D.N. Borza (France)
Holography, Model, Speckle, Vibration, Estimation, Damage
The paper presents some developments in the field of mechanical parameter estimation and damage detection based on the interaction between the full-field holographic vibration measurement data and a numerical model. The full-field of vibration amplitudes:measured experimentally for different eigenmodes offers the possibility to detect local variations of material parameters as well as damage detection. The direct correlation between the experimental and the numerical vibration modes is difficult because of the different data format and scale and of laser speckle noise. Also, the phase unwrapping of holographic vibration patterns is not always possible. In this paper a new strategy is proposed, consisting in comparing directly the holographically obtained vibration fringe patterns with simulated fringe patterns produced by the numerical model. The high speckle noise inherent to electronic holography results is addressed by developing two new interferometric methods, namely the quasi-binary method and the true time-average method. The multiplicative phase noise covering the data is almost completely eliminated. As a result, the experimental and numerical data to be correlated become highly coherent. Local parameter estimation and damage detection according to different criteria are discussed.
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