Progress in NDT of resistance spot welding of aluminium using ultrasonic C-scan

An ultrasonic C-scan technique was evaluated for non-destructive testing (NDT) of resistance spot welding of aluminium. It was established through fundamental trials that removal of surface indentation from the welding electrode is necessary in order to obtain credible non-destructive assessments of aluminium spot weld size and shape. The non-destructive test results showed good correlation with peeled samples and metallographic cross sections. The technique also provided further fundamental understanding of aluminium resistance spot welding (RSW) process; especially with respect to the presence of an outer fused ring. The fundamental aspect of this study was underpinned using the NDT technique for a real assembly; challenging the technique with access issues, different material combinations, multiple joint stacks and independent measurements. The non-destructive test analyses obtained correlated well with actual tear down results and offered further encouragement that the C-scan technique is viable as a production tool if a suitably flattened surface can be provided.

► Developed novel enabling methodologies for Ultrasonic C-scan in NDT of aluminium resistance spot welds.
► Correlated results of NDT with destructive tests and microstructures.
► Established successful application of NDT for production assemblies.
► Furthered fundamental understanding of RSW process.