Influence Of Initial Deformation And External Restraint On Welding Distortion In Thin-plate Welded Joints And Structures

With the growing depletion of fossil energy and the worsening of the environment,the requirement for reducing the energy consumption and the pollution of transportation become more and more urgent.Being an effective way to achieve energy conservation and emissions reduction,the lightweight manufacture is the current trend.Welding technology is the key process of the lightweight manufacture in the industry like automotive industry and fusion welding is one of the most widely used metal welding methods.The discordant of instantaneous thermal strain of welding materials is given by the heat generations and lead to welding deformation.Moreover,welding-induced deformation will be a serious problem for the reason that the relatively stiffness of thin-plate or thin-plate structure is small.Since welding deformation of welded components can be early controlled by applying reverse deformation and external restraint,the research on the effects of the initial deformation and external restraint to welding deformation is necessary.Based on ABAQUS software,a thermo-elastic-plastic finite element method considered material nonlinearity and geometric nonlinearity was used to simulate the welding temperature and deformation of mild steel thin-plate weld joints in freedom condition.In addition,on the basis of this method,a thermo-elastic-plastic finite element method is developed with considering both material nonlinearity,geometrical nonlinearity and boundary nonlinearity to simulate the welding temperature and deformation of mild steel thin-plate weld joints in external restraint.The effectiveness of two kinds of finite element method used in this study was verified by comparing the simulated results with the measured data.By means of research combined experiment method with simulation method,the effects of the initial deformation and external restraint to welding deformation is revealed.What's more,the simulation method is used to explore effects of initial deformation and external restraint to welding deformation in complex thin-plate structure and the results of these studies can provide a valuable reference to direct production practice.The conclusions are summarized as follow: 1)The initial deformation can affect welding deformation by changing the relative position of weld bead and neutral plane.When weld heat input is large,the initial deformation can change the type of welding deformation and have small effect on the value of welding deformation.When weld heat input is small,the initial deformation can change the type and the value of welding deformation.2)Butt welding joint is achieved in external restraint and the external restraint is released after welding.When thin-plate buckling deformation occurs,the external restraint can change the type of welding deformation and have small effect on the value of welding deformation.When thin-plate buckling deformation not occurs,the external restraint can change the value of welding deformation and have small effect on the type of welding deformation.3)The finite element method used in this study can accurately predict the welding deformation of fillet-welded joint structure.Because of the extremely large welding deformation,the final deformation of fillet-welded joint structure is not sensitive to initial deformation.4)The finite element method used in this study can accurately predict the welding deformation in window frames of car's door,this result could be used to guiding production practice and theoretically directing the welding clamp design of car's door.