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20 March 2006 Fault detection and localization using measured surface vibration and local inversion
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We present progress we have made in developing a structural acoustic-based methodology allowing interior fault detection and localization in plate-like structures using only processed vibration data readily available on the structure's surface. Our methods use measurements of surface displacement associated with vibration of the structure caused by externally applied forces. These forces can be created simply by a local actuator in direct contact with the structure or in some cases by an incident airborne acoustic wave. The measured normal surface displacements, uz(x, y), are then inverted locally using various mathematically optimized algorithms in order to obtain a desired material parameter, for example, the elastic modulus, whose spatial variation then serves to detect and localize the fault. This structural acoustic approach is not limited to any particular length scale requiring only that the structure be mechanically excited at frequencies for which the structural wavelength is within an order of magnitude of the fault dimension and that the dynamic surface displacements be mapped with a spatial resolution smaller than the fault size. We present the results of deploying the structural acoustic technique in the US Capitol Building to locate faults within plaster walls and ceilings bearing large expanses of precious nineteenth century frescoes, in composite airframe skins in laboratory experiments to detect and locate de-bonding of thin (~1mm) stiffeners and frames, and in micro-structures to detect and locate faults in silicon micro-oscillators and their supporting structures with resolutions approaching 1μm.
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J. A. Bucaro, A. J. Romano, J. F. Vignola, B. H. Houston, and P. B. Abraham "Fault detection and localization using measured surface vibration and local inversion", Proc. SPIE 6176, Nondestructive Evaluation and Health Monitoring of Aerospace Materials, Composites, and Civil Infrastructure V, 61760I (20 March 2006);

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