Guidelines for the rail grade selection
M. Tomicic-Torlakovic, University of Belgrade, Faculty of Civil Engineering, Belgrade, Serbia Over the years the rail steel manufacturing process and quality of material produced have improved significantly through alloy design and/or head treatment procedure. The objective of this paper is to give the recommendations for the application of the available rail steel grades in accordance with the accessible investigations. The main source are the results of the Innotrack project in correlation with Euronorm prEN 13674-1. The conclusion for the Serbian Railway is made.
Linear friction welding of rail materials: Thermal analysis and resulting microstructures of pearlitic and bainitic steels
Friction welding, a solid state process, is a method that uses heat produced from friction. The produced heat in combination with an external pressure joins the two pieces of material in a weld. Friction welding has several benefits such as lower heat input compared to conventional welding, resulting in a narrower heat affected zone (HAZ), low environmental impact and no melting-solidification phenomena resulting in a structure free of impurities which gives better fatigue properties. These benefits are of particular interest to an ongoing EU-project ”Innovative Weld Processes for New Rail infrastructures” (WRIST). The present study considers the linear friction welding method (LFW), a method based on relative linear motion of two pieces under compression. A thermal finite element analysis is performed for the LFW process for two different steels, R260 and B360. For the simulations different heat generation models, pressures and welding times are used in different combinations. The microstructure, based on the cooling rates obtained from the simulations, is presented and then validated to experiments. Reaching the microstructures pearlite and bainite and avoiding the microstructure martensite are crucial for the functionality of the resulting weld for both R260 and B360. It is found that avoiding the formation of martensite is difficult when using the provided welding parameters from the experiments. As a contribution to the WRIST project it is recommended to preheat the material, which was not included in previous experiments. If preheating of the material is considered, it is demonstrated that martensite can be avoided for R260, but not entirely avoided for B360.
Review of Literature on Probability of Detection for Magnetic Particle Nondestructive Testing
Abstract : A critical review of the available literature concerning the minimum reliably detectable defect size aNDI for magnetic particle testing (MPT) in aerospace applications is presented. Four probability of detection (POD) studies relevant to detection of fatigue cracks in aircraft components were found over the period 1968 to 2011. As the statistical methods used in these four previous studies were either outdated or otherwise deficient, the original data were reanalysed using currently accepted techniques. A meta-analysis of the results is presented, with emphasis on statistical inferences for the defect size expected to be detected with 90% POD. It is shown that the minimum reliably detectable defect size aNDI = 2.0 mm currently specified by the Royal Australian Air Force for wet fluorescent magnetic particle inspection using the continuous method is consistent with estimates of the average performance of MPT derived from the reanalysis of the literature.