Lehigh University
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Resolve Vol. 1, 2014

Researchers achieve peak performance with advanced sensor systems

Professor Sibel Pamukcu (center) and students (left to right) Erinn Bonshak, Scott Cohen and Kepha Abongo test projectile impacts on clay embedded with sensors.

The innovative use of advanced sensor systems, says Sibel Pamukcu, could enhance the protection provided by soldier’s helmets and armor and also help locate pipeline leaks and other underground events.

Fiber-Bragg Grating (FBG) sensors are used routinely to measure strain, temperature and other environmental factors, says Pamukcu, professor of geotechnical engineering in the department of civil and environmental engineering. The sensors do this by detecting subtle changes in light refraction within the fibers.

Pamukcu and researcher Qingsong Cui have tuned FBG sensors to help provide more accurate measurements of the forces transmitted when a projectile strikes a soldier’s helmet.

Even when tests show that armor prevents a projectile from penetrating, says Pamukcu, researchers have found that soldiers can still suffer internal injuries.

“The projectile impact creates powerful force fields that are very fast, measured in microseconds, and that travel over very short distances,” says Pamukcu. Current testing methods may not pinpoint those forces because they capture average impact forces, not peaks.

Cui has tuned FBG sensors to resolve events as short as 20 microseconds, while Pamukcu has designed a prototype sensor system that has the potential to accurately measure the size and velocity of stresses a person experiences from projectile impact. The researchers embedded an array of sensors inside a form made of ballistic clay, which mimics the consistency of the human body, and tested a variety of impacts.

“The whole event takes only 400 microseconds,” says Pamukcu. “In the spatial resolution that we attempted, we were able to capture the peak strains that other sensors might miss.”

Pamukcu also works with associate professor Liang Cheng of computer science and engineering to improve the ability of underground wireless sensors to detect subsidence, or the infiltration of contaminants from a fracking well or pipeline leak. They have developed a method of measuring changes in the attenuation of underground radio signals to determine that a geo-hazard event has occurred.

“We’re talking about long distances and very spread-out applications,” Pamukcu says. Wireless sensors can be placed along the length of a pipeline, for example. Rather than testing for oil or gas at many points along the pipeline, they have set up wireless sensors to detect changes in the transmission between two sensors along the line.

“If we get oil or gas coming through (between sensors) the dielectric constant and the electrical conductivity of the ground will change and the baseline attenuation will change,” Pamukcu says. “When we have these sudden changes we can say there may be something going on, and then we can apply more precise diagnostic sensing in that area.”

The wireless sensors can also be tuned to detect signal fluctuations that result from changes in the mass density of the ground between sensors, says Pamukcu. This can provide early detection for potential leaks.

Pamukcu gave a keynote lecture titled “Geosensing for Developing Sustainable Responses to Environmental Hazards Underground” at ASCE’s GeoCongress 2014 in Atlanta in February.

Posted on Monday, April 07, 2014

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