Imagerie à courants de Foucault pour l'évaluation non-destructive de structures rivetées aéronautiques

An eddy current imager (ECI) based on a magneto-optical concept for the high resolution direct magnetic field visualization was developed. This device is mainly intended to the non-destructive evaluation of aeronautical riveted lap joints. Firstly, the optimization of the ECI components was carried out thanks to 3D finite element computations and experimentation. Its complete characterization was also made. Secondly, the study of the ECI measurements was made, thanks to a laboratory made lap joints mock-up featuring defects buried down to 8mm and placed side by side the rivets. This study underline the requirement of an algorithm which enable the enhancement of defect visualization compare to the rivets. This method, based on the principal component analysis, was developed and several modes were defined and evaluated for the visualization of buried defects, potentially oriented around the rivets. Finally, two algorithms based on the maximum likelihood was studied in order to obtain an automatic detection and characterization of buried defects . that algorithms give good results and allow the localization of buried defects with 80% probability. The whole study enabled the development of a new ECI prototype destined to in situ controls. Its performances are better than the prototype used in this thesis.