RT: A source of ionising radiation positioned at on one side of item to be inspected, and a photographic film placed in close proximity to the other side. The radiation is partly absorbed during transmission and differences in material thickness or absorption qualities are recorded on the film giving a full-size image showing internal detail. The higher the Material density more radiation absorbtion will occur.
Processed films are called radiographs, Industrial radiography requires X-rays or gamma rays to reveal hidden flaws in solid objects. X-ray radiography is generated electrically by means of a high voltage X-ray tube. Gamma rays are produced by the natural disintegration of nuclei in a radioactive isotope. Common types being Iridium 192 and Cobalt 60. Radiography's main benefits are that it provides a non-destructive method of detecting hidden flaws in materials and fabrications and provides a permanent record. Radiography is particularly good at detecting volumetric flaws such as voids, gas pores and solid inclusions, It is also good at determining the nature and dimensions (length and width) of flaws - however it cannot be used to measure through-thickness of defects.
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