Shear wave testing, also known as angle beam inspection, is an ultrasonic testing technique used primarily for weld inspections.
A probe consisting of an ultrasonic transducer coupled with a plastic or epoxy wedge introduces an ultrasonic beam at an angle into a test area. As the probe is moved back and forth along the area, it can detect discontinuities in the weld based on the reflection and refraction of the ultrasonic beam.
Straight beam techniques are well-suited for finding defects that are oriented parallel to the surface of a material. But straight beams are often not effective when inspecting welds where defects are commonly not parallel to the surface.
The combination of awkward weld geometry and the presence of a weld crown or bead typically requires inspections from the side of a weld using beams generated at an angle. Consequently, shear wave testing is the most commonly used technique for weld inspection.