Evaluation of technical vs economic decisions in rail grinding
Rail is a significant capital asset for railway companies. It contributes more than half of the capital assets of railway infrastructure. Recent rail inspection data using Ultrasonic rail testing has shown increasing number of rail defects, failures and causing disruptions to rail services. This cost can be further increased when the track quality is poor. In recent years, railroads have been purchasing over 500,000 tons of rails per year at an estimated total cost of US $1.25 billion for replacement of worn out and degraded rails. Rail grinding is considered as viable means in reducing the impacts of rail defects and failures. Rail grinding can result in improved curving performance (wheel/rail interaction) and prevents crack initiation and propagation of surface cracks due to RCF. This paper focuses on analysis of rail degradation process and development of mathematical model considering technical and economic decisions in rail grinding to rail infrastructure owners.
SYSTEMS ENGINEERING APPROACH TO THE WHEEL-RAIL INTERFACE
Traditional approaches to wheel-rail interface problems have been to develop tools for solving individual problems rather than addressing the system as a whole. This approach can result in the solutions firstly being incomplete because only a part of the problem has been addressed; secondly having an adverse effect because the solution has had unconsidered repercussions elsewhere in the system; and thirdly gaps and incompatibilities occurring between the separate problem solving tools. The application of systems engineering enables the understanding and modelling of the whole system with a view to being able to assess and evaluate the implications of a change throughout that system. The integrated approach being adopted in this project should help ensure the safe, reliable and effective operation of the systems that rely upon the wheel-rail interface. The demands on the wheel-rail interface in the UK are increasing with heavier loads and higher speeds, as required by a rail network for the 21st Century. Rail failure from this interaction is caused by excessive wear, resulting in an adverse rail profile, or by fatigue crack growth, which may propagate to total failure. Microstructural changes result from the contact stresses in the surface layers associated with the wheel-rail interaction and influence the wear rate and fatigue crack initiation. These microstructural changes depend on numerous factors including the loading pattern (axle load, contact patch area, etc) and the steel (composition and initial microstructure) used. This paper outlines the systems engineering approach being adopted to consider the wheel-rail interface and highlights the metallurgical input. For the covering abstract see ITRD E122683.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.