Finite Element Analysis Of Residual Stress For Welded Joint Of 7A52 Aluminum Alloy Before And After Surface Nanocrystallization

7A52 super-hard aluminum alloy is a kind of material commonly used in welded components of military vehicles. In this paper, based on surface nanocrystallization(SNC) test of TANDEM MIG welded joint of the alloy, by finite element software ANSYS, a finite element analysis was made on residual stress of the welded joint before and after surface nanocrystallization. The impact on the welding residual stress that be made by SNC was discussed profoundly in theory, in order to provide theoretical guidance for the SNC test research of the welded joint of 7A52 aluminum alloy. The main results and conclusions were obtained as follows:(1) The calculation results of welding temperature field indicate that: Through the use of“Birth and Death”element technology of ANSYS, the dynamic process of filling weld is achieved in the process of multi-pass welding, and is basically in line with the actual testing process. The maximum temperature of weld zone can reach 837℃, and be consistent with theoretical calculation.(2) The calculation results of welding stress field indicate that: The longitudinal residual stresses of weld zone are both tensile stress. The values of tensile stress are between 24 and 99MPa along the direction of plate width, but the maximum tensile stress is 68MPa along the weld direction. The transverse residual stresses of weld zone include not only tensile stress but also compressive stress. Along the direction of plate width, there are both tensile stress, and the maximum value is 22MPa. But along the weld direction, there is compressive stress at both ends, and the maximum value is 16MPa. There is tensile stress in the middle of the weld, and the maximum value is 22MPa.(3) The calculation results of stress field of solution-artificial aging treatment indicate that: The longitudinal residual tensile stress of weld zone decreased. Along the direction of plate width, the maximum tensile stress reduced to 56MPa from 99MPa that of before solution treatment. But along the weld direction, the maximum tensile stress reduced to 56MPa from 68MPa that of before solution treatment. The transverse residual stresses of weld zone include not only tensile stress but also compressive stress. Compared with the pre-solution treatment, tensile stress decreased, and compressive stress increased. Along the direction of plate width, there are both tensile stress, and the maximum tensile stress reduced to 18MPa from 22MPa that of before solution treatment. But along the weld direction, there is compressive stress at both ends, and the maximum compressive stress increased to 17MPa from 16MPa that of before solution treatment. There is tensile stress in the middle of the weld, and the maximum tensile stress reduced to 18MPa from 22MPa that of before solution treatment.(4) The calculation results of SNC stress field indicate that: As the High-Energy Shot Peening(HESP) time increased gradually, along the directions of plate width and weld, the longitudinal and transverse residual stress were changing as follows: The tensile stress decreased gradually and converted to compressive stress, and the compressive stress increased gradually. Saturation time of HESP is 30min. The longitudinal residual stresses of weld zone include not only tensile stress but also compressive stress. Along the direction of plate width, the maximum tensile stress reduced to 27MPa from 56MPa that of before HESP, and the maximum compressive stress increased to 27MPa from 10MPa that of before HESP. Along the weld direction, the maximum compressive stress is 13MPa, and the maximum tensile stress reduced to 27MPa from 56MPa that of before HESP. The transverse residual stresses of welded joint are both compressive stress. The maximum compressive stress is 20MPa along the direction of plate width, and the maximum compressive stress increased to 39MPa from 17MPa that of before HESP along the weld direction.