| As a link between the rail of the railway track and the structure beneath it,fastening systems are used to secure the rail position and prevent the rail from moving vertically and horizontally or tipping over,while providing the necessary elasticity and insulation properties.However,with the increase in high-speed train speed and frequency of use,the vibration and shock from wheel-rail excitation cause fatigue deterioration in the fastening system,leading to wheel-rail damage that is often not isolated.Therefore,it is urgent to further study the fatigue deterioration characteristics of the fastening system under the action of compound damage.This thesis studies the deterioration fatigue mechanism of the WJ-7 fastening system under wheel-rail combined injury excitation.The main research contents include:(1)Establishment of a three-dimensional finite element simulation model of the WJ-7 fastening system.Taking CRH380 B EMus and CRST II plate-type ballastless track structure fastening system as an example,the refined WJ-7 fastening system three-dimensional finite element model,high-speed vehicle track rigid-flexible coupling system dynamics simulation model,and wheel-rail composite damage incentive model were constructed.Using the multi-body dynamics theory and finite element co-simulation technology,the buckling pressure load of the buckling system under wheel-rail combined excitation was obtained through the dynamic simulation model.It was then imported into the finite element model of the WJ-7 buckling system,which provided a simulation platform and data support for subsequent research on the static and dynamic characteristics of the system.(2)Static performance analysis of the WJ-7 fastening spring clip.The initial buckling pressure in the installation process of the fastening system will affect the dynamic performance of the fastening system.The three-dimensional finite element model of the WJ-7 fastening system was used to study the distribution law of stress,displacement,and plastic strain of the fastening spring under different initial buckling pressures.It was found that the concentrated area of stress and plastic strain of the fastening spring under different buckling pressures was at the root of the fastening system.With the increase of buckling pressure,the maximum area of stress and plastic strain of the spring clip expanded,and the maximum displacement of the spring clip was located at the lower jaw of the front end of the spring clip.When the buckling pressure reaches a certain value,the lower jaw of the front end of the spring clip is close to the iron cushion plate,resulting in an increase of stress in the front end of the spring clip.(3)Dynamic response analysis of the WJ-7 fastening spring clip.Using the established three-dimensional finite element simulation model of the WJ-7 fastening system,the changes of force,vibration acceleration and Von-Mises equivalent stress of the fastening system under single excitation and compound damage of wheel and rail damage were studied,respectively.It was found that the force,vibration acceleration and Von-Mises equivalent stress of the fastener under compound damage increased with the change of parameters compared with that under single damage.At the same time,based on the modal analysis of the spring clip of the fastening system,the internal relationship between the wheel-rail composite damage parameters and the fatigue damage of the spring clip was studied from the frequency domain perspective.It was found that the resonance effect of the spring clip would be triggered under the action of the composite damage,leading to an increase in the vibration amplitude of the spring clip.(4)Fatigue life prediction of the spring clip of the WJ-7 fastening system.Based on the static and dynamic performance analysis results,the risk points of fatigue fracture of the spring clip were proposed.Using the theory of fatigue strength and life analysis,the S-N life curve of the spring clip was used to predict the fatigue life of the spring clip under the dynamic load.The fatigue life of the spring clip under single and compound damage of wheel and rail was studied.The study found that the fatigue life of the spring clip under composite damage was much smaller than that of the single damage of wheel and rail and the design fatigue life requirement of the spring clip. |
