T.O. 33B-1-1Glossary 34FILM SPEED (RT): A measure of the rate at which a film responds to a given amount of radiation. Slower filmsrequire a longer period of time to reach the same film density than a fast film under the same exposure conditions.FILM UNSHARPNESS (RT): See UNSHARPNESS.FILM VIEWER (RT): See FILM ILLUMINATOR.FILTER (RT): A layer of absorptive material which is placed in the beam of radiation for the purpose of absorbing raysof long wavelengths to control the quality of the radiograph.FILTERS (UT, ET): Filters are electrical circuits designed to eliminate various frequencies from a circuit output orinput. Filter may be low pass (high frequencies suppressed), high pass (low frequencies suppressed) or band pass(frequencies outside a specified range suppressed).FILTRATION: See INHERENT FILTRATION.FILTRATION (RT): The use of a filter to alter the characteristics of a radiation beam.FINE CRACK: A discontinuity in a solid material with a very fine opening to the surface, but possessing length anddepth greater than the width of this opening; usually depth is many times the width.FINISH:(1) Surface condition, quality or appearance of a metal.(2) Stock on a forging to be removed when finish machined.FIRE SCALE: Oxide subscale formed just under the surface of certain alloys when they are annealed in air.FISH EYES: Areas on a fractured steel surface having a characteristic white crystalline appearance.FISSION: The splitting of a heavy nucleus into two roughly equal parts (which are nuclei of lighter elements)accompanied by the release of a relatively large amount of energy and frequently one or more neutrons. Fission canoccur spontaneously, but usually it is caused by the absorption of gamma rays, neutrons, or other particles.FISSION PRODUCTS: Nuclei formed by the fission of heavy elements. They are of medium atomic weight, andalmost all are radioactive. Examples: strontium-90, cesium-137.FISSIONABLE MATERIAL: Any material readily fissioned by slow neutrons, for example, uranium-235 andplutonium-239.FIT: The amount of clearance or interference between mating parts.FIXER (RT): A chemical solution that removes unexposed silver halide crystals from film emulsion.FIXING (RT): The procedure used in film processing that removes all of the undeveloped silver salts of the emulsionfrom the surface of the film, thus leaving only the developed latent image.FLAME HARDENING: A method of hardening where the surface layer is heated by a high temperature torch and thenquenched.FLAKES: Short discontinuous internal fissures in ferrous metals attributed to stresses produced by localizedtransformation and decreased solubility of hydrogen during cooling after hot working. In a fractured surface, flakes
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