Research On Mechanism And Control Method Of Abnormal Wear Of Straddle-type Monorail Vehicle Running Wheel Tire

Running wheel tire of straddle monorail vehicles suffers serious uneven wear,due to its special structure characteristics,including large tire quantities and over constraint condition,and its specific tracking line with many bending but small curvature radius.It not only brings many safety,economic and environmental problems,but also hinders the further spread of straddle monorail transportation in the world.In this paper,the mechanism and control method of uneven wear of running wheel tire were studied from the perspective of vehicle structure parameters,tire structure parameters and track beam tread configuration.Firstly,a straddle monorail vehicle model with 15 degrees of freedom,considering radial and lateral characteristics of running wheel tires,was established and verified.In order to fully consider the operating conditions of straddle monorail vehicles,the Persson friction model and Grosch wear model were correlated according to the friction and wear test results.The correlated friction and wear model fully consider the influence of sliding speed,contact pressure,temperature,etc.According to the correlated friction model,a finite element model of running wheel tire was established and verified by the test.The ground pressure,longitudinal shear stress,lateral shear stress,longitudinal slip velocity and lateral slip velocity of running wheel tire in small bending were analyzed.A series of evaluation indices of wear and uneven wear of running wheel tire were defined.The uneven wear phenomenon of running wheel tire was reproduced by the wear weight and skewness of the inner and outer shoulder and crown of each tire.Secondly,an indirect evaluation index of wear and uneven wear of running wheel tire was defined by exploring the influence of sideslip angle,roll angle and their combination on the wear and uneven wear of running wheel tire.Based on the indirect evaluation index,the influence of vehicle usage factors(speed,load,super elevation angle of track beam)on the wear of running wheel tires was researched.It was found that the uneven wear of the running wheel tires can be mitigated by reducing the vehicle speed appropriately,reducing the super elevation angle of the track beam and increasing the load properly.Also,the effects of secondary suspension parameters and primary suspension parameters on the wear and uneven wear of running wheel tires were studied.The results showed that lateral and vertical stiffness of secondary suspension,running wheel tire and horizontal tire have obvious impact on uneven wear of each tire,appropriate selection of these parameters can ease the uneven wear.For example,the sideslip angle of front and rear running wheel tire of front bogie was selected as0.2°,0.2°,-0.2°,-0.2° comparing the initial values 0.5°,0.3°,-0.4°,-0.2°.Next,the excitation source of running wheel tire during the operation of straddle monorail vehicles was analyzed,and it was preliminarily judged that the lateral excitation transmitted from horizontal wheel to running wheel may excite its lateral low-order mode and cause uneven wear.Therefore,the finite element model of running wheel tire was established and verified by free mode test,single tire restraint test and double tire combined restraint test.It was found that the frequency of the lateral first-order mode of the running wheel tire decreases with the increase of the number of constraints,which greatly increasing the excitation probability of the lateral first-order mode.In order to truly reflect the modal characteristics of the running wheel tire,the rolling effect was considered in the finite element model,and the first lateral working mode was calculated according to the traveling wave theory.The effects of speed,load,tire pressure and side slip angle on the front and rear running wave frequencies of the first lateral working mode of running wheel tire were analyzed,and the relationship between front and rear running wave difference and the wear deflection value of running wheel tire was studied.It was proposed that the front and rear running wave difference can be used as the evaluation index of uneven wear of running wheel tire.Based on this,the influence of the arrangement angle and elastic modulus of the belt steel cord on the front and rear traveling wave difference of the running wheel tire was analyzed,and the angle and elastic modulus of the belt steel cord were optimized.Moreover,it was also found that increasing the radial stiffness and reducing the lateral stiffness of the running wheel tire are beneficial to mitigate its uneven wear.Then,the relationship between tire wear and uneven wear of running wheel with inclined plane configuration,concave function configuration and convex function configuration was studied respectively.The concept of "virtual camber angle" was introduced to optimize the configuration of inclined plane.However,due to the secondary distribution of tire load and other reasons,the optimized inclined plane configuration only had a good effect on the inner tire,but had a reverse effect on the outer tire.Therefore,the influence of curved surface configuration on the wear and uneven wear of inner and side tires was studied.The power function was used to construct the concave and convex function tread respectively.The results showed that the convex function tread can significantly improve the wear and uneven wear of the outer tire,while the concave function configuration can significantly improve the wear and uneven wear of the inner tire.Therefore,the composite function configuration of running tread was proposed,that is,the running tread section at the inner tire was concave function,while that of the outer tire was convex function.The optimization results showed that,compared with the inclined plane configuration,the wear deflection value of inner tire and outer tire decreased by 8.9% and 5.5% respectively,and the total wear amount decreases by 0.2%.Finally,the tire model and tread configuration of running wheel were reconstructed to furtherly correlate the dynamic model of straddle type monorail vehicle.Based on this,the influence of using factors on the wear and uneven wear of each tire of running wheel was analyzed.The results showed that proper reduction of vehicle turning speed and super high angle,appropriate increase of vehicle load are beneficial to mitigate the wear and uneven wear of each running wheel tire.The effects of secondary suspension vertical,longitudinal and lateral stiffness,and horizontal wheel lateral stiffness,vertical stiffness and its preload on the wear and uneven wear of running wheel tires were also studied.The optimized results showed that the wear state of each tire can be significantly optimized by reducing the sideslip angle of front and rear running wheel tile by 25% and 50% respectively.