Percorrer por autor "Maia, N.M.M."
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- Damage localisation in beams using the ritz method and speckle shear interferometryPublication . Santos, J.V. Araújo; Lopes, Hernani; Ribeiro, J.E.; Maia, N.M.M.; Vaz, M.A.P.A novel numerical-experimental technique is developed in order to minimise some of the difficulties exhibited by others damage localisation approaches. The present technique relies on the computation of undamaged rotation fields using the Ritz method and the Timoshenko beam theory, while the measurement of damaged rotation fields is performed by speckle shear interferometry.
- Damage localisation in beams using the ritz method and speckle shear interferometryPublication . Santos, J.V. Araújo; Lopes, Hernani; Ribeiro, J.E.; Maia, N.M.M.; Vaz, M.A.P.A novel numerical-experimental technique is developed in order to minimise some of the difficulties exhibited by others damage localisation approaches. The present technique relies on the computation of undamaged rotation fields using the Ritz method and the Timoshenko beam theory, while the measurement of damaged rotation fields is performed by speckle shear interferometry. Two damage localisation indicators are also presented, which, instead of being based on the second derivative of displacement fields, are based on the first spatial derivative of rotation fields. These damage localisation indicators, the modified curvature difference (MCD) and the modified damage index (MDI), were applied successfully in the localisation of damage in two clamped-clamped aluminium beams.
- Localization of damage in beams using interferometric techniquesPublication . Lopes, Hernani; Ribeiro, J.E.; Santos, J.V. Araújo; Maia, N.M.M.Two interferometric techniques and their applications in structural damage identification are presented in this paper. Out-of-plane displacement fields of modal response are measured with a pulsed electronic speckle pattern interferometric system(ESPI). The modal rotation fields, defined as the spatial derivative of the displacement field, are measured with a pulsed speckle shearography system. The measurements using these two interferometric systems are compared with measurements from experimental modal analysis and results from finite element analysis. This comparison shows that these two interferometric techniques, which allow non-contact, full-field measurements, are well suited to the measurement of modal response. A damaged beam with free-free boundary conditions is analyzed. The damages studied are small cuts perpendicular to the beams longitudinal axis. The bending moments and shear forces, which are related to the second and third order spatial derivatives of the modal displacement field, in the undamaged and damaged states are computed using numerical differentiation techniques. The damage is localized by looking for maximum values and/or perturbations of damage indicators based on bending moments and shear forces along the beam. The pulsed speckle shearography system leads to a significant improvement in the computation of bending moments and shear forces and, therefore, better damage localizations than the ones obtained with the pulsed ESPI system.