Product Code: ICA11_408

Defect Detection and Sizing in Laser-Welded Aluminum Welds, Using Laser-Generated Ultrasounds
Authors:
Gael Diot, Institut Maupertuis; Bruz France
Afia Kouadri-David, INSA de Rennes; Rennes France
Henri Walaszek, CETIM; -
Laurent Dubourg, Institut Maupertuis; Bruz France
Jihed Flifla, ECAM de Rennes; Bruz France
Sylvain Guegan, INSA de Rennes; Rennes France
Eric Ragneau, INSA de Rennes; Rennes France
Presented at ICALEO 2011

Embedded welding defects, such as porosity, cracks, are generally observed during laser welding of aluminum. Non Destructive Inspection (NDI) after processing could be a way of assuring an acceptable weld quality. Nowadays, NDI techniques to control the inside of a weld are often limited to X-Rays or ultrasounds. However, these techniques are expensive (X-rays) or not contact-less (ultrasounds) limiting the applicability. The present paper shows the use of a Laser Ultrasound (LU) technique to inspect porosities in 2-mm thick sheet lap welds. The LU technique implements a pulsed Nd:YAG laser to generate ultrasounds in the material and a heterodyne Nd:YAG laser interferometer to measure the echo. This contact-less technique improves the NDI flexibility in regard of the geometry and surface quality of analyzed components while increasing the inspection speed. First experimentations resulted in the detection of 2-mm holes drilled in bulk aluminum sheets and the measurement of the shape and size of these defects is possible. On-going investigation shows the applicability of the LU technique to detect
porosities in aluminum laser welds. Finally, the use of signal processing is also carried out to increase, in a first step, the signal-to-noise ratio and therefore enhances the defect detection.