Journal Published Online: 13 April 2010
Volume 38, Issue 5

Lamb Waves Technique Applied to the Characterization of Defects in Friction Stir Welding of Aluminum Plates: Comparison with X-Ray and Ultrasonic C-Scan



Friction stir welding presents several advantages when compared with conventional arc welding processes, mainly in the welding of aluminum alloys. However, this welding technology leads to some degradation in the mechanical properties of welds, namely defect formation, which demands suitable nondestructive testing methods. The most common defects are mainly cold laps and voids, as a result of the large plastic deformation and hardening of the material as well as its complex flow behavior. In particular, the void appearance frequency may be correlated with the weld travel speed, though other welding parameters may contribute to the phenomenon. The purpose of this paper is to characterize such defects using conventional x-rays and ultrasonic C-scan, and a new method based on ultrasonic guided waves. The proposed new method presents as an attractive solution when large structures need to be inspected since propagation over long distances from a single probe position is possible with low attenuation. Additional characteristics such as straightforward inspection and testing fastness make the technique very cost effective. Test samples were fabricated using aluminum alloys of 3 mm in thickness, with different travel speeds and overlapping welds. This welding procedure gave rise to different defect sizes. Experimental results using both conventional and ultrasonic guided waves methods have confirmed the presence of the defects.

Author Information

Santos, M.
Dept. of Electrical and Computer Engineering, CEMUC, Univ. of Coimbra, Coimbra, Portugal
Santos, J.
Dept. of Electrical and Computer Engineering, CEMUC, Univ. of Coimbra, Coimbra, Portugal
Pages: 6
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Stock #: JTE102397
ISSN: 0090-3973
DOI: 10.1520/JTE102397