Noise and Vibration Mitigation for Rail Transportation Systems Proce
This volume contains the contributions to the 10th International Workshop on Railway Noise, held October 18–22, 2010, in Nagahama, Japan, organized by the Railway Technical Research Institute (RTRI), Japan. With 11 sessions and 3 poster sessions, the work
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Summary Friction between sliding surfaces decreases as the velocity of sliding increases (‘falling friction’). This paper investigates the velocity-dependent friction relationships in non-Hertzian models of wheel-rail rolling contact. The effect of falling friction on tangential stress distribution and slip is examined. In otherwise steady rolling with constant creep, falling friction introduces a stick-slip oscillation to the trailing edge of the contact. This oscillation is increasingly unstable with increasing creep. The stick-slip behaviour at the trailing edge leads to sudden changes in the tangential stress distribution in the stick zone, including intermittent slip at the leading edge of the contact.
1 Introduction Over the last 40 years, significant efforts have been made to model and understand the sources of rolling noise [1]. The fundamental source of rolling noise is the roughness of the wheel and rail surfaces. Increasingly, the attention of researchers is being drawn to the mechanisms of roughness development and growth. Initial interest in roughness growth mechanisms was driven by the problem of corrugation. More recently, attention is being paid to broadband roughness development with a view to reducing noise by maintaining relatively smooth tracks and also with the aim of reducing the need for rail grinding. The theory of contact mechanics and friction is fundamental to studies of wheel-rail wear and roughness development. However, models of wheel and rail wear, roughness and corrugation development often simplify the contact problem. It is common to assume Hertzian contact theory to predict the stress distribution in the contact patch, even though this is valid only for specific geometries. It is also T. Maeda et al. (Eds.): Noise and Vibration Mitigation for Rail Trans. Sys., NNFM 118, pp. 33–41. springerlink.com © Springer 2012
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B.E. Croft, E.A.H. Vollebregt, and D.J. Thompson
common to assume a constant coefficient of friction throughout the contact area. These assumptions have been necessary partly because of the high computational cost of alternative theories. However, making these assumptions about the contact conditions when modelling roughness or corrugation development affects the conclusions that are reached [2,3]. Studies have shown that friction between sliding surfaces decreases as the velocity of sliding increases (‘falling friction’). Velocity-dependent friction coefficients have been used in models of wheel squeal [4], but only in conjunction with simplified models of the tangential stress distribution relying on local traction-displacement relationships (e.g. FASTSIM). This paper investigates more sophisticated friction laws in non-Hertzian models of wheel-rail rolling contact, using a variational method, which incorporates full linear elastic th
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