| As a traditional machining technology and connection method,welding technology is widely used in automobile manufacturing,shipbuilding and aerospace industry,which holds the dominant position in the national industry.However,welding is a highly nonlinear processing technology containing thermodynamics,metal microstructure transformation and uneven diffusion of hydrogen concentration,in the process of which the difference in the weld and metal temperature unit activity not only causes the welding residual stress and welding deformation after welding,but also affects the fatigue life of the structure.The traditional empirical method and analytical method are not perfect enough in accuracy as well as efficiency,making it hard to guide welding industrial production.With the improvement of the computer hardware level and the application of the finite element method,on the basis of the actual welding process,taking the three direct coupling relations of the welding mechanics(stress strain field),heat(temperature field)and metallography(microscopic state organization)into account,and the residual stress,welding deformation and hydrogen diffusion of welding parts can be with measured and analyzed in high efficiency and precision.Welding residual stress,welding deformation and hydrogen diffusion concentration are the important factors that affect the crack of the structure.There are many factors that affect these three factors,such as the constraints of mechanical boundary conditions,the position of weld in weld,the number and direction of welding and the heat treatment process after welding.However,the effect of part sequence is rarely mentioned,especially in the study of the effect of welding sequence on hydrogen diffusion mass fraction.Meanwhile,due to the complexity of the structure of industrial production and the large quantity of the weld,the suitable welding sequence then plays an important role in the residual stress,the deformation of welding parts and the decrease of hydrogen diffusion concentration.Therefore,how to analyze the residual stress,deformation and deformation of the welding parts,the concentration of hydrogen diffusion accurately and efficiently from various aspects and different research background has always been a focus in the field of welding numerical simulation.In view of the above research background,based on the heat transfer theory and actual welding experience of the welding structure,employing the direct coupling algorithm and the Dflux heat source subprogram written in the large finite element analysis software ABAQUS and Fortran language,taking the T-joint structure as the research object,this paper develops four different welding sequences form the perspective of the different heat source loading process of the weld of the left and right sides of the weld,and studies the influence of welding sequence on the residual stress and welding deformation of 6063 aluminum alloy materials of T-joint.The results show that the welding sequence exerts little influence on the equivalent residual stress and the transverse residual stress size and distribution of the T joint.The size of residual stress can be affected to some extent.Among all schemes,the longitudinal residual stress produced by scheme 1 and 3 welding parts is the smallest while and the maximum longitudinal residual stress is produced by scheme 4.The welding sequence has a great influence on the welding deformation of T-joint.The deformation caused by scheme 2 is the largest while the deformation caused by scheme 4 can be reduced by about 38%.As the diffusion of hydrogen is not obvious in the traditional aluminum alloy materials,the effect of four different welding sequences on the hydrogen diffusion concentration is studied with the T-joint of HQ130 steel as the research object.The results show that the welding sequence has little influence on the peak concentration of diffusible hydrogen,but has a great influence on the distribution of diffusible hydrogen. |
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