PROCEEDINGS ARTICLE | March 28, 2006
Proc. SPIE. 6177, Health Monitoring and Smart Nondestructive Evaluation of Structural and Biological Systems V
KEYWORDS: Beam splitters, Ferroelectric materials, Imaging systems, Cameras, Ultrasonography, Polymers, Composites, Inspection, Ultrasonics, Transducers
Ultrasonic NDI methods have an impressive record of applications on metallic and composite structures. However, limitations arise from the need for a wet couplant between the specimen and the transducer and the rather long inspection times necessitated by point-by-point scanning of large structures. To overcome these constraints, a dry-contact large-area ultrasonic imaging system is being developed for real-time high-resolution NDI applications. This system includes the following: a large ultrasonic source, either piezoelectric or laser-based, a polymer dry-couplant, and a commercially available real-time ultrasonic CCD camera displaying easy-to-interpret images rather than A-scans. Applications of this real-time high-resolution ultrasonic imaging system on metallic and composite structures, using either PZT or laser-based ultrasound generation as the source, are presented. Aluminum and unidirectional and woven composites have been investigated. Images acquired in both through-transmission and pulse-echo modes are presented. Images of artificial defects of different types and shapes in the investigated materials will be demonstrated. The latest developments of the imaging system, with laser-based ultrasound generation as the source, are also reported. The laser-based source provides an efficient solution for some applications of the imaging system. In this configuration, the ultrasound is generated in a 1in. diameter area by an expanded laser beam which heats a constrained absorbing polymer layer. The soft polymer layer is also used as dry couplant to transmit the ultrasound between the test sample and the imaging system.
