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Shearografia Laser: state-of-the-art technology for real-time inspections of materials and components


May 29th 2012

This technique is used to inspect adhesive-bonded joints in carbon fibre, sandwich panels with carbon fibre-reinforced polymer very common in Aeronautics


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Shearografia Laser: state-of-the-art technology for real-time inspections of materials and components
Among the variety of technologies carried out by CATEC, there is the Laser Shearography (LS) an optic interferometry method providing real-time important inspection results which is being positively used in sectors like Aeronautics, Energy and Naval, among others.

This technology uses the coherent, monochromatic properties of laser light to generate speckle patterns. The component to be inspected is illuminated by the laser. The surface reflects the light creating a speckle pattern at the viewing plane, which can be processed to provide information such as the presence of defects, material degradation or residual stress. The system records the speckle pattern from an unstressed component surface. The surface is then stressed and a new speckle pattern generated, recorded and stored.

The computer subtracts the speckle patterns from each other, thus forming an image made up of series of characteristic black and white fringes, representing the surface strain in the area of interest. If a defect such as a void or disbond exists, this will affect the surface strain and the defect can be revealed by the fringe pattern developed.

By applying a small load, the material will deform. A nonuniform material quality will generate a nonuniform movement of the surface of the test object. A new shearing image is recorded at the loaded state and is compared with the sheared image before load. If a flaw is present, it will be seen. Particularly, the LS technique is used to inspect adhesive-bonded joints, sandwich panels with carbon fibre-reinforced polymer very common in Aeronautics.

This NDT techniques is non-contact and can by applied in several industrial sectors for the detection of surface and subsurface defects, and can be also applied to a wide range of materials (like composites and metals). They also allow the inspection of large areas and detects failures, flaws, indentations and cracks by impacts originated while repairing, etc.

This technology is at the interested entities and companies’ disposal. For further information, you can contact Fernando Lasagni, responsible for the Area of Materials and Processes.



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