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Published On: Feb 04, 2004 04:24 PM
Total entries in this category:
Published On: Feb 04, 2004 04:24 PM
Was that an earthquake?
I'm not sure, but I'll double check the volt meter
connected to my final coat of high gloss...
Smart
paint
A dab of paint could soon warn engineers when
bridges are in danger of shaking themselves to pieces. A researcher at the
University of Newcastle upon Tyne says that the "smart paint" will allow
engineers to build lighter, cheaper and more elegant
structures.
Vibrations can produce fatigue cracks in structures like bridges and oil rigs that can lead to catastrophic failure. So engineers tend to make their structures more robust than they need to be.
"Especially where failure could mean lives are lost, engineers over-design to ensure they don't get failures," says Jack Hale, who developed the paint.
Hale's paint is able to sense vibrations because it is loaded with a fine powder of a piezoelectric material called lead zirconate titanate (PZT). When PZT crystals are stretched or squeezed they produce an electrical signal that is proportional to the force.
Vibrations can produce fatigue cracks in structures like bridges and oil rigs that can lead to catastrophic failure. So engineers tend to make their structures more robust than they need to be.
"Especially where failure could mean lives are lost, engineers over-design to ensure they don't get failures," says Jack Hale, who developed the paint.
Hale's paint is able to sense vibrations because it is loaded with a fine powder of a piezoelectric material called lead zirconate titanate (PZT). When PZT crystals are stretched or squeezed they produce an electrical signal that is proportional to the force.
Crystal
squeezing
To test the idea, Hale sprayed a patch of
smart paint 5 centimetres square onto a metal beam and coated it with a second
layer of an electrically conductive paint. He then applied a voltage to the
paint to align the crystals at right angles to the surface. This ensures the PZT
crystals produce a signal whatever direction the beam is stressed: stretching it
makes the paint layer thinner and squeezes the crystals; compressing the beam
does the reverse.
Hale then attached electrodes to the beam and the conductive paint. Tapping the beam made it vibrate, which stretched and compressed the patch of paint. The harder he hit the beam the larger the voltage he recorded.
Hale says engineers could use the paint to monitor vibrations throughout the lifetime of a structure, allowing them to calculate much more accurately when fatigue is becoming a problem.
"They'd be able to design lighter, more elegant and cheaper structures, because they'd know if they were getting towards the end of its life," he says.
Hale then attached electrodes to the beam and the conductive paint. Tapping the beam made it vibrate, which stretched and compressed the patch of paint. The harder he hit the beam the larger the voltage he recorded.
Hale says engineers could use the paint to monitor vibrations throughout the lifetime of a structure, allowing them to calculate much more accurately when fatigue is becoming a problem.
"They'd be able to design lighter, more elegant and cheaper structures, because they'd know if they were getting towards the end of its life," he says.
Muddled
signal
The new paint is a much easier way of
measuring vibrations than conventional strain gauges, says Hale. "If they're not
on right, you get false
readings."
However, Derek Smith of the Dynamics and Vibration Group at Cambridge University warns that Hale's system would be unable to tell in which direction a vibration is strongest because it measures strains in all directions at once.
"You might get a muddled signal out and not be certain what was going on," he says. "It could still be useful, though, because an awful lot of strain patterns are unidirectional." Hale will test the paint on the Gateshead Millennium Bridge across the Tyne later this month.
However, Derek Smith of the Dynamics and Vibration Group at Cambridge University warns that Hale's system would be unable to tell in which direction a vibration is strongest because it measures strains in all directions at once.
"You might get a muddled signal out and not be certain what was going on," he says. "It could still be useful, though, because an awful lot of strain patterns are unidirectional." Hale will test the paint on the Gateshead Millennium Bridge across the Tyne later this month.
Posted: Wed - February 4, 2004 at 04:20 PM