What is it about?

Wheel impact forces develop at the wheel/rail interface due to the presence of defects in the running surface of the wheel and/or the railhead. This paper reports on wheel impacts caused due to permanently dipped rail joints characterised by high frequency impact forces of high amplifications of static load that occur for a very short duration, followed by relatively low frequency, lower amplitude forces that occur for a longer duration. These impact forces are affected by the design of components adjacent to the wheel and the rail, namely the bogie primary suspension and rail seat pads; the influences of stiffness and damping characteristics of these components are investigated. A modified 3D wagon-track system dynamics simulation model that accounts for defects in track is used to obtain the impact force time series which is converted to impact force factors and compared with a set of field measured data reported in the literature. A simplified equation for the determination of impact force factors due to dipped rail joints is also proposed and validated.

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Why is it important?

It is observed that many research studies have been conducted to estimate P1 and P2 forces considering empirical formulae, simulations, field testing etc. Measurement techniques are sometimes complex. An obvious question arises – is there any simple method to estimate P1 and P2 forces considering both track design and operational parameters. This paper addresses this question. The simulation results of this paper for P1 and P2 forces correlate well with previous predictions, giving a lower bound of prediction of P1 and P2 impact forces at dipped rail joints. This can help improve the design process of track structures.

Perspectives

This paper provides a simple empirical formula of estimating wheel impact forces occurred at dipped rail joints. It is very accurate and easy to use.

Dr Nirmal Kumar Mandal
Central Queensland University

Read the Original

This page is a summary of: Impact forces at dipped rail joints, Proceedings of the Institution of Mechanical Engineers Part F Journal of Rail and Rapid Transit, June 2014, SAGE Publications,
DOI: 10.1177/0954409714537816.
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