Rolling-sliding laboratory tests of friction modifiers in dry and wet wheel-rail contacts

Friction management has been carried out extensively in the majority of railway networks in the last few years. A popular practice is the application of friction modifiers to increase the adhesion level in contaminated wheel-rail contacts. Two friction modifiers have particularly been used or tested on several railway networks as adhesion enhancers to facilitate the traction and braking operation under poor adhesion conditions. However, for assessment of the performance the railway operators and infrastructure managers mostly rely on practical observations that do not elucidate completely the effectiveness and side effects of these adhesion enhancers. In this paper, the constituents of the two friction modifiers are identified and the solid components are analyzed. A twin-disk roller rig has been used to study their performance in dry and wet contacts under closely controlled laboratory conditions. The adhesion characteristics of both friction modifiers are examined for different slip ratios. Furthermore, the wheel and rail disks are examined after a series of dry tests to analyze the mass loss, the surface damage, the change in surface hardness and roughness, and the subsurface deformation caused by the friction modifiers compared to dry clean contacts. (C) 2009 Elsevier B.V. All rights reserved

Sprachmacht auf engstem Raum

Audio films enable blind and visually impaired people to enjoy a feature film. An audio film consists of the original audio track of the film and the audio description. This film description compensates for the video track of the film. It is therefore a purely auditory media text. Translation studies consider the work of audio descriptors as an intercodal translation process and as a part of audiovisual translation. Maher Tyfour examined the concrete implementation of audiodescription on a corpus of image translations for the Munich Tatort series. His focus was on the city's staging. By comparing them with the original video tracks of the feature films, he illustrates the intertextual relationship between original and translation. In the analysis he identifies the strategies of the audio descriptors that are partly unconsciously implemented in the translation process, explains them and discusses them in terms of text and translation studies. Maher Tyfour studied English at the University of Damascus (Syria) before coming to Germany in 2009. After completing his master's degree in Intercultural German Studies at the Georg-August University of Göttingen, he earned his doctorate at the University of Hildesheim. He works as a teacher of English and German as a second language in Saxony

Sprachmacht auf engstem Raum

Audio films enable blind and visually impaired people to enjoy a feature film. An audio film consists of the original audio track of the film and the audio description. This film description compensates for the video track of the film. It is therefore a purely auditory media text. Translation studies consider the work of audio descriptors as an intercodal translation process and as a part of audiovisual translation. Maher Tyfour examined the concrete implementation of audiodescription on a corpus of image translations for the Munich Tatort series. His focus was on the city's staging. By comparing them with the original video tracks of the feature films, he illustrates the intertextual relationship between original and translation. In the analysis he identifies the strategies of the audio descriptors that are partly unconsciously implemented in the translation process, explains them and discusses them in terms of text and translation studies. Maher Tyfour studied English at the University of Damascus (Syria) before coming to Germany in 2009. After completing his master's degree in Intercultural German Studies at the Georg-August University of Göttingen, he earned his doctorate at the University of Hildesheim. He works as a teacher of English and German as a second language in Saxony

Influence of Different Application of Lubricants on Wear and Pre-existing Rolling Contact Fatigue Cracks of Rail Materials

Rolling contact fatigue (RCF) of rail can be a significant problem affecting safety and maintenance. Rail materials have been optimized to reduce it, but not enough is known about how friction management products applied to the rail affect crack growth. This study presents experimental results carried out to explore the influence of different lubricants and application orders on wear and pre-existing RCF cracks in rail materials. The results indicate that the types or properties of lubricants have a vital role in the wear rate and fatigue crack growth characteristics of rail materials after conditioning with 5000 dry cycles to initiate cracks. Using a different application order of two lubricants has a significant influence on the crack growth angles in the rail rollers

Tribological behaviour of microalloyed and conventional C–Mn rail steels in a pure sliding condition

This paper compares the tribological behaviour of microalloyed rail steel with conventional C–Mn rail steel under different test conditions (load, temperature and humidity). Pin-on-disc tribological tests were performed inside a climate chamber under different loads (20, 30 and 40 N), relative humidity (15, 55 and 70%) and temperatures (20 and 40 ℃). After the friction and wear tests, the worn surfaces were analysed using both confocal and scanning electron microscopies. The results obtained show that the use of microalloyed steel in railway applications under severe conditions (high loads and humidity) could lead to increased service life of the rails and could extend the time between maintenance operations

A review of friction models in interacting joints for durability design.

This paper presents a comprehensive review of friction modelling to provide an understanding of design for durability within interacting systems. Friction is a complex phenomenon and occurs at the interface of two components in relative motion. Over the last several decades, the effects of friction and its modelling techniques have been of significant interests in terms of industrial applications. There is however a need to develop a unified mathematical model for friction to inform design for durability within the context of varying operational conditions. Classical dynamic mechanisms model for the design of control systems has not incorporated friction phenomena due to non-linearity behaviour. Therefore, the tribological performance concurrently with the joint dynamics of a manipulator joint applied in hazardous environments needs to be fully analysed. Previously the dynamics and impact models used in mechanical joints with clearance have also been examined. The inclusion of reliability and durability during the design phase is very important for manipulators which are deployed in harsh environmental and operational conditions. The revolute joint is susceptible to failures such as in heavy manipulators these revolute joints can be represented by lubricated conformal sliding surfaces. The presence of pollutants such as debris and corrosive constituents has the potential to alter the contacting surfaces, would in turn affect the performance of revolute joints, and puts both reliability and durability of the systems at greater risks of failure. Key literature is identified and a review on the latest developments of the science of friction modelling is presented here. This review is based on a large volume of knowledge. Gaps in the relevant field have been identified to capitalise on for future developments. Therefore, this review will bring significant benefits to researchers, academics and industrial professionals

Full-scale testing of laser clad railway track; case study - testing for wear, bend fatigue and insulated block joint lipping integrity

This paper reports on a series of tests which were carried out on full-scale sections of rail that had been treated by laser cladding aiming to create a layer (~1-2mm) of high performance material on the rail head. Experiments were designed to measure wear, lipping of insulated block joints (IBJs) and bending fatigue of clad samples. The wear rate of the clad samples was between 78- 89% lower than that of the standard R260 reference sample. Cladding of either side of an insulated block joint greatly improves its lipping resistance and allows it to withstand approximately 3 times the energy input into the contact compared to a standard un-clad IBJ. A section of rail clad with martensitic stainless steel was subject to bend fatigue testing and ran out to 5,000,000 cycles at a stress range of 350 MPa matching the performance of an unclad R260 rail. Although there is no standard for the bend testing of laser clad rail this performance exceeds the performance requirements of the NR/SP/TRK111 standard which governs the bend testing of flash but welded rail

The role of slip ratio in rolling contact fatigue of rail materials under wet conditions

Rolling contact fatigue (RCF) of rail is a significant factor affecting the maintenance and service safety of railway track. While the driving parameters are known, clearer relationships are needed with fatigue life. The objective of this study was to explore the role of slip ratio in the development of RCF cracks and fatigue life of rail materials under a water lubricated condition. The results indicate that slip ratio has a vital and interesting influence in the wear and RCF life of rail materials. With an increase of slip ratio from 0 to 0.3%, fatigue life of rail materials has an obvious decrease. As slip ratio increases to 1%, the life increases. Then, RCF life has a drop as slip ratio changes from 1% to 5% and 10%. This may be a comprehensive effect resulting from various contact characteristics of stick area and slip area in the contact area and a competitive relationship between wear and RCF. The increase of slip ratio significantly increases the growth angle of cracks and transforms the damage mechanism of rail materials from slight surface fatigue to serious fatigue and pitting damage

Sprachmacht auf engstem Raum : Die Inszenierung der Stadt in den Hörfilmen der Münchner Tatort-Filmserie

Audio films enable blind and visually impaired people to enjoy a feature film. An audio film consists of the original audio track of the film and the audio description. This film description compensates for the video track of the film. It is therefore a purely auditory media text. Translation studies consider the work of audio descriptors as an intercodal translation process and as a part of audiovisual translation. Maher Tyfour examined the concrete implementation of audiodescription on a corpus of image translations for the Munich Tatort series. His focus was on the city's staging. By comparing them with the original video tracks of the feature films, he illustrates the intertextual relationship between original and translation. In the analysis he identifies the strategies of the audio descriptors that are partly unconsciously implemented in the translation process, explains them and discusses them in terms of text and translation studies. Maher Tyfour studied English at the University of Damascus (Syria) before coming to Germany in 2009. After completing his master's degree in Intercultural German Studies at the Georg-August University of Göttingen, he earned his doctorate at the University of Hildesheim. He works as a teacher of English and German as a second language in Saxony.</jats:p