| ABSTRACT: | PORTABLE AND HYBRID LASER GENERATION / AIR-COUPLED DETECTION SYSTEM FOR
NON DESTRUCTIVE INSPECTION
E. Guilliorit and H. Tretout
Dassault Aviation, Argenteuil, France
Conventional ultrasonic techniques for NDT of materials manufactured by the aeronautic industry need an
immersion medium, or a coupling agent between the sample to be inspected and a piezoelectric transducer.
Laser-based ultrasonic techniques provide a number of advantages over the standard above methods such as
non contact generation and detection, ability to operate on curved and rough surfaces, but remain a complex
and very expensive technology. This review presents a portable head using a hybrid laser generation/air-
coupled detection system for ultrasonic non-destructive inspection. The equipment is made of a low-cost
Nd:YAG pulsed laser linked to a multimode optical fiber to generate Surface Acoustic Waves (SAW).
Instead of a long-pulse detection laser coupled to an interferometer, a small air-coupled ultrasonic transducer
is used to perform the detection. A compact probe holder supporting the optical assembly and the air-
coupled transducer has been designed, and integrated with an XY scanner system to move the probe above
the sample. Inspection tests are carried-out on representative samples, and the performances of the portable
head are evaluated for surface and subsurface defect detection in metallic and composite materials. Finally,
the advantages and disadvantages of the concept are discussed compared to conventional ultrasonic and fully
laser-based techniques.
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