Vol. 3, No. 9, 2008

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ISSN: 1559-3959
A wave-based damage index for the analysis of the filtered response of damaged beams

Nicole Apetre, Massimo Ruzzene, Sathyanaraya Hanagud and S. Gopalakrishnan

Vol. 3 (2008), No. 9, 1605–1623
Abstract

This paper introduces a wave propagation-based damage index which relies on the evaluation of the strain energy distribution associated with propagating waves. The presence of localized damages typically distorts the wavefield by causing reflections and diffractions. The evaluation of such distortions, in reference to the wavefield corresponding to the undamaged structure, can be used as an indicator which potentially locates, quantifies and classifies the damage.

The damage index formulation is first illustrated through a numerical model of a beam with a small notch, modeled as a localized thickness reduction. The beam’s wave propagation response is simulated through the combined application of perturbation techniques and the spectral finite element method. The perturbation approach and a first order model for the beam capture the coupling between bending and axial behavior caused by the damage, and allow the prediction of mode conversion phenomena. The perturbation solution allows direct comparison between undamaged and damaged strain energy contributions, which are directly associated with perturbation solutions of different orders. The resulting damage index locates the damage along the beam length and estimates its severity.

Experimentally, the damage index is implemented by considering full wavefield measurements obtained through a scanning laser vibrometer. The undamaged reference response is derived directly from measurements on the damaged component, through the application of a filtering procedure operating in the wavenumber/frequency domain.

Keywords
damage measure, damage index, notched beam, spectral finite element method, perturbation techniques, first order beam theory
Milestones
Received: 19 December 2007
Accepted: 18 October 2008
Published: 1 November 2008
Authors
Nicole Apetre
School of Aerospace Engineering
Georgia Institute of Technology
270 Ferst Drive
Atlanta, GA 30332
United States
Massimo Ruzzene
School of Aerospace Engineering
Georgia Institute of Technology
270 Ferst Drive
Atlanta, GA 30332
United States
http://www.ae.gatech.edu/people/mruzzene/
Sathyanaraya Hanagud
School of Aerospace Engineering
Georgia Institute of Technology
270 Ferst Drive
Atlanta, GA 30332
United States
S. Gopalakrishnan
Department of Aerospace Engineering
Indian Institute of Science
Bangalore, 560012
India
http://www.aero.iisc.ernet.in/~krishnan