NDTnet 1998 Aug, Vol.3 No.8

Full-Text - Abstract

Laser-ultrasonics, a technique which uses lasers for the generation and detection of ultrasound circumvents a number of limitations associated with conventional ultrasonics and offers an attractive and even unique method for inspecting and characterizing aeronautic materials. The technique operates without contact and large standoff distance from the inspected part (tens of centimeters to meters). The normalcy requirement of classical ultrasonics is eliminated, since generation occurs at the surface of the material and detection is performed directly off its surface, so parts with complex geometries can be more easily inspected. Materials that have been designed for operation at elevated temperature can also be tested in their normal conditions of use.

In this presentation, we will describe the technology that has been developed, which comprises a high power short pulse laser for ultrasound generation, a long pulse receiving laser for detecting ultrasound off the surface, a demodulating interferometer and a data analysis system for data acquisition and processing. When the technique is used for imaging, an optical scanner and imaging software are also used.

Applications will be described in three areas. First, the technique has been applied to the inspection of a wide variety of polymer-matrix composite materials (solid laminates, laminates with woven fibers), having various shapes and structures (planar, curved, honeycomb), with various flaws (implanted defects, manufacturing defects, disbonds, flaws produced by impact) and surface conditions (bare surfaces, painted surfaces). It has been in particular demonstrated directly on a aircraft in a maintenance hangar. A second application is the detection of disbonds and corrosion in aluminum lap joints of aircraft skins and the detection of the corrosion around fasteners. A third application consists in the thickness determination and characterization of thermal barrier coatings used on engine blades.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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