Finite Element Analysis And Experimental Verification Of Welding Residual Stress Controlled By Ultrasonic Impact Treatment

Welding structure is an indispensable connection mode in engineering construction.However,because of the existence of welding residual stress,the performance of components is affected,which endangers the safety of equipment.Ultrasonic impact treatment(UIT)is widely used because of its high efficiency and convenience.At present,the research of UIT is mostly through experimental means.And the accuracy of the simulation method needs to be improved due to the simplification of impact process and input parameters.Aiming at the problem,an improved numerical simulation method for accurately describing the UIT has been proposed in this paper.UIT was decomposed into two stages: the impact pin movement stage and the impact pin action stage.The simulation results were obtained by coupled calculation of welding process and UIT,and the accuracy of the finite element analysis was verified by comparison with the experimental results.The influence of relevant parameters on the calculation results in UIT simulation was studied.The main work and conclusions were as follows:(1)The impact pin rebound model was established to simulate the impact pin movement stage,in which the impact and rebound of the impact pin driven by the mechanical vibration of the waveguide,obtaining the stress and deformation of the stress-free specimen and the motion law of the impact pin.According to the analysis,the movement of the impact pin shows the law of increasing frequency and deepening indentation depth with the time,and tends to be stable in a short time.And the motion frequency of the impact pin is much lower than that of the waveguide.(2)The motion of the impact pin under different parameters was simulated,and the effects of the waveguide amplitude,the waveguide frequency and the gap between the impact pin and the sample surface on the motion law of the impact pin were analyzed.The results show that the waveguide amplitude has the greatest influence on the indentation depth of the impact pin,the gap between the impact pin and the sample surface has the least influence.The gap between the impact pin and the sample surface has the greatest influence on the movement frequency of the impact pin,and the waveguide frequency has the least influence.(3)The thermo-mechanical sequential coupling repair welding model and the dynamic ultrasonic impact model were established,in which the input parameters of the impact model were calculated by the impact pin motion simulation based on the impact pin rebound model,obtaining the welding temperature field and the residual stress field before and after UIT.It is found that the effect of UIT on the reduction of welding residual stress is remarkable.And the accuracy of the simulation method is verified by comparing the simulation results with the experimental results.(4)The model of UIT processing the weldment including the impact pin and the repair welding specimen was established,and the effects of the indentation depth,the impact frequency and the impact time of the impact pin on the reduction of welding residual stress were analyzed.The results show that the indentation depth of the impact pin has the greatest effect on the reduction of welding residual stress,while the impact frequency of the impact pin has little effect on the reduction of welding residual stress.