Dan Brabie

Dynamic simulation of derailments and its consequences

This article describes the necessary prerequisites and methodology in progress for studying train vehicle derailments and means of minimising the risk of catastrophic consequences. A comprehensive model has been developed and used in the multi-body system (MBS) simulation software for studying pre- and post-derailment vehicle behaviour. An axle-mounted brake disc and vertically extended bogie frames have shown empirically, as well as by MBS simulations, a potential to favourably influence the sequence of events in case of wheel flange climbing derailments. The MBS simulation methodology has been presented. Examples of how critical geometrical parameters affect the ability of these mechanisms to act as substitute guidance are presented. Further, a finite element (FE) model is developed for studying the impact phenomenon between a rail vehicle wheel and concrete sleepers. In particular, the proposed FE model will be used for obtaining hysteresis data for the wheel–sleeper force as functions of concrete indentation, for further development of the MBS simulations technique.

Post-derailment dynamic simulation of rail vehicles : Methodology and applications

An earlier developed multi-body system post-derailment module, that predicts the wheelsets’ behaviour after impact with concrete sleepers, is upgraded to account for possible wheel–rail fastener impact situations, after train derailments at high speed. The vertical stiffness describing the wheel–fastener impact behaviour is calibrated and validated based on two authentic derailment cases. Geometrical specifications that permit a brake disc and a bogie frame to act as substitute guidance mechanisms after flange climbing derailments on curved track are presented for an X 2000 trailer car. Further, an introductory analysis on the post-derailment vehicle behaviour on tangent track after a ‘flange on rail head’ derailment condition is also presented as a function of bogie yaw resistance. The risk of carbody overturning after derailments on tangent track is assessed as a function of coupler height and carbody centre of gravity as well as bogie transversal beam position.

An Overview of Some High-speed Train Derailments: Means of Minimizing Consequences Based on Empirical Observations

Abstract Studies published on rail vehicles— post-derailment behaviour as a means of minimizing consequences are surprisingly scarce. This paper sets a first step to reduce this lack of knowledge by analysing a collection of incident/accident case studies, with the main focus on the course of events immediately after derailments. This is mainly with respect to whether the train stays upright and close to the track centre-line and is ‘safe’ or deviates laterally with a probable serious consequence. Accordingly, an empirical database is established containing as much relevant information as possible of past incidents and accidents occurring at speeds over 70 km/h due to mechanical failure close to the running gear/track interface, as well as other causes that ultimately brought the train into a derailed situation. Although two derailments are never the same, certain patterns appeared to emerge based on the descriptions available in each incident or accident report. Mechanical restrictions between axles and bogie frames appear to minimize the risk of derailments after an axle failure on the outside of the wheel. Once derailed, evidence suggests that certain low-reaching parts on the wheelset or the bogie frame may act as substitute guidance mechanisms, thereby minimizing large lateral train deviations. However, for a large number of events, the available information does not allow conclusions based on observations only. This paper is the first in a forthcoming series dealing with the possibilities of minimizing devastating consequences of high-speed derailments by appropriate measures and features in the train design including the running gear.

On Minimizing Derailment Risks and Consequences for Passenger Trains at Higher Speeds

The first part of this article deals with the possibility of preventing wheel climbing derailments after an axle journal failure by implementing mechanical restrictions between the wheelsets and the bogie. A multi-body system (MBS) computer model is developed to account for such an axle failure condition, which is successfully validated by comparing the pre-derailment sequence of events with two authentic cases. An extensive parameter analysis on the maximum vertical and longitudinal play between the wheelset and the bogie, required to prevent a high-speed power or trailer car to derail, is performed for various combinations of running conditions in curves. Once an actual derailment has occurred on conventional passenger trains at 200 km/h, extensive MBS simulations are performed on the feasibility of utilizing alternative substitute guidance mechanisms, such as low-reaching parts of bogie frame, axle box, or brake disc, as means of minimizing the lateral deviation. Results are presented in terms of geometrical parameters that lead to a successful engagement with the rail for a total of 12 different derailment scenarios. These are caused by an axle journal failure, an impact with a small object on the track, or a high rail failure. Minimizing the lateral deviation is also investigated by means of restraining the maximum coupler yaw angle and altering the bogie yaw stiffness. Time-domain simulations are also performed in terms of lateral track forces and derailment ratio when negotiating a tight horizontal ‘S-curve’. Further, the articulated train concept is investigated in terms of the post-derailment vehicle behaviour after derailments on tangent and curved track at a speed of 200 km/h. In this respect, a trainset consisting of one power car and four articulated passenger trailer cars is modelled in the MBS software. Results in terms of lateral deviation and maximum carbody roll angle are presented as a function of different inter-carbody damper characteristics and running gear features. The feasibility of these damper characteristics is also tested in terms of lateral track forces and derailment ratio when negotiating a tight horizontal S-curve.