Impedance-based structural health monitoring

Impedance-based structural health monitoring (SHM) uses high frequency vibrations produced by a piezoelectric sensor/actuator to "interrogate" a structure to find damage. A model is generally not needed for the basic damage identification problem with the method. However, modeling becomes necessary when more information is needed for more complex functions of the SHM system, such as estimation of remaining life.  In addition, suitable models would aid in more accurately identifying and locating damage and in designing the SHM system.  Because of the high frequencies used for excitation of the structure, finite element modeling may not be computationally efficient.  The spectral element method (SEM) is used in combination with electric circuit analysis for impedance modeling.  SEM more accurately models higher frequency vibrations than finite element methods since the mass is modeled exactly and it incorporates higher order models more easily. The size of SEM models is also comparatively very small, so that they may be eventually incorporated in on board data processing systems for a self-contained SHM module. Simulations of sensor multiplexing, high frequency response and the inclusion of damage have been performed.

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