Development of an ultrasonic inspection system to detect kissing bonds in friction stir welded components

The StirScan project will develop a NDT inspection system in order to address the challenging problem of detecting kissing bonds in friction stir welds (FSWs). “Kissing bonds” are a concern with FSWs (especially in the aerospace and automobile sectors). Such defects can reduce the fatigue performance of joints and are very difficult to detect (or accurately size) using existing NDT methods. This concern limits the adoption of FSWs for some critical components.

The StirScan project proposes the use of two combined ultrasonic techniques: the linear high frequency ultrasonic technique (HFUT) and the non-linear ultrasonic technique (NLUT). Kissing bonds in FSW may contain closed and partially closed parts. The HFUT will be developed to detect the open part and the NLUT will be developed to detect closed parts of kissing bonds. In order to assess this novel inspection approach a number of tasks are required, including design of inspection methods, design and fabrication of ultrasonic probes, and manufacture of FSW components containing kissing bonds, etc. These tasks will be described and discussed in this paper.