Analysis of residual stresses in rails during the straightening process

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 time-consuming. 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.