Long-term rail damage evolution in railway crossings
Doktorsavhandling, 2020

To accommodate the passage of wheels in intersecting traffic routes, fixed railway crossings have discontinuous rails leading to an intense load environment due to repeated wheel-rail impacts. This gives rise to high costs associated with repair and maintenance of the rails in the crossing. For given traffic conditions, several approaches to crossing design can be undertaken to mitigate the material degradation and hence reduce the life cycle cost. In the present thesis, the option of selecting a more suitable crossing material is explored.

To obtain a guideline for material selection, the in-track performance of different materials during the life of a crossing needs to be predicted. In this work, an existing simulation methodology is extended by improving its robustness and computational efficiency. The methodology is able to account for the dynamic vehicle-track interaction, resolve the elasto-plastic wheel-rail contact, and consider the main damage mechanisms related to the running surface of a crossing rail. In this thesis, the methodology is updated by including a metamodel of plastic wheel-rail normal contact, which is introduced to meet the computational challenge of performing a large number of finite element simulations. The metamodel is based on the contact theory of Hertz. It is shown that the metamodel yields accurate results while accounting for the inelastic material behaviour.

The simulation methodology is applied to several test cases. In the first study, it is employed to compare the short-term performance of two rail steel grades that are commonly used in crossings: the fine-pearlitic steel R350HT and the austenitic manganese steel Mn13. A representative load sequence generated by means of Latin hypercube sampling, taking into account variations in worn wheel profile, vehicle speed and wheel-rail friction coefficient, is considered. After 0.8 million gross tonnes (MGT) of traffic, it is predicted that the use of rolled Mn13 will result in approximately two times larger ratchetting strain as compared to the R350HT. In the second study, the methodology is used to simulate approximately 12 MGT of traffic in a crossing. The results of the simulations are compared with data measured in the field. It is shown that the simulations are in good qualitative agreement with the measurements. Finally, the methodology is used to quantify the difference in long-term damage between crossings with different crossing angles. As expected, the crossing with the largest crossing angle is subjected to the highest impact loads and exhibits the most damage after 52 MGT of simulated traffic.

wheel-rail contact mechanics

Dynamic vehicle-track interaction

wear

FEM

switches \& crossings

S\&C

metamodel

plasticity

Opponent: Dr. Valeri L. Markine, Faculty of Civil Engineering and Geo-Sciences, Delft University of Technology, The Netherlands

Författare

Rostyslav Skrypnyk

Chalmers, Mekanik och maritima vetenskaper, Dynamik

Metamodelling of wheel–rail normal contact in railway crossings with elasto-plastic material behaviour

Engineering with Computers,; Vol. 35(2019)p. 139-155

Artikel i vetenskaplig tidskrift

R. Skrypnyk, U. Ossberger, B. A. Pålsson, M. Ekh, J. C. O. Nielsen. Long-term rail profile damage in a railway crossing: Field measurements and numerical simulations

R. Skrypnyk, B. A. Pålsson, J. C. O. Nielsen, M. Ekh. Influence of crossing angle on long-term damage evolution in railway crossings

Why are rails made of steel, and why are certain steel grades better than others in various railway applications? The first question is rather easy to answer: rails and wheels made from steel provide low rolling resistance. This in turn reduces the energy needed to make the trains move and, therefore, decreases the environmental impact of the railway transport. The second question is more difficult to answer. For the application in a railway crossing, it is particularly difficult to predict which steel grade will perform better in the long term.
 
A railway crossing is part of a railway turnout (also known as switch and crossing, commonly abbreviated S&C). Turnouts provide flexibility to railway operations by allowing trains to change between tracks via a switching device that can alternate between branching track paths. However, there is a price to pay for this flexibility. Because of the design with discontinuous rails, crossing rails are subjected to a more intense load environment than regular (stock) rails leading to larger degradation rates and maintenance costs. For these reasons, it is necessary to understand how the choice of crossing material will influence the long-term resistance to mechanical damage.
 
In this thesis, a numerical tool for predicting the long-term damage in railway crossings is presented. It includes a procedure to mimic a representative load environment for the crossing and models to simulate the resulting plastic (permanent) deformation and wear (removal of material from the contact surface). The tool is applied for a comparison of two steel grades commonly used in railway crossings, namely the fine-pearlitic steel R350HT and the austenitic manganese steel Mn13. To validate the predicted results, the tool has been applied to simulate the long-term damage of a given crossing and the results have been compared to field measurements. The tool can be used for design optimisation of crossing geometries and materials, as well as aid in the planning of preventive maintenance.

Optimering av material i spårväxlar (CHARMEC TS17)

Chalmers järnvägsmekanik (CHARMEC), 2015-05-27 -- 2020-07-30.

Ämneskategorier

Tribologi

Infrastrukturteknik

Farkostteknik

Styrkeområden

Transport

ISBN

978-91-7905-308-6

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4775

Utgivare

Chalmers tekniska högskola

Online

Opponent: Dr. Valeri L. Markine, Faculty of Civil Engineering and Geo-Sciences, Delft University of Technology, The Netherlands

Mer information

Senast uppdaterat

2020-05-11