FREQUENCY (FUNDAMENTAL) (UT): In resonance testing, the frequency at which the wavelength is twice the
thickness of the examined material.
FREQUENCY (INSPECTION) (UT): Effective peak ultra-sonic wave frequency used to inspect the test part.
FREQUENCY (PULSE REPETITION) (UT): The number of pulses per second.
FRESNEL ZONE (UT): See NEAR FIELD.
FRETTING (FRETTING CORROSION): Action that results in surface damage, especially in a corrosive environment,
when there is relative motion between solid surfaces in contact under pressure.
FRILLING (RT): See SLOUGHING.
FULL-WAVE RECTIFIED SINGLE-PHASE AC: This is rectified alternating current for which the rectifier is so
connected that the reverse half of the cycle is turned around, and fed into the circuit flowing in the same direction as
the first half of the cycle. This produces pulsating D.C., but with no interval between the pulses. Such current is also
referred to as single-phase full-wave D.C. It is also known as unidirectional current, single phase.
FULL-WAVE RECTIFIED THREE-PHASE AC: When three-phase alternating current is rectified the full-wave
rectification system is used. The result is D.C. with very little pulsation - in fact only a ripple of varying voltage
distinguishes it from straight D.C. It is also known as unidirectional current, three phase.
FURRING (MT): Buildup or bristling of magnetic particles due to excessive magnetization of the component under
examination resulting in a furry appearance.
FUSION: The process by which two light nuclei combine to form a heavier nucleus.
GADOLINIUM-153: A radioisotope of the element gadolinium.
GAIN: See SENSITIVITY.
GALVANIC CORROSION: Corrosion consisting of two dissimilar conductors in an electrolyte, or two similar
conductors in dissimilar electrolytes.
GAMMA, FILM (RT): See GRADIENT.
GAMMA INFINITY (RT): The maximum gamma that can be achieved by prolonged development of a photographic
GAMMA RADIOGRAPHY (RT): The process whereby a photographic image of an object is produced by gamma
radiation that has penetrated through the object.
GAMMA RADIOGRAPHY SYSTEM (RT): All components necessary to make radiographic exposures with gamma
radiation, including the exposure device, source assembly, control, and other components associated with positioning
the source such as source guide tubes, exposure head, and collimators, if used.
GAMMA-RAY SOURCE (RT): A quantity of a radionuclide that emits gamma radiation suitable for radiography.
GAMMA-RAY SOURCE CONTAINER (RT): See CONTAINER, GAMMA-RAY SOURCE