ROD-ANODE TUBE (RT): A special type of X-ray tube in which the target is situated at the outer end of a long
tubular anode. It usually produces panoramic radiation.
ROENTGEN ® (RT): The international unit of the quantity of X or gamma radiation which cause the emission of ions
carrying 1 electrostatic unit quantity of charge per 0.001293 grams of air. It is usually employed to express the
radiation output of a given source in terms of roentgens per hour at one meter (Rhm). Under the International System
of Units this will be expressed in coulombs/kilogram (1 r = 2.579560 x 10-4 C/ kg).
ROENTGENS PER HOUR AT ONE METER (RT): A specification of the output of a source of X- or gamma radiation
in terms of the exposure rate, in roentgens per hour, measured in air at a distance of one meter from the source.
ROLL BENDING: Curving sheets, bars and sections by means of rolls.
ROLL FLATTENING: Flattening of sheets, that have been rolled in packs, by passing them separately through a two-
high cold mill, there being virtually no deformation. Not to be confused with roller leveling.
ROLL FORGING: Forging with rotating dies that are not full round, the desired shape, either straight or tapered, being
produced by a groove in the dies.
ROLL FORMING: Metal forming by the use of power-driven rolls whose contour determines the shape of the product.
Sometimes used to denote power spinning.
ROLL STRAIGHTENING: Straightening of metal stock of various shapes by passing it through a series of staggered
rolls, the rolls usually being in horizontal and vertical planes.
ROLLING: Reducing the cross-sectional area of metal stock, or otherwise shaping metal products, through the use of
ROOT CRACK: A crack in either the weld or heat-affected zone at the root of a weld.
ROOT OF JOINT: The location of closest approach between parts of a joint to be welded.
ROOT PENETRATION: The depth to which weld metal extends into the root of a joint.
ROTATING-ANODE TUBE (RT): An X-ray tube in which the anode can rotate. The axis of rotation is offset from the
axis of the electron beam, so that the focus lies on a circle on the rotating surface.
ROUGHNESS: Relatively finely spaced surface irregularities, the height, width and direction of which establish the
predominant surface pattern.
ROUGHNESS HEIGHT RATING: Quantitative expression of the roughness of a surface; arithmetical average,
normally expressed in microinches, of the absolute values of surface height deviation from the mean surface height.
Abbreviation is rhr.
RT: Symbol for the radiographic method of nondestructive testing/inspection.
RUPTURED METAL: See BURSTS.
RUST: A corrosion product consisting of hydrated oxides of iron. Applied only to ferrous alloys.