appear as bright silvery areas; on an etched surface they appear as short, discontinuous cracks. Also called shatter
cracks and snowflakes.
FLANGE: The projecting annular rim around a cylinder that is used for strengthening, fastening, or positioning.
FLANGE RADIUS: The radius formed at the junction of a flange and the wall of a casting.
In forging, the excess metal forced between the upper and lower dies.
In die casting, the fin of metal that results from leakage between the mating die surfaces.
In resistance butt welding, a fin formed perpendicular to the direction of applied pressure.
FLASH LINE: The line of location of flash formed around a forging.
FLASH MAGNETIZATION (MT): Magnetization by a current flow of very brief duration.
FLASH POINT: The lowest temperature at which a substance will decompose to a flammable gaseous mixture. The
temperature at which the vapor air mixture first ignites is the flash point. This temperature can be determined by
raising the temperature of the liquid in accordance with the pre-determined schedule, and periodically introducing a
flame or other ignition means immediately above the surface.
FLASH TUBE (RT): An X-ray tube designed for use in flash radiography.
FLASH X-RAY: Term used to describe the technique in which a tube capable of producing very short (10 to 100
nanoseconds) high intensity pulses of radiation are used for special radiographic investigations.
FLAT BOTTOM HOLE (UT): A type of reflector commonly used in reference standards. Abbreviation is FBH.
FLAW: An imperfection in an item or material that may or may not be harmful. See DISCONTINUITY.
FLAW SENSITIVITY (RT): See SENSITIVITY, DEFECT.
FLOW LINES: A fiber pattern frequently observed in wrought metals, which indicates the manner in which the metal
flows during deformation. The pattern is made more visible by acid etching.
FLOW STRESS: The uniaxial true stress required to cause plastic deformation at a particular value of strain.
FLUORESCENT (RT): The emission of electromagnetic radiation by a substance as the result of the absorption of
electromagnetic or corpuscular radiation having greater unit energy than that of the fluorescent radiation. Fluorescence
is characterized by the fact that it occurs only so long as the stimulus responsible for it is maintained. The
characteristic X-radiation emitted, as a result of absorption of X-rays of higher frequency is a typical example of
fluorescence. Property of emitting visible light as the result of and only during, the absorption of radiant energy from
some other source (i.e., black light).
FLUORESCENT DYE PENETRANT (PT): A highly penetrating liquid which fluoresces when subjected to ultra-violet
or black light, used to produce luminous indications of surface flaws or discontinuities.
FLUORESCENT MAGNETIC PARTICLE INSPECTION (MT): The inspection process employing magnetic materials
which have been coated with a material that fluoresces when activated by light of suitable wavelength.