Opening Plenary Session
École Centrale de Lille
Braking technologies in railways.
Strengths and weaknesses. Specificities and trends. Ideas for the future
Former Senior Vice-President and Technical Director, Alstom
The railway transport is a very specific system compared to other modes, the wheel-rail one is dependent on strong characteristics such as adhesion, servo control and safety. At the same time, increase of speed, need for capacity, search for performance and economy, always within absolute safety limits, are more and more demanding.
The development of more and more efficient and sophisticated wheel-slide protection devices (the equivalent of the “ABS” of cars) is therefore a must. The increase of speed requires new technologies of the braking devices, from cast-iron disks and organic pads to high-tensile steel and sintered metal pads. The concern for reducing rolling noise leads to the removal of shoes directly acting on wheels, which at the same time has a negative impact on adhesion between wheel and rail.
On the other hand, railway systems offer solutions that are not possible for other modes: the permanent link between train and electrical power supply offers a smart way of saving energy and particles through regenerative braking (almost all modern electrical trains are equipped). The metallic and magnetic characteristics of rail offer a good opportunity to go past the limitations of wheel-rail adhesion, by using electromagnetic pads directly pushed down on the rail or, better, eddy-current systems on the rail.
Disc Wear and Disc Wear Particles
Seong Kwan Rhee
SKR Consulting LLC
The public is becoming increasingly concerned about environmental pollution. Examples include noise, particles and chemical pollution. Certainly brakes contribute to these types of pollution.
Over the years, the brake community assumed the main villain was the friction material, in spite of the fact that the friction material interacts with the disc, together generating squeal and wear particles.
Recent investigations reveal that discs wear out at a rate similar to friction materials as measured in weight and brake squeal is closely related to disc wear and the resulting disc wear particle transfer to the pad surface. It is also shown that friction and wear differences between the inner and the outer plate of the disc lead to low and high frequency brake squeals respectively as their microstructure and hardness differ from one another.
Concepts for squeal-free and emission-free brake systems will be explored.