Research And Analysis Of Wheel/rail Contact Stiffness And Contact Damping Of High-speed Train

With the continuous development of railway trains to high speed,the requirement of wheel/rail contact is higher and higher,and when the high-speed wheel/rail contact surface is subjected to normal contact load,it is easy to produce small angular displacement and line displacement,which makes the contact surface material elastic-plastic deformation.Not only the joint surface stores energy but also consumes energy,it shows that the contact stiffness and contact damping exist in the interface which detrimental effect on the static and dynamic characteristics of high-speed trains.The influence of wheel/rail surface characteristics on contact stiffness and contact damping is prominent,the surface roughness and hardness of CRH2 A high-speed train group are tested by TR100 pocket surface roughness meter and AT100 hardness tester,the values of which are tested at 25,000,50,000,75,000 and 100,000 km respectively.With the increase of running mileage,the value of roughness decreases gradually,and hardness is gradually stable between 50000-75000 km,and then increases gradually.The roughness and hardness reach the maximum after rotary dressing.Fractal dimension is an effective method to express roughness value.The RMS method is used to calculate the negative exponential relationship between fractal dimension and surface roughness.Hardness parameters can be input into the finite element model by elastic modulus,and the relationship between hardness and elastic modulus can be established,and the almost positive linear relationship between them is obtained.These measured data provide necessary conditions for accurate calculation of wheel/rail contact stiffness and damping.Based on fractal theory,the wheel/rail contact numerical model corresponding to different roughness is obtained by Matlab programming,and the data of each point is extracted,and the discrete point cloud data is reconstructed to form the rail surface with different roughness.A simplified wheel/rail contact model with different rough surfaces is established by using ABAQUS.The wheel is a discrete rigid body,the rail is a flexible body,and the contact area is refined mesh by CPS4 I,and different material parameters are set according to different working conditions.The wheel/rail contact stiffness and damping are simulated by loading displacement load on the rail bottom.According to the basic theory of contact stiffness and contact damping,the fractal theory and finite element method which accord with the wheel/rail contact characteristics are discussed,and the contact load,friction coefficient and surface roughness are analyzed,and the influence of surface hardness and running mileage on wheel/rail contact stiffness and contact damping are analyzed too.The simulation results show that the wheel/rail normal contact stiffness increases with the increase of normal load,surface hardness and running mileage,and contrary to the law of roughness change,and the friction coefficient has little effect on normal contact stiffness.The tangential stiffness has a nonlinear relationship with normal load,friction coefficient and surface hardness,and increases with the increase of them.However,the relationship with roughness is more complicated and it shows that it increases first and then decreases,the maximum tangential contact stiffness is obtained at roughness of 0.6 um or so.Within 100,000 km of train running,the tangential stiffness of wheel/rail is basically controlled between 5000-7000(N/mm).The trend of change has the stage of growth,the stage of descent,and the stage of stationary at the same time.The normal damping increases with the increase of normal load,friction coefficient,hardness and mileage,but it has a negative relationship with roughness.The tangential contact damping increases with the increase of normal load,friction coefficient and surface hardness,but increases first and then decreases with the increase of surface roughness.When the train runs with different mileage,the variation of tangential contact damping is not obvious,growth and downward trends of which coexist.