| With the continuous advancement of urbanization in China,intercity bullet trains connecting important cities and urban rail transit have developed rapidly.In order to ensure the stability of vehicles running at high speed on the straight line between cities,the bogie needs to provide a large primary positioning stiffness,while a good curve passing performance needs a small primary positioning stiffness.Variable stiffness arm node is a suspension element that can meet this demand.This thesis mainly studies the variable stiffness arm node.The main work and conclusions are as follows:(1)The structural characteristics and working principle of variable stiffness arm node are analyzed,and the bench test of variable stiffness arm node is carried out to obtain its static stiffness,dynamic stiffness,dynamic damping and other mechanical properties,which provides data support for the research on the dynamic characteristics of variable stiffness arm node.The experimental results show that the dynamic stiffness of variable stiffness arm node is close to its static stiffness at low frequency,and its dynamic stiffness increases with the increase of excitation frequency.When the excitation frequency increases to about 6 Hz,the dynamic stiffness changes gradually,and the dynamic stiffness at high frequency increases to about 3 times that at low frequency.The dynamic damping decreases with the increase of excitation frequency,and the phase angle first increases and then decreases with the increase of excitation frequency.(2)Combined with the theories of hydrodynamics,the lumped parameter model of variable stiffness arm node is established,and the theoretical expression of its dynamic characteristics is deduced.The model adopts the modeling method of linearizing the inertial channel,which can reflect the system state of variable stiffness arm node to a certain extent.Based on the bench test data,the characteristic points of the characteristic curve and the method of programming solution are used to identify the parameters of the lumped parameter model.Then,on the basis of considering the nonlinear factors such as liquid flow and inertial channel,the nonlinear mechanical model of AMESim variable stiffness arm node is established.Taking the dynamic characteristic curve as the reference standard and comparing with the bench test results,the verification shows that the simulation accuracy of the model is high.(3)Using AMESim nonlinear mechanical model of variable stiffness arm node,the effects of rubber main spring,hydraulic cavity volume stiffness,equivalent piston area and inertia channel parameters on the dynamic characteristics of variable stiffness arm node are studied in turn.The results show that the stiffness of rubber main spring mainly affects the initial value of dynamic stiffness change.The larger the volume stiffness and equivalent piston area of the hydraulic chamber,the larger the variation range of its dynamic stiffness and the greater the dynamic damping at low frequency,and the influence of the change of equivalent piston area is greater than that of the volume stiffness of the hydraulic chamber.With the increase of the length of the inertial channel,the variation range of its dynamic stiffness remains unchanged,but the variation rate increases;The influence of cross-sectional area of inertial channel on dynamic stiffness is opposite to that of length.(4)A joint simulation model is established by using AMESim variable stiffness arm node mechanical model and SIMPACK vehicle dynamics model of an intercity bullet trains to deeply study the influence of variable stiffness arm node on vehicle dynamics performance in the actual working process.The results show that taking the intercity bullet trains as an example,the vehicle with variable stiffness arm node can effectively reduce the wheel offset angle and wheel rail wear when crossing the curve,and the safety index of vehicle passing through the curve will be improved under the condition of ensuring the stability and stability of straight-line operation;Among them,the reduction of wheel offset angle and wheel rail wear of vehicles on R500 curve are 33.96% and 21.50% respectively,and will decrease with the increase of radius. |
