| Nano machining |
The machining of silicon chips typically less than 1 nm thick. |
| Nanomanufacturing |
1. The manufacture of nanoscale materials. 2. The manufacture of components or devices that have critical dimensions of order 1 nm. |
| Nanomaterial |
A material defined by the European Commission as ‘A natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range 1–100 nm. In specific cases and where warranted by concerns for the environment, health, safety or competitiveness the number size distribution threshold of 50% may be replaced by a threshold between 1 and 50%.’ |
| Nanoparticles |
Particles with dimensions of order 1 nm which have either been introduced into microstructures for reinforcement or are present as impurities. |
| Nanotechnology |
The science and engineering of materials that have been structured on length scales of 1–100 nm, resulting in modified physical properties owing to changes in the ratio of surface area to volume (atoms on surfaces having different symmetry from those in the bulk) and because many of the fundamental physical processes that underpin the properties of materials have a characteristic length scale of a few nm, so that alteration of microstructure at the nm level alters the bulk properties. |
| Natural aging |
Spontaneous aging of a supersaturated solid solution at room temperature. |
| Natural unit system (n.u. system) |
A non-SI system of units, based on fundamental constants, used in high-energy and particle physics. The n.u. of speed is the speed of light in a vacuum, c0 = 299 792 458 m/s. |
| Nautical mile (M) |
A special unit of distance employed for marine and aerial navigation. The conversion to SI is 1 M = 1 852 m. |
| Net weight (Unit N) |
The difference between the gross weight of any container including its contents and the tare weight of the empty container. |
| Neutralization number |
An ASTM number given to quenching oils that reflects the oil’s tendency towards oxidation and sludging. |
| Newton (N) |
The basic unit of force in the SI system, defined as the force that results in an acceleration of 1 m/s2 when acting on a 1 kg mass. |
| Newton’s law of gravitation |
(Newton’s law of universal gravitation) Any two bodies exert a gravitational force of attraction F on each other directed along the line joining their centres of mass, in magnitude proportional to the product of their masses and inversely proportional to the square of the distance r between them. |
| Newton’s law of viscosity |
The shear stress between two parallel layers of fluid is proportional to the velocity of one relative to that of the other, and inversely proportional to the distance between them. The constant of proportionality is the dynamic viscosity μ. For a Newtonian fluid μ is independent of pressure gradient, shear stress, and strain, but may change with temperature and pressure. |
| Nipple |
A device containing a non-return valve screwed into a lubrication point through which grease may be introduced, for example into a bearing. |
| Noble metals |
Metallic elements from periods (rows) 5 and 6 of the periodic table, namely ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold. They resist corrosion and oxidation and are used for electrical contacts, thin-film circuits, and electroplating. Gold, silver, and platinum used for jewellery are also known as precious metals. They have face-centred cubic crystal structure and good ductility. |
| Nominal diameter |
The ‘‘catalog diameter’’ of a fastener. Usually roughly equal to the diameter of the body, or the outer diameter of the threads. |
| Nominal power (Unit kW) |
1. For an internal combustion engine, the average power output of a typical production engine under normal working conditions measured according to SAE standard J 1349/ISO 1585. 2. For an electric motor, the rated equivalent mechanical power output. |
| Nominal size |
The intended size of a component. The actual size will depend on manufacturing tolerances. |
| Nominal stress |
The stress at a point calculated on the net cross section by simple elasticity theory without taking into account the effect on the stress produced by stress raisers such as holes, grooves, fillets, etc. |
| Non-ferrous metal |
Strictly, all metals and alloys that do not contain iron, but usually taken to mean aluminium- and copper-based alloys. |
| Nonlinear behavior |
A fastener or joint system is said to exhibit nonlinear behavior when the relationship between the External load on the joint and deformation of the parts is nonlinear, or when the relationship between increasing Preload and deformation is nonlinear. |
| Normal stress |
The stress component perpendicular to a plane on which forces act. Normal stress may be either tensile stress or compressive stress. |
| Normal stress (Unit N) |
A stress in a fluid (such as pressure) or a solid, that is perpendicular to the surface on which it acts. The surface may be a real external surface or an imaginary internal one. |
| Normal temperature and pressure (NTP) |
Reference conditions defined by NIST as 20°C and 1 atm. |
| Normality |
The principle that the vector sum of plastic strain increments is perpendicular to the yield surface. |
| Normalizing |
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. |
| Notch brittleness |
Susceptibility of a material to brittle fractureat points of stress concentration. For example, in a notch tensile test, the material is said to be notch brittle if the notch strengthis less than the tensile strength of an unnotched specimen. Otherwise, it is said to be notch ductile. |
| Notch depth |
The distance from the surface of a notched 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. |
| Notch ductility |
The percentage reduction in area after complete separation of the metal in a tensile test of a notched specimen. |
| Notch strength |
The maximum load on a notched tensile-test specimen divided by the minimum cross-sectional area (the area at the root of the notch). Also known as notch tensile strength. |
| Nut |
An internally-threaded fastener used with externally-threaded bolts. Usually hexagonal in shape but there is a multitude of other geometries, such as square, for special purposes and different gripping tools. |
| Nut |
A metal fastener of square, hexagon or other shape, having an internal thread which screws onto a bolt, stud or arbor. |
| Nut box mechanism |
In a lathe it is used to engage and disengage the lead screw for thread cutting. This comprises a pair of half-nuts capable of sliding in vertical slides in or out of mesh with the lead screw. |
| Nut factor |
An experimental constant used to evaluate or describe the ratio between the torque applied to a fastener and the Preload achieved as a result. |
| Nut splitter |
A tool for removing rusted-on and corroded nuts from bolts. It consists of a stiff steel ring that is placed around the nut. A screw thread passing through the ring bears diametrically on a wedged-shape tip that indents and cuts though a face of the nut. |
| Nut thickness |
The nut thickness shall be the overall distance measured parallel to the axis of nut, from the top of the nut to the bearing surface, and shall include the thickness of the washer face where provided. |
