What phenomenon occurs when an ultrasonic beam passes through the interface between two dissimilar materials at an angle?

When an ultrasonic beam encounters the interface between two dissimilar materials at an angle, refraction occurs. Refraction is the bending of the ultrasonic wave as it passes from one medium to another, which is caused by the difference in the wave speeds of the two materials. This phenomenon is crucial in ultrasonic testing because it affects how signals are transmitted and received.

As the ultrasonic beam enters the second material, its velocity changes due to the material’s density and elastic properties. The change in speed leads to a change in direction of the wave, which can be described by Snell's Law. This principle is fundamental in ensuring accurate interpretations of the inspection results, as incorrect angles can lead to miscalculations in flaw detection or sizing.

Reflection occurs when the beam bounces back from a surface, diffraction is the spreading of a wave as it passes through an opening or around an obstacle, and absorption refers to the loss of energy as the wave propagates through a material. While these phenomena also play important roles in ultrasonic testing, they do not specifically describe the interaction of an ultrasonic beam with dissimilar materials at an angle.