In ultrasonic NDT, what type of imperfections can be detected?

Ultrasonic Non-Destructive Testing (NDT) is a widely used technique that employs high-frequency sound waves to detect imperfections within a material. The method is particularly effective for identifying both surface and subsurface imperfections.

When ultrasonic waves are transmitted into a material, they can reflect back upon encountering discontinuities such as cracks, voids, or inclusions both on the surface and beneath it. This capability allows for a comprehensive inspection of the material's integrity. The analysis of the reflected signals provides insights into the nature, size, and location of the imperfections.

Surface imperfections, like cracks or corrosion, can be detected as the wave interacts directly with the material's surface. Meanwhile, subsurface flaws such as internal cracks or porosity become evident as the sound waves penetrate deeper and reflect back from these discontinuities.

Given these characteristics of ultrasonic NDT, the assertion that it can identify both surface and subsurface imperfections captures the technique's full capabilities, making the selected answer the most accurate.