Study On The Relationship Between Operating Modal And Shoulder Wear Of Straddle-type Monorail Trains' Running Wheel Tires

In the operation of straddle monorail trains in Chongqing,serious shoulder wear occurred on the running wheel tires and caused a series of problems of safety,environment,and operation cost.Therefore,the study on mechanism and control method of shoulder wear of straddle monorail train tires is of important theoretical significance and engineering application value.Compared with other modes of transportation,the straddle monorail train has special running mechanism: the super static nature of the bogie,the multi wheel system,and frequent turns with small curvature of the track beam.The contact characteristics between running wheels and the track beam are important prerequisites for studying the shoulder wear of running wheel tires.In order to describe the contact characteristics between the tire and the track beam more accurately,the advantages and disadvantages of the micro analytical and phenomenological model were taken into consideration,and the friction model of the wheel and track beam of the straddle monorail train was put forward.The friction and wear test bench were used to test the rubber friction characteristics of the tread.The effect of the contact pressure and slip velocity on the rubber friction coefficient was studied for establishment of the finite element analysis model of the running wheel tire.The modal test equipment was used to obtain the free mode of 205/55R16 radial tire and the restraint mode of twin tire,and compared with the finite element simulation results,the reliability and accuracy of the finite element modeling method for the radial tire were verified.Based on that,the finite element model of 345/85R16 running tire was established,and the free mode,single tire restraint mode and twin tire restraint mode were simulated and calculated.The first order torsional vibration modes of the wheel tires in different constraints were the same,all of which were inclined along the forward direction of the tire.When the tire was rolling under this mode for a long time,it was easy to wear off.The first order torsion frequency of the wheel tire under twin tires combined restraint conditions is 2.4% and 1.3% lower than that of other conditions,and it was easier to be in the frequency range of shoulder wear.Therefore,the first order torsional mode of the tire was more easily triggered for twin tires.In order to study the influence factors of shoulder wear of the running wheel tire,based on the traveling wave theory,the working mode considering the rolling effect was calculated using the finite element models of the single and twin tire of the running wheel.The results showed that the first order torsional frequencies of the single wheel and twin tire both bifurcate,that is,the frequency of the forward traveling wave was greater than that of the backward traveling wave,and the frequency of the forward traveling wave(or backward traveling wave)in the first order torsional modal in the two installation modals were the same.To facilitate the calculation,taking the single tire as the research object,the frequency difference between forward and backward traveling waves was calculated.The influences of external factors such as load,velocity,inflating pressure and side slip angle on the frequency difference between the forward and backward traveling waves of first order torsion were analyzed.The results showed that with the increase of load,speed,side deflection angle and the decrease of the inflating pressure,the traveling wave frequency difference increased.and the effect of the side angle was larger than that of the load,velocity,and inflating pressure on the difference of the traveling wave frequency difference.In order to explore the effect of tire structural parameters on tire deflection,the influence of the structural parameters,such as the arrangement angle and the elastic modulus of the steel cord,on the frequency difference between the forward and backward traveling waves of first order torsion of the running wheel tire was analyzed by the finite element method.The results showed that the angle difference between the steel cord of belt 2 and 3 and the elastic modulus of the steel cord of the 0 degree belt were positively related to the difference of the traveling wave frequency difference of the tire,and the proper change of the angle difference of the steel cord of the belt 2 and 3 or the elastic modulus of the steel cord of the 0 degree belt could reduce the shoulder wear.It was of certain engineering significance to solve the problem of shoulder wear of running wheels.