The squat problem remains a concern to many railways, especially in Europe. More testing and more modelling is being done internationally to better understand this problem. This project has contributed to this improved understanding. Particular issues to be understood are summarised in this section. The exact conditions of temperature and pressure under which a WEL (white etching layer) can form on the surface of a rail need to be clarified. Tests done at the University of Queensland are consistent with a conventional view that the austenisation temperature on the rail surface must be exceeded to form a WEL, however, they do show evidence that multiple passes are required. WEL detection using eddy current techniques has the potential to be developed into a routine inspection tool. Residual stresses in a rail with a WEL have been measured with neutron diffraction testing, including an examination of near-surface stresses on a finer grid than has been used previously. The resolution is still not fine enough to distinguish the stress at the edges of the WEL. A fully convincing explanation of the growth of a squat is yet to be achieved. A model of squat growth incorporating 3D plastic deformation and using continuum damage mechanics rather than linear elastic fracture mechanics may help progress this issue. A 2D study reported here gives some indication of how the surface depression develops and the changes to contact pressure associated with it. More can be done to understand and predict the transient dynamic loading experienced by the track in situations where squats are found near turnouts, crossings, etc. and the resulting degree of heating of a rail, with modern traction control systems. The growth rate of Australian urban squats has been measured, indicating growth that is not accelerating much with increased crack size. This partly reflects the redistribution of contact pressure that occurs as the crack grows, modelled here in plane strain conditions. Further study should be done of the time (or tonnage) until evidence of 'baby squat' damage appears, and to what extent specific wheel-slip events control the crack initiation, rather than an accumulation of damage.


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    Title :

    Rail squats: Progress in understanding the Australian experience


    Contributors:


    Publication date :

    2013


    Size :

    12 Seiten, 15 Bilder, 1 Tabelle, 35 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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