New methodology for rail grade selection
Dekra Rail and Delft University of Technology are currently investigating to develop a new methodology which will predict the expected damage development of a rail over time depending on the occurring load. The goal of the research is to gain more insight in wear and fatigue behavior of the various rail grades in order to justify the choice of rail material per location and to plan maintenance more effectively and at lower costs.
The research is done on behalf of Dutch infrastructure manager ProRail. Bart Schotsman, system specialist at ProRail: “In the 90’s we mainly focused on hard materials and different rail profiles. We also started grinding the rail more frequently. Unfortunately, these hard materials are expensive in purchase and maintenance, so logically we wanted to start working with cheaper, softer materials. But in order to do so, we need to first figure out what the wear and fatigue behavior of the materials is in different applications. In the context of his PhD research, I got in touch with Martin Hiensch of Dekra Rail about this matter.
To answer the main question that ProRail has, it was Hiensch’s proposal to use the two-disc research method. This method means that the wheel-rail contact is simulated on scale in a lab using one disc of wheel material and one disc of rail material. The set-up in the two-disc machine is carefully chosen in order to ballance the chosen axial force, slip and geometry, aiming at realistic contact conditions.
“An important benefit of the two-disc method is that we can manage and control the settings of the wheel-rail load conditions. When we would test ‘in the field’, we experience a lot of variation caused by for instance different vehicles, axle load, speed, or even influences of the weather. For the set-up of damage models and the prediction of the behavior of the rail under specific circumstances, it is important to keep the spread of load conditions as small as possible”, Hiensch said.
The use of the two-disc machine is not unique, but the application is. Schotsman: “Often, the two-disc machine is used for testing materials under extremely heavy loads. When you significantly increase the load, the direct impact is visible much quicker. However, this method only tests wear and in Martin’s two-disc research, the model to be validated is focused on wear and fatigue damage (cracks). This makes the approach unique.”
The project is currently in the validation phase. Schotsman hopes that, with Dekra’s research, he can take the first step to a more targeted purchase and maintenance plan for ProRail’s rail. Hiensch: “When the result of this validation is positive, we will move on to the next phase in the project; deriving damage functions for rail qualities for which these currently are not available. Eventually, the intended damage functions will allow infrastructure managers to choose rail material based on the given loading conditions and maintenance process, which leads to an optimal performance. Optimal in terms of costs, but also especially in terms of reliability and availability of the rail system.”