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Aerospace Engineering


Damage Detection Phase I SBIR Project funded by US Army

Onboard Structural Health Monitoring (SHM) systems can be used to augment or replace conventional maintenance routines. The most obvious benefit of an onboard SHM system is to alert the operators of a vehicle to possible catastrophic situations. That is, if the vehicle were to enter an operational regime which overstresses a critical component, the diagnostic and prognostic capabilities of the SHM program would provide adequate forewarning.



All of these items enable a program that supports a vehicle to achieve reduced life cycle costs. Roughly 11% of the total operating costs for an aircraft is attributed to maintenance An updated approach to maintenance schedules that reduces these costs would make a vehicles operation more cost effective. Currently, most maintenance programs rely on a safe life approach where components are replaced at prescribed times even though they may still be structurally viable. Components that exhibit minor damage may still able to carry loads. A condition based approach to maintenance allows the part to be removed only when the part reaches a state where additional damage would be catastrophic. This type of approach would reduce wasteful inspection costs and replacements. It has been shown that parts replaced based on an operator inspected maintenance schedule were still usable In a few studies, more than 10% of the removed parts were still viable but were removed based on faulty diagnosis by the operator during the maintenance schedule.

Techno-Sciences, Inc. (TSi), in collaboration with the Smart Structures Laboratory of the Alfred Gessow Rotorcraft Center at the University of Maryland (UMD) and Bell Helicopter are working under a Phase I Army SBIR contract to develop an innovative, wireless damage detection methodology that examines a structure using energy harvesting, wireless data acquisition, and a suite of sensors with innovative signal processing. The structure is treated as a medium through which structural waves travel. Using a novel sensor array, and signal processing approach, the response of the structure can be deconstructed into wave propagation components. Each point on the sensor array is an element which gathers dynamic strain data from the underlying substructure. The sensor array is directly attached to the structure and the sensing elements utilize the piezoelectric effect as the transduction mechanism. Polyvinylidene fluoride (PVDF) piezoelectric material are exploited for this project, which are simple to manufacture and conforms to match the shape of the structure of interest. The capabilities of the sensor array can be adjusted to fit the appropriate requirements of the damage detection scheme employed. This type of sensing mechanism can be easily attached to the structure and does not alter the behavior of the underlying structure. Coupled along with appropriate power harvesting technologies and wireless data transmission capabilities, the sensor array can form a fundamental element through which a damage detection methodology is formed to enhance a SHM program.
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