Noninvasive measurements of structural damage by laser scanning vibrometer: an experimental comparison among different exciters

Paolo Castellini; Enrico Esposito; Nicola Paone; Enrico Primo Tomasini

doi:10.1117/12.339862

8 February 1999 Noninvasive measurements of structural damage by laser scanning vibrometer: an experimental comparison among different exciters

Paolo Castellini, Enrico Esposito, Nicola Paone, Enrico Primo Tomasini

Author Affiliations +

Proceedings Volume 3585, Nondestructive Evaluation of Aging Materials and Composites III; (1999) https://doi.org/10.1117/12.339862
Event: Nondestructive Evaluation Techniques for Aging Infrastructures and Manufacturing, 1999, Newport Beach, CA, United States

Abstract

Frescoes, icons and composite materials show analogies in terms of defects, both present layer-to-layer detachments and delaminations and surface cracks; past experiences demonstrated that the study of surface vibrations could be used to locate defects position and size. At present a non- invasive diagnostic system is under development and the aim of this work is to propose and compare different kinds of structural exciters. After initial measurement set-ups based on accelerometers and impact hammers, a novel system based on laser vibrometers and acoustic stimulation has been assembled; full remote and contactless investigation of detachments and delaminations is thus possible with a very high accuracy. At present three different types of acoustic sources are employed: unbaffled standard loudspeakers, horn loudspeakers and an elliptic mirror sound focuser. The last source has been developed to concentrate sound power in a very small area so to excite only localized defects of the structures and void annoying noises to be propagated around them. A new kind of exciter, namely a piezo actuator, has also been introduced in the measurement chain and its effectiveness in finding defects in icons will be demonstrated. This paper will present experimental result gathered from sample showing differences in data due to different exciting sources. A comparison with results furnished by traditional techniques will be shown.

Citation Download Citation

Paolo Castellini, Enrico Esposito, Nicola Paone, and Enrico Primo Tomasini "Noninvasive measurements of structural damage by laser scanning vibrometer: an experimental comparison among different exciters", Proc. SPIE 3585, Nondestructive Evaluation of Aging Materials and Composites III, (8 February 1999); https://doi.org/10.1117/12.339862

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