Radiography Testing is a NDT Process, By using radiant energy in the form of neutrons, X-rays (or) Gamma rays for Non Destructive examination of an opaque objects in order To produce a graphical record on sensitized films which indicates the comparative soundness of the obeject being tested. The process in which a material/specimen is exposed to radiation (X-RAYS OR Gamma Rays) and the discontinuity is recorded on the film and further film is developed in a darkroom to get the permanent record of the discontinuity. The indication on a radiograph film is just an area of “with difference in Density” Hence darker area (or) a lighter area forms the indication on the radiograph. The appearance of the indication on the radiograph is due to “DIFFERENTIAL ABSORPTION” Different materials are having different rate of absorption when it falls on the material. Radiography technique requires for the area where radiography has to be done to be evacuated during the testing period. This is done with Ir-192 or Se-75 sources and X-ray machines.
Principle of Radiographic Testing is ““DIFFERENTIAL ABSORPTION of PENETRATING RADIATION”.