Integration of digital image correlation and thermoelasticity for experimental analysis of operational modal shapes

Abstract

Full-field optical techniques provide valuable information for the analysis of mode shapes thanks to their high density of measurement points,  providing very detailed maps, in a non-invasive way that avoids alterations of the dynamic behaviour of the specimen. Digital image correlation  and thermoelastic stress analysis are two of the most interesting ones. The first provides displacement fields that can be three-dimensional if a calibrated stereoscopic system is used. The second uses a thermographic camera to determine the stress invariant. Given the complementary  nature of these magnitudes, this study deals with the integration of the displacement and stress fields by means of a calibrated set of a  stereoscopic system and a thermographic camera which, through spatial triangulation, allow the association of the measurements to the same  spatial point on the specimen. For this purpose, typical laboratory setups have been carried out for the characterisation of operational modal  shapes of resonances. The integration has allowed a more accurate interpretation of the behaviour of the specimen, identifying the regions with  the highest mechanical stress. This shows the advantages of integration compared to the isolated analysis of displacement and/or stress  measurements that are usually carried out and proves the potential for the development of optical techniques at a scientific and industrial level,  opening up new avenues of study.