The measurement of the modal strain fields using digital shearography

¹ ESTIG – Polytechnique Institute of Bragança –Cp. St Apolónia, Apr. 134 - 5301-857 Bragança
² DEMEGI – Faculty of Engineering, University of Porto, R Dr Roberto Frias, 4200-465 Porto, Portugal

^a e-mail: hlopes@ipb.pt

Abstract

This work presents a Michelson shearography interferometer configuration associated with stroboscopic double illumination technique for the measurement of modal rotation fields and their strain fields on a clamped circular aluminium plate. The speckle pattern is frozen by the synchronization between the LASER illumination and the modal vibration of the object. The quantitative evaluation is performed for each digital shearogram using a time modulation technique. The setup of double illumination LASER with out-of-plane opposite sensitivity allows the two phase maps measurement of the modal spatial gradient. The modal rotation and strain fields are extracted by the combination of this two digital phase maps. Image processing techniques are applied on the phase maps to obtain full-field measurements using a dedicated post-processing algorithm. Finally, is presented a comparison between the experimental measurement and the numerical solution.