HALL EFFECT (MT): The phenomenon wherein a voltage is generated across the opposite edges of an electrical
conductor carrying current and placed in a magnetic field. The generated voltage differential is mutually perpendicular
to the direction of current flow and the applied magnetic field.
HAMMER FORGING: Forging in which the work is deformed by repeated blows. Compare with press forging.
HARDENABILITY: In a ferrous alloy, the property that determines the depth and distribution of hardness induced by
HARDENER (RT): An agent incorporated into the fixer solution to harden the emulsion during the fixing process.
The acid hardener prevents the swelling of the emulsion and facilitates the drying process.
HARDENING: Heating metal to within its critical range as in annealing, followed by rapid cooling as in quenching.
HARD FACING: Depositing filler metal on a surface by welding, spraying or braze welding, for the purpose of
resisting abrasion, erosion, wear, galling and impact.
HARDNESS: Resistance of metal to plastic deformation, usually by indentation. However, the term may also refer to
stiffness or temper or to resistance to scratching, abrasion or cutting.
HARDNESS TESTING: By means of instruments such as Brinnel, Rockwell, Scleroscope, Vickers, etc.
HARD RADIATION (RT): A term used to describe qualitatively the more penetrating types of radiation.
HARDWARE FINISH: Refers to an especially smooth, as cast, surface which requires a minimum of preparation for
HARD X-RAYS: A term used to express the quality or penetrating power of X radiation. Hard X-rays are very
HARMONICS (UT): Those vibrations that are integral multiples of the fundamental frequency; used in resonance
HASH: Numerous, small indications appearing on the viewing screen of the ultrasonic instrument indicative of many
small inhomogeneities in the material and/or background noise; also known as grass.
HEADING: Upsetting wire, rod or bar stock in dies to form parts having some of the cross-sectional area larger than
the original. Examples are bolts, rivets, and screws.
HEADS: The clamping contacts on a stationary magnetizing unit.
H & D CURVE (HURTER AND DRIFFIELD) (RT): See CHARACTERISTIC CURVE.
HEADSHOT (MT): A term used colloquially to designate the magnetizing current passing through a part or a central
conductor while clamped between the head contacts of a stationary magnetizing unit for the purpose of circular
HEALTH PHYSICS: A term in common use for that branch of radiological science dealing with the protection of
personnel from harmful effects of ionizing radiation.
HEAT (MELT) OF METAL: A quantity of metal manufactured from one melt.
HEAT-AFFECTED ZONE: That portion of the base metal which was not melted during brazing, cutting or welding,
but whose microstructure and physical properties were altered by the heat.