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The 1st Joint International Conference on Multibody System Dynamics
May 25-27, 2010, Lappeenranta, Finland
Numerical Simulation of Railway Vehicle Derailments
Vladislav Yazykov, Dmitry Pogorelov, Vitaly Simonov, Gennady Mikheev,
Roman Kovalev, Dmitry Agapov, Nikolay Lysikov
Laboratory of Computational Mechanics
Bryansk State Technical University
bul. 50-let Oktyabrya 7, 241035 Bryansk, Russia
email: yazykov@umlab.ru
ABSTRACT
The program which is intended for the simulation of train derailment processes and the identification of
causes of derailments is considered in this paper. Train derailments can be caused by many reasons. In
some derailment cases, the causes of derailments are obvious, for example railway vehicle or track faults,
obstacles on the tracks and so on. In other cases especially for freight trains, derailments can occur due to
loss of the lateral guidance at the wheel and rail interface. For this case, it is more difficult to understand
the reason. It could be wheel flange climbing, gauge widening, rail rollover, and track panel shifting [1].
The numerical simulation of railway vehicle dynamics by using multibody system approach can help to
analyze such kinds of derailments and find its real causes.
Keywords: multibody system dynamics, train dynamics simulation, railway safety.
1 DESCRIPTION
The program for the simulation and analysis of train derailments is being developed in Laboratory of
Computational Mechanics of Bryansk State Technical University. This program is based on the
mathematical core of Universal Mechanism (UM) software (www.umlab.ru). The program allows users to
simulate the dynamics of different kinds of railway vehicles with various initial conditions and analyze
obtained results.
As a result of dynamics simulations, the output parameters such as safety factors for the determination of
risk of wheel climbing, lateral forces in wheel-rail contact and forces between wheelset and bogie frame
which show the probability of gauge widening and track panel shifting, longitudinal in-train forces which
high values can be the cause of intercar coupling failure and other parameters are available for the
posterior analysis.
At first a vehicle or train model according to the real object parameters should be chosen. An expert can
analyze dynamics of separate railway vehicles, tractive connections of several vehicles and train with
simplified vehicle models or detailed 3D vehicle models.
For analyzing the safety parameters in running-out mode, 3D model of a separate railway vehicle can be
used. The program includes a database of vehicle models which are multibody systems, Figure 1. This
database contains most of operating Russian locomotives and cars. All models are parameterized, so it is
possible to take into account the real parameters of the investigated railway vehicle.
Figure 1. Railway vehicle database.
From the point of view of derailment risk, freight cars are the most dangerous vehicles, so freight car
models should be very detailed and accurate. Models of freight cars with two types of bogie: three-piece
bogie and Y25 bogie can be used for derailment simulation in the program [2]. For adequate simulation of
the three-piece bogie it is necessary to introduce in the model a number of contact force elements which
lead to stiff equations of motion. For example, UM model of three-piece bogie has 54 degrees of freedom
and more 80 contact points. Such contact force elements are introduced in the bogie model between
wheelsets and side frames, between wedges in the friction system, between the bolster and side frames,
and in the pivot unit between the bolster and the car body. It makes possible to take into account the real
shapes of frictional wedges. Real contact parameters are so high that it leads to a sharp decrease of a step-
size and an increase of time efforts. In order to accelerate the simulation process analytical solutions for
elements of Jacobian matrices of force elements were obtained and implemented in UM. It made the
simulation of freight wagons several times faster. The models of freight car with three-piece bogie are
shown in Figure 2.
Figure 2. UM models of freight cars with three-piece bogie.
The model of Y25 bogie has 50 degrees of freedom. More than 40 force elements are applied for the
description of the bogie suspension, different structural components and contact interactions. In
particular, springs of the suspension are modeled by viscoelastic force elements with bilinear stiffness.
Special force elements are used for modeling Lenoir links, the center pivot, side bearings, interactions of
the pusher with the spring holder and the axle-box, and the axle-box with friction surfaces of the bogie
frame that allows taking into account dynamical properties of these elements in details. The UM model of
this bogie is presented in Figure 3.
Figure 3. UM models of Y25 bogie.
For the estimation of in-train longitudinal forces at various train operation modes, simplified train models
in which vertical and lateral dynamics are neglected are used. All vehicles of such train model have one
translational degree of freedom. The motion of a train model in a curve is modeled by introduction of an
additional resistance force which depends on vehicle mass, curve radius and in some models on vehicle
speed. In transient curves, the resistance force increases from zero value to the value for a curve of
constant radius and decreases to zero again. When traveling on a tangent track with a grade, the additional
longitudinal component of gravity force is introduced. Separate vehicles of a train are connected by force
elements which simulate intercar couplings. As a rule, bipolar forces are used for this. A train model is
created by using the Train wizard tool, Figure 4.
Figure 4. Train wizard tool.
In Figure 5, UM model which contains two-section electric locomotive and 60 freight cars created by
using this tool is presented.
Figure 5. UM train model of electric locomotive and 60 cars.
If it is necessary to take into account the influence of in-train forces on safety factors, simplified train
models with a tractive connection of several 3D vehicle models which dynamics is most interesting
should be considered, Figure 6. Numerical experiments show that as a rule connections of 3-5 3D models
of vehicles are enough for the advanced analysis of rail vehicle dynamics.
Figure 6. 3D tractive connection in the middle of simplified train model.
After an expert should set the simulation parameters such as inertia parameters, wheel and rail profiles,
initial velocity, traction or braking forces, railway track profile and so on. Then the simulation process
starts.
The simulation results are represented as a report in table and graph forms which contains the
performances listed below:
safety factors,
lateral and vertical forces in wheel-rail contact,
normal forces on wheel tread and flange,
forces between wheelset and bogie frame,
in-train forces (for train models) and so on.
Eventually an expert taking into account the simulation results and safety factor values can give his
opinion about the most probable causes of derailments.
This program is used in Diagnostic Center of Moscow Railways for analyzing the causes of train
derailments.
Acknowledgments
The research is supported by the Russian Foundation for Basic Researches, grant No 08-01-00677-а.
References
[1] IWNICKI, S. D. Handbook of Railway Vehicle Dynamics. CRC Press, London, 2006.
[2] KOVALEV, R., LYSIKOV, N., MIKHEEV, G., POGORELOV, D., SIMONOV, V., YAZYKOV, V.,
ZAKHAROV, S., ZHAROV, I., GORYACHEVA, I., SOSHENKOV, S. AND TORSKAYA E. Freight car models
and their computer-aided dynamic analysis. Multibody System Dynamics 22, 4 (2009), 399–423.
3D tractive connection of
locomotive and 2 tank-cars in train
