Research Magazine 2006

Engineers work to create healthier structures

Health management most often refers to your personal health. But another type of health management also affects your well-being—the structural health of the building you live and work in, the vehicle you drive or fly in, the bridge you cross.

Researchers in UT Arlington’s College of Engineering are working to make you feel safer in these places.

Like physicians who consult outside their expertise and gather information to plan an effective health regimen, researchers from several engineering backgrounds are teaming to develop integrated health management systems for such varied applications as aircraft and power distribution networks. These systems consist of wireless networks of microsensors and actuators, energy harvesting and wireless communications microdevices, as well as architectures and algorithms for sensor placement, diagnostics, prognostics, condition-based maintenance, learning and error recovery.

The Automation & Robotics Research Institute (ARRI) is home to highly interdisciplinary investigations involving faculty and research scientists with backgrounds in aerospace, computer science, electrical, materials science and mechanical engineering. Driven by the demand for increased safety and lower operating costs, they are developing smart micro-machine technologies that may result in revolutionary, intelligent systems superior to existing sensor networks. The world-class team includes Haiying Huang, Woo Ho Lee, Frank Lewis, Shashank Priya, Dan Popa and Jeongsik Sin.

“Our approach is ‘concept to commercialization,’ ” ARRI Director Harry Stephanou said. “We’re not just a think tank pitching ideas that may or may not have practical applications. And we are not interested in modifying old systems. We take the ‘integrated’ in integrated health systems seriously. Our systems are designed to be imbedded in new structures, containing more abilities such as ‘smart’ materials that self-diagnose problems.”

Take, for example, a helicopter, which must undergo scheduled maintenance. This often demands that part of the aircraft be destroyed or fully replaced due to lack of knowledge of actual material health.

Look at the rotor blades, which can’t be taken apart to examine. While the blades are designed to cut through four-inch trees, this ability does not prevent micro-fractures due to prolonged impacts during extreme operating conditions and natural elements like repeated exposure to small, sharp sand particles.

An ARRI-designed system might employ an optical fiber-based sensor system to monitor real-time changes in blade material strain. Advanced signal processing and control algorithms would correct for known disturbances. Additional algorithms would optimize data comparisons between measured and baseline parameters and perform necessary alerts when certain conditions are present. Critical components would be tracked with complete component histories.

Energy to power the sensor and communication networks would be harvested using piezoelectricity (generating electricity from mechanical forces, and vice versa). Materials science researchers at UT Arlington have developed piezoelectric materials that produce several times the energy of existing, commercially available units.

The result? A maintenance program based on actual structural needs rather than an arbitrary schedule, reduced costs and increased safety.

This is not a fanciful concept. Earlier this year, the Office of Naval Research awarded an $800,000 grant to ARRI researchers to investigate sensor arrays to monitor the health of rocket motor fuel and other equipment.

Long-term degradation of rocket motors can lead to unexpected disasters, environmental contamination or operational malfunction. To prevent such events, ARRI researchers will focus on two health-monitoring sensors: a microspectrometer for in situ analysis of the chemical composition (detectable out-gassing) and a crack detector based on piezoelectric ceramic patches. Sensors can be deployed inside a storage/transportation container for long-term monitoring.

A second thrust of the project involves using micro-electromechanical arrays for flight control surfaces such as fins, elevators and flaps. Novel materials that fabricate these arrays will replace conventional steering actuators and be able to survive in harsh environments.

— Roger Tuttle