Analysis of residual stresses in rails during the straightening process
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(2021) 43:1
TECHNICAL PAPER
Analysis of residual stresses in rails during the straightening process Mateus Fortes Carvalho1 · Leonardo Dantas Rodrigues1 · Erb Ferreira Lins1 Received: 21 August 2020 / Accepted: 9 November 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract The straightening process is the main cause of residual stresses in the manufacture of rails. It is a non-trivial process with cyclic plastic loads, solid–solid contact and complex geometry, which computational simulation is often complex and timeconsuming. In this work, a new methodology was developed by means of a quasi-static modeling instead explicit dynamic. This methodology was proved to be effective and fast. Sixteen cases were simulated, and a C-shaped pattern for longitudinal stress, as seen through the literature, was obtained in the most of them, even with large variations between the main parameters: the yield strength, the tangent modulus and the initial curvature of the rail. The longitudinal normal residual stresses were higher than the transversals ones, as expected. The results obtained by simulations were the basis for the use of a Gaussian process regressor to predict the residual stresses from any initial parameters. This tool confirmed that the parameters that more affect the final state of residual stresses are, in this order, yield strength, tangent modulus and curvature. This is relevant information, since the hardest data to obtain in practice are the initial curvature of rail. Both simulation methodology and the statistical Gaussian process tool could be useful to perform life fatigue analysis in rails, since this needs the initial state of residual stresses to be more reliable. Keywords Rail straightening · Residual stress · Finite element method · Gaussian process
1 Introduction In the fabrication of railway rails, after the hot rolling step and cooling stage, the rail is bent in a straightening machine. This bending cycle applies large deformations on the rail and will remove any curvatures, but, as it is applied in a cold rail, large residual stress will often arises in final product. [3]. Experimental measures of the residual stress in a new, straightened rail usually show a C-shaped curve for the longitudinal stress distribution, that is, tensile stress found in head and foot and compressive stress in the web. It was shown in [25] that this residual stress contributes significantly to fail of rail during service.
Technical Editor: João Marciano Laredo dos Reis. * Mateus Fortes Carvalho [email protected] Leonardo Dantas Rodrigues [email protected] 1
Institute of Technology, Federal University of Pará, Belém, Pará, Brazil
Some studies show that the state of residual stresses is quickly modified when the rails come into operation, but these changes are restricted to the rail head [11, 17, 21, 22]. Therefore, they remain relevant, mainly in the rail foot, where the bending stresses and residual ones are both tensile [19]. Furthermore, the CEN (European Committee for Stan
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