Non-steady rolling contact mechanics has been investigated for non-steady creepage, normal load, and contact geometry. The tangential problem was solved using the variational method by Kalker for half-space contact, and the relationship between the contact force and the non-sleady parameters has been analysed using a system identification method in order to determine if an approximate linear system can be found to represent the non-steady contact mechanics. The history of the non-steady creepage and normal load was prescribed consisting of a reference steady state and a fluctuating part. The case considered for the non-steady contact geometry was longitudinal vertical irregularities which resemble rail corrugation problems, and equal shallowness factors were used to categorise the irregularities in order to fit transfer functions. The proposed approach has been successful in dealing with the case in which creepage is only the non-steady parameter, and there is a linear relationship between fluctuating creepage and creep force. Transfer functions have been found to represent the non-steady contact mechanics in a manner similar to that described with frequency-dependent Kalker coefficients developed by Knothe and Gross-Thebing and Gross-Thebing. The non-steady creep forces calculated by the variational method under fluctuating normal load have shown the non-linearity of the problem and no simple linear system has been identified. Although the system is non-linear, the non-steady effect due to varying normal load has been found less significant compared with that due to varying creepage if both cases were normalised using the same reference and it was shown that the phase angle between the creep force and normal load is smaller (< 45°). The predicted creep forces due to non-steady contact geometry have been analysed for sinusoidal longitudinal vertical irregularities for the wavelength range from 3α to 20α, where a is the longitudinal contact patch semi-axis. For irregularities with the same shallowness factor, transfer functions have been fitted with good agreement. However, it is believed that there will still be difficulties in using transfer functions in practice as the shallowness factor and reference creepage both influence the transfer function. Overall, the non-steady phenomenon exists for partial slip condition and there are complicated relations between the creep force and non-steady parameters. In reality, all non-steady parameters can be present simultaneously and the reference state for creepage, normal load, and shallowness factor for longitudinal vertical irregularities can also vary. All these give difficulties even though a transfer function can be identified for a single non-steady parameter or a simple case. The time-domain approach is then the only available and reliable method to give accurate results. For the full slip condition, the problem either disappears for non-steady creepage and geometry or can be considered by a simple sliding contact model.


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    Title :

    Non-linearity of non-steady rolling contact mechanics under the half-space assumption


    Contributors:
    Ren, L. (author) / Xie, G. (author) / Iwnicki, S.D. (author)


    Publication date :

    2011


    Size :

    20 Seiten, 17 Bilder, 5 Tabellen, 16 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English





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