Advanced technique for non-destructive testing of friction stir welding of metals

In this paper a new non-destructive testing (NDT) system focusing on micro size superficial defects in metallic joints is presented. The innovative system is composed by a new type of eddy currents probe, electronic devices for signal generation, conditioning and conversion, automated mechanized scanning and analysis software. The key original aspect of this system is the new type of eddy currents probe. This new probe provides enhanced lift-off immunity and improved sensitivity for micro size imperfections. The probe concept was studied using a Finite Element Method (FEM) tool and experimental verified using a standard defect. The testing results on some friction stir welding (FSW) specimens clearly show that the system is able to detect superficial defects less than 60 μm deep, which significantly increases the actual state of the art in NDT reliability for micro imperfections detection. The system can be applied to a broad range of industries which include manufacturing, maintenance and engineering companies.