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Elze, Germany

Bongini E.,SNCF | Grassie S.L.,RailMeasurement Ltd. | Saxon M.J.,Orwell
Notes on Numerical Fluid Mechanics and Multidisciplinary Design | Year: 2012

A series of tests have been undertaken on the French railway system to examine whether a commercially available system based on axlebox accelerometers offers a viable method of measuring amplitudes of railhead roughness that are significant for wheel/rail rolling noise. The HSRCA system that was tested gives repeatable measurements and a good estimate of acoustic roughness provided the measuring speed is similar to that at which the system is calibrated and the dynamic behaviour of the trackform is similar to that on which the system is calibrated. The tests described below will demonstrate tentatively that the HSRCA offers a promising means of undertaking noise monitoring of a railway network. © 2012 Springer. Source

Grassie S.L.,RailMeasurement Ltd.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit | Year: 2012

In the 1970s, a rolling contact fatigue defect that was christened a squat was identified on the British railway network, primarily at first on the West Coast Main Line. Two productive decades of international research on squats followed, which later contributed to a rapid understanding of gauge corner cracking, which differs in detail but is similar in many important respects to a classic squat. In the last 10-15 years, a rail defect that is superficially similar to the classic squat has appeared on several railways. This has been investigated in some detail, initially in Australia and more recently also in Europe as part of the Innotrack project. These investigations have both assumed that the investigated defect is a classic squat. This paper reviews research on the squat and on its younger cousin. It forms the basis for a companion paper that presents original observations from track and detailed metallurgical examinations of specimens of the more recent squat-type defect. The review in this paper is used in the companion paper to identify features of the two types of defects that are similar and those that are significantly different. © 2011 Authors. Source

Grassie S.L.,RailMeasurement Ltd.
9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, CM 2012 | Year: 2012

The tangential forces on a rail resulting from a combination of traction and curving are considered. These forces are a significant component of both wear and shakedown. These two simple mechanisms can be used to understand most types of damage that occur on both rails and wheels. Source

Grassie S.L.,RailMeasurement Ltd.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit | Year: 2012

Railway noise is excited by irregularities on the running surfaces of wheels and rails, with rails being more significant for most of the wavelength and frequency range of interest. Measurements are presented that demonstrate the significance of irregularities in the 100-1000 mm wavelength range (corresponding roughly to 25-250 Hz) on ground-borne noise, and show that a reprofiling specification to address reductions in low frequency noise should address these longer wavelengths. Differences are demonstrated between irregularities in the 6.3-2000 mm wavelength range on a dedicated high speed line, and on heavy haul, mixed traffic, metro and light rail systems. Although the sample size is small for the high speed and heavy haul systems, the lowest levels of irregularity were nevertheless found on the high speed line. Heavy haul systems also have low levels of irregularity, which are below the limit specified in the acoustic standard ISO 3095. Metro systems are distinguished by corrugation, higher levels of short wavelength roughness corresponding perhaps to roughening from consistently high traction and braking, and significant differences between high and low rails in some curves. In one case shown here the high rail is amongst the smoothest in an entire sample of dozens of rails whereas the corresponding low rail is by far the most heavily corrugated and irregular. Light rail systems have relatively high levels of irregularity, particularly at short wavelengths. This may result from sanding to enhance adhesion. Reprofiling in general reduces irregularities below the level stated in ISO 3095, except at wavelengths of less than 30 mm for which irregularities are consistently greater after reprofiling than before. Reprofiling is particularly effective in reducing irregularities in the 30-500 mm wavelength range, in which irregularities are typically reduced by 10 dB but in some cases by 20-30 dB. Irregularities to the ISO 3095 limit spectrum exist immediately after some forms of grinding. The best results are obtained from reprofiling that is undertaken to an appropriate specification that is conscientiously monitored. © IMechE 2012. Source

Grassie S.L.,RailMeasurement Ltd.
CM 2015 - 10th International Conference on Contact Mechanics of Wheel / Rail Systems | Year: 2015

Several railways suffer from a defect that has been christened a "stud", which appears superficially similar to a squat but is very different in character. Although both initiation and propagation of studs are poorly understood, at least a couple of railways have already benefitted from exploiting the less malevolent nature of studs, particularly the fact that these do not themselves initiate transverse defects. This paper is based primarily on field work undertaken in NSW to reveal some of the characteristics of stud defects, in particular in contrast to rolling contact fatigue (RCF) of which squats are a classical example. This work has been supplemented by a very much smaller sample of field work undertaken in Switzerland and metallurgical analysis of studs that was undertaken at Sheffield University of samples from Swiss Railways. Studs are associated with sites where there is high traction, such as the exit from stations. In NSW they commonly initiate at about 10°-20° to the vertical towards gauge on the high rail in curves, then grow into the rail at an angle of about 20° to the surface. Studs can at first develop very quickly e.g. to a depth of 2.2mm in 6MGT. The stud fans out across the rail from the initial surface crack, developing across the rail at a substantially constant depth of 3-6mm. If the stud is left, it may rise to the surface at the opposite side of the railhead, giving rise to an ugly spall with a fracture surface typical of a conventional fatigue crack. There is no evidence whatsoever that studs become transverse defects, nor should this occur with a crack that develops across rather than along the rail as there is an absence of flexure to drive the crack. Studs have grown in rails in which there is no significant plastic work, and accordingly also no significant depth of compressive residual stress. These characteristics are very different from classical squats. Although some transverse defects (TDs) have been associated with studs, both gauge corner cracking (GCC) and studs have coincided in all of the cases examined. In these cases the TD has clearly developed in the conventional and well understood manner from the GCC. The stud has given rise to a dynamic load that accelerates growth of the TD. But if the GCC had not existed, the TD would not have developed. The paper provides some guidance on treatment and maintenance of studs as well as updating a hypothesis that still rests substantially on circumstantial evidence. Source

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