The Research On Temperature And Residual Stress Field By Flux Band Constrained Arc Welding

High-strength steel metal sandwich panels have the advantages of high s pecific strength,high specific rigidity,fire resistance and light weight,which is widely used in ships,vehicles and other industries.In this paper,Flux band constricting arc welding(FBCA)of high-strength steel metal sandwich panels is used to obtai n a well-formed weld joint and solve the problem that the face plates and core plate can’t be fully fused by laser welding.The research focus of this paper is mainly on the analysis of welding temperature field,residual stress field and deformation field.Therefore,an infrared thermal imaging system and a stress-strain test system were constructed to study the temperature distribution during w elding,the residual stress and deformation after welding,At the same time,the finite element simulation of the short and long welds of the T-joint was performed to analyze and predict the stress and strain evolution during the process.In order to obtain a high-strength steel metal sandwich plate T-joint weld with high assembly accuracy and excellent weld quality.In this paper,by improving the welding fixture and testing a variety of welding processes,a well-formed weld joint with fully fused panels and core plates is obtained.At the same time,the welding parameters of 25 V,280A,45cm/min is the best parameters.Based on the infrared thermal imaging system,the temperature distribution of different welding process on the face-plates was observed,and it was found that under different welding processes,the temperature distribution of the molten pool and the near-seam area had a large difference,and the temperature distribution difference increased with the increase of welding heat input.In the length direction of the weld,the temperature gradient at the front end of the weld pool increases as the welding heat input increases.In the direction of the vertical weld,the temperature drop gradient under the large process parameters much greater than that of the small process parameters,and the temperature difference in the direction of the vertical weld bead of different welding current welding is smaller than that of different welding speeds or different voltage welding.At the same time,the research also found that the temperature and the degree of burnout of the flux band basically increased with the increase of welding parameters,but the unburned flux bands didn’t undergo a large temperature change with the progress of the welding process.A hybrid heating model coupled by a gaussian face heat so urce and cylindrical volume heat source is used to analysis characteristics of welding-induced temperature distribution during the process of the FBCA T-joint welding.The thermal contact conductance is considered emphatically between the fixture and work piece during the simulation.By comparing the results between the experiment and simulation,it is found the cross section of the joint,the area of the HAZ and welding thermal cycling curves are basically consistence between the experiment and simulation,which proves the validity and feasibility of the hybrid heat source model on the analysis of this method.At the same time,it was found that the residual stress is concentrated on the weld and its vicinity,which is much lower than the yield stress of the material.And the residual deformation is acceptable,that the maximum distortion happened on the edge of the panel,according to the experimental measurements.This indicates that the FBCA can effectively control the residual deformation of high-strength steel T-joints,which improves the reference for the welding of sandwich panels.Finite element analysis of stress field and strain field in different test areas of long welds of T-joint by using straight-through welding and three kinds of segmented welding.In terms of residual stress,the residual stresses obtained by straight-through welding and segment welding in different directions and test areas are mainly concentrated in the near-seam area.In different test areas,the residual stresses obtained from the simulation of straight-through welding show a similar distribution law in all directions compared to the segmented welding,while the segmented welding in the middle of the weld will appear more complicated distribution of stress in the transverse and thickness direction at the junction of the two welds.In terms of value of stress,the residual stresses generated by the straight-through welding and the segmented welding in the transverse and thickness directions are much smaller than the longitudinal stress,and the residual stress at the welding junction of the segmented welding is less than that obtained by the straight-through welding,but it is greater than the straight-through welding in other areas Income.By comparing the residual stresses obtained from the segmented welding and the straight-through,it is found that the straight-through welding has the smallest residual stress in the long weld of the T-joint.In the finite element analysis of the residual strain of the long weld of the T-joint,in different test areas,the residual strain simulated by the tr ansverse and thickness directions of the straight-through welding and the segmented welding in the near seam area shows compressive deformation.When it is far from the near seam area,the compression deformation is decreasing,and the compressive deformat ion continues to the edge of the sheet in the transverse direction,and it changes to tensile deformation in the thickness direction and reaches the peak value;in the longitudinal direction,the longitudinal strain distribution obtained by segment welding is quite different from that obtained by straight-through welding.In terms of value of residual strain,the transverse and longitudinal residual strains of segmented welding and straight-through welding are much smaller than those obtained in the thickne ss direction,and the difference of the strain values generated by the segmented welding in the middle and rear end of the weld is small,but greater than that generated in the middle of weld;There is a certain difference in the residual strain generated by straight-through welding at the front end,middle and rear end of the weld,however,the difference is small.Through the comparative analysis of the strains generated in the front,middle and rear ends of the long weld by straight-through welding and segmented welding,it can be seen that the residual strain obtained by sequence 3,welding from the middle of the long weld to the two ends of the long weld of T-joint in turn,in the front end and middle section is the smallest,and the residual strain obtained in the straight-through welding simulation is the smallest at the rear end of the weld,but the difference from the residual strain obtained in sequence 3 at the rear end of the weld is small.Therefore,the sequence 3 in segmented welding—residual strain from the middle of the long weld to the two ends in sequence is the smallest overall.