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An indentation hardness testing procedure, usually relying on indentation force versus tip displacement data, to make assessments of the resistance of surfaces to penetrations of the order of 10 to 1000 nm deep.
(1) Any deposit in the earth’s crust consisting of uncombined metal. (2) The metal in such a deposit.
Spontaneous aging of a supersaturated solid solution at room temperature. See also aging. Compare with artificial aging.
See true strain.
See nondestructive evaluation.
See nondestructive inspection.
See nondestructive testing.
See net shape.
(1) The reduction of the cross-sectional area of a material in a localized area by uniaxial tension or by stretching. (2) The reduction of the diameter of a portion of the length of a cylindrical shell or tube.
Localized reduction in area of a specimen during tensile deformation.
The shape of a powder metallurgy part, casting, or forging that conforms closely to specified dimensions. Such a part requires no secondary machining or finishing. A near-net shape part can be either one in which some but not all of the surfaces are net or one in which the surfaces require only minimal machining or finishing.
Mechanical twin in ferrite.
(1) A gas flame in which there is no excess of either fuel or oxygen in the inner flame. Oxygen from ambient air is used to complete the combustion of CO2 and H2 produced in the inner flame. (2) An oxyfuel gas flame in which the portion used is neither oxidizing nor reducing. See also carburizing flame , oxidizing flame , and reducing flame.
Embrittlement resulting from bombardment with neutrons, usually encountered in metals that have been exposed to a neutron flux in the core of the reactor. In steels, neutron embrittlement is evidenced by a rise in the ductile-to-brittle transition temperature.
Contour cutting of sheet metal by use of a rapidly reciprocating punch that makes numerous small cuts.
See angle of bite.
Introducing nitrogen into the surface layer of a solid ferrous alloy by holding at a suitable temperature (below Ac1 for ferritic steels) in contact with a nitrogenous material, usually ammonia or molten cyanide of appropriate composition. Quenching is not required to produce a hard case. See also bright nitriding and liquid nitriding.
Any of several processes in which both nitrogen and carbon are absorbed into the surface layers of a ferrous material at temperatures below the lower critical temperature and, by diffusion, create a concentration gradient. Nitrocarburizing is performed primarily to provide an antiscuffing surface layer and to improve fatigue resistance. Compare with carbonitriding.
The positive direction of electrode potential, thus resembling noble metals such as gold and platinum.
(1) A metal whose potential is highly positive relative to the hydrogen electrode. (2) A metal with marked resistance to chemical reaction, particularly to oxidation and to solution by inorganic acids. The term as often used is synonymous with precious metal.
A potential more cathodic (positive) than the standard hydrogen potential.
no-draft (draftless) forging
A forging with extremely close tolerances and little or no draft that requires minimal machining to produce the final part. Mechanical properties can be enhanced by closer control of grain flow and by retention of surface material in the final component.
Graphite in nodular (rounded) form as opposed to flake form (see flake graphite ). See also ductile iron and spheroidal graphite.
See preferred term ductile iron.
The stress at a point calculated on the net cross section without taking into consideration the effect on stress of geometric discontinuities, such as holes, grooves, fillets, and so forth. The calculation is made using simple elastic theory.
nondestructive evaluation (NDE)
Broadly considered synonymous with nondestructive inspection (NDI). More specifically, the quantitative analysis of NDI findings to determine whether the material will be acceptable for its function, despite the presence of discontinuities. With NDE, a discontinuity can be classified by its size, shape, type, and location, allowing the investigator to determine whether or not the flaw(s) is acceptable. Damage tolerant design approaches are based on the philosophy of ensuring safe operation in the presence of flaws.
nondestructive inspection (NDI)
A process or procedure, such as ultrasonic or radiographic inspection, for determining the quality or characteristics of a material, part, or assembly, without permanently altering the subject or its properties. Used to find internal anomalies in a structure without degrading its properties or impairing its serviceability.
nondestructive testing (NDT)
Broadly considered synonymous with nondestructive inspection (NDI).
That direction perpendicular to the plane of working in a worked material. See also longitudinal direction and transverse direction.
Heating a ferrous alloy to a suitable temperature above the transformation range and then cooling in air to a temperature substantially below the transformation range.
Concentration of alloying constituents that have low melting points in those portions of a casting that solidify last. Compare with inverse segregation.
An aqueous solution containing one gram equivalent of the active reagent in 1 L of the solution.
The stress component that is perpendicular to the plane on which the forces act. Normal stress may be either tensile or compressive.
The radius of the rounded portion of the cutting edge of a tool.
Relates to the severity of the stress concentration produced by a given notch in a particular structure. If the depth of the notch is very small compared with the width (or diameter) of the narrowest cross section, acuity may be expressed as the ratio of the notch depth to the notch root radius. Otherwise, acuity is defined as the ratio of one-half the width (or diameter) of the narrowest cross section to the notch root radius.
Susceptibility of a material to brittle fracture at points of stress concentration. For example, in a notch tensile test, the material is said to be notch brittle if the notch strength is less than the tensile strength of an unnotched specimen. Otherwise, it is said to be notch ductile.
The distance from the surface of a test specimen to the bottom of the notch. In a cylindrical test specimen, the percentage of the original cross-sectional area removed by machining an annular groove.
The percentage reduction in area after complete separation of the metal in a tensile test of a notched specimen.
A test specimen that has been deliberately cut or notched, usually in a V-shape, to induce and locate point of failure.
Ratio of the resilience determined on a plain specimen to the resilience determined on a notched specimen.
Cutting out various shapes from the edge of a strip, blank, or part.
A mechanical press used for notching internal and external circumferences and also for notching along a straight line. These presses are equipped with automatic feeds because only one notch is made per stroke.
notch rupture strength
The ratio of applied load to original area of the minimum cross section in a stress-rupture test of a notched specimen.
The extent to which the sensitivity of a material to fracture is increased by the presence of a stress concentration, such as a notch, a sudden change in cross section, a crack, or a scratch. Low notch sensitivity is usually associated with ductile materials, and high notch sensitivity is usually associated with brittle materials.
The maximum load on a notched tension-test specimen divided by the minimum cross-sectional area (the area at the root of the notch). Also called notch tensile strength.
Material of a quality adequate for use in nuclear application.
The initiation of a phase transformation at discrete sites, with the new phase growing on the nuclei. See also nucleus (2).
(1) The heavy central core of an atom, in which most of the mass and the total positive electric charge are concentrated. (2) The first structurally stable particle capable of initiating recrystallization of a phase or the growth of a new phase and possessing an interface with the parent metallic matrix. The term is also applied to a foreign particle that initiates such action.
(1) A small mass of metal, such as gold or silver, found free in nature. (2) The weld metal in a spot, seam, or projection weld.
See strain-hardening exponent.