Fraunhofer-Gesellschaft

Publica

Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.

Laser based spot weld characterization

 
: Jonietz, Florian; Myrach, Philipp; Rethmeier, Michael; Suwala, Hubert; Ziegler, Mathias

:

Chimenti, D.E. ; American Society for Nondestructive Testing -ASNT-, Columbus/Ohio:
42nd Annual Review of Progress in Quantitative Nondestructive Evluation 2015 : Incorporating the 6th European-American Workshop on Reliability of NDE - volume 35; Minneapolis, Minnesota, 26-31 July 2015
Woodbury, N.Y.: AIP, 2016 (AIP Conference Proceedings 1706)
ISBN: 978-0-7354-1353-5
Art. 100010, 9 pp.
Annual Review of Progress in Quantitative Nondestructive Evaluation <42, 2015, Minneapolis/Minn.>
European-American Workshop on Reliability of NDE <6, 2015, Minneapolis/Minn.>
English
Conference Paper
Fraunhofer IPK ()

Abstract
Spot welding is one of the most important joining technologies, especially in the automotive industry. Hitherto, the quality of spot welded joints is tested mainly by random destructive tests. A nondestructive testing technique offers the benefit of cost reduction of the testing procedure and optimization of the fabrication process, because every joint could be examined. This would lead to a reduced number of spot welded joints, as redundancies could be avoided. In the procedure described here, the spot welded joint between two zinc-coated steel sheets (HX340LAD+Z100MB or HC340LA+ZE 50/50) is heated optically on one side. Laser radiation and flash light are used as heat sources. The melted zone, the so called "weld nugget" provides the mechanical stability of the connection, but also constitutes a thermal bridge between the sheets. Due to the better thermal contact, the spot welded joint reveals a thermal behavior different from the surrounding material, where the heat transfer between the two sheets is much lower. The difference in the transient thermal behavior is measured with time resolved thermography. Hence, the size of the thermal contact between the two sheets is determined, which is directly correlated to the size of the weld nugget, indicating the quality of the spot weld. The method performs well in transmission with laser radiation and flash light. With laser radiation, it works even in reflection geometry, thus offering the possibility of testing with just one-sided accessibility. By using heating with collimated laser radiation, not only contact-free, but also remote testing is feasible. A further convenience compared to similar thermographic approaches is the applicability on bare steel sheets without any optical coating for emissivity correction. For this purpose, a proper way of emissivity correction was established.

: http://publica.fraunhofer.de/documents/N-404540.html