Examinando por Autor "Lopez-Alba, Elias"
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Ítem Comparative of conventional and alternative Digital Image Correlation techniques for 3D modal characterisation(Elsevier, 2020-02-01) Molina-Viedma, Ángel; Felipe-Sese, Luis; Lopez-Alba, Elias; Díaz, Francisco A.The integration of Fringe Projection and 2D-DIC is a low-cost optical technique which employs a single camera for full-field 3D displacement measurements using RGB colour encoding to filter coexisting fringe and speckle patterns out from a single image. In this work, this technique was explored together with conventional 3D-DIC for challenging modal analysis on a large aeronautical panel under random excitation. Modal identification was performed using the Least-Squares Complex Exponential approach. Multiple degree-of-freedom methods have been avoided in previous works or just employed in one direction due to high memory requirements to process 3D full-field data. In this work, the 3D modal characterisation was addressed with especial mention to mode shapes. Hardware limitations makes FP + DIC less sensitive than 3D-DIC and hence more suitable for lower frequencies. Nevertheless, the obtained modal parameters showed high agreement and hence FP + DIC demonstrated to be a cost-effective alternative for 3D modal analyses.Ítem Thermoelastic effect in modal shapes at high frequencies using infrared thermography(Elsevier, 2021-02-01) Molina-Viedma, Angel J; Felipe-Sesé, Luis; Lopez-Alba, Elias; Diaz, Francisco A.Infrared thermography is employed by different methodologies and techniques to perform characterisations and evaluations in solids, typically related to fracture mechanics and damage, based on monitoring heat generation or temperature changes. In this study, the limits of the current technology for Thermoelastic Stress Analysis (TSA), usually employed under low-frequency loads, are explored to characterise temperature fields associated to the first stress invariant in mode shapes. Higher frequencies are especially emphasised in this research. Eleven modes of a plate were analysed, reaching frequencies over 2000 Hz. High correlation coefficients were obtained in comparison with the first stress invariant fields of a finite element model, with a detriment as the mode’s order increases. In those cases, this study highlights the combined influence of the specimen response and mode shape stiffness as well as the progressively shorter integration time.