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Developments in NDT of Friction Stir Welding Using Eddy Currents

Santos, T. S. ; Vilaça, P. ; Rosado, L. S. ; Piedade, M. S. ; Ramos, P.M.

Developments in NDT of Friction Stir Welding Using Eddy Currents, Proc European Conf. on Non-Destructive Testing, Moscow, Russia, Vol. 2, pp. 88 - 89, June, 2010.

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Abstract
Friction Stir Welding (FSW), as well as others solid state welding processes, frequently originate micro defects of less than 100 micron depth. The morphology and location of these defects lead to a high loss of mechanical properties of the welded joints, particular under fatigue. Moreover, actual NDT reliability in characterizing and sizing these defects still remains a challenge. This paper reports the development of an innovative eddy current (EC) probe, and its application to FSW. The new EC probe presents innovative concept issues, allowing 3D induced current in the material, a lift-off independence, and an easy interpretation of the signal based on a comprehensible qualitative change. The new EC probe was performed on standard defects and aluminium alloys processed by FSW. All results were compared with conventional helicoidally and planar spiral EC probes. The results allow concluding that the new EC probe is able to detect and sizing micro root defects on FSW with 60 micros depth.