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|NDT.net Issue - 2014-09 - NEWS |
From 23 to 26 September 2014, Fraunhofer IZFP engineers present a new and enhanced generation of test equipment for rapid and reliable determination of residual stresses in rims at InnoTrans in Berlin, (hall 23B, booth 206).|
In the case of a car, the braking operation is carried out in seconds jamming on the brakes and shortly afterwards the vehicle has stopped. But with a fully loaded freight train weighing lots of tons braking takes much longer on long descents braking, which is required to prevent the trains unwanted acceleration, can even take more than 30 minutes. For the wheels and brakes this long braking time means hard work such a strong mechanical loading and heating of the wheels may cause so-called tensile residual stresses, which can lead to cracks in the wheel tread and worst case to wheel breakage. Geislinger Steige and Tauernbahn are best examples for routes that cause heavy endurance stress in wheels. Their strong inclinations and partly narrow radii require the permanent use of the wagons´ block brakes which generate the braking force by pressing the brake shoes against the tread of the wheels.
Photo: Determination of residual stresses in freight train wheels © Uwe Bellhäuser