machinery combination which occurs at the primary stages of ultrasonic welding will disappear with the welding time increased. The main spread of ultrasonic welding is dislocation diffusion. Welding pressure, welding energy, the hardness and yield strength plays decisive role in the quality of welding joint.Thermal-structure coupled finite element model which is two dimensions and axial symmetry is built and the temperature field and stress field of titanium alloy ultrasonic welding with different welding parameters are analysed by ABAQUS software. The results show that high temperature mainly concentrates upon weld interface and the highest temperature(1172.4℃) is located in the center of the weld interface and the temperature at the edge of the welding head is half of the one in the center of the weld interface. Temperature rise for welding rises sharply in the first10ms, but with the time increased, the growth of temperature rises become gentle. The maximum stress occurs in the center of the top surface of the anvil and it increases slightly with the increase of the welding pressure. The second largest stress occurs in the place of the interface under welding head edge of titanium alloy and it increases significantly with the increase of the welding pressure.This paper studies the rapid prototype for titanium alloy smart structure and sensing properties of FBG electroplated with nickel which is embedded in the structure of titanium alloys directly or indirectly by the method of ultrasonic welding. The experimental results for FBG embedded directly in the structure of titanium alloys show that titanium alloy is not suitable to be the matrix for the FBG to embedded in. But the experimental results for FBG embedded indirectly in the structure of titanium alloys show that the temperature sensitivity for FBG electroplated with nickel and embedded in the structure of titanium alloy is2.13times of FBG which is not electroplated with nickel and is1.11times of FBG electroplated with nickel. Therefore, The approach of studying FBG in this paper is one of the feasible methods.