| This thesis reviewed the development of low floor vehicle and the latest progress of evaluation method for fatigue strength of railway vehicle at home and abroad.The finite element modeling method of riveting connection of steel-aluminum hybrid carbody,the engineering method of assessing the fatigue strength of carbody based on DVS1608 standard and DVS1612 standard,and the visualization method of fatigue strength were studied.In recent years,in order to achieve the goal of reducing the weight of the low floor vehicles on the premise of meeting the requirements of structural strength,steel-aluminum hybrid carbody connected with pulling rivet is used in part of low floor vehicles.Riveting overcomes the limitations of welding technology.However,due to the tedious process of establishing solid finite element model of the riveting structure and the inefficient analysis,it is difficult for finite element simulation of the vehicle product in the design stage.In order to continuously shorten the design cycle of vehicle products,three methods of establishing the simplified finite element model of the riveted structure were proposed and verified.Discreting the riveting plate with shell element,and using MPC184 rigid beam element to simulate the rivet rod.On this basis,the connection between the rivet rod and the riveting plate was simulated by using the shell element,the CERIG rigid element and the MPC contact element binding algorithm respectively.In the end,an engineering method for evaluating the strength of large-scale riveted structures by using simplified model and sub-model technique was proposed.Several widely-used fatigue assessment standards of steel structure and aluminium alloy material were introduced comparatively in this thesis.The contents and application process of DVS1608 and DVS1612 standards were emphatically analyzed.The program of the nominal stress methods for assessing the fatigue strength introduced in the DVS1608 and DVS1612 standards were realized by the FORTRAN language.The content and storage format of the RST file date of ANSYS14.5 were analyzed in detail in this thesis,and the RST file was read and written directly by FORTRAN language with OpenMP parellel programming technology based on that.The node composition and storage form of the element solution of SOLID185,SOLID186,SOLID187 and SHELL181 were analyzed in detail.On the basis of accurate reading of the element solution,the solution of stress component of node in the Cartesian coordinate system was solved by average method and Coordinate transformation formula of stress tensor.Based on weld node files,FORTRAN subroutines were programmed to automatically identify the weld direction and the weld quality grade,and calculate the nominal normal stress and nominal shear stress related to the weld direction.The concept of the utilization of material was introduced to evaluate the static strength of structure based on the fourth strength theory,and evaluate the fatigue strength of structure based on the DVS1608 and DVS1612 standards.An interactive and friendly system of the calculation and visualization of steel-aluminum hybrid body strength was composed using the hybrid programming technology of VC++ and FORTRAN.The material utilizations of static strength and fatigue strength were written to the RST file,and then the visualization of structural strength was achieved using the postprocessing function of ANSYS14.5 software.A finite element model of 100% low floor steel-aluminum hybrid riveting structure body was established on HyperMesh software platform.The load cases and load values of fatigue strength for the body were designed according to the EN 12663-1 and VDV 152 standards.The ANSYS14.5 software was used to calculate the load cases of the finite element model.The visualization of the fatigue strength of the car body is carried out based on the calculated RST file. |
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