Theoretical And Experimental Study On Fatigue Life Of Welded Hollow Spherical Joints Based On Modified Nominal Stress

With the rapid development of social economy,the function of industrial plants is becoming more and more complete and the structure is more and more complex.In particular,the fatigue life of the plate grid joints under the action of hanging cranes is an important capability for the safe and reliable service of industrial buildings.Many industrial plant accidents show that the fatigue problem of the plate frame which bears fatigue load can not be ignored.Therefore,the research of network frame nodes is very important.In this paper,on the basis of mechanical related theory,this paper proposes a modified method based on the nominal stress method,combining the welding hollow spherical joints,especially the welded hollow ball joints,especially the welded hollow ball strong steel pipe weak(hereinafter referred to as the "strong tube weak").Fe-safe fatigue analysis software is used to simulate fatigue test to estimate the fatigue life of welded hollow spherical joints.(1)According to the nominal stress method,and considering the micro damage toughness,residual stress and stress concentration coefficient,size effect,surface processing and so on in welding,the formula of fatigue comprehensive correction coefficient is obtained.The S-N curve of Q235 steel is modified to estimate the fatigue life of welded hollow ball joints.(2)ABAQUS finite element analysis software and FE-Safe fatigue analysis software are used to model static load and cyclic loading analysis to estimate the fatigue life of the joint.(3)Through static loading test and fatigue test of the MTS servo machine,the stress concentration factor and nodal fatigue life of the specimen are obtained.(4)To analyze and compare the results of the above three kinds of life,to get a more accurate,economical and reasonable fatigue life estimation method,and to popularize it.