Ultrasonic simulation to design a high frequency ultrasonic technique to inspect friction stir welded components

摘要

Friction Stir Welding (FSW) is a relatively new solid-state joining technique for aluminium alloys, which offers good joint performance and excellent reproducibility. The use of FSW is of particular interest to the aerospace and wider transport sector. Compared with commonly used riveting joining methods, the adoption of FSW can result in increased joining speed, higher stress tolerance and longer service life. Wide adoption of FSW in safety critical applications will depend upon the availability of a reliable inspection method able to detect small defects (< 0.3mm), to ensure structural integrity. This paper presents the simulation work carried out using CIVA software in order to design a high frequency inspection technique for the detection of flaws smaller than 0.3mm in friction stir welded components such as plates and other complex geometry components. Apart from the small size of the defects to be detected, inspection challenges also include limited access to the inspection area, complex component geometry, geometrical restrictions, curved inspection surface, etc. Due to the geometrical restriction, a high angle incident beam must be used. Inspection over an area containing changing curvature causes significant defocusing of the ultrasonic beam and hence severely decreases inspection sensitivity. This problem was solved using an aluminium wedge.