Analysis On The Fatigue Life Of Co-use Of Weld And Bolts Joint

Co-use of Weld and Bolts Joint is a supplement and development of connection types of weld and bolts.Co-use joint has been already applied widely in the civil and mechanical engineering because of its help to enhance the bearing capacity and narrow the geometry size of joint.Many researchers have made a great deal of experimental researches and theoretical analysis on co-use of weld and bolts joint under static load up to now.The results have made prominent progress about its working mechanism and combined efficiency.However there are few studies regarding its fatigue property under cyclic load.In this paper,we focused on the fatigue property of co-use joint with transverse fillet weld and high-stress bolts.Firstly we compared the difference of fatigue life and fatigue mechanism between weld joint and co-use joint and analyzed the influence of high-stress bolt on the fatigue life.From the test results,we arrived at the fatigue life of co-use joint was far above the weld joint's and the site of fatigue fracture was different.The crack initiation of co-use joint was weld toe and propagated along the thickness direction of base metal.The high-stress bolt in the co-use joint can effectively extend the fatigue life by reducing the force of weld,increasing the connection stiffness of structure and restraining the crack propagation.The fatigue life of co-use of weld and bolts joint was estimated via both the nominal stress method and the equivalent structural stress method.But the estimation life of the join was of great difference to the real one due to the S-N curve of nominal stress method could not completely consider the influence of high-stress bolt on fatigue life of co-use joint.Equivalent structural stress method directly selected the nodal force and nodal moment of weld position,then the influence of high-stress bolt had already be included in the analysis.Based on above method,we verified that the finite element grid size had no effect on the result of fatigue life.Then Estimation results agreed well with test results and the error was less than 10%.The result indicated the applicability of equivalent structural stress method to estimate the fatigue life of co-use joint with transverse fillet weld and high-stress bolts.This work may be a useful reference for engineering practice to obtain the quite reasonable prediction of the joint fatigue life.