Research On The Fatigue Life Of Welded Joints-tower Crane Based On The Equivalent Structural Stress Method

With the rapid development of urbanization,tower cranes are more and more widely used in the urban construction,and some problems are also urgent to study and solve.Welding is a common connection form in the metal structure of the tower crane.Because of the geometric discontinuity,stress concentration often occurs,which challenges the fatigue resistance in the using process.However,the fatigue at the weld is often ignored.After the research,it is found that the fatigue failure of the tower crane often occurs at the weld joints.Therefore,the in-depth discussion and analysis on the welding joints of the tower crane will have certain social values.In this paper,the equivalent structural stress method is used to study the fatigue life on the welded joints of the tower crane Qtz250.The specific research work is as follows:1.Using the finite element analysis software,through the study of the model simplification principle and the working load combination,the whole finite element model of the QTZ250 tower crane is established.Through the static analysis under three working conditions,the strength and stability of the tower crane are checked to meet the requirements of the engineering design,and the dangerous points of the structure under three working conditions are determined;2.The finite element substructure on the welding joints of the tower crane including weld details is established,and the transformation from the overall load to the substructure load is completed,which provides stress data for the subsequent fatigue life calculation;3.By using the Ansys life-and death-element method and adding Gauss heat source,the whole process of temperature rise / fall of the welding joint is simulated,and the results of temperature field analysis as well as the thermal stress field analysis are given.The distribution of the welding residual stress on three paths is obtained;4.The verity module of FE-SAFE is used to analyze the fatigue life on the welding joints of the tower crane,and the maximum number of cycles is checked to meet the design requirements;and the influence on the size of the weld joints for the fatigue life of the weld is studied by changing the size of the weld joints.