NDT Methods: Radiography
Radiography Is a non-destructive method of inspecting materials for
hidden flaws by utilizing the ability of electromagnetic radiations
of short wave-length to penetrate these materials. The value of the
ability lies in the fact that the penetrating radiation is absorbed
by the material to a degree dependent upon its composition and
thickness. Since the amount of radiation emerging from the opposite
side of the material can be detected and measured on film,
variations in this amount or intensity of radiation are used to
determine thickness or composition of the material.
Because of the penetration and absorption capabilities of X and Gamma radiation, radiography is used to test a variety of non-metallic products and metallic products such as welds, castings, forgings and fabrications. Since it is capable of revealing discontinuities (variations in material composition or density) in a variety of dissimilar materials, radiographic testing is a primary non-destructive test method.
Radiographic testing usually requires exposing film to X or Gamma rays that have penetrated a specimen, processing the exposed film and interpreting the resultant radiograph. There are many variables in these procedures and successful completion of any test is dependent upon understanding and control of the variables. Because of the inherent energies emitted by the radiations employed are harmful to human organisms, special care and procedures must be followed when handling radiographic radiation emitting equipment.