Research On Fatiguebehaviour Of Stainless Steel Welded Tubular T-joints

Due to its strong corrosion resistance,good low temperature toughness and high specific strength,stainless steel is not only used to manufacture non-structural components such as doors and windows,stairs and facade decoration,but also used in structural components of infrastructure such as bridges,ports and offshore platforms.With the rapid development of economy and related technologies,a variety of new steel tube joints have emerged in the steel tube structural system,among which the intersecting joints are the typical representatives.Once the intersecting node appears,it is widely used in practical engineering due to its clear force transmission,beautiful shape,convenient connection,and steel saving.In recent years,domestic scholars have carried out research on the mechanical properties of stainless steel intersecting joints,but the fatigue performance of stainless steel intersecting joints is slightly lagging behind.There are great differences between stainless steel and traditional carbon steel in material properties and welding performance.The lack of research results is bound to limit the development and application of stainless steel materials.Therefore,it is necessary to carry out related research on fatigue performance of stainless steel tubular joints.In this paper,the T-joints stainless steel tubular joints are taken as the research object.Based on the hot spot stress method,the fatigue performance of joints under axial load is experimentally studied.The main work is as follows :(1)The stress concentration factor test is carried out based on the stainless steel tubular intersecting joints,and the maximum hot spot stress position is located at the saddle point of the supervisor.The distribution law of the stress concentration factor SCF value at the weld toe from the saddle point to the crown point is obtained.The test results are compared with the CIDECT design guidelines for hollow pipe structures and the LR code of the British Classification Society,and it is concluded that the LR code has better applicability.(2)Based on the fatigue performance test of stainless steel tubular intersecting joints,it is concluded that the first position of the crack is consistent with the maximum stress position and the crack is gradually expanded from the saddle point to the crown point on both sides.The stiffness degradation of the joint can be roughly divided into three stages.The results show that after the crack appears in the fatigue loading process,the position strain of the node will change abruptly,and the stress amplitude of the saddle point of the intersecting node is significantly larger than that of the crown point.In terms of fatigue life prediction,AWS/API specification is conservative for fatigue life prediction of stainless steel T-type tubular joints,and CIDECT specification has better applicability.(3)Based on the material parameters obtained from the material property test,the ABAQUS finite element analysis software was used to construct the simulation model.Combined with the fatigue analysis software FE-SAFE,the stress distribution and fatigue performance of stainless steel T-shaped tubular joints were analyzed.The simulation results were compared with the test results,and it was verified that the simulation results using the shell element model with welds were in good agreement with the test results.The effect of parameter β and γ on SCF value isdifferent.The SCF value of branch and main tube decreases with the increase of parameter β,but increases with the increase of parameter γ.Finally,it is concluded that it is feasible to analyze the fatigue life of coherent joints by ABAQUS combined with FE-SAFE.