InSb-based camera improves train braking
Researchers from the Ecole Universitaire d Ingénieurs de Lille (EUDIL) are using InSb-based infra-red (IR) cameras to optimize the braking performance of France s Train à Grande Vitesse (TGV) express trains.
Working in partnership with infrared camera specialist CEDIP, and brake pad manufacturer Flertex, they aim to improve management of the heat load on brake discs.
For a TGV train traveling at 300 km/h (186 mph) to make an emergency stop within the mandatory 3500 m each brake disc has to dissipate a staggering 14 MJ of energy within just 80 seconds.
The IR cameras allow identification of "hot spots", a dangerous phenomenon in frictional parts that can cause either damage and early failure, or unacceptable braking performance such as brake fade or low frequency vibrations.
The team is employing CEDIP s latest high-speed IR camera (JADE) to take images of a steel brake disc in action, effectively capturing a thermal snap-shot of the disc showing its temperature distribution and ability to dissipate heat.
Operating in the 3-5 µm region at a 200Hz frame rate, the camera measures hotspots ranging from 300-1200 °C on the disc s braking surface.
Using an experimental rig to simulate TGV rolling stock, temperature measurements were made while the brake disk was spinning and during its braking phase. Reducing the camera s integration time down to 10 µs enabled the team to freeze-frame the disc s motion.
"Thanks to the high frequency and high resolution of JADE cameras, our observations give new information on the conditions of hot spot appearance," said CEDIP spokesperson, Pierre Bremond. He added: "Thermal low cycle fatigue may be occurring and our first results show a relation with the development of cracks on the disc surface."
Results of the study have allowed EUDIL to improve the brake cladding, in terms of shape and the type of material.
• A version of this article first appeared at http://optics.org
