The contact area and pressure distribution in a wheel/rail contact is an essential information required in any fatigue or wear calculations to determine design life, re-grinding, and maintenance schedules. As wheel or rail wear or surface damage takes place the contact patch size and shape will change. This leads to a redistribution of the contact stresses. The aim of this work was to use ultrasound to nondestructively quantify the stress distribution in new, worn, and damaged wheel-rail contacts. The response of a wheel/rail interface to an ultrasonic wave can be modeled as a spring. If the contact pressure is high the interface is very stiff, with few air gaps, and allows the transmission of an ultrasonic sound wave. If the pressure is low, interfacial stiffness is lower and almost all the ultra-sound is reflected. A quasistatic spring model was used to determine maps of contact stiffness from wheel/rail ultrasonic reflection data. Pressure was then determined using a parallel calibration experiment. Three different contacts were investigated: those resulting from unused, worn, and sand damaged wheel and rail specimens. Measured contact pressure distributions are compared to those determined using elastic analytical and numerical elastic-plastic solutions. Unused as-machined contact surfaces had similar contact areas to predicted elastic Hertzian solutions. However, within the contact patch, the numerical models better reproduced the stress distribution, as they incorporated real surface roughness effects. The worn surfaces were smoother and more conformal, resulting in a larger contact patch and lower contact stress. Sand damaged surfaces were extremely rough and resulted in highly fragmented contact regions and high local contact stress.


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    Title :

    Experimental characterization of wheel-rail contact patch evolution


    Contributors:

    Published in:

    Publication date :

    2006


    Size :

    12 Seiten, 18 Bilder, 5 Tabellen, 22 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




    Wheel-rail contact

    Bouteloup, M. | Engineering Index Backfile | 1949



    Determination of the wheel rail contact patch in semi-Hertzian conditions

    Ayasse, JB / Chollet, H | Taylor & Francis Verlag | 2005