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Shock and Vibration
Volume 2014, Article ID 607125, 10 pages
http://dx.doi.org/10.1155/2014/607125
Research Article

Localization of Transversal Cracks in Sandwich Beams and Evaluation of Their Severity

1Department of Mechanics, “Eftimie Murgu” University of Resita, P-ta Traian Vuia 1-4, 320085 Resita, Romania
2Department of Mechanical Construction and Production, Ghent University, Technologiepark Zwijnaarde 903, 9052 Zwijnaarde, Belgium
3Department of Mechanics, University Politehnica of Bucharest, 313 Splaiul Independentei, 060042 Bucharest, Romania

Received 12 July 2013; Accepted 10 March 2014; Published 1 June 2014

Academic Editor: Nuno Maia

Copyright © 2014 G. R. Gillich et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

An algorithm to assess transversal cracks in composite structures based on natural frequency changes due to damage is proposed. The damage assessment is performed in two steps; first the crack location is found, and afterwards an evaluation of its severity is performed. The technique is based on a mathematical relation that provides the exact solution for the frequency changes of bending vibration modes, considering two terms. The first term is related to the strain energy stored in the beam, while the second term considers the increase of flexibility due to damage. Thus, it is possible to separate the problems of localization and severity assessment, which makes the localization process independent of the beams cross-section shape and boundary conditions. In fact, the process consists of comparing vectors representing the measured frequency shifts with patterns constructed using the mode shape curvatures of the undamaged beam. Once the damage is localized, the evaluation of its severity is made taking into account the global rigidity reduction. The damage identification algorithm was validated by experiments performed on numerous sandwich panel specimens.