What is the primary purpose of liquid penetrant testing?

The primary purpose of liquid penetrant testing is to identify surface discontinuities in materials. This non-destructive testing method utilizes a penetrant liquid that is applied to the surface of the material being examined. The penetrant seeps into any surface flaws or discontinuities, such as cracks, porosity, or laps, that are open to the surface. After a specified dwell time, the excess penetrant is removed, and a developer is applied to draw out the penetrant from these defects, making them visible for inspection.

This technique is particularly effective because it can reveal very fine surface defects that may not be detectable through other methods. It's crucial in quality control and assurance processes across various industries where material integrity is paramount, such as aerospace, automotive, and manufacturing. Other options, such as inspecting internal components or measuring material thickness, fall outside the capability of liquid penetrant testing, as this method focuses solely on surface conditions.