Limitation of Ultrasonic Inspection

As with all NDT methods, ultrasonic inspection also has its limitations, which include:
1) Surface must be accessible to transmit ultrasound.

2) Skill and training is more extensive than with some other methods.

3) It normally requires a coupling medium to promote the transfer of sound energy into the test specimen.

4) Materials that are rough, irregular in shape, very small, exceptionally thin or not homogeneous are difficult to inspect.

5) Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise.

6) Linear defects oriented parallel to the sound beam may go undetected.

7) Reference standards are required for both equipment calibration and the characterization of flaws.

The above introduction provides a simplified introduction to the NDT method of ultrasonic testing. However, to effectively perform an inspection using ultrasonics, much more about the method needs to be known. The following pages present information on the science involved in ultrasonic inspection, the equipment that is commonly used, some of the measurement techniques used, as well as other information.