Abstract
This paper describes several interferometric techniques and their applications in structural damage identification. With that objective in mind, damaged aluminum beams with clamped-free and free-free boundary conditions are analyzed. Different damages cases are inflicted by creating small cuts perpendicular to the beams longitudinal axis, being the damage, therefore, characterized by the dimensions of these cuts. The out-of-plane displacement field of modal response is measured with an electronic speckle pattern interferometric system. The static and dynamic rotation fields, defined as the spatial derivative of the displacement field, are measured with two different speckle shearography systems. Second and third order spatial derivatives of the displacement field, which are related to the bending moment and shear force, are computed by differentiation techniques. The cuts locations are determined by looking for maximum values and/or perturbations of damage indicators based on bending moments and shear forces. This method is validated by comparing its results with numerical ones, from which the most suitable interferometric technique is chosen.
Highlights
The pursue of reliable structural damage identification methods has attracted the scientific and technical community for decades
The shear force indicator (SFI) indicator is not able to locate the cuts, since, as stated before, the shear force is computed by differentiating twice the rotation field measured with the pulse speckle sherography system and differentiating thrice the displacement field measured with the electronic speckle pattern interferometry (ESPI) system
Several interferometric techniques and their applications to damage localization of cuts in beams were described in this paper
Summary
The pursue of reliable structural damage identification methods has attracted the scientific and technical community for decades. Damage identification methods based on fringe pattern classification have been improved by the application of neural networks techniques and the combination of experimental measurements and numerical simulations results [16,17,18]. The introduction of temporal or spatial phase modulation techniques for full evaluation of the phase maps of the interference pattern have allowed the increase in resolution of the measurements and the subsequent evaluation of the surface response field [12] In these cases, the damage identification is performed based on local perturbations of the measured fields. In the context of damage identification, Pandey et al [2] applied a numerical differentiation of modal displacement fields using the central differences method This technique shows to be ineffective, since it relies on sparse experimental noisy measurements. Proposed displacement, rotation, bending moment and shear force damaged indicators
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