How do X-ray and gamma-ray testing methods reveal internal flaws in materials?

In materials testing, X-ray and gamma-ray methods detect internal and external flaws by passing radiation through a material and capturing the resulting image on photographic film.1

The effectiveness of these techniques relies on the differential absorption of radiation as it travels through the object. Because materials vary in density, composition, and homogeneity, they absorb radiation at different rates; internal flaws or structural inconsistencies create variations in this absorption that are revealed in the final image. This allows for the nondestructive inspection of components, such as castings, that are otherwise inaccessible to direct observation.2

In some instances, X-rays can be focused on a specific plane within a material, which provides a three-dimensional description of both the geometry and the precise location of a flaw. These methods are essential for ensuring the integrity of materials without causing damage to the structures being tested.12