00:00 Hatfield
Rail Disaster (archive news footage – APTN
Low
CU shot rail track
Wide
rail track Virgin mainline train passes through
Wide
local passenger service pulling into station
CU
rail connectors on local passenger service
Wide
Japanese bullet train
Tilt
down Department of Physics building
Focus
pull flowers to department of Physics sign
MS
crack depth gauge information poster
MS
signal enhancement information poster
CU
diagram electromagnetic acoustic transducers
Wide
Dr Steve Dixon and Dr Rachel Edwards at equipment
Pan
from CU Dr Rachel Edwards to computer display
MS
electromagnetic acoustic transducers being moved
on
Section
of rail
MS
Dr Rachel Edwards pointing at computer display
CU
computer display
Guide Voice: Hatfield October 2000. One of the
worst train crashes in recent history killed four and injured 102
people. Nearly two years earlier engineers had identified a
form of fatigue known as gauge corner cracking, in the rail which
eventually broke and caused the crash.
Since Hatfield the pursuit of safety has become even more of a
concern for the rail and train operators but checking thousands of
miles of track for defects and wear and tear is a slow and costly
process.
However, soon every train, whether high speed mainline or a
local service, passenger or freight, could be carrying a device
that continuously checks the rails for defects, no matter how fast
the train is travelling.
Even the Japanese bullet trains capable of speeds of 300
kilometres an hour could use this detection system when fully
developed because the ultrasound waves it employs travel at 3000
metres a second.
This new technology is the brainchild of The University of
Warwick’s Physics Department, which has just been awarded
funding from the Engineering and Physical Sciences Research Council
to develop their discovery from the lab into a device that can be
used in the real world.
Dr Steve Dixon and colleague Dr Rachel Edwards have taken a pair
of electromagnetic acoustic transducers which generate and detect
ultrasound waves and found a way to propagate a wave along the
track from which they can measure cracks and defects faster and
more accurately than existing systems.
01:27 Sot Dr Steve Dixon, Department of Physics,
University of Warwick - "The approach we’re
using here is non-contact. This means that it is much more
practically viable to operate the system, there is no need to
maintain good contact with the couplings. Because we’re using
a separate generator and detector we don’t have the same
physical limitations of the inspection speed of a conventional
system which may be limited to doing inspections on line at around
30 mph."
01:55 CU
Dr Steve Dixon pointing at cracked rail
CU
detector passing over cut in rail
Wide
ultrasound pulse generator
CU
detector passing over cut in rail (different angle)
CU
computer screen displaying peaking and troughing in
Frequency
graph
MCU
electromagnetic acoustic transducers
MS
Dr Rachel Edwards at computer display
MCU
electromagnetic acoustic transducers tilt up to CU Dr Steve
Dixon
MS
Dr Rachel Edwards pointing at computer display
CU
frequency graph on computer display
Wide
Dr Steve Dixon and Dr Rachel Edwards
Focus
pull CU glasses to graph on computer display
Guide Voice: Gauge corner cracking small
fissures in the rail surface which were the pre-cursor to the
Hatfield crash are one of the problems detected by this method.
To test its accuracy they have created cuts of measured depth
into the rail surface then they generate an ultrasound pulse along
the surface of the rail and record its behaviour on a computer
As the detector moves close to a defect the surface wave
reflected from the defect can interfere with the incident wave to
give a larger amplitude signal. However at speed the most reliable
measurements are made on the portions of the wave that have passed
under a defect. This is an accurate method as the defect can be
detected anywhere between the transducers during the
measurement.
The wave used is termed wideband –containing many
frequencies in a single pulse and how the defect changes these
frequencies and the amplitude of the wave are both measured as it
passes through a defect
02:49 SOT Dr Steve Dixon - “A good
analogy to use is that we have a piano, we hit all the keys at once
there’s lots of different frequencies there, we use a
programme called the Fourier transform to break all that down and
tell us what frequencies are present in the pulse. With the waves
that we’re looking at, lower frequencies waves travel to
lower depths so if we can break down the wave into these different
frequency components we have another means of saying how deep the
defect is by looking at the proportion of the wave frequencies and
sneak underneath the defects compared to those that are blocked. We
can combine that with just the amplitude measurement so if you like
we have two ways of checking and giving us information on the depth
of the defect.”
03:37 CU
researcher at Laser Michelson Interferometer
ECU
Laser Michelson Interferometer
Graphic
– wave behaviour
Guide Voice: In order to be certain of the way
the wave behaves they used a Laser Michelson Interferometer which
measures surface displacements down to a size smaller than an atom
to take a series of measurements of the rail in order to build up a
highly accurate image of how the wave behaves, which they’ve
animated on a computer. Having proved their discovery the next step
is to build a device that will work on a train
04:00 Dr Steve Dixon: - “We’re
hoping that the companies that are already committed to involvement
in the project such as network rail, London Underground, SercoRail
and a couple of SMEs in addition to the rail manufacturers Corus
that we’ll be able to have a very rounded and good overview
as to what is required from the industry, we want to take our
research from the lab and put it into the real world and make
something that is useful for these people.”
04:26 Wide
rail track – Virgin mainline train passes through
Guide Voice: If they succeed they can transform
every train in the country into a highly sophisticated rail
monitoring system that routinely examines the tracks for any
potential defect, radically improving the safety and efficient
management of the rail network.
04:43 Ends
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