Reducing wheel wear from the perspective of rail track layout optimization

Wheel wear (W-wear) is one of the most critical issues affecting vehicle-track performances and operating costs. Currently, the works on W-wear behavior and W-wear reduction are mainly based on four aspects: wheel-rail (WR) tribology, WR profile, vehicle structure design and active control of vehicle suspensions. Little attention has been paid to the effects of track layout parameters, such as superelevation, gauge, and cant. To supplement the existing research, this work aims to investigate the relationship between W-wear and track layout parameters and ultimately reduce W-wear through optimizing track layout parameters. The framework consists of a series of steps. Firstly, a multibody dynamics simulation (MBS) model of an Sgnss wagon with 55 degrees of freedom (DOFs) is built. Then, taking a 375-m-radius curve as a case, the influence of track layout parameter (superelevation, gauge, and cant) on W-wear and vehicle derailment safety is investigated based on Kriging surrogate model (KSM). Finally, based on optimized results obtained by KSM and particle swarm optimization (PSO), two optimal regions and three reasonable suggestions concerning the layout of a 375-m-radius curve are given from the perspective of reducing W-wear. This study is promising for the parameter setting of those dedicated lines, on which the train speed is usually fixed, such as metro, light rail, and tram.

Assessing Derailment Potential of Partially Filled Railroad Tank Cars

The increase of tank car trains carrying oil in North America has increased safety concerns especially with regards to transit through populated areas in the aftermath of the 2013 Lac-Mégantic accident. Among other things, this has further led to the desire to have accurate models to predict the dynamic behavior of tank cars for assessing derailment safety. In pursuit of this, the FRA has funded research to develop a tank car model which includes the behavior of the fluid inside tank cars, so that the resulting forces can be accurately depicted in multi-body dynamic modeling codes without the use of computational fluid dynamics. Prior analytical research on linear fluid sloshing has been adapted to create a mechanical model (pendulum–mass system) that estimates the lateral fluid motion and resulting forces which can be added to a dynamic model of the tank car. The developed model parameters are compared to other works in which mass and frequency parameters are derived. The model derivation, equations, and comparison to test data are included in this paper. Parametric results are provided showing trends associated with different levels of fluid fill.

Quasi-Static Curve Negotiation Analysis of Railway Vehicle Considering Nonlinear Air Suspension LV and DPV Flow Characteristics

Accurate prediction of vehicle curve negotiation performance is critically important for evaluation of railway vehicle safety. Although multibody dynamics vehicle simulation has been widely utilized for the vehicle performance evaluation, nonlinearities associated with the air suspension behavior are vastly simplified and the air mass flows of the leveling valve (LV) and differential pressure valve (DPV) are neglected in many cases. It is, however, known that changes in the air spring pressure caused by the LV and DPV make a non-negligible impact on the vertical wheel load variation and the derailment safety in small radius curved tracks. Therefore, this paper presents a numerical procedure for the analysis of the coupled vehicle and air suspension system behavior, considering nonlinearities associated with LV and DPV flow characteristics. To enable quick and accurate prediction of the history-dependent LV-induced wheel load unbalance and its impact on the derailment safety, quasi-static vehicle motion solvers for the fully coupled vehicle and air spring system flow equations are developed. Several numerical examples are presented to demonstrate the simulation capabilities developed in this study and numerical results are validated against the test data.

Study of the derailment safety index Y/Q of the low-floor tram bogies with different types of guidance of independently rotating wheels

Modern tram designs use different conceptions of how to implement the low-floor functionality. The key construction part is the bogie running gear which has to accommodate the lower part of the tram body. To adjust the low-floor level, many low-floor tram bogies have different types of guidance of independently rotating wheels with no central axle between the two wheels. Lack of self-steering mechanism in the form of central axle coupling or an external guiding device creates several inherent problems, such as insufficient guiding and excessive wear. Another important context is the safety against derailment when the vehicle negotiates a curved track. In this study the dynamic behaviour of non-powered bogies with different types of guidance of independently rotating wheels are presented using computer simulation models. The simulation results of the Y/Q index are compared for the two track configurations (curved and tangent sections) and four different kinds of bogie running gear.