Analysis Of The Influence Of Weldirag Residual Stress On Steel Pipe-Welded Hollow Spherical Joints

Welded hollow spherical joint with circular steel tubes(hereinafter referred to as "pipe-spherical" joints)is one of the commonly used forms of suspension cranes in the space grid structure.Due to the limitations of its manufacturing process,welding residual stress is inevitably generated at the joint weld.The superposition of the residual stress near the weld and the cyclic reciprocating load of the crane makes the fatigue performance of the joint face a huge challenge,and it is necessary to study the residual stress of the joint welding.This article is jointly funded by the National Natural Science Foundation of China(51708384),the Shanxi Province Scholarship Program for Scholarly Scholars(DC1900000602)and the Shanxi Basic Research Youth Fund Project(201901D211017),based on the finite element simulation software ABAQUS,The welding process of the "pipe-spherical" joints was numerically simulated,and the distribution of the instantaneous temperature field on the joints and the residual stress field after welding was analyzed.By an axially stretching symmetrical welding joint,an asymmetrical welding joint and the joint without welding residual stress,the existence of welding residual stress and the influence of welding residual stress on the uneven stress distribution of joints under different welding processes are discussed.The main research work and conclusions are as follows:1.Using the finite element software ABAQUS to model the "pipe-ball" joint,considering the non-linearity of the material properties with temperature,using the life-and-death element technology to achieve solder filling and heat source movement,the joint welding process was numerically simulated,The instantaneous temperature field of the joint is obtained,and the shape and temperature variation law of the node temperature field are analyzed.The results show that during the welding process,the heat-affected zone above600?on the side of the steel tube is about 3 times that of the hollow sphere;the temperature field simulation results describe the process of temperature quenching and heat shock at the joint weld well,and the temperature field is verified accuracy.2.Using the thermal analysis finite element model,the heat transfer unit is converted into a stress unit,and the indirect coupling method is used to numerically simulate the symmetric welding residual stress field of the "pipe-spherical" joint.The blind hole method was used to verify the accuracy of the numerical simulation results of the welding residual stress field.The welding residual stress field is divided into two regions for analysis: the first region is the location of the welded joint,the stress field has a large influence range,and it is the region where the maximum residual stress is located;This area has a stable temperature field,and the residual stress cloud is more regular than the area I.3.Two sets of measuring points are selected symmetrically in the second area of the joint residual stress field,and the results of the measuring points are plotted as a scatter plot.The residual stress gradually decreases with the increase of the distance from the welding toe in the axial direction of the steel pipe,and the residual stress value decreases first and then increases in the radial direction of the hollow ball within 14 mm from the welding toe.In the range of14 mm to 18 mm,the residual stress value decreases gentle.In the circumferential direction of the welding toe,the residual stress stress curve of the welding of the steel pipe and the hollow sphere is symmetrical,and the change trend is the same,but the residual stress value of the steel pipe at the welding toe is higher than that of the hollow sphere.4.For the study of two kinds of welding form of node stress non-uniform welding residual stress,the asymmetric welding node welding residual stress field is simulated,asymmetric welding residual stress in steel tube axial,radial and symmetry with the hollow sphere welding residual stress distribution are the same,the weld toe rings to the direction,asymmetric welding residual stress distribution and symmetric half of welding residual stress distribution are the same.5.The finite element software ABAQUS was used to perform axial static tensile and cyclic loading on symmetric welded joints,asymmetric welded nodes and ideal joints.The analysis found that: the welding residual stress aggravates the uneven stress distribution at the welding toe,and at the same time changes the location of the hot spot stress at the joint,the uneven distribution of stress at the welding toe of the steel pipe increases;the welding residual stress makes the joints toe at the joints under cyclic load and the uneven stress distribution is more obvious.