Analysis Of Influence Of Undercut Defect On Stress Concentration Of Hollow Ball Joints In Grid Welding

The space grid structure has the advantages of light weight,large span,fast construction and beautiful appearance,and is widely used in various buildings in China.The welded hollow ball node is used as the main node form in the grid structure and is widely used.However,the fatigue problem has always been an important reason for restricting the promotion and application of the grid structure.The cross section of the welded hollow ball joints in the grid structure changes greatly,and it belongs to the space stress state,and the stress concentration of the pipe ball joint is heavier.In addition to this,welding defects are common in the welding process of the joints,and the welding defects have a great influence on the stress concentration of the joints.Stress concentration is one of the important factors for fatigue damage of components and nodes.In this paper,the following research work is carried out on the stress concentration of welded hollow ball joints of different specifications in the flat grid structure:1?Using ABAQUS finite element analysis software,the effects of different structural details on the stress concentration factors at the weld toe and spherical weld toe of welded hollow ball joints were analyzed and the joint stress distribution law was obtained.The relevant influencing factors include the wallthickness T and diameter D of the welded hollow sphere,the wall thickness t and the diameter d of the steel tube.2 ? Using ABAQUS finite element analysis software,the effects of the degree of the same bite defect on the stress concentration coefficient at the weld toe and the spherical weld toe of the welded hollow ball joint were studied,and the joint stress distribution law in the presence of undercut was obtained.3? Through multi-factor regression analysis,the calculation formulas of stress concentration factors at the weld toe and spherical weld toe of the steel pipe without defects are obtained.The correction factor ? of the undercut defect is introduced,and the numerical solution of the stress concentration factor at the weld toe and the spherical weld toe of the steel tube is obtained,which provides a reference for the actual project.