Characterization of self-piercing rivet joints using X-ray computed tomography

Self-piercing rivet (SPR) joining is a process that has been adopted in the automotive industry, and it is important to be able to characterize SPR joints non-destructively. X-ray computed tomography (CT) allows visualizing the internal structure of the sample whilst preserving the workpiece. In this work, the application of X-ray CT to SPR joint characterization is investigated. Many features of a riveted joint can be observed. This includes the boundary between sheet interfaces and the positions where the substrates and rivet meet, which are important to quality assessment. In the case of similar materials, some of these features become difficult to observe but the presence of adhesive between the sheets enables the features to be more easily observed. Furthermore, substrate fracture and rivet cracks, radial cracks and the asymmetry of SPR joints can be detected due to the difference in greyscale to the surrounding materials. It is also revealed that image resolution plays an important role in defect detectability of the X-ray CT technique.