Study On The Evolution Of Stress And Strain In The Process Of Controlling Welding Stress And Deformation In Aluminum Alloy Sheet By Trailing Ultrasonic Vibration

Aluminum and its alloys are widely used in industrial manufacturing because of their excellent physical and mechanical properties. However, the welding deformation in thin aluminum alloy plate is easy to occur in the process of welding, seriously affecting the quality of products and resulting in great waste and economic losses.Welding with trailing ultrasonic vibration is a new method of controlling welding deformation, which overcomes the shortcomings of traditional methods. When welding torch is traveling, the ultrasonic vibration moves at the same speed to extend weld metal continuously and compensates compressive plastic strain in the course of heating, so that residual stress and welding deformation can be controlled. Based on the method, finite element simulation and experimental verification was applied to study the evolvement law of dynamic stress and strain during the welding process,further explaining the mechanism of controlling welding deformation in thin alloy aluminum sheets with trailing ultrasonic vibration.The classical mechanical model of Inherent strain theory was introduced to explain the basic principle of controlling welding deformation in thin alloy aluminum sheets with trailing ultrasonic vibration. Finite element method was employed to conduct the numerical simulation calculation of temperature fields of LY12 aluminum under conventional TIG welding and analyze the distribution of temperature field. As a result, the plastic strain zone was determined. Based on the temperature field analysis result, the evolution of dynamic strain and stress was respectively studied under the conventional welding condition and the ultrasonic vibration. Three different changes in stress and strain during the welding with trailing ultrasonic vibration were found through comparisons. Subsequently, the welding temperature field was measured by the infrared thermal image and multi-channel temperature and the comparison between experimental results and simulated results showed good agreement between them, which verified the correctness of the temperature field simulated results. The residual strain under the two different conditions was measured respectively by staticstrain gauge, applying the sectioning method. The experimental data was in good agreement with the simulated data and its correctness simulated results were verified indirectly.The results show that welding with trailing ultrasonic vibration can effectively reduce residual stress and deformation caused by welding. Under supersonic wave vibration force, weld mental at high temperature which located in the position from a certain distance behind molten pool was obviously extended and due to the amounts of extension, the value of inherent strain would varies.