Which type of surface defects can liquid penetrant testing effectively reveal?

Liquid penetrant testing (LPT) is specifically designed to detect surface-breaking defects in non-porous materials. This testing method involves applying a penetrant solution to the surface of a material, allowing it to seep into cracks or openings that are exposed on the surface. After a designated dwell time, the excess penetrant is removed, and a developer is applied to draw out any penetrant from the defects, making them visible under ultraviolet or white light.

Surface-breaking defects include cracks, porosity, and other discontinuities that occur on or just below the surface. LPT is highly effective for these types of defects because it directly targets flaws that can be accessed by the penetrant material. In contrast, other types of defects, such as internal defects, material inclusions, and thickness variations, may not be detectable using LPT as they do not necessarily manifest at the surface or do not allow for the penetrant to enter effectively. This focus on surface-breaking flaws makes liquid penetrant testing a valuable tool in quality control and failure analysis within various industries.