CRITICAL ANGLE (UT): The angle of the incident sound beam with respect to the normal to an interface, beyond
which a given mode of refracted beam will not exist.
CRITICAL SIZE: The established flaw size deemed to be detrimental to the serviceability of the product criteria. The
acceptance/rejection levels established by design engineering required limits to meet design performance.
CROSS TALK (UT): The signal leakage (acoustical or electrical) across an intended barrier, such as signal leakage
between the transmitting and receiving transducer elements of a dual search unit.
CRT: Abbreviation for cathode ray tube.
CRYSTAL (UT): See TRANSDUCER ELEMENT.
CRYSTAL MOSAICS (UT): Two or more crystals mounted in the same plane in one holder and connected so as to
cause all crystals to vibrate as one unit.
CRYSTALS (X-CUT) (UT): Section cut so that its thickness is parallel to the X-axis of the crystal. A thickness-
extensional mode of vibration occurs when excited.
CRYSTALS (Y-CUT) (UT): Section cut so that its thickness is parallel to the Y-axis of the crystal. A thickness- shear
mode of vibration occurs when excited.
CRYSTALS (Z-CUT) (UT): Section cut 50 that its thickness is parallel to the Z-axis of the crystal. Piezoelectric effect
is restricted to the X and Y-axis; therefore mode of vibration is width-extensional.
C-SCAN (UT): A data presentation method generally applied to pulse echo techniques yielding a two dimensional plan
view of the scanned surfaces of the part. Through gating, only echoes arising from the interior of the test object are
indicated. In the C-scan no indication is given of the echo depth.
CUMULATIVE DOSE (RADIATION) (RT): The total dose resulting from repeated exposure to radiation of the same
region or of the whole body.
CUPOLA: A cylindrical vertical furnace for melting metal, especially gray iron, by having the charge come in contact
with the hot fuel, usually metallurgical coke.
CURIE (RT): A unit of measure to express the rate at which a radioactive material decays. It is defined as that quantity
of any radioactive material in which 3.7 x 1010 disintegrations per second are occurring. Under the new International
System (SI) of Units, the curie will be replaced by disintegrations per second (1 Curie = 3.70 x 1010 disintegrations per
CURIE POINT (MT): The temperature at which ferromagnetic materials become nonmagnetic and can no longer be
magnetized by outside sources. The range of temperatures is 1200°F-1600°F.
CURRENT: The flow of electrons through a conductor. It is measured in amperes, milliamperes or microamperes.
CURRENT FLOW METHOD (MT): See CIRCULAR MAGNETIZATION.
CURRENT INDUCTION METHOD (MT): See INDUCED CURRENT MAGNETIZATION.
CUTIE-PIE (RT): A colloquial term applied to a portable instrument equipped with a direct reading meter used to
determine the level of radiation in an area.
CYANIDING: Introducing carbon and nitrogen into a solid ferrous alloy by holding above Acl in contact with molten
cyanide of suitable composition. The cyanided alloy is usually quench hardened.