title: Inspection of thick welded joints using laser-ultrasonic SAFT.
abstract: The detection of defects in thick butt joints in the early phase of multi-pass arc welding would be very valuable to reduce cost and time in the necessity of reworking. As a non-contact method, the laser-ultrasonic technique (LUT) has the potential for the automated inspection of welds, ultimately online during manufacturing. In this study, testing has been carried out using LUT combined with the synthetic aperture focusing technique (SAFT) on 25 and 50mm thick butt welded joints of steel both completed and partially welded. EDM slits of 2 or 3mm height were inserted at different depths in the multi-pass welding process to simulate a lack of fusion. Line scans transverse to the weld are performed with the generation and detection laser spots superimposed directly on the surface of the weld bead. A CCD line camera is used to simultaneously acquire the surface profile for correction in the SAFT processing. All artificial defects but also real defects are visualized in the investigated thick butt weld specimens, either completed or partially welded after a given number of passes. The results obtained clearly show the potential of using the LUT with SAFT for the automated inspection of arc welds or hybrid laser-arc welds during manufacturing.
authors.affiliation: National Research Council Canada, 75 de Mortagne Blvd., Boucherville, Quebec J4B 6Y4, Canada. Electronic address: daniel.levesque@cnrc-nrc.gc.ca.
authors.forename: D
authors.initials: D
authors.lastname: Lévesque
authors.affiliation: IHI Corporation, 1 Shin-nakahara-cho, Isogo-ku, Yokohama 235-8501, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Asaumi
authors.affiliation: National Research Council Canada, 75 de Mortagne Blvd., Boucherville, Quebec J4B 6Y4, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Lord
authors.affiliation: National Research Council Canada, 75 de Mortagne Blvd., Boucherville, Quebec J4B 6Y4, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Bescond
authors.affiliation: IHI Corporation, 1 Shin-nakahara-cho, Isogo-ku, Yokohama 235-8501, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Hatanaka
authors.affiliation: IHI Corporation, 1 Shin-nakahara-cho, Isogo-ku, Yokohama 235-8501, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tagami
authors.affiliation: National Research Council Canada, 75 de Mortagne Blvd., Boucherville, Quebec J4B 6Y4, Canada.
authors.forename: J-P
authors.initials: JP
authors.lastname: Monchalin
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D007090:Image Interpretation, Computer-Assisted; D007834:Lasers; D008422:Materials Testing / Q000295:instrumentation*; D008670:Metals / Q000032:analysis / Q000737:chemistry*; D061088:Photoacoustic Techniques / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000295:instrumentation*; D014896:Welding / Q000295:instrumentation*
chemical_list: D008670:Metals
keywords: Laser ultrasonics; Synthetic aperture focusing technique; Thick weld inspection