For about 150 years, the steel rail has been at the very heart of the world's railway systems. The rail works in a harsh environment and, as part of the track structure, it has little redundancy; thus, its failure may lead to catastrophic derailment of vehicles, the consequences of which can include death, injury, costs and loss of public confidence. These can have devastating and long‐lasting effects on the industry. Despite the advances being made in railway permanent way engineering, inspection and rail‐making technology, continually increasing service demands have resulted in rail failure continuing to be a substantial economic burden and a threat to the safe operation of virtually every railway in the world. This paper presents an overview of rail defects and their consequences from the earliest days of railways to the present day.
Despite substantial advantages in material development and in periodic non-destructive inspection together with periodic grinding and other measures in order to guarantee safe service, fatigue crack propagation and fracture is still in great demand as emphasised by the present special issue. Rails, as the heart of the railway system, are subjected to very high service loads and harsh environmental conditions. Since any potential rail breakage includes the risk of catastrophic derailment of vehicles, it is of paramount interest to avoid such a scenario. The aim of the present paper is to introduce the most important questions regarding crack propagation and fracture of rails. These include the loading conditions: contact forces from the wheel and thermal stresses due to restrained elongation of continuously welded rails together with residual stresses from manufacturing and welding in the field, which is discussed in Section 2. Section 3 provides an overview of crack-type rail defects and potential failure scenarios. Finally the stages of crack propagation from initiation up to final breakage are discussed.
KurzfassungEisenbahnschienen können unter Betriebsbedingungen brechen. Mit Hilfe der Bruchmechanik lassen sich das Risswachstums- und Bruchverhalten der Schienen untersuchen. Um dieses Verhalten z.B. im Hinblick auf die zerstörungsfreie Prüfung der Schienen im Gleis analysieren zu können, müssen die folgenden Einzelheiten bekannt sein:Betriebs- und Bruchbedingungen (Schienentyp, Radkräfte, Biegemomente, Temperaturen, Normalkräfte und Eigenspannungen),die bruchmechanischen Eigenschaften des Schienenstahls unter Betriebsbedingungen,die Form der Risse und die entsprechenden Spannungsintensitätsfaktoren.Für Schienen des Typs R65 sind die Spannungsintensitätsfaktoren für Querrisse, die von der Fahrfläche ausgehen, mit dem FEM-Programm ANSYS berechnet worden für die radkraftbedingte Biegung, für Temperatur-Normalkräfte sowie für die Längseigenspannungen.
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