| Rubber components are an important part of the suspension system of high-speed trains,which complex nonlinear characteristics have a significant influence on vehicle dynamics.In this thesis,a nonlinear model of rubber joint is established for railway vehicle dynamics analysis,reflects characteristics of the dynamic stiffness and damping of the rubber components,and match the computational speed requirements of the dynamics calculation.A vehicle dynamic simulation model considering the non-linear characteristics of the longitudinal stiffness of the arm node was established.Through numerical simulation,the influence laws of the non-linear stiffness of the arm node on the vehicle dynamic performance such as hunting and curve passing ability were intensively studied.The specific researches are as follows:(1)Typical simulation conditions,such as car body hunting and bogie hunting,are used to study the influence of longitudinal stiffness and damping of the arm node on the vehicle’s critical speed,hunting frequency and the limit cycle of hunting movement.When stiffness of arm node is small,lower damping increases the critical speed for small equivalent conicity vehicles.On the contrary,it decreases the critical speed for high equivalent conicity vehicles.Reducing the stiffness of the arm node significantly increases the nonlinear critical speed of small taper vehicles and change the shape of the limit cycle diagram.Conversely,large tapered vehicles require higher stiffness at the arm node to increase the nonlinear critical speed and increase the speed at which the bogie encounters a large value lateral displacement.(2)The K-V dynamic simulation model was used to investigate the effect of the longitudinal stiffness of the arm node and the wheel track friction coefficient on the vehicle curve passing performance.The effect of wheel lubrication and wheel flange lubrication on the curving performance was compared.Based on the result,reducing the stiffness of the swing-arm join and wheel lubrication both significantly reduce wheel wear and advance curve passing safety,while flange lubrication only reduces wheel wear.(3)In combination with typical hunting frequency and curve passing frequency,the frequency characteristics of longitudinal stiffness and damping of the arm node are put forward.In low frequency,smaller stiffness avoids carbody hunting of the small tapered vehicle due to bogie hunting coupled with body modal,besides,the arm node longitudinal damping needs to be lower.In high frequency,larger stiffness to ensure that the large tapered vehicle has a high critical speed,and prevent bogie hunting.When passing a small radius curve,smaller joint stiffness in the low frequency and high displacement reduce the wheel-rail force and wear.(4)For the Maxwell force element model,the influence of the nonlinear characteristic curves of series spring and series damping on the dynamic stiffness and damping of the force element is analyzed.Firstly,linear increases the series stiffness and series damping,respectively increase the high-frequency dynamic stiffness and low-frequency dynamic damping of the force element.The damping nonlinearity determines the frequency-dependent non-linear curve style of the dynamic stiffness.Based on dynamic stiffness and dynamic damping varying with amplitude and frequency in a dynamic test,Maxwell model with nonlinear series spring and series damping was applied to study the non-linear dynamic model of rubber joint.its experimental results are in high-grade agreement with the model.(5)Different nonlinear curves models of longitudinal dynamic stiffness of the swing-arm joint are generated,including the frequency-amplitude change rate of stiffness,the concavity of nonlinear stiffness,etc.This model was brought into the nonlinear dynamics simulation model of the high-speed train.The laws of influence of longitudinal stiffness nonlinear features of the arm node on the vehicles dynamic performance are studied,especially on Hopf bifurcation and hunting frequency under high-speed conditions.Each nonlinear curves of stiffness have no significant influence on the nonlinear critical velocity.At high speed,decreasing stiffness deteriorates the hunting stability.The arm node with a small dynamicstatic stiffness ratio may be more advantageous to operational safety.The use of "convex" dynamic stiffness curves is also beneficial in the bogie hunting movement.Longitudinal stiffness of the arm node decreases with the growing amplitude,which is unfavorable for the stability of the bogie hunting movement in ultra-high-speed and car body hunting movement in high-speed. |
