The Effect Of Different Boundary Restraints On Residual Stress And Deformation Of Typical Welded Joint For Low Alloy Steel

Welding is a rapid heating and cooling process,the weld region cannot expand and contract freely owing to the constraints of the surrounding workpiece body,and the welding residual stress and deformation will inevitably occur in the workpiece after cooling.The presence of welding residual stress not only reduces the load-bearing capacity and fatigue strength of the component,but also increases the risk of its brittle fracture.In addition,welding deformation will also have an adverse effect on the appearance and processing accuracy of the product.There are many factors affecting the welding residual stress and deformation.In addition to the material factors,welded joint form,welding process parameters and other factors.,the external and internal boundary restraint states of the welding specimen have a significant impact on the residual stress and deformation.Therefore,it is of great significance to study the welding residual stress and deformation of low alloy steel under different restraints for the safety assessment of steel structures.Based on the finite element software ABAQUS,the thermal-elastic-plastic finite element method was used in this paper to study the influence of different boundary restraints(free condition,fixture restraint,structural restraint,transverse restraint)on the residual stress and deformation of Q345 steel plate butt joints,the changes of residual stress and deformation before and after release of boundary restraints were analyzed,and then clarifies the efficiency of various restraints to control welding deformation.Moreover,according to the characteristics of thick plate T-joints,the influence of structural restraints caused by stiffeners on the residual stress and deformation of thick plate T-joints was studied,and the effect of the distance between the stiffener and backplate(L)and the width of stiffener(D)on the residual stress and deformation of thick plate T-joints was numerically analyzed.The results show that:(1)For the plate butt welded joint,each boundary restraint can significantly affect the transverse residual stress of the plate butt welded joint,and the transverse residual stress distribution under different restraint conditions is remarkably different,but the boundary restraint has little effect on the longitudinal residual stress of the plate butt welded joint.After the boundary restraint was released,the transverse and longitudinal residual stresses of the plate butt welded joint are reduced,and the peak values of residual stresses are lower than those under free condition.(2)Each restraint condition can effectively control the welding deformation of the plate butt welded joint,the control efficiency of the angular distortion under clamp restraint and structural restraint are 58.4% and 65.2%,respectively.Although the transverse restraint condition can best control the welding deformation,its restraint strength is too strong,which is difficult to achieve in practical engineering applications.Therefore,in practical engineering applications,it is recommended to use structural restraint to control the welding deformation of thick plate welded joint.(3)For T-joints,before removing the stiffener,the structural restraint can substantially reduce the welding residual stress of both the web and flange surfaces facing the stiffener and slightly rise the welding residual stress of both the web and flange surfaces facing away from the stiffener.After the removal of the stiffener,the welding residual stress of the T-joint can be recovered to a certain extent,which is slightly lower than the welding residual stress of the T-joint under free condition.(4)The structural restraint can effectively control the angular distortion of the web,but the control efficiency of the angular distortion of the web will be reduced after removing the stiffener.For thick-plate T-joints with the stiffener,the welding residual stress and angular distortion of the web decrease with the increase of the distance between the stiffener and the backing plate(L)or the stiffener width(D).In the cases of high levels for L or D,it is less efficient to reduce the welding residual stress and angular distortion by increasing L or D.Additionally,properly adjusting the stiffener location can control the angular distortion of the web more effective than changing the stiffener dimensions.