Study On The Fatigue Performance Of Welded Hollow Sphere Nodes With Constant Amplitude Based On The Influence Of Welding Defects

As one of the main structural types of large-span space structures,the grid structure is widely used in industrial and public buildings.The welded hollow ball node is the most widely used node type in the mesh structure.The quality of the welded joints in the nodes affects the safety of the nodes.Therefore,it is necessary to carry out research on the welded hollow sphere nodes at the toe of the pipe ball welds.This paper explores the effect of weld defects on the fatigue performance of welded hollow sphere nodes with initial defects(weld residual stress)through experiments and numerical simulations.The specific research content,methodology and research results of this paper are as follows:1.using Visual-Environment software and call the Sysweld calculation module to complete the test specimen two weld foot size(weld width 4mm,weld height 8mm.weld width 3mm,weld height 9mm.)modeling.The temperature and stress fields at the weld toe of the welded hollow ball node tube ball welds were obtained.The distribution and magnitude of weld residual stresses at both weld toe sizes were obtained by viewing the results.2.this chapter is based on the blind hole method and ultrasonic impact method,with the help of self-designed new pedestal and ultrasonic impact machine to complete the welded hollow sphere node of the pipe ball weld toe at the determination and elimination of welding residual stresses.Plasticity correction of the final test results and the results are plotted into a sample curve for comparative analysis,the distribution and size of the weld residual stress at the toe of the weld with defective welded hollow sphere node pipe ball welds and the degree of ultrasonic impact to eliminate the weld residual stress.3.This paper addresses the fatigue performance of welded hollow sphere nodes with defects,with the help of Amsler fatigue testing machine,completed the node’s constant amplitude fatigue test.Through the test results show the fatigue performance with defects welded hollow sphere nodes of constant amplitude.Through the specimen damage macro fracture analysis of the specimen damage causes.And the fatigue data results of the final steel tube toe drawn into the S-N curve,with the help of the S-N curve proposed with defects welded hollow sphere node steel tube weld toe at the fatigue design method.This paper provides the basis for the determination of residual stress in the node welding and provides a reference for the design of the drilling pedestal.In addition,the constant amplitude fatigue test of welded hollow sphere nodes with defects also provides a valuable basis and theoretical reference for the revision of national codes.