Building Of Ultrasonic Stir Compound Welding System And Study On Ultrasonic Effect

Ultrasonic stir compound welding is based on friction stir welding by attaching an ultrasonic longitudinal vibration, changing the plastic flow of metal and providing a pathway of additional regulatory energy field to improve weld quality by through the strong effect of ultrasonic vibration. Present studies have shown that the ultrasonic agitation has had a positive effect on the welding, the average weld strength of ultrasonic stir compound welding improves and the weld grain refines. The metal activity of ultrasonic stir compound welding strengthened, mobility of the weld metal enhanced and stability of weld quality significantly improved than friction stir welding.To investigate the impact and mechanism of the ultrasonic vibration on weld, based on the longitudinal oscillation equation of ultrasonic horn with random variable cross-section and the principle of the vibration system, the Physical and mathematical models were established. Based on the above, The main structure of the different frequency of ultrasonic vibration system transducer, horn and tool rod was designed. The computer simulation of the new designed ultrasonic vibration System was Performed by employing the FEM soft ware ANSYS, through which the dynamic performance parameters were acquired.The new designed ultrasonic vibration system was tested through the impedance analyzer and amplitude measuring instrument, through which the Longitudinal resonant frequency, the amplitude of the displacement and other key performance parameters was tested. Mechanism of the ultrasonic was analyzed, through the ultrasonic stir compound welding experiments of thickness of2.7mm2519A aluminum alloy. By comparing of the residual stress measurement, defect detection, mechanical properties, microstructure, the results show that residual stress was lower,compared with low friction stir, which, with ultrasonic agitation positive residual stress,moreover the residual stress of front weld was lower, but the back residual stress was not far off, In addition, the residual stress of Central weld have significantly reduced. Defect detection have shown that the defect rate of ultrasonic stir compound welding was significantly reduced than FSW. Tensile test have shown that the strength of both kinds weld was similar, but the of strength ultrasonic stir compound welding is more stable. Microstructure shows the grain of ultrasonic stir compound welding is smaller and more uniform than FSW and the heat affected zone and thermo-mechanically affected zone is significantly reduced, comparing to FSW.By comparing the experimental results,the ultrasonic vibration in reducing weld residual stress,weld defect rate and improved the mechanism of weld was analyzed combining with the ultrasonic mechanical vibration effect, heat effect and volume effect.