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SUMMARY:Measuring microns on rails: can we really do it and if so\, how? -
  Dr Stuart Grassie\, RailMeasurement Ltd
DTSTART:20180309T160000Z
DTEND:20180309T170000Z
UID:TALK102550@talks.cam.ac.uk
CONTACT:46601
DESCRIPTION:MEASURING MICRONS ON RAILS: CAN WE DO IT AND IF SO\, HOW?\n\nA
 BSTRACT\nDynamic loads giving rise to vibration and noise are excited by i
 rregularities\, in particular so-called “corrugation” on the running s
 urfaces of both wheels and rails. The amplitude of irregularity that gives
  rise to significant load and noise can be tiny. A typical contact stiffne
 ss between wheel and rail is 1.5GN/m\, so an irregularity of 10m can gi
 ve rise to 15kN dynamic load. A 50m irregularity at a sufficiently high
  frequency causes loss of contact. Anyone who travels on the Piccadilly Li
 ne to Heathrow (or on many other LU lines) may wonder why it is so noisy: 
 the roaring at a pretty consistent frequency of 500Hz is almost entirely a
  result of rail corrugation.\n\nThese irregularities have to be measured\,
  not only for purposes of research\, but also to maintain the rails and en
 sure that irregularities are removed satisfactorily. The irregularities ar
 e typically removed using a reprofiling train (Network Rail has recently b
 ought 4 grinding trains\, each with forty-eight 30kW grinding motors\; mil
 ling is also used\, particularly to remove significant depths of material)
 . Much of the disruption on London Underground on weekends results from re
 profiling: the whole of the Victoria Line is reprofiled annually. The stan
 dard to which reprofiling is undertaken essentially requires that irregula
 rities with an amplitude of at most a few microns remain on the rail.\n\nI
 f the maintenance contractor is to do this job properly\, rails have to be
  measured both before and after reprofiling. Those measurements have to be
  accurate to microns and\, preferably\, they should be made from the repro
 filing train itself. RailMeasurement Ltd (RML) have developed equipment th
 at is probably the “state of the art” in this area. The original equip
 ment\, the hand-held “Corrugation Analysis Trolley” (CAT) is based on 
 an instrument made in CUED in the 1970s. Unfortunately\, although the prec
 ision of the CAT is better than a micron\, it is suitable neither for meas
 uring freshly reprofiled rails nor for use on a train.\n\nRML’s RCA can 
 be used on a train\, even when the rail is being ground or milled. RML rec
 ently won a contract to supply one of these to Crossrail to measure longit
 udinal irregularities to what are essentially acoustic requirements. CATs 
 and RCAs are made in St Ives and supplied worldwide: more than 90% of what
  we make is exported.\n\nSome results from both types of equipment will be
  shown\, and\, with luck\, both a CAT and a measuring wheel from an RCA wi
 ll be available for inspection.\nReferences\n\n1 SL Grassie\, “Rail irre
 gularities\, corrugation and acoustic roughness: characteristics\, signifi
 cance and effects of reprofiling on different types of railway system”\,
  Journal of Rail and Rapid Transit\, Procs of I mech E\, 2012\, 226F\, 542
 -557\n\n2 SL Grassie\, “Routine measurement of long wavelength irregular
 ities from vehicle-based equipment”\, in “Noise and vibration mitigati
 on for rail transport systems”\, David Anderson et al (eds)\, Notes on N
 umerical Fluid Mechanics and Multidisciplinary Design\, 2018\, vol 139\, c
 hapter 24
LOCATION:JDB Seminar Room\, CUED
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