NiTi shape memory alloy is widely used for its excellent superelasticity and shape memory effect. As a solid phase bonding technology, it has certain advantages in the bonding of NiTi shape memory alloy flakes. It is difficult to study the mechanism of ultrasonic welding by means of experimental observation because of its instantaneous and complicated welding process. Aiming at the problem that the temperature is difficult to monitor in the ultrasonic welding process, a two-dimensional finite element analysis model of NiTi shape memory alloy ultrasonic welding is established by ANSYS, the influence of ultrasonic amplitude on the distribution of welding temperature field is investigated. The thermocouple temperature measuring platform is built to collect the temperature data of welding test process, and the validity of the finite element analysis model is verified. Based on the numerical simulation results, the connection mechanism of NiTi alloy ultrasonic welding is analyzed. The results show that the welding temperature field is positively correlated with the amplitude. The maximum welding temperature increases by about 45℃ for every 5 μm increase in amplitude under the fixed welding condition. The test results show that the simulation results are in good agreement with the test data. The maximum temperature differs only by 4℃, and the error does not exceed 3% of the maximum temperature. Combining the test results with the simulation results, the NiTi alloy does not melt during the ultrasonic process, and the joint is a solid phase connection. © 2020 Journal of Mechanical Engineering.
