In our Resarch and Development activities we combine the theoretical knowledge with long practical experience in several areas of railway technology and manufacturing. For an efficient research we can support our project partners with various research labs at the University. One of our strenght is our multidisciplinary approach bringing together the expert knowledge from different departments.
Key resarch areas
- Design and simulation of railway components
- Wheel/rail-contact improvement, brake technology, friction material characterisation and optimisation
- Vehicle dynamics, simulation and optimisation of fuel consumption
- Crashworthiness of railway vehicles, design of crash absorbers and deformation tubes
- Support in case of damage (material investigations, SPM etc.) and product optimisation
Various tests show that the coefficient of friction from a brake pad can change up to ±40% and more depending on the history of brake applications. In the design of the brake system of a train unrealistic assumptions of the friction behaviour could lead to an over- or underestimation of the stopping distance resulting in possible critical events or increased brake pad wear. Due to the high number of parameters influencing the frictional behaviour of a brake pad an analytical calculation of the coefficient of friction does not lead to satisfying results.
The target of Neurobrake is to develop a procedure which allows the estimation of the frictional behaviour for each single brake event based on artifical neural networks and fuzzy logic. The training of the neural network is based on dynamometer tests which were made available by our industrial partner Federal-Mogul. The Neurobrake module is directly linked to route profile simulation which allows the estimation of the change in friction during a complete train run.
The traditional way to minimise brake squeal is to use special silent brake pads. The design of these brake pads includes damping devices and a special formulation of the friction material. Both makes the silent brake pads more expensive than standard pads.The target of the research work is to modify the brake control in a way that brake sqeal does not occur even with standard brake pads. The brake performance (and the stopping distance) must not change compared to existing systems.
The target of this project is to analyse the microstructure of the surface to obtain relevant parameters for friction and wear. The analysis is based on a laser surface scanner and a patch detection software. In the final stage the analysis of large parts (50x50mm) of a brake pad including an automated evaluation of the measured data should be possible.
Figure: Friction-relevant microstructure (patch) on a sintered brake pad (own picture)
The transfer of energy recuperated during braking back in the overhead wire is standard in electric locomotives or electric power cars of multiple units. We have developed a concept to use the recuperated energy in diesel powered vehicles by creating hydrogen on-borad (HyRec). The hydrogen can be easily stored and injected in the motor replacing diesel fuel. Depending on operating conditions and the route profile fuel savings up to 28% can be possible.
With this concept we won the first prize in the Deutsche Bahn AG Innovation Challenge 2016 with a prize value of 25 000 EUR.
The target is to further develop the concept and to proof that it is possible to design a diesel locomotive with a lower primary energy consumption than a comparable electric locomotive.
To analyse traction and brake systems it is important to simulate a train run with a specific route profile taking into account the most relevant parameters on traction and brake. To achieve a proper analysis we are developing a vehicle dynamics simulation based on
- international route profiles calculated from geodata available in internet sources,
- traction systems and power trains taking into account engine, hydraulic torque converters and axle gearboxes
with the target to
- predict fuel consumption and recuperation potential,
- calculate running times and achievable speeds and
- optimise systems components and controls.
The simulation is based on MATLAB/Simulink. The improvement of the simulation is also part of the teaching activities (Bachelor and Master thesis).
Figure: Distance, speed, acceleration and engine power of a diesel loco (own graph)
Brake discs made of cast iron are cost efficient and show very good thermal behaviour - unfortunately the cracking resistance is very low. Compared to this material brake discs made of cast steel show a significantly better crack resistance - unfortunately they are neithter cost efficent or do they show a good heat transfer. The target ist to create a hybrid brake disc with a ventilated core made of cast iron combinded with a friction layer made of special heat and wear resistant steel. The hybrid disc would use the postive material characteristics of cast iron and steel where needed and avoid the negative sides of the materials. The problem is that a proper bond between carbon-rich iron and steel can hardly be achieved with traditional manufacturing methods. With additive manufacturing we have reached a high-strength substance-to-subtance bond between these materials and created a hybrid iron-steel disc material.
Figure: Microstructure of wear resistant steel layer - top - on lamellar cast iron base - bottom (own picture)
Railway brake systems must be able to safely stop trains with more than 1.000 tons from speeds higher than 350 km/h. The best high-performance brake systems is not able to show its capabilities if the brake torque created by the brake cannot be transferred into a brake force and decceleration. The limiting factor is the adhesion between wheel and rail expressed by the coefficient of adhesion. Under proper conditions the coefficient of adhesion reaches values up to 0.40 and more. To have a safety margin brake systems are usually designed with adhesion values of 0.15 to 0.17. But in case of wet rails and leaves on the rails the adhesion level can drop to values lower than 0.05 (!) resulting in longer stopping distances. Railway operators therefore reduce the maximum speed on affected locations to be on the safe side. Sanders are widely used to improve adhesion, but the come with other risks (isolation). We are working on methods to improve the adhesion by conditioning the rail head with on-board devices which work independently from sand or other media to always allow a safe train operation.