Stress corrosion cracking detection using non-contact ultrasonic techniques

• Two techniques are shown for detecting and locating stress corrosion cracks (SCCs).
• Surface maps clearly identify SCC, resolving spatial extent and geometric alignment.
• Laser detection approach resolves defects that are close together or close to edges.
• Electromagnetic acoustic transducer (EMAT) approach offers some benefits.

In this work a method is presented for detecting and locating stress corrosion cracking (SCC) in stainless steel pipe samples. The method combines laser generation and either laser or electromagnetic acoustic transducer (EMAT) detection, scanning the generation point across the sample surface. Using laser-generated ultrasonic waves that interact with the cracks, and performing time–frequency analysis techniques to examine changes in the generated wavemodes, surface plots that clearly resolve the spatial extent and geometric alignment of the cracks are created and presented here. The method is demonstrated using components removed from service after exhibiting SCC.