Proceedings of the 5th International Conference on Integrity-Reliability-Failure, Porto/Portugal 24-28 July 2016

Editors J.F. Silva Gomes and S.A. Meguid

Publ. INEGI/FEUP (2016)

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PAPER REF: 6205

DYNAMIC LOADS IN RAILWAY TRACTION AND SHOCK

COUPLERS

Paulo Kurka(*)

, Alberto Oliveira Junior, Lucas Barnabé, Mariana Perazzo, Auteliano Antunes

Faculty of Mechanical Engineering, State University of Campinas, UNICAMP, Brazil

(*)Email: kurka@fem.unicamp.br

ABSTRACT

The work presents computational models for simulation of in-train coupler forces due to

typical freight railway vehicles operation. In-train coupler forces are determined as well as the

conditions in which the impact occur, helping engineers to access the train operational

conditions. In this study, a sample railway track profile is used, which considers slopes, curve

and braking operation. Such a model reproduces the behaviour of the dynamic system when

non-linear forces such as traction, pneumatic braking, draft gear, propulsion resistance and

friction are applied, yielding the in-train forces and lateral forces that actuate in the train

composition. The model consists of one locomotive and two wagons, connected by hysteretic

draft gear mechanisms. The draft gear model and the non-linear forces application influences

the dynamic behaviour of the railway vehicles in a realistic manner. Such results can lead to

an improvement in safety in railways as the accurate prediction of in-train forces and impact

conditions can reduce derailment events and increase components life time, providing cost

reduction of freight train operation..

Keywords: Longitudinal dynamics, railway vehicles, couplers, draft gears, in-train forces,

train kinematics, train dynamics, non-linear forces..

INTRODUCTION

In order to ensure safe, efficient and stable operation conditions of railway vehicles, it is

necessary to study its longitudinal, vertical and lateral dynamic behaviour.

Although it is possible to combine these behaviours in a single model, it is usually complex

and time consuming from the computational point of view. Each aspect of railway vehicle

dynamics is therefore modelled separately, as a technique to reduce computational time

simulation, yielding accurate predictions of the investigated phenomena [1].

In this work, in-train coupler forces and the lateral loads that actuate on the train composition

are modelled in the MatLab/Simulink platform to provide a realistic simulation tool that can

be used for training human ivers under different operational conditions.

A Longitudinal Dynamics study is proposed, in which a composition with one locomotive and

two cars are modelled as a system of three discretized masses connected with non-linear

stiffness and damping models representing the couplers and draft gears of the railway

vehicles. All the forces input such as traction, propulsion resistance, pneumatic braking, draft

gear stiffness and damping models are non-linear approximating the computational model to

the real world model of a train composition.

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This paper presents firstly the longitudinal dynamics modelling of railway vehicles by

describing the assumptions adopted in each model and also the characteristics of each force

curve. Train modelling, couplers and draft gears, pneumatic braking, traction forces and train

force resistances due to friction, track grade and curvature are discussed along the

longitudinal dynamics modelling. The dynamics simulation is presented secondly, assessing

the dynamic behaviour of a train composition running on a standard track profile. Simulation

results are finally presented and discussed, with suggestions for future improvements of the

computational model.

RESULTS AND CONCLUSIONS

The train dynamic behaviour is assessed during its travel on the proposed track. The velocities

of the train cars are shown in Figure 1.

Fig. 1 - Velocity profile of train composition cars along the sample track

The first 90 seconds of the curve correspond to the acceleration stage, where the train travels

the first 1004 meters of the straight line of the track. The brakes are applied at time instants of

113 s and 130 s, during the downslope part of the track with 1000 m of length, preceding the

quarter circumference curve. The train is accelerated again, via application of the traction

force at time instants 232 s and 323 s, in order to contour the track corner and overcome the

straight upslope part of the track, respectively, until increasing smoothly its velocity from 400

seconds and beyond.

Figure 2 displays the oscillatory behaviour of cars velocities after the cease of the traction

force, which induces in-train efforts in the couplers and draft gears.

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Fig. 2 - Oscillatory characteristic of the cars velocity

Figure 3 shows the couplings forces along the track. Peak forces occur around the moments of

changing of speed of the composition. Coupler forces in the first draft gear (Coupler 1) are

larger than in the second (Coupler 2) due to acceleration imposed by the traction force of the

locomotive and due to the mass of wagons following up the locomotive.

Fig. 3 - Coupler forces in each draft gear of the train composition

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The modelling methodology employed in this work encompassed many aspects of

longitudinal dynamics in railway engineering, such as the tractive and resistance forces,

stiffness and damping characteristics of couplers and draft gears. The usage of a particle

system in order to represent the cars of the train composition reduces the computational effort

while still providing an accurate response of longitudinal train dynamics, allowing the

simulation of the model in real-time. The application of non-linear functions adds to the

model a realistic response, approximating the computational model to the responses obtained

in real situations.

ACKNOWLEDGMENTS

The authors gratefully acknowledge the funding of V ALE/SA- Brazil.

REFERENCES

[1]-V. Garg, R. Dukkipati, "Dynamics of railway vehicle systems", Academic Press, New

York, United States, 1984.

[2]-C. Cole, S. Iwnicki, "Handbook of railway vehicle dynamics", CRC/Taylor & Francis,

Boca Raton, United States, 2006.

[3]-T. Dahlberg, S. Iwnicki, "Handbook of railway vehicle dynamics", CRC/Taylor &

Francis, Boca Raton, United States, 2006.

[4]-P. R. G. Kurka, "Vibrações de Sistemas Dinâmicos: Análise e Síntese", Elsevier, Rio de

Janeiro, Brasil, 2015.