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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 110
Edited by: J. Pombo
Paper 252

Thermo-Mechanical Effects in the Formation Mechanism of Rail Squats

M. Naeimi1, Z. Li1, R. Dollevoet1, J. Wu2, R.H. Petrov2,3 and J. Sietsma2,3

1Section of Railway Engineering, Faculty of Civil Engineering and Geoscience, Delft University of Technology, The Netherlands
2Department of Materials Science and Engineering, Delft University of Technology, The Netherlands
3Department of Materials Science and Engineering, Ghent University, Belgium

Full Bibliographic Reference for this paper
M. Naeimi, Z. Li, R. Dollevoet, J. Wu, R.H. Petrov, J. Sietsma, "Thermo-Mechanical Effects in the Formation Mechanism of Rail Squats", in J. Pombo, (Editor), "Proceedings of the Third International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 252, 2016. doi:10.4203/ccp.110.252
Keywords: thermo-mechanical effect, finite element, plastic strain, temperature, white etching layer, squats, thermal stress.

A three-dimensional elasto-plastic finite element (FE) tool has been developed to study the thermo-mechanical originations of squats in rails. The initiation process of rail squats is in principle related to the response of materials against cyclic loading. The thermo-mechanical issues in this process are not yet clear, due to the complicated wheel-rail interaction and the variability of the loads, parameters and material properties. This paper examines the role of thermo-mechanical-related causes on the formation mechanism of squats using numerical modelling. Assuming a range of material behaviour, thermal softening and temperature dependencies, the sliding wheel-rail contact problem is investigated using a three-dimensional FE tool. The temperature rise and thermal stress due to the frictional heat, generated at the contact surface of the wheel and rail, are taken into account. The magnitudes and distributions of thermo-mechanical stresses on rail surface are calculated for realistic loading conditions. Particular attentions are paid to the temperature rise, residual stress and plastic strain with thermal effects under high tractive forces.

The outputs are used to scrutinise if the so-called white etching layer is formed as a result of the temperature rise, needed for structural phase change and to consider the role of plastic deformations.

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