The most commonly used method of producing shear waves in immersion testing is:

• A. By transmitting longitudinal waves into a part in a direction perpendicular to its front surface
• B. By using two crystals vibrating at different frequencies
• C. By using Y cut quartz crystal
• D. By angulating the search tube or manipulator to the proper angle

Answer: (D)

In immersion testing, you generate shear waves most reliably by using the angle beam method: tilt the transducer (or the wedge) to a specific angle so the incident longitudinal wave enters the part at an oblique angle. At that angle, energy is mode-converted at the interface and a shear wave is launched inside the material. The angle is chosen so the refracted wave inside the metal is the shear mode, following Snell’s law and the material’s wave speeds. This approach is why angling the search tube to the proper angle is the standard way to produce shear waves in immersion UT. The other options don’t create the shear wave in the part: normal perpendicular transmission yields primarily longitudinal waves, using two crystals at different frequencies doesn’t convert to shear waves, and a Y-cut quartz crystal isn’t about generating shear waves in immersion.