What is a limitation of using shear waves in Ultrasonic Testing?

In Ultrasonic Testing (UT), shear waves, also known as S-waves, have specific limitations related to their propagation characteristics. The assertion that shear waves cannot propagate through liquids is fundamentally correct, as shear waves require a medium that can transmit shear stress. This means a solid material is necessary for their propagation because liquids and gases do not provide the necessary structural integrity to support shear stress.

Shear waves rely on particle movement perpendicular to the direction of wave propagation, which is only feasible in solids. In contrast, longitudinal waves, which can travel through both liquids and solids, can adequately assess materials in a liquid state. This gives shear waves an inherent limitation when it comes to testing materials that are liquid or in a gaseous state; they simply cannot be used to inspect these types of media effectively.

Therefore, the inability of shear waves to propagate through liquids encapsulates one of the significant limitations of this method in ultrasonic testing applications.