Prediction And Control Of Welding Stress And Deformation In Constructional Steel Structures Based On Finite Element Analysis

Steel structures have been widely applied in construction field due to their light self-weight,high strength,excellent seismic performance and recyclability.Fusion welding technology is the main connection method of steel structures.Residual stress caused by welding process has negative impact on the bearing capacity,stability and safety of constructional steel structures.Welding deformation not only affects the appearance quality of the product,but also reduces the assembly accuracy of steel structures.Therefore,how to predict and control welding stress and deformation is extremely important to ensure safety and integrity of construction steel structures.In this paper,based on ABAQUS software,a sequential coupled thermo-elastic-plastic finite element method(FEM)was developed to simulate the welding temperature field,residual stress and deformation.In order to obtain the welding residual stress and deformation accurately and efficiently,a high accuracy material model and calculation methods for engineering applications were developed.Using the developed calculation methods,the welding stress of the diaphragm in a square tubular column-H beam was simulated and regulated,and the angular distortion of thick-plate T-joints with single V-groove was controlled.An accurate and efficient material model is essential for solving practical engineering problems with the FEM.Based on ABAQUS software,a FEM with considering mechanical properties of welded metal,strain hardening,annealing softening effect and solid-state phase transformation(SSPT)was developed to simulate the welding residual stress and deformation of Q345 steel butt-welded joint.Following material factors were discussed in the material model: the yield strength of the base metal and welded metal was separately considered;isotropic hardening model and annealing softening model were applied;the diffusion type SSPT and non-diffusion SSPT were respectively simulated using JMAK equation and K-M relation.The effects of these material factors were studied on the calculation accuracy and efficiency of the welding residual stress and deformation.In order to accurately and efficiently predict the welding residual stress and deformation of Q345 steel butt-welded joint,the mechanical properties of the base metal and welded metal should be separately consiered,as well as the strain hardening and annealing softening effect,and the SSPT can be ignored.Constructional steel structures are usually made of thick-plate welded-joints with many welding passes,which have huge calculation scale.In order to improve the calculation efficiency,the influences of instantaneous heat source model and the mesh density in the longitudinal direction were investigated on the welding residual stress and deformation of thick-plate T-joint.The results show that the calculation method of instantaneous heat source model can obtain the welding residual stress with considerable accuracy in a short time,and the mesh density in the longitudinal direction has slight influence on the welding residual stress.However,the calculation method of instantaneous heat source model seriously underestimates the welding deformation.Using the calculation method of the instantaneous heat source model,the influence of the pattern of lumped welding passes was studied on the welding residual stress of thick-plate butt joint.In order to ensure the calculation accuracy of welding residual stress,the correction formula of total heat input of lumped passes model was proposed.The results show that the pattern of lumped surface passes significantly underestimates the welding residual stress in and near the cover passes of the welded joint.The patterns of lumped filler passes can accurately predict the welding residual stress on the surface of the welded joint,but slightly increase the welding residual stress in the filler passes zone of the welded joint.This study provides efficient calculation methods for predicting welding residual stress of large steel structures.Square tubular column-H beam consists of a large number of cruciform joints and T-joints.The diaphragm of the square tubular column and the flange of the H-beam have the tendency of lamellar tearing.In this paper,the welding residual stress and the peak stress during the whole welding process in the through-thickness direction were used to evaluate the mechanical factor of lamellar tearing.The welding stress distribution of the square tubular column-H beam was simulated using the FEM with instantaneous heat source model.By comparing the welding stress of the diaphragm and the flange in the through-thickness direction,it is found that the region and magnitude of the high peak stress of diaphragm are larger than those of the flange.A cruciform joint model with the diaphragm was established,and its welding stress was calculated using the FEM with instantaneous heat source model and lumped passes model.The welding stress of the diaphragm in the through-thickness direction was regulated from three aspects: welding sequence,pass arrangement and strength grade of welded metal,to alleviate the lamellar tearing tendency of the diaphragm.The results can provide theoretical guidance for alleviating lamellar tearing from the mechanical factor.In the actual production,the angular distortion of thick-plate T-joint with single V-groove is a very prominent problem.In this paper,optimization of pass arrangement,structural restraint and preseeting methods were respectively used to control the angular distortion of thick-plate T-joint with single V-groove.In order to accurately predict the angular distortion,the moving heat source model was used to simulate the welding heat input.The results show that the pass arrangement that welding passes are attached to the flange with surfacing welding can reduce the angular distortion by 32%.The structural restraint method can reduce the angular distortion by 69%.The initial presetting was determined by the FEM,and the presetting method can nearly eliminate the angular distortion.In this paper,the prediction and control of welding stress and deformation of constructional steel structures were systematically investigated based on the FEM.It is of great scientific significance to establish high accuracy material model and calculation methods for engineering applications.It is of important engineering application value to regulate the welding stress of constructional steel structures and control the angular distortion of thick-plate welded-joints.