Damage identiﬁcation in beams using speckle shearography and an optimal spatial sampling

Mininni, M.; Gabriele, S.; Lopes, H.; Santos, J. V. Araújo dos

http://hdl.handle.net/10400.22/9968

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Authors

Mininni, M.

Gabriele, S.

Lopes, H.

Santos, J. V. Araújo dos

Abstract(s)

Over the years, the derivatives of modal displacement and rotation ﬁelds have been used to localize damage in beams. Usually, the derivatives are computed by applying ﬁnite differences. The ﬁnite differences propagate and amplify the errors that exist in real measurements, and thus, it is necessary to minimize this problem in order to get reliable damage localizations. A way to decrease the propagation and ampliﬁcation of the errors is to select an optimal spatial sampling. This paper presents a technique where an optimal spatial sampling of modal rotation ﬁelds is computed and used to obtain the modal curvatures. Experimental measurements of modal rotation ﬁelds of a beam with single and multiple damages are obtained with shearography, which is an optical technique allowing the measurement of full-ﬁelds. These measurements are used to test the validity of the optimal sampling technique for the improvement of damage localization in real structures. An investigation on the ability of a model updating technique to quantify the damage is also reported. The model updating technique is deﬁned by the variations of measured natural frequencies and measured modal rotations and aims at calibrating the values of the second moment of area in the damaged areas, which were previously localized.