COLLIMATION: The process by which a divergent beam of energy or particles is converted into a parallel beam.
COLLOIDAL (MT): A liquid suspension of solid particles in which the particles will not settle on standing.
COLLOIDAL SUSPENSION (MT, PT): An intimate mixture of two substances, one of which, called the dispersed
phase (or colloidal), is uniformly distributed in a finely divided state through the second substance, called the
dispersion medium (or dispersing medium); the dispersion medium or dispersed phase may be gas, liquid, or solid.
Also known as colloidal dispersion; colloidal system.
COLOR-CONTRAST DYE (PT): A dye which can be used in a penetrant to impart sufficient color intensity to give
good color contrast in indications against the background of the surface being tested, when viewed under white light.
COLOR-CONTRAST PENETRANT: A penetrant incorporating a dye - usually nonfluorescent - sufficiently intense to
give good visibility to flaw indications under white light.
COLUMNAR STRUCTURE: A coarse structure of parallel columns of grains, having the long axis perpendicular to
the casting surface.
COMBINATION DIE (DIE-CASTING): A die having two or more different cavities for different castings.
COMBINATION SCREENS (RT): A pair of intensifying screens in which the front screen (to be placed on the tube
side of the film) is usually thinner than the back screen.
COMBINED STRESSES: Any state of stress that cannot be represented by a single component of stress; that is, one
that is more complicated than simple tension, compression or shear.
COMMERCIAL SOLVENTS: A liquid containing no emulsifiers and having chemical properties similar to those
exhibited by solvents conforming to Government Specifications TT-N-97 and A-A-2904.
COMPARATIVE TEST BLOCK (see REFERENCE STANDARD): An intentionally cracked metal block having two
separate but adjacent areas for the application of different penetrants so that a direct comparison of their relative
effectiveness can be obtained. Can also be used to evaluate penetrant test techniques or test conditions, or both.
COMPENSATOR: An electrical matching network to compensate for circuit impedance differences.
COMPLETE FUSION: Fusion that has occurred over the entire base-metal surfaces exposed for welding.
COMPOSITE FILTER (RT): A filter of two or more materials chosen so that the longer wavelengths of a beam are
readily absorbed, and within this range undesirable radiation transmission is avoided. The materials are usually
arranged so that the second material filters secondary radiation produced in the first material and so on. A particular
example is the Thoraeus Filter which consists of 0.44 mm of tin, 0.25 mm of copper and I mm of aluminum in this
order in the beam of radiation.
COMPOSITE PLATE: An electrodeposit consisting of layers of at least two different compositions.
COMPOUND: A chemical combination of elements.
COMPRESSIONAL WAVE (UT): Waves in which the particle motion or vibration is in the same direction as the
propagated wave. Same as longitudinal wave. See LONGITUDINAL WAVES.
COMPRESSIVE STRENGTH: The maximum stress developed in a material when located in compression. For
practical purposes, the compressive yield strength is considered as the maximum compressive strength, particularly in
the case of wrought metals.