Sensors can detect damage that may be invisible to the naked eye
During 2011’s deadly onslaught of earthquakes, floods and tornadoes, countless buildings had to be evacuated while workers checked to make sure they were stable. The events served as a reminder that most structures are still inspected by a decidedly low-tech method: the naked eye. To speed the process and make it more accurate, investigators are researching electronic skins, evolutionary algorithms and other systems that can monitor the integrity of bridges, buildings, dams and other structures in real time. To automatically detect tiny faults and relay their precise locations, civil engineer Simon Laflamme of the Massachusetts Institute of Technology and his colleagues are devising a “sensing skin”—flexible patches that glue to areas where cracks are likely to occur and continuously monitor them. The formation of a crack would cause a tiny movement in the concrete under a patch, causing a change in the electrical charge stored in the sensing skin, which is made of stretchable plastic mixed with titanium oxide. Every day a computer attached to a collection of patches would send out a current to measure each patch’s charge, a system that Laflamme and his colleagues detail in the Journal of Materials Chemistry
Another engineer is applying a similar concept to bridges. To monitor deterioration inside suspension bridge cables, Raimondo Betti of Columbia University and his collaborators are testing 40 sensors in cables in New York City’s Manhattan Bridge (above). The sensors track temperature, humidity and corrosion rate.
Although these sensors can detect damage that occurs after they have been installed, what about damage a structure had beforehand? Roboticist Hod Lipson of Cornell University and his colleagues have developed a computer model that simulates an intact structure and runs algorithms that evolve this model until it matches data that sensors provide, which can reveal a broader scope of damage.
Others are not yet convinced of these projects’ benefits. “There does not exist, yet, enough research and data that economically support continuous and timely maintenance,” Laflamme says. Another concern might be the yet to be studied long-term performance of the systems, especially in harsh environments—a matter for future research.
Source of Information : Scientific American Magazine
Showing posts with label Engineering. Show all posts
Showing posts with label Engineering. Show all posts
Tuesday, December 6, 2011
Saturday, March 6, 2010
WINGED VICTORY
A YACHT WITH AN ENORMOUS WING FOR A SAIL COULD WIN IT ALL
AT THE AMERICA’S CUP RACE THIS MONTH
This year, the rules have all but disappeared for competitors in the world’s oldest international trophy competition, the America’s Cup sailing race. Motorized sails are fine, the single-hull rule is out, and in the case of the BMW Oracle Racing team’s boat, even sails are optional. Instead, the largest wing ever constructed could catch enough wind to make the yacht the fastest yet. Conventional fabric sails are unreliable. “Wind speed and direction change by the second,” says Mike Drummond, the design director for the BMW Oracle Racing team. “The crew must constantly maneuver the mainsail to maintain maximum speed.” A sail’s leading edge often ripples, particularly when tacking into the wind, increasing drag and causing the sail to lose the airfoil shape that helps propel the boat. In contrast, it takes just one sailor a few clicks on a computer to immediately swing the 190-foot-tall carbon-fiber-and-Kevlar wing into position, where it will hold its shape regardless of conditions. With the wing, Drummond says the 90-foot trimaran can sail up to 5 percent, or about one knot, faster. In the months leading up to the February 8 race day, Drummond’s team noticed a few drawbacks to the new design. In strong winds, where sailors would normally shrink a soft sail, the one-size wing can grab too much wind and destabilize the boat. And in choppy waters, the extra weight can cause the craft to pitch front to back. “Still, overall, it’s obvious that the boat goes faster,” Drummond says. “We used to measure performance gains in hundredths of a knot. Now we measure it in tenths of a knot or more.”—COREY BINNS
WING
The 7,700-pound wing includes a single piece that rotates around the mast and eight flaps that catch or shed wind in different directions for thrust. Engineers claim that the wing—80 percent longer than a Boeing 747’s—can achieve twice the power of a soft mainsail.
MAST
Fiber-optic sensors in the mast and hull reflect light differently when stretched. A computer converts these changes into stress loads in real time to predict material failures and alert the crew if strong winds could snap the mast.
SAIL
A camera system photographs the soft sail, analyzes its shape and height, and compares the measurements with past performance data to suggest the optimal setup.
SMART SAILING Electronic sensors feed 26,000 data points every second—such as the wind speed, pitch of the waves, and stress on the boat—to a computer to calculate the optimum wing-sail configuration.
Source of Information : Popular Science February 2010
AT THE AMERICA’S CUP RACE THIS MONTH
This year, the rules have all but disappeared for competitors in the world’s oldest international trophy competition, the America’s Cup sailing race. Motorized sails are fine, the single-hull rule is out, and in the case of the BMW Oracle Racing team’s boat, even sails are optional. Instead, the largest wing ever constructed could catch enough wind to make the yacht the fastest yet. Conventional fabric sails are unreliable. “Wind speed and direction change by the second,” says Mike Drummond, the design director for the BMW Oracle Racing team. “The crew must constantly maneuver the mainsail to maintain maximum speed.” A sail’s leading edge often ripples, particularly when tacking into the wind, increasing drag and causing the sail to lose the airfoil shape that helps propel the boat. In contrast, it takes just one sailor a few clicks on a computer to immediately swing the 190-foot-tall carbon-fiber-and-Kevlar wing into position, where it will hold its shape regardless of conditions. With the wing, Drummond says the 90-foot trimaran can sail up to 5 percent, or about one knot, faster. In the months leading up to the February 8 race day, Drummond’s team noticed a few drawbacks to the new design. In strong winds, where sailors would normally shrink a soft sail, the one-size wing can grab too much wind and destabilize the boat. And in choppy waters, the extra weight can cause the craft to pitch front to back. “Still, overall, it’s obvious that the boat goes faster,” Drummond says. “We used to measure performance gains in hundredths of a knot. Now we measure it in tenths of a knot or more.”—COREY BINNS
WING
The 7,700-pound wing includes a single piece that rotates around the mast and eight flaps that catch or shed wind in different directions for thrust. Engineers claim that the wing—80 percent longer than a Boeing 747’s—can achieve twice the power of a soft mainsail.
MAST
Fiber-optic sensors in the mast and hull reflect light differently when stretched. A computer converts these changes into stress loads in real time to predict material failures and alert the crew if strong winds could snap the mast.
SAIL
A camera system photographs the soft sail, analyzes its shape and height, and compares the measurements with past performance data to suggest the optimal setup.
SMART SAILING Electronic sensors feed 26,000 data points every second—such as the wind speed, pitch of the waves, and stress on the boat—to a computer to calculate the optimum wing-sail configuration.
Source of Information : Popular Science February 2010
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