Examinando por Autor "Molina-Viedma, Ángel J."
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Ítem Experimental evaluation of effective stress intensity factor using thermoelastic stress analysis and digital image correlation(Elsevier, 2020-02-25) Díaz, Francisco A.; Vasco-Olmo, José M.; López Alba, Elías; Felipe-Sesé, Luis A.; Molina-Viedma, Ángel J.; Nowell, DavidDuring the last decades, the debate over the mechanisms governing fatigue crack shielding has been mainly focused on demonstrating the existence of fatigue crack closure and the difficulties on quantifying the induced stress during crack propagation. Hence, most adopted experimental methods have been based on the direct or indirect measurement of contact loads between crack surfaces as the crack starts closing. Nevertheless, these methods depend on many factors sometime difficult to control, which has contributed to question their reliability by many authors. For this reason, two modern well established, full-field, non-contact experimental techniques, namely Thermoelastic Stress Analysis (TSA) and 2D Digital Image Correlation (2D-DIC), have been analysed to evaluate the influence of crack shielding during fatigue experiments conducted on two aluminium alloys (Al2024-T3 and Al7050) tested at different stress ratios. In the particular case of TSA, the technique appears to have a great potential in the evaluation of fatigue crack shielding since crack tip events are inferred directly from the temperature changes occurring at the crack tip rather than from remote data. Experimental data from both techniques have been employed in combination with two different mathematical models based on Muskhelishvili’s complex potentials to infer the effective range of stress intensity factor. Results from both techniques agree quite well, showing a variation in the stress intensity factor range as the R-ratio changes from 0.1 to 0.5 and illustrating the potential ability of both techniques to account for the shielding effect due to crack closure.Ítem Exploiting phase-based motion magnification for the measurement of subtle 3D deformation maps with FP+ 2D-DIC(Elsevier, 2022-05-31) Felipe-Sesé, Luis; Molina-Viedma, Ángel J.; Pastor-Cintas, Manuel; López-Alba, Elías; Díaz, FranciscoPhase-Based Motion Magnification (PBMM) is an effective methodology to visualise imperceptible phenomena based on magnifying periodic subtle movements on image sequences. Moreover, the integration of the optical techniques Fringe Projection and 2D Digital Image Correlation (FP + 2D-DIC) make it possible to obtain 3D displacement maps employing a single camera. In this study, the integration of PBMM with FP + 2D-DIC is exploited for the determination of subtle 3D displacements. An initial solid-rigid test validates of the combination of those techniques. A later test, employing a cantilever beam, demonstrates its correct performing in the determining of Operational Deflection Shapes. In both cases, the results are compared with those obtained with 3D-DIC and Scanning Laser Doppler Vibrometer (SLDV) to evaluate the relation between the magnification factor and the result obtained. Finally, the potential of the proposed integration for the determination of complex mode shapes is demonstrated by obtaining the ODSs of an industrial component.Ítem FP+DIC for low-cost 3D full-field experimental modal analysis in industrial components(ELSEVIER, 2019-04-07) Felipe-Sesé, Luis; Molina-Viedma, Ángel J.; López-Alba, Elías; Díaz, Francisco A.High Speed 3D Digital Image Correlation has reached notorious popularity in dynamic characterisations because of the full-field non-invasive performance. It is being especially relevant for experimental modal analysis due to the importance of the modal parameters to define the dynamic behaviour. However, the economic cost of a stereoscopic system of two high speed cameras is a main concern regarding traditional instrumentations. In the search for low-cost alternatives, different methodologies have arisen that employ a single camera for 3D measurements. One approach consists in obtaining a stereo-vision in a single image using, for instance, a mirror system. These approaches involve important field of-view restrictions. An interesting approach employs the full resolution by combining Fringe Projection and 2D-DIC for out-of-plane and in-plane displacements, respectively. In this study, this technique is explored to perform experimental modal analysis in a large non-flat aeronautical panel. The validation of the results has been performed using accelerometer measurements during an impact hammer test. The results of the study stand this technique as an attractive low-cost technique for 3D full-field modal characterisations of complex components