Introduction to the structure and contents of the Special Issue

There are fourteen articles in this Special Issue, and they fall into five important groups. The short summary below tries to give a flavour of the articles in each group. Review articles. Cannon, Edel, Grassie and Sawley provide an extensive overview of rail defects and their consequences, together with a history of the problems and an evaluation of their present importance which is also quantified in economic terms. Materials and stresses and contemporary types of failure are discussed. Information is given on statistics, defect management procedures, regulations, defect classification, grinding, modelling etc. The article includes 73 references. Iwnicki reviews the development of simulation methods for wheel–rail contact forces. A mathematical description of the problem is given and the nature of the vertical and the lateral forces is clarified. Calculated results for both a locomotive and a passenger coach are validated using measured track data. The highest stresses are found for flange contact of the locomotive. Smith emphasizes the importance of the wheel–rail interface for safe railway operations. He gives a brief history of the development of rails and wheels. Three recent failures are described: the Eschede accident (June 1998), the derailment at Sandy (June 1998) and the derailment at Hatfield (October 2000). Monitoring, maintenance and non-destructive testing. Ishida, Akama, Kashiwaya and Kapoor give the current status regarding theory and practice for rail integrity in Japan. The occurrence of rolling contact fatigue (RCF) and corrugation and wear and as well as the use of preventive grinding and lubrication are reported. Modelling and laboratory experiments are described. Magel, Roney, Kalousek and Sroba present an article on the development of modern grinding practice, including ‘preventive grinding’, as a result of field experience and expert intuition. Only recently have practical models, which have emerged from theory and laboratory experiments, been applied to rail grinding. Today's methods depend on modern, high-capacity grinding machines. Marais and Mistry report on the success of defect management at the heavy haul iron ore line between Sishen and Saldanha Bay in South Africa. An effective system for detection, by ultrasonics, of defects in welds and of RCF defects has been developed. The adopted measures have eliminated derailments and have meant increased capacity of the line. Damage, fatigue and fracture of rails. Dang Van and Maitournam put forward a method to predict rail damage and point out the importance of correct modelling of the plastic deformations and the residual stresses under repeated rolling contact. Numerical examples demonstrate the method in two and three dimensions for different types of defects. Franklin, Chung and Kapoor develop a new computer model that in an efficient manner simulates ratchetting wear in rails. The influence of material data and wheel–rail creepage is demonstrated in a parametric study. Fletcher, Franklin and Kapoor present a ratchetting-based computer model that allows for simultaneous simulation of wear, crack initiation and early crack propagation. Plots from the model are processed using an image analysis technique and promising comparisons with results from twin-disc tests are reported. Ringsberg and Bergkvist study the growth of short (0.1–0.5 mm) surface cracks using both elastic and elastoplastic models. Crack face lubricants and fluid entrapment are treated for combined normal and tangential loads. The results are verified by use of data from the literature. Phenomena in the wheel–rail interface. Böhmer, Ertz and Knothe find that high temperatures occur in a thin layer of the rail when in contact with the wheel. The temperatures can be up to 300 °C when tractive forces are present. The induced thermal stresses promote plastification and crack initiation. Fischer, Daves and Werner discuss flash temperatures during wheel–rail rolling contact. A model is presented in which the local contact conditions of plastification, roughness and pressure are accounted for. Numerical examples are given. New rail materials. Hiensch, Franklin, Nielsen, Ringsberg, Weeda, Kapoor and Josefson report from the EU project INFRA-STAR on the development of a two-material rail for long life and low noise. Computer modelling, metallurgical research, twin-disc tests and field experiments have been carried out. Promising results regarding RCF are presented. Sawley and Kristan provide research results on new bainitic steels. Encouraging performance regarding both wear and RCF has been found in twin-disc tests, in accelerated full-scale tests and for rails used in revenue service. Further research is recommended.