| With the continuous development of rail transit in China,the indirect fastener system has been widely used in the subway lines in China because of its good elastic brought by the two elastic pad.However,the elastic pad is composed of polymer material,which has the elastic characteristics of hyperelasticity under large load and deformation.For the indirect fastener system,the rail pad will be in a non-uniform state due to the overturning of the rail caused by the transverse force.The basepad will be in a state of high pre-pressure due to the excessive preloading force applied by the bolt,both of which will cause the basepad to reflect hyperelastic characteristics,which leads to the existing design methods can not accurately describe the stiffness characteristics of the indirect fastener system.Therefore,in order to explore the hyperelasticity of indirect fastener system design,the influence of vertical stiffness to give some reference to the design of the indirect fastener system,this article embarks from the indirect fastener system structure,the indirect fastener system combination stiffness are divided into ironbase above combination stiffness and ironbase the following combination stiffness of two parts,The effects of hyperelasticity on the combined stiffness on the ironbase and the combined stiffness under the ironbase were studied respectively.Firstly,according to the basic theory of hyperelasticity and the stress-strain states of standard tests,the uniform fitting method of the hyperelastic parameters under different unit test conditions is established,and the model was verified by comparing the measured load displacement curves in the simulation of laboratory test process.Secondly,the influence of hyperelasticity on rail torsional deformation is analyzed by means of laboratory test and simulation,and the torsional deformation state of rail under actual stress is analyzed.Finally,based on the laboratory test results and the finite element simulation method,the influences of deformation characteristics of the ironbase and the hyperelastic characteristics of the basepad under the ironbase on the combined stiffness of the plate under the plate are analyzed,and the corresponding theoretical calculation model is established.The research in this paper is expected to provide some reference for the stiffness design of indirect fastener system.The main research conclusions are as follows:(1)The hyperelasticity of rubber material will lead to obvious nonlinear characteristics of the hyperelasticity of the rail pads and base pads in the range of 0～200 k N,while Yeoh model can fit the hyperelasticity characteristics of the elastic pads well,and the load displacement curve obtained by simulation is close to the measured results.(2)The influence of the hyperelasticity of the elastic pad on the stiffness of the rail pad is mainly reflected in the preloading state of the rail pad.The change of the preloading state will directly affect the actual stiffness of the rail pad,thus affecting the torsional deformation of the rail and the actual expansion of the gauge.Under both normal and abnormal stress conditions,the calculation results of torsional deformation under hyperelasticity are smaller than the linear elastic design results,which will further affect the wheel-rail contact calculation.In addition,the tendency of rail torsional deformation will be further strengthened because the torsional deformation moment of vertical force and the transverse force are in the same direction under the abnormal stress state of rail.(3)The combined stiffness of the indirect fastener system under the ironbase will be affected by the deformation of the ironbase and the hyperelastic characteristics of the basepad,which can be verified well with the measured results.At the same time,the error between the traditional model and the measured results can be reduced by increasing the thic kness of the ironbase or decreasing the distance between the anchor bolts.(4)by considering the actual ironbase under state of non-uniform bias of ironbase composite stiffness,the influence of introducing nonlinear continuous bearing model obtained plate on elastic foundation beam model under the combined stiffness calculation model,at the same time considering the deformation of ironbase and the hyperelastic of base pad to the composite stiffness under the ironbase,the influence of the maximum error of 2.68% with the test result. |
