CONTROLLED AREA (RT): A defined area in which the occupational exposure of personnel to radiation or to
radioactive material is under the supervision of an individual in charge of radiation protection. (This implies that a
controlled area is one that requires control of access, occupancy, and working conditions for radiation protection
CONVEX: Curved or rounded as the exterior of a spherical or circular form viewed from without; opposite of concave.
COOLIDGE TUBE (RT): An X-ray tube in which the source of the bombarding electrons is a heated filament in the
COOLING CRACK: See CRACKS, COOLING.
COOLING STRESSES: Residual stresses resulting from non-uniform distribution of temperature during cooling.
CORE (MT): In reference to an electromagnetic inspection, it is a laminated steel conductor located within the
electrical winding of a hand-held yoke or probe. Also, laminated steel conductor used in conjunction with a
magnetizing coil to produce a stronger collapsing field in induced current magnetization of ring-shaped parts.
CORNER EFFECT (UT): The strong reflection obtained when an angle beam is directed normal to the intersection of
two perpendicular reflectors.
CORONA: In spot welding, an area sometimes surrounding the nugget at the faying surfaces, contributing slightly to
overall and strength.
CORROSION: The deterioration of a metal by chemical or electrochemical reaction with its environment or other
CORROSION EMBRITTLEMENT: The severe loss of ductility of a metal, resulting from corrosive attack, usually
intergranular and often not visually apparent.
CORROSION FATIGUE: Effect of the application of repeated or fluctuating stresses in a corrosive environment
characterized by shorter life than would be encountered as a result of either the repeated or fluctuating stresses alone or
the corrosive environment alone.
COULOMB: A unit of electric charge in the practical system of units. It contains 3 x 109 electrostatic units (see
ESU) of charge.
COUPLANT (UT): A substance (usually liquid) used between the search unit and test part to permit or improve
transmission of ultrasonic energy into the test part.
COUPLING (ET): An interaction between systems or between properties of a system.
CRACK: A discontinuity that has a relatively large cross-section in one direction and a small or negligible cross-
section when viewed in a direction perpendicular to the first.
CRACKS COLD: A crack, which occurs in a casting after solidification, due to excessive strain generally resulting
from non-uniform cooling.
CRACK CONTAMINANT: Material which fills a crack and which may prevent penetrants from entering.
CRACKS COOLING: In bars of alloy or tool steels, are the result of uneven cooling after rolling and usually are deep
in a longitudinal direction, but are not straight.