Influence of nonlinear geometry parameters of wheel-rail contact on dynamic vehicle performance

In order to explore the relationship between geometry nonlinearity of wheel-rail contact and dynamic vehicle performance, a new nonlinear geometry parameter of wheel-rail contact, namely the composite equivalent conicity, was proposed and its influence on the vehicle dynamics was analyzed as the wheel wear increases. The linear equivalent conicity was weighted by the proportion of the contact width difference corresponding to the different lateral displacement of the wheelsets to obtain the composite equivalent conicity. The worn wheel profiles were measured and the changes of different wheel-rail contact geometry parameters with the increase in running mileage were compared. A vehicle dynamics model was established based on UM, and the relationship between the composite equivalent conicity and wheel wear under the excitation of track irregularity was discussed along with the impact on vehicle dynamics. The results show that the composite equivalent conicity takes into account the change of the wheel-rail contact geometry, and is not affected by the local wear of the large displacement of the wheelsets in the calculation. This means that it could more truly reflect the non-linear state of the wheel-rail contact. Compared with the equivalent conicity, the composite equivalent conicity is more sensitive to the magnitude of track irregularity under the excitation of low and medium irregularity levels. There is a clear correspondence between the composite equivalent conicity and the dynamic vehicle performance. The vehicle stability decreases as the composite equivalent conicity increases. Besides, when the composite equivalent conicity exceeds 0.29, the dynamic vehicle performance indices tend to stabilize. Through the use of the composite equivalent conicity, the track irregularity level and dynamic vehicle performance could be evaluated, which has certain guiding significance for the design and maintenance of rail vehicles. © 2022, Central South University Press. All rights reserved.