What primarily limits the use of ultrasonic NDT?

The primary limitation of ultrasonic non-destructive testing (NDT) is the requirement for perfectly smooth surfaces. Ultrasonic testing relies on the propagation of sound waves through materials, and any surface roughness, irregularities, or contamination can affect the transmission of these sound waves, potentially leading to inaccurate readings or failure to detect flaws. Therefore, for ultrasonic NDT to be effective, the surfaces being tested must be adequately prepared and relatively smooth to ensure that the ultrasonic waves can travel properly and return accurate results.

While there are skill and training requirements associated with ultrasonic testing, as well as considerations for report writing and application range, these factors are secondary to the necessity of having an appropriate surface condition in order to successfully execute the testing method.