Study On Theory And Application Of Straightening Switch Rail Of High Speed Turnout

High smoothness is the basic of increasing train's speed when passing through turnout,of improving the passengers' comfort and of ensuring the train's safety.So the manufacturing accuracy of high speed turnouts is very highly required.Straightening switch rail is one of key technology steps in manufacturing of high speed turnouts.The shape of straightened switch rail has a great influence on accuracy including turnout' s smoothness etc.,and the residual stress has influence on service life of turnouts.At present straightening of switch rail remains at lower level,which mainly depends on workers' experiences.To get qualified switch rail,the switch rail need to be straightened many times. The failed products don' t meet the requirement of correction,often occur in the workshop.The working efficiency is low,and working inten -sity is great.These have influences on manufacturing progress,and will increase the manufacturing costs.According to characteristics of straightening switch rails,base on elastic-plastic theory,the theory and key technology in straightening switch rail of high speed turnouts are studied by theoretical analysis and FEM.The research work is divided into the following areas:(1)Study on theory of straightening switch railBase on the basic theory of press straightening,the force analysis model of straightening switch rail with complex section characteristics is established to analyze the regional distribution of elasticity -plasticity,straightening stress,residual stress,straightening defle -ction and residual geometric shape by using elastic-plastic theory. Mechanism of straightening switch rail is studied,and corresponding calculating formulae are built.The regional distribution of elasticity -plasticity equation,stress equation and deflection equation are solved by numerical method. (2) Simulation of straightening switch rail by FEMBecause calculating the parameters of straightening complex section components is impossible,the vertical straightening,lateral straighte -ning and bending are simulated by elastic-plastic FEM with three dimensional solid finite element.The geometric shape change,straighte -ning stress and residual stress are simulated in detail.The results show that the geometric shape change,the distribution of straightening stress and residual stress are different between vertical straightening and lateral straightening.The geometric shape change,the distribution of straightening stress and residual stress are similar between lateral straightening and bending.So the deformation processes of vertical straightening,lateral straightening and bending are different.Experiments on straightening switch rails are carried out to verify the elastic-plastic FEM and the calculate model.The results show that the discrepancy between FEM results and experiment results is small.The PEM and the calculate model can be used to simulate straightening switch rail.(3)Study on key process parameters of straightening switch railLoading distance and pressed bending amount are the two key process parameters of straightening.The change laws of residual geometric shape, straightening stress,residual stress and straightening force are analyz -ed with different loading distance and pressed bending amount.The results show that the residual geometric shape,straightening stress, residual stress and straightening force decrease with loading distance increasing,and increase with pressed bending amount increasing.(4)Study on effect of the initial deformation and straightening part in straightening switch railThe residual geometric shape,straightening stress and residual stress are analyzed in different initial deformation switch rails straightening.The results show that under the same parameters of straightening,the residual deflection,the straightening stress and residual stress differ little.The residual stress and shape change in different bending orientations are different.The residual geometric shape,straightening stress and residual stress are analyzed in different part of switch rails straightening. Because the bending modulus is small at cut part of switch rail,the straightening force,residual curvature,straightening stress and residual stress are smaller.(5)Study on technology of straightening switch rail and straightening quality evaluationThe determination way and principle of fulcrum and load action point were summarized and analyzed.The pressed bending amount in straightening and bending by FEM is calculated.The results show that the greater loading distance,the greater pressed bending amount at the same original bending radius.The greater original bending radius,the smaller pressed bending amount at the same loading distance.The greater residual stress, the greater original bending radius.The greater loading distance,the greater pressed bending amount in bending curve switch rail,but the residual stress of bottom differ little.The evaluation way of straightening switch rail is built.According to production practice and technical requirements of high speed turnouts, the inspecting content of straightening switch rail is analyzed and discussed.The way of inspecting various inspecting content is studied. The results can give reference for evaluating the quality of straighte -ning switch rail of high speed turnouts.