Static Analysis And Multiaxial Fatigue Analysis Of Railway Vehicle’s Bogie Frame

Bogie is a critical part of the railway vehicles,and it withstands the impact caused by line irregularities and loads from all directions during the service work.Bogie frame is an essential part of the bogie,and it is a large and complex welded structure.In this way,the bogie frame will bear complex load types during the service work,and it makes the bogie frame on a state of multiaxial stress during the service work,and thus enduring multiaxial fatigue fracture.Aiming at the characteristics of the multiaxial fatigue for welded structure,the types of fatigue stresses used in welded structures were firstly presented in the present paper.Then,with the influence of loading path on the multiaxial fatigue strength considered,the Moments of Load Path(MLP)method was introduced.Based on the definition and characteristics of structural stress,the present works are summarized as follow:Firstly,the relevant literature was searched to collect the multiaxial fatigue experiment data of welded structures from home and abroad,and the test data was analyzed.The corresponding Finite Element Model of the welded joints was created on the FE software Hypermesh in two modeling methods:shell elements and solid elements then.Next,the Structural Stress Concentration Factorfor the welded joints was calculated,and the multiaxial fatigue strength of the welded joint was evaluated based on the MLP method,the IIW multiaxial criterion,and the Eurocode multiaxial criterion.The impact of the Finite Element Modeling methods selected for the multiaxial fatigue strength evaluation of welded joints was analyzed.The master S-N curve was introduced to calculate the fatigue life,and the calculated results was compared with the experiment results to evaluate the accuracy on the lifetime prediction of the multiaxial fatigue.The results show that the MLP method based on structural stress has a better distribution of the S-N curve in the multiaxial fatigue strength assessment,and the selection of the finite element modeling method has little impact on the multiaxial fatigue strength assessment of the welded joints.As in the multiaxial fatigue lifetime prediction for welded structure,the accuracy of the MLP method can also be guaranteed.Finally,taking a certain type of bogie frame as an example,the finite element model of the bogie frame is created in the FE software Hypermesh,and the static load conditions were selected and applied to the bogie frame,and the FE model was imported into ANSYS for calculation to assess whether the static design requirements were met.The classical IIW standard was introduced to evaluate the uniaxial fatigue strength of the bogie frame,and the areas to be evaluated in multiaxial fatigue were picked.Finally,based on the MLP method,FE post processors ANSYS and FE-Safe were used to evaluate the multiaxial fatigue results of the selected evaluation areas.Results show that the bogie frame meets the static strength,and fatigue requirements by IIW recommendation was met.The minimum calculated fatigue lifetime of the selected areas by MLP method was over 1.0×10~7 times,which met the design requirements on multiaxial fatigue assessments.The research work contained in this dissertation has offered scientific basis for multiaxial fatigue assessment on complex welded structure,and it has important theoretical reference and thus significance on engineering application.