A New NDT System for Micro Imperfections Detection: Application to FSW and FSpW

摘要

The geometry, localization and microstructural nature of some material imperfections lead to significant difficulties in their identification when using existent conventional and advanced Non-Destructive Testing (NDT) techniques. A paradigmatic example is the micro defects of less than 100-50 μm from Friction Stir Welding (FSW) and Friction Spot Welding (FSpW). In order to overcome this problem, a new NDT system was developed and tested. This innovative system consists of: new patented eddy current (EC) probes; electronic generation, conditioning and signal acquisition; automated mechanized scanning and dedicated NDT software. The new EC probe allows a 3D induced current in the material, and an easy interpretation of the signal based, not on the absolute value, but on a comprehensible perturbation of the signal. The results from an analytical simulation fully agree with the experiments.The experimental results in AA2024 welded by FSW clearly show that this system is able to detect imperfections around 50 μm, which contribute to increase the reliability on NDT of micro imperfections.