In this paper, an approach for assessing the accuracy of different simplified contact theories has been presented and applied to typical cases for which railway VSD packages are used. The main characteristic of the approach is that it takes a statistically oriented view. This yields a better insight into the behaviour of the methods in diverse circumstances than is obtained when only a small number of (basic) circumstances are used in the comparison. The range of contact parameters that occur for realistic vehicles and tracks are assessed using simulations with the Vampire VSD package. This shows that larger values for the spin creepage occur rather frequently. With this distribution of contact parameters, different contact theories have been compared. This showed that the USETAB and FASTSIM approaches give considerably better results (rms differences of 5-10%) than the linear theory, Vermeulen-Johnson, Shen-Hedrick-Elkins and Polach methods (15-60%), when compared with the complete theory of the CONTACT program. A table-based approach therefore appears preferable in most cases. Such an approach allows for very fast calculations and delivers the most accurate results. The accuracy may be improved over that of the USETAB program as well, by calculating a new table with CONTACT with a finer grid than was used before. A drawback of table-based schemes is that they cannot easily deliver the distribution of surface tractions over the contact area, which may be required in some cases, e.g. for the calculation of wear and/or RCF. Further, it is difficult or impractical to calculate a table for more realistic circumstances such as non-Hertzian contact, more elaborate friction laws or including time-dependent effects. In these circumstances, the FASTSIM method is the preferred alternative. An interesting question now concerns the practical relevance of the inaccuracies presented in this article. Not much is known on the impact of wheel-rail contact modelling on the simulation of railway vehicle dynamics, which is why the Manchester Contact Benchmark was defined. On the one hand, the inaccuracies in the contact algorithm might be masked by other inaccuracies in the vehicle dynamics simulation. On the other hand, there may be other inaccuracies in the contact modelling as well. So far we have not considered non-Hertzian effects or the space and time-varying nature of friction (environmental factors, humidity). Another aspect concerns limitations of the complete theory, which applies to 'scrupulously clean surfaces'. To this end, more research into wheel-rail contact modelling and the effects on VSD simulation is required.


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    Title :

    Assessing the accuracy of different simplified frictional rolling contact algorithms


    Additional title:

    Untersuchung zur Genauigkeit vereinfachter friktionaler Rollkontakt-Algorithmen


    Contributors:

    Published in:

    Vehicle System Dynamics ; 50 , 1-3 ; 1-17


    Publication date :

    2012


    Size :

    17 Seiten, 8 Bilder, 1 Tabelle, 33 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English





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