Examinando por Autor "MOLINA-VIEDMA, ANGEL"
Mostrando 1 - 2 de 2
- Resultados por página
- Opciones de ordenación
Ítem Comparison of lock-in correlation and a novel periodogram method for experimental multi-harmonic thermoelastic analysis(ELSEVIER, 2022-07-12) MOLINA-VIEDMA, ANGEL; FELIPE-SESÉ, LUIS; LÓPEZ-ALBA, ELIAS; DÍAZ GARRIDO, FRANCISCO ALBERTOLock-in correlation is a simple, efficient and widely employed method for thermoelastic stress analysis under cyclic loading. Frequency domain analysis of the thermoelastic signal using the Fourier transform has been also valuable for researchers, even though it presents some drawbacks. In this paper, a new frequency-domain method for thermoelastic analysis through periodograms using Welch’s averaging method has been developed. This method supplies the lack of phase shift information of the simple Fourier transform for thermoelastic signals and considerably reduce the data size. This work evaluates its performance against lock-in correlation through two experiments with opposite features for multi-harmonic analysis. One experiment consisted in the analysis of the thermoelastic signal in a plate with a centred hole, exhibiting a stress concentration and using the second harmonic as an indicator of the non-linearities. The second experiment consisted in the characterisation of mode shapes thermal maps during the simultaneous excitation of multiple specimen resonances. In comparison with the stress concentrator experiment, here the level of the thermal signal is lower and the number of frequencies to analyse is higher. The analysis of the thermal maps by both methods revealed that they yield practically identical results for any experiment. However, the evaluation of the computation efficiency highlights that the periodogram method has fewer memory requirements whereas, in terms of computation time, lock-in correlation is more efficient to analyse fewer frequencies in short image sequence tests, being the periodogram method more efficient for the opposite case.Ítem Damage identification in frame structures using high-speed digital image correlation and local modal filtration(WILEY, 2020-05-01) MOLINA-VIEDMA, ANGEL; PIECZONKA, LUKASZ; MENDROK, KRZYSZTOF; LOPEZ-ALBA, ELÍAS; DÍAZ-GARRIDO, FRANCISCO ALBERTOThis paper presents a technique for vibration-based damage detection and localization in engineering structures based on the high-speed three-dimensional Digital Image Correlation (HS 3D-DIC) and local modal filtration. The efficacy of the proposed procedure is demonstrated on a frame structure with different severities of localized damage. The full-field vibration data acquired under the white noise excitation provided the input to the damage identification algorithm. The spatial density of sensors on a test structure is one of the critical factors in the accurate localization of damage. Hence, the use of vision-based vibration measurement methods, such as the Digital Image Correlation (DIC) is very advantageous as it provides full-field quantification of dynamic displacement fields in three dimensions. Both numerical simulations with the use of Finite Element (FE) code and experimental tests with the use of high-speed digital cameras were performed to confirm the validity of the proposed approach. The research confirmed that it is feasible to use the proposed approach to detect and localize damage in a frame structure under random vibration excitation with a localization accuracy of a few percent of the field of view dimensions. On the basis of the obtained results, we believe that there is a great practical potential of this approach when applied to real-life engineering structures.