APPLICATION OF A 2-LAYER SEMIANALYTICAL MODEL FOR THE IMPROVEMENT OF LASER-ULTRASONIC GENERATION

The new laser-based ultrasound model presented in this paper takes int o account the layered structures generally encountered in aeronautic m aterials (painted metals, composites, lapped joints...) which are subj ected to impacts, fatigue and corrosion. The structure is supposed to be a plate made of two layers of different materials. The sample prese nts a cylindrical orthotropy. Validations of the model are performed b y comparing the results it provides with experimental measurements usi ng a Nd:YAG pump laser and an interferometric detection. The symmetry of the model allows fast calculation and prediction of the displacemen ts over a long time period. These advantages are used to study the imp rovement of the laser-ultrasonic generation, by varying the thickness of the first layer in the case of a NDT strippable pal nt layer coveri ng a metal layer. (C) 1998 Published by Elsevier Science Ltd. All righ ts reserved.