Development Of Polyurethane Limit Spring For High Speed Maglev Train

In the vertical dynamic system of high-speed train,the limit spring is one of the key components of the secondary suspension system.Because of its nonlinear stiffness,low vibration frequency and hysteresis characteristics,it can absorb and consume vibration energy through the plastic deformation of damping materials,so it is widely used as the limit element of air spring for rail transit vehicles at home and abroad.Compared with the current high-speed railway and EMU,the high-speed maglev train has faster running speed,stronger carrying capacity and higher comfort requirements.The existing limit spring can not meet its technical conditions.Therefore,it is necessary to develop the limit spring suitable for the performance requirements of high-speed maglev train.On the basis of consulting a large number of relevant literature at home and abroad and the research and analysis of high-speed rail EMU limit spring,combined with the technical conditions of high-speed maglev train limit spring,the polyurethane limit spring for high-speed maglev train is developed.Firstly,the damping mechanism and working mechanism of the limit spring are studied,and the structural parameters of the limit spring are preliminarily established.Through the study of the hyperelastic constitutive model of polyurethane material,the material parameters are determined,and the static simulation of the polyurethane limit spring is carried out with the help of ABAQUS finite element software,and the structure of the limit spring is designed and optimized According to the results,the structure of extrusion die and flow channel were designed,and then the flow field of extrusion flow channel was analyzed by using POLYFLOW finite element software through the study of polyurethane melt constitutive model.According to the analysis results,the structure and process parameters of extrusion flow channel were optimized.Finally,the polyurethane limit spring of high-speed maglev train was trial produced by extrusion molding method,and the trial production was completed The properties of the samples were tested.The main contents of this paper are as follows:(1)By consulting the relevant literature at home and abroad,the polyurethane material and its processing method,hyperelastic constitutive model,melt constitutive model,damping mechanism and working mechanism of the limit spring are studied.Combined with the technical conditions of the limit spring of high-speed maglev train,the structure design of the limit spring is completed.(2)Through the research on the properties of different polyurethane materials,the material parameters are preliminarily determined,and the polyurethane material with Mirathane-E190 is selected to prepare the required samples;the stress-strain properties under uniaxial tension,multiaxial tension and plane tension are tested through experiments,and the constitutive model is fitted according to the experimental data,and the fitting error is analyzed to finally determine the Ogden N5 as a hyperelastic constitutive model,the static simulation analysis of the limit spring is carried out by using this model and ABAQUS finite element analysis software,and the structural parameters of the limit spring are optimized according to the analysis results.When the outer diameter is 80mm,the inner diameter is 21mm and the height is 80mm,the displacement load curve meets the requirements of technical conditions.(3)According to the structural parameters of the limiting spring,the extrusion die and the flow channel were designed.The rheological properties of polyurethane melt were tested by capillary rheometer,and the Carreau melt constitutive model was fitted.The mold flow was analyzed by using POLYFLOW finite element software.Through the analysis of the velocity field and pressure field of the head runner,the optimum technological parameters are determined as follows:the length of the forming section is 145mm,the melt temperature is 190℃～200℃,and the inlet flow rate is 8000mm~3/s.(4)The polyurethane limit spring for high-speed maglev train was trial manufactured by extrusion molding method,and its performance was tested.The test results showed that the static stiffness of polyurethane limit spring was between2250N/mm and 2500N/mm;the low temperature stiffness coefficient is less than 1.5 at-25℃,less than 2.0 at-40℃and more than 0.8 at 50℃;After fatigue,the static stiffness of the limit spring decreases no more than 10%;after aging,the static stiffness changes less than 10%.