Ductile Fracture Test And Finite Element Analysis Of X-shaped Circular Steel Tube Intersection Under Static Loa

In recent years,steel pipe structures have become increasingly common in large buildings.Due to the advantages of good mechanical performance,simple and beautiful appearance,and good economic benefits of circular steel pipe intersecting nodes,they are often used in large buildings such as airports,high-speed railway stations,and sports venues.While circular steel pipe intersecting joints are widely used,there is also a certain risk of fracture,so it is necessary to study the fracture behavior and stress performance of the joints.In previous studies,the research on the bearing capacity of nodes has mostly focused on the moment of node cracking,with little consideration given to the changes in the mechanical performance and fracture ultimate bearing capacity of nodes after cracking.That is,few scholars have considered the impact of crack propagation on the fracture ultimate bearing capacity of nodes after cracking.This article takes the X-shaped circular steel pipe intersection node as the research object,explores the influence of crack propagation after node cracking on the ultimate bearing capacity of the node fracture,and studies the stress process after node cracking,analyzing the changes in mechanical and deformation properties of the node after cracking.In this paper,using a combination of experimental and finite element analysis methods,the VGM and SWDM microscopic fracture criteria are programmed into the VUSDFLD subroutine to analyze the fracture process and the impact of crack propagation on the ultimate fracture bearing capacity of X-shaped circular steel tubular joints.The accuracy of the finite element analysis of joints using the VUSDFLD subroutine is verified.Finally,through parametric analysis,the law of the change of the fracture limit bearing capacity of the joint with the geometric parameters of the joint is obtained,and the mechanical properties of the joint during the crack propagation stage are explored.The main research content and results of this article are as follows:(1)Compiling VGM fracture criterion into a subroutine can well simulate the fracture process and crack propagation path of nodes.The finite element simulation results are consistent with the experiments,indicating that using the subroutine to simulate the fracture of nodes has good accuracy,and VGM microscopic fracture criterion has good applicability and accuracy in predicting node cracking.(2)Through comparative analysis of joint tests and numerical simulations,it is found that when cracks begin to appear in a joint,the bearing capacity of the joint gradually increases with the increase of displacement under the condition of slow load growth;When the node reaches its maximum bearing capacity,the crack width of the node increases with the increase of displacement,and the bearing capacity of the node decreases rapidly.(3)When the main pipe diameter of a node remains unchanged,the ultimate fracture bearing capacity of the node varies with the geometric parameters of the nodeβ And the degree of influence gradually decreases;The ultimate fracture bearing capacity of a node varies with the geometric parameters of the node γ And the degree of impact gradually increases.When the wall thick Ness of the main pipe of a node is constant,the ultimate fracture bearing capacity of the node varies with the geometric parameters of the node τ The degree of influence gradually weakens as it increases.(4)Parametric analysis of nodes indicates that the geometric parameters should be appropriately increased β、γ It can improve the bearing capacity of joints after cracking,and reduce τ It can improve the bearing capacity of joints after cracking γ It can improve the deformation ability of joints after cracking.