Study Of The Ultrasonic Welding And Resistance Heat Assisted Welding Process Based On Simulation Analysis

Ultrasonic welding(USW)is a green and efficient joining technology,which has recently been extensively study.However,the mechanisms of welding are still not clearly understood.This is due to the complex nature of mechanical-thermal-metallurgical interaction at the welding interface that occurs during the welding process,which leads to quality and robustness of the joints needing to be increased.Resistance heat assisted high power ultrasonic welding(RUSW)is a promising welding technology,which will hopefully improve the welding process and promote welding quality by the addition of resistance heat generated from the current flowing through the welding interface.There are very few studies about RUSW and it is still in the initial stage of research.This study investigates Cu/Al ultrasonic welding,which is widely used in the new energy field.Moreover,the finite element analyses and experimental methods are used to investigate the behavior and mechanism of USW and RUSW,which can provide theoretical basis for optimization and application of USW and RUSW.The finite element model of USW and RUSW have been developed based on the commercial ANSYS software.In order to accurately simulate the electrical-thermal-mechanical coupling,the work of friction at each contact,heat of plastic deformation in materials,contact resistance,ultrasonic softening,and temperature-dependant properties of materials have been considered in the models.These models were verified by comparison of predicted interface temperature,sonotrode displacement and the weld cross-section profile with the experimental results.The simulation results are in consistence with the experimental results.This demonstrates that the model can be used to investigate the USW and RUSW process.Along with the temperature and plastic strain distribution,the materials penetration during USW process has been investigated by the model.The results show that the maximum temperature occurs at the sonotrode/copper interface,sonotrode tip teeth penetration into the upper specimen starts at an earlier stage and increases rapidly,reaching the maximum,but anvil tip penetration into lower specimen starts later and increases slowly.The plastic deformation area of the welding zone increases exponentially,and then keeps constant.The total plastic strain of welding zone is approximate proportional to the displacement of the sonotrode tip.The thickness of intermetallic has been predicted by consideration of temperature and ultrasonic action at the plastic deformation area.The result shows that the thickness of intermetallic layer is dominated by ultrasonic action rather than interface temperature,and increases as the welding time increases.The mechanism of weld interface action in RUSW has been studied.The influence of additional resistance heat on ultrasonic welding has also been investigated by comparing of simulated interface temperature and plastic deformation at the same time.The advantage of RUSW is reflected by comparing the simulation results of RUSW with the longer USW duration.The resistance heat can significantly increase the interface temperature,accelerate the penetration process of the teeth and promote the plastic deformation in the specimens simultaneously.A thinner intermetallic compound(IMC)layer is obtained for distribution with similar interface temperature and plastic deformation.The interface temperature in RUSW is greater than the sum of single ultrasonic energy and resistance heat.The welding pressure affects friction work and contact resistance,which changes with temperature.The interface temperature in RUSW first increases and then decreases with increase in pressure.