Embedded welding defects, such as porosity, cracks, are generally observed during laser welding of aluminium. 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 contactless 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 aluminium 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 aluminium 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.
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