Thermal fatigue due to breaking of railway wheels can be modelled by FEM analysis, by using an appropriate description of the material behaviour and of the power flux distribution, from these computations cracks behaviour can be predicted. The drag breaking produces an homogenous heating of the wheel surface, while on the contrary the emergency breaking produces a strong heating localised within two narrow bands. During that emergency breaking the material is plastically deformed in compression within those two bands, leaving after cooling, a tensile residual stresses. After that first cycle, the following cycles produce a damaging fatigue cycle within the zone plastified by the emergency breaking. These computations have been confirmed by the observations of the thermal fatigue cracks pattern, which is entirely localised within the two hot bands produced by the emergency breaking. During the first emergency breaking, small areas which diameter is around one millimeter are heated over the transformation point of the alloy. On cooling, small cracks appear within these areas. Subsequently, every breaking cycle, even station entrance cycles may lead to crack growth. However, the stress intensity factor computations show that the cracks should grow up to a maximum size of 20 mm.
Thermal fatigue of a railway wheel
Thermische Ermüdung eines Eisenbahnrades
EUROMAT, EUROMAT, 1999 ; 312-316
2000
5 Seiten, 4 Bilder, 2 Tabellen, 2 Quellen
Conference paper
English
Reliability evaluation on fatigue fracture of railway freight wheel
Tema Archive | 2009
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