The radiographic testing method is used for the detection of internal flaws in many different materials and configurations. An appropriate radiographic film is placed behind the test specimen and is exposed by passing either X rays or gamma rays (Co-60 & Ir-192 radioisotopes) through it. The intensity of the X rays or gamma rays while passing through the product is modified according to the internal structure of the specimen and thus the exposed film, after processing, reveals the shadow picture, known as a radiograph, of the product. It is then interpreted to obtain data about the flaws present in the specimen. This method is used on wide variety of products such as forgings, castings and weldments. Some of the advantages of radiographic testing include:
(1) It can be used to inspect large areas at one time.
(2) It is useful on wide variety of materials.
(3) It can be used for checking internal malstructure, misassembly or misalignment.
(4) It provides permanent record.
(5) No calibration needed on the job site.
(6) Devices for checking the quality of radiograph are available.
(7) Interpretation of radiographs can be done in comfortable conditions.