SHEET: A flat-rolled metal product of some maximum thickness and minimum width arbitrarily dependent on the type
of metal. It is thinner than plate.
SHEET SEPARATION: In spot, seam or projection welding, the gap which exists between faying surfaces surrounding
the weld, after the joint has been welded.
SHIELD: A layer or mass of material used to reduce the passage of ionizing radiation.
SHOCK-PROOF (RT): A term applied to those components of the high-voltage circuit of X-ray equipment which are
entirely surrounded by grounded metal enclosures, e.g., shock-proof tube, shock-proof cable.
SHOCK-PROOF TUBE (RT): An X-ray tube surrounded by a grounded conducting enclosure.
SHOE (UT): Device used to adapt a straight beam search unit for use in a specific type of inspection such as inspection
of a curved surface, angle beam or surface wave inspection, inspection around a fastener hole, etc. Also, see WEDGE.
SHORTNESS: A form of brittleness in metal. It is designated as cold, hot, and red, to indicate the temperature
range in which the brittleness occurs.
SHOT PEENING: Cold working the surface of a metal by metal-shot impingement.
SHRINK MARK: A surface depression on a casting that sometimes occurs next to a thick section that cools more
slowly than adjacent sections.
SHRINKAGE CAVITIES: Cavities in castings caused by lack of sufficient molten metal as the casting cools.
SHRINKAGE CAVITY (ON RADIOGRAPH): A small bubble in metal that appears as a dendritic, filamentary, or
jagged darkened area on a radiograph film.
SHRINKAGE CRACKS: Hot tears associated with shrinkage cavities.
SHRINKAGE POROSITY OR SPONGE (NONFERROUS ALLOYS,
RADIOGRAPHIC): A localized lacy, or honeycombed, darkened area on a film that indicates porous metal.
SHUTTER (RT): A device that incorporates a movable shield used to block the useful beam emitted from an X-ray tube
assembly or source housing.
SIDE LOBE ENERGY (UT): Ultrasonic energy emitted from a search unit to the sides of the main sound beam.
SIEVERT (Sv): The SI unit of any of the quantities expressed as dose equivalent. The dose equivalent in sieverts is
equal to the absorbed dose in grays multiplied by the quality factor (1 Sv = 100 rems).
SIGNAL (UT): Vertical deflection from the base line on an A-scan.
SIGNAL-TO-NOISE RATIO (UT): The ratio of the signal from the variable of interest (flaw, thickness change or
conductivity change) to signals from variables which are of no interest (lift-off, geometry and finish changes and
SILKY FRACTURE: A metal fracture in which the broken metal surface has a fine texture usually dull in appearance.
Characteristic of tough and strong metals.
SILVER HALIDE (RT): A compound of silver with one of the halogen elements, e.g., silver bromide.