On the nonlinear hunting stability of a high-speed train bogie

The hunting phenomenon is an intrinsic swaying motion appearing in railway vehicles due to the vehicle's forward speed and the wheel-rail contact forces. Hunting motion consists of wheelset and other vehicle's components oscillations that arise above a certain vehicle's speed known as critical or hunting speed. These oscillations are of unstable nature and represent a safety hazard as they could lead to the vehicle's derailment. This article analyses the stability of a bogie nonlinear model for a Spanish high-speed train when this is travelling at speeds near the hunting speed. The vehicle's stability is studied by means of root loci methods, and the value of the critical speed is found. In addition to this, the behaviour of the vehicle is studied in both stable and unstable regions and the existence of limit cycles is discussed in this work. Finally, a sensitivity analysis of the axle load and suspension parameters is performed. The results show that the axle load, the vertical stiffness of the primary suspension and the lateral damping of the secondary suspension have a significant influence on the value of the critical speed.The research work described in this paper is part of the R&D and Innovation projects MC4.0 PID2020-116984RB-C21 and MC4.0 PID2020-116984RB-C22 supported by the MCIN/AEI/10.13039/501100011033 and by the Universidad Carlos III de Madrid through the "Ayudas para la movilidad de investigadores de la UC3M en centros de investigación nacionales y extranjeros en sus dos modalidades 2019" project

On the nonlinear hunting stability of a high-speed train bogie

The hunting phenomenon is an intrinsic swaying motion appearing in railway vehicles due to the vehicle’s forward speed and the wheel–rail contact forces. Hunting motion consists of wheelset and other vehicle’s components oscillations that arise above a certain vehicle’s speed known as critical or hunting speed. These oscillations are of unstable nature and represent a safety hazard as they could lead to the vehicle’s derailment. This article analyses the stability of a bogie nonlinear model for a Spanish high-speed train when this is travelling at speeds near the hunting speed. The vehicle’s stability is studied by means of root loci methods, and the value of the critical speed is found. In addition to this, the behaviour of the vehicle is studied in both stable and unstable regions and the existence of limit cycles is discussed in this work. Finally, a sensitivity analysis of the axle load and suspension parameters is performed. The results show that the axle load, the vertical stiffness of the primary suspension and the lateral damping of the secondary suspension have a significant influence on the value of the critical speed

Vehicle/track interaction under the conditions of high speed railway operation

This paper deals with the issue of dynamic effects of a high-speed railway vehicle on the track. Some aspects of vehicle/track interaction at higher speeds are described. In this context, a multi-body model of high-speed railway vehicle was created and several simulation scenarios were performed with this model. Furthermore, the simulations were evaluated with a focus on selected characteristics of the vehicle/track interaction

Safety investigation of partially filled railway tank cars

The adverse effects of liquid cargo slosh on dynamic responses and safety performance of partially filled road vehicles are well known. The general-purpose railway tank car may also encounter partial fill conditions due to variations in density of the liquid cargo and track load limit. The additional slosh forces and moments from the partially filled state of the tank may further affect the wheel-rail forces, dynamic response, and safety of the rail vehicles. The coupled sloshing cargo and vehicle system dynamics have been investigated in only a few studies because of complexity and high computation demand. The objective of this study is to investigate the influence of liquid cargo sloshing on the dynamic performance of railway tank cars. Other than detail modelling, the topics of lateral dynamics, curving performance and switch passing responses of partially filled railway tank cars through a co-simulation approach have been addressed in this dissertation. The nonlinear damping characteristics of friction wedges in the secondary suspension of a freight wagon are investigated considering non-smooth unilateral contact, multi-axis motions, slip-stick conditions, and geometry of the wedges. The parameters of the contact pairs within the suspension were identified to achieve smooth and efficient numerical solutions while ensuring adequate accuracy. The friction wedge model was integrated into the multibody dynamic model of a three-piece bogie to study the effects of wedge properties on hunting characteristics. The resulting 114-degrees-of-freedom wagon model incorporated constraints due to side bearings, axle boxes, and the centre plates, while the wheel-rail contact forces were obtained using the FastSim algorithm. The simulation results were obtained to study hunting characteristics of the wagon in terms of critical speed and the predominant oscillation frequency. The study also examined the effects of wedge friction and geometry on lateral stability characteristics of the freight car. The results showed subcritical Hopf bifurcation of dynamic responses of the wagon. The parametric study showed an increase in the wedge angle, friction coefficient, and springs free length to yield higher critical speed. The validated dynamic model of the wagon is further used to investigate the effects of liquid sloshing on hunting speed of partly filled tank car. An analytical liquid slosh model is used to capture dynamic response of the liquid cargo in a horizontal cylindrical tank using up to five fundamental modes in the roll plane under lateral as well as yaw motions of the tank car. The liquid slosh model is co-simulated with the comprehensive nonlinear model of a railway tank car to evaluate the lateral dynamic response of the tank car. The results suggest that fill levels and the corresponding slosh forces can adversely affect the lateral stability performance and yield lower critical hunting speed of railway tank car. The influence of liquid cargo sloshing on the dynamic performance of railway tanker in a typical curve negotiation is further examined using the proposed coupled co-simulation model. The performance measures include car roll angle, unloading of the wheelset and derailment quotient. The results clearly demonstrate that partial state of the tank car and resulting slosh could lead to a significantly larger dynamic response of the system and may result in separation of wheel and rail contact at lower forward speed in comparison to the rigid cargo assumption. Dynamic simulations of partially filled railway tank cars without fluid slosh consideration will thus lead to underestimation of overturning critical conditions on the curving manoeuvres. Above performance measures in a switch-passing manoeuvre is finally examined for different fill ratios and switch geometries. The results obtained for the coupled vehicle and liquid slosh model clearly showed strong interactions between the switch-induced transient liquid slosh and vehicle dynamics for the partial-fill ratio of 60% and less. The effect of fluid slosh on the car body roll angle and wheelset unloading ratio was observed to diminish with fill ratio above 90%. Neglecting the contributions due to dynamic slosh force and roll moment may lead to overestimation of the critical speed in switch-passing manoeuvres if the car is partially filled

Running Dynamics of Rail Vehicles

The investigation of rail vehicle running dynamics plays an important role in the more than 200 year development of railway vehicles and infrastructure. Currently, there are a number of new requirements for rail transport associated with the reduced environmental impact, energy consumption and wear, whilst increasing train speed and passenger comfort. Therefore, the running dynamics of rail vehicles is still a research topic that requires improved simulation tools and experimental procedures. The book focuses on the current research topics in railway vehicles running dynamics. Special attention is given to high-speed railway transport, acoustic and vibrational impact of railway transport to the surroundings, optimization of energy supply systems for railway transport, traction drives optimization and wear of wheels and rails

Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version