Study On The Influence Of Amplitude-Dependent And Frequency-dependent Dynamic Characteristics Of Rubber Pads On Wheel-rail Dynamic Response In High Speed

The rubber pad of rail fastener system is the importantcomponents of unballasted track structure which has elasticity and damping performance,and its dynamic mechanical properties have an important effect on the vehicle-track system vibration and wheel-rail interaction.It is known that the basic parameterscharacterizedynamic mechanical properties of rubber padchange with the variety of temperature and frequency,and are related to the strain amplitude.As a result,it is important to study the influence of temperature,frequency and amplitude on thedynamic mechanical propertiesof rubber pad in unballasted track fastener system.And then we can easy to analyze its influenceon random vibration response of wheel-rail system,especially for high frequency vibration.Firstly,combined with the knowledge of nonlinear friction force model,the paper has took vossloh 300 type fastener which is commonly used in unballasted track of 350km/h speed line as test object,and designed experiments which identify parameters of nonlinear friction force model and fixed-frequency variable temperature of the model.After calculating the parameters of the nonlinear friction force model,the variation law of the fastener stiffness and the loss factor of rubber pad with temperature in the range of-60??20? is analyzed which considers friction force or not considers.The results show:With the decrease of temperature,the influence of friction on the storage stiffness and the loss factor is reduced,while the influenceof friction on the loss factor is much greater than the impact on storage stiffness.Combined with the principle of temperature and frequency equivalent,the paper gets the changelaw of storage stiffness and the loss factor,the results show:With the increase of frequency,the influence of friction on the storage stiffness and the loss factor is reduced,while the influenceof friction on the loss factor is greater than the impact on storage stiffness.The constitutive relationof fractional derivative Zener model in time domain can be transformed into the storage stiffness and the loss factor's formula in the frequency domain,the fractional derivative Zener model's calculated parameters can be obtained by fitting the changing curveof rubber pad's storage stiffness and loss factorunder the circumstance of considering or not considering friction forcein frequency domain.On the basis of wheel-rail dynamics theory,this article deduced nonlinear friction force model and fractional derivative Zener modal and take them into the calculation formula of vehicle-rail coupling vertical dynamic system to analysis the influences of amplitude-dependent and frequency-dependent dynamic characteristics of rubber pads on the dynamic response of vehicle-rail coupling vertical dynamic system in time domain.The results show:?1?Amplitude-dependent and frequency-dependent dynamic characteristics of rubber pads has significant influences on traffic safety,wheel unloading rate will grow rapidly when frequency-dependent dynamic characteristics of rubber pads is took into consideration,but it has a appropriate reduction when amplitude-dependentcharacteristics of rubber padsis took into consideration.?2?The frequency-dependent dynamic characteristics of rubber pads can significantly increase the interaction between wheel and rail,and the existence of amplitude-dependentcharacteristics of rubber pads will appropriate cut the appropriate of interaction between wheel and rail.?3?Both the amplitude-dependent characteristics orthe frequency-dependent dynamic characteristicsof rubber pads have little influence on train smoothness.?4?x₂,the key parameter of nonlinear friction force model,whose reduction has similar effects on dynamic response of vehicle-rail coupling vertical dynamic system with the increase of Ffmax,which is another key parameter of nonlinear friction force model.Transform part of the calculation results of the time domain dynamic response by FFT and 1/3 frequency doubling?Asymptotic only?to analysis the influence of amplitude-dependent and frequency-dependent dynamic characteristics of rubber pads on broadband vibration of wheel-rail system,the results show:ignore the amplitude-dependentdynamic characteristics of rubber pads will man-madeenlarge the frequency-dependent dynamic characteristics of rubber pads,which may enlarge the high frequency vibration response of wheel-rail system.?2?Amplitude-dependent dynamic characteristics will effectively alleviate the negative effects caused by frequency-dependent dynamic characteristics,especially for the high frequency part.?3?Both the reduction of key parameterx₂and the increase of key parameterFfamax an extenuate the negative effects caused by amplitude-dependentdynamic characteristics of rubber pads,and the influence of the reduction of key parameter x₂ is bigger.