When angle beam contact testing a test piece, increasing the incident angle until the second critical angle is reached results in:

When angle beam contact testing a test piece, increasing the incident angle until the second critical angle is reached results in:

• A. Production of a surface wave
• B. Total reflection of a surface wave
• C. 45 degree refraction of the shear wave
• D. None of the above

Answer: (A)

In angle-beam testing, the energy entering the test piece must satisfy Snell’s law for the available wave modes inside the material. As you increase the incident angle, the bulk waves inside the plate become less able to propagate as distinct P or S waves along the depth, and energy starts to travel along the surface as a Rayleigh surface wave. Reaching the second critical angle marks this transition, so a surface wave is produced. This surface wave travels along the surface at a velocity lower than the bulk waves and is particularly sensitive to near-surface features.

In angle-beam testing, the energy entering the test piece must satisfy Snell’s law for the available wave modes inside the material. As you increase the incident angle, the bulk waves inside the plate become less able to propagate as distinct P or S waves along the depth, and energy starts to travel along the surface as a Rayleigh surface wave. Reaching the second critical angle marks this transition, so a surface wave is produced. This surface wave travels along the surface at a velocity lower than the bulk waves and is particularly sensitive to near-surface features.