A dynamic finite element model helps to explain how impact loads and other forces acting on the crossing nose of a turnout are influenced by parameters such as wheel profile, train speed and axleload. Damage to the crossing is related to the levels of contact pressure and slip. We have been developing a finite element model which simulates a wheel running over a crossing in the facing direction. Parameters such as the train velocity, wheel profile, axleload and crossing support resilience can be varied to examine their influence on the impact loadings. Using simplified analytical models, it is thus possible to explore the origins of the contact pressures and slip velocity between the contact points which lead to RCF (rolling contact fatigue) damage. Our dynamic model describes the wheels transition from the wing rail to the crossing nose over a distance of 3 m. The geometry represents a rigid crossing with a curve radius of 760 m and no superelevation of the wing rail. One wheel is modelled with finite elements, and the second wheel is accounted for by its influence on the rolling velocity of the wheelset. The impact of the wheel on the nose is caused by a change in its direction of movement, due to the wheel tread conicity, and the angle between the relative wheel movement before and after the impact is mainly determined by the contact geometry. Good measurement data are needed to predict the crack growth rate per load cycle, and as yet the necessary measurements have not been made in realistic mixed mode conditions. So although the model results show the way that plastic adaption and residual stresses can influence the loading of cracks, no firm conclusions can yet be drawn about an optimum regarding the performance and lifespan of the trial materials. However, it is clear that taking a general approach and integrating all of the significant parameters into the models can produce reliable predictions of a crossing's performance.
Understanding the loading of turnout crossings. Simulation
Railway Gazette International ; 168 , 8 ; 32-35
2012
4 Seiten, 12 Bilder, 3 Tabellen, 9 Quellen
Article (Journal)
English
Anpressdruck , Ausbreitungsgeschwindigkeit , axiale Verschiebung , Eigenspannung , Eisenbahnschiene , Ermüdungslebensdauer , Finite-Elemente-Methode , Fließspannung , Hochgeschwindigkeitsbahn , Messwert , Oberflächenriss , Rissfortpflanzung , Materialermüdung , Risstiefe , Schlupf (Zugbeanspruchung) , Stoß (Schlag) , Wälzpressung , Weiche , Winkelgeschwindigkeit
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