Penetrant Testing & Radiographic Testing.pdf

The major distinction between x rays and gamma rays

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frequencies than X-rays as seen in the figure. The major distinction between X-rays and gamma rays is the origin where X-rays are usually artificially produced using an X-ray generator and gamma radiation is the product of radioactive materials. Both X-rays and gamma rays are waveforms, as are light rays, microwaves, and radio waves. X-rays and gamma rays cannot be seen, felt, or heard. They possess no charge and no mass and therefore, are not influenced by electrical and magnetic fields and will generally travel in straight lines. However, they can be diffracted (bent) in a manner similar to light.
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Nature of Penetrating Radiation
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Source of X-rays and Gamma rays X-ray Generator X-rays are generated by directing a stream of high speed electrons at a target material such as tungsten, which has a high atomic number. When the electrons are slowed or stopped by the interaction with the atomic particles of the target, X-radiation is produced. This is accomplished in an X-ray tube.
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Source of X-rays and Gamma rays Radio Isotope (Gamma-ray) Source Manmade radioactive sources are produced by introducing an extra neutron to atoms of the source material. As the material gets rid of the neutron, energy is released in the form of gamma rays. Two of the most common industrial gamma-ray sources for industrial radiography are Iridium-192 and Cobalt-60. These high energies make it possible to penetrate thick materials with a relatively short exposure time.
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RADIOGRAPHY CONSIDERATIONS & TECHNIQUES Radiographic sensitivity is a measure of the quality of an image in terms of the smallest detail or discontinuity that may be detected. Radiographic sensitivity is dependent on the contrast and the definition of the image. Radiographic contrast is the degree of density (darkness) difference between two areas on a radiograph. Contrast makes it easier to distinguish features of interest, such as defects, from the surrounding area.
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RADIOGRAPHY CONSIDERATIONS & TECHNIQUES Radiographic definition is the abruptness of change in going from one area of a given radiographic density to another. Like contrast, definition also makes it easier to see features of interest, such as defects, but in a totally different way. Radiographic Density The term “radiographic density” is a measure of the degree of film darkening (darkness of the image). Technically it should be called “transmitted density” when associated with transparent -base film since it is a measure of the light transmitted through the film.
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Viewing Radiographs Viewing Radiographs After the film processing, radiographs are viewed using a light-box (or they can be digitized and viewed on a high resolution monitor) in order to be interpreted. In addition to providing diffused, adjustable white illumination of uniform intensity, specialized industrial radiography light-boxes include magnifying and masking aids. When handing the radiographs, thin cotton gloves should be worn to prevent fingerprints on the radiographs.
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  • Fall '19
  • developer, Nondestructive testing

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