NDT can be used without destroying or damaging a product or material. NDE may be used to determine material properties, such as fracture toughness, formability, and other physical characteristics. Involves the use of penetrating gamma or X-radiation to examine parts and products for imperfections. An X-ray machine or radioactive isotope is used as a source of radiation.
Radiation is directed through a part and onto film or other media.
The resulting shadowgraph shows the internal soundness of the part. Possible imperfections are indicated as density changes in the film in the same manner as an X-ray shows broken bones. Surface imperfections distort the field and concentrate iron particles near imperfections. Excess dye is then removed from the surface, and a dry developer is applied. The developer acts as blotter, drawing penetrant out of imperfections open to the surface.