Definitions
(technical scientific engineering & mathematical)
High definition values for all constants referred to in this definition page are provided in CalQlata's UniQon calculator.
1D (line) 
A one dimensional shape: a straight line 
2D (plane) 
A two dimensional shape: a planar or 'flat' shape that becomes invisible if viewed 'edgeon' 
3D (body) 
A three dimensional shape: a shape with volume and mass 
Acceleration (a) 
Constant rate of change in velocity (velocity ÷ time) 
Acid 
A corrosive substance at the low end of the pH scale (<7) Acids turns blue litmus paper pink but does not affect pink litmus paper The acidic component of water is H⁺. Mix acid with alkaline and the resultant substance tends towards neutral. 
Acute (angle) 
An angle between 0° and 90° 
Added Mass Coefficient 
A coefficient that represents the additional mass of water displaced by a body in which it is immersed: Whilst there are certain circumstances where an added mass coefficient can exceed 1.0, it is a rare occurrence that is invariably due to complex shapes see Added Dragtechnical help 
Adiabatic 
A process that generates a variation in the volume, pressure and/or temperature of a substance, but no heat is added to the system (from outside) or lost to its surroundings (from inside) see Thermodynamics 
Aerobe 
An organism that can only live in the presence of free oxygen 
Aerobic 
The breathing (respiration) of free oxygen and its conversion to energy 
Age Hardening 
A hardening process that occurs with time with no added chemicals or energy see also Marageing 
Air (the Earth) 
The earth's atmosphere is divided into the following layers: 99.999622% of the Earth's air (atmosphere) comprises the following gases: Properties# @ sea level and 273.15K: 
Alkaline 
A base substance at the high end of the pH scale (>7) Alkalines turns pink litmus paper blue but does not affect blue litmus paper The alkaline component of water is OH⁻. Mix alkaline with acid and the resultant substance tends towards neutral 
Alloy 
An alloy is a compound (mixture) of more than one metal. A steel alloy normally refers to an iron compound with more than trace amounts of elements other than and in addition to: carbon, manganese, phosphorus and sulphur. 
Alpha Iron 
Pure iron (< 1,183 K) with a body centre cubic crystal structure will contain up to 0.001% carbon in solution 
Alpha Particle 
A Helium Nucleus (2 Neutrons and 2 Protons) The emission of an alpha particle from an atom's nucleus (alpha radiation) will decrease its atomic mass by 4 (or the atomic number by 2) 
Alternating Current (AC) 
Alternating current (and voltage). Electricity that rises and falls in cycles normally in the form of a 'sinewave' and normally between Plus and Minus the design current. AC current is normally supplied by a generator and used for highpower applications (>100W) such as freestanding industrial and domestic equipment. see also DC (electrical), Apparent Power, True Power, Phase Angle and Power Factor 
Ampere (A) 
Unit of electrical current. One Ampere is equal to one coulomb passing through a conductor in one second. 
Amplitude 
A displacement that represents half the total fluctuation in a complete cycle, or the maximum deflection of a beam or particle from a central datum 
Anaerobic 
Respiration that does not use free oxygen to generate energy 
Angle of Repose (θ) 
The smallest angle at which an object will slide down a flat surface under its own weight (or contact force) excluding the effects of stiction, chemistry or magnetism 
Angular Velocity (ᶜ/s) 
The rotational velocity of a body spinning about a central axis, which is measured in radians per second 
Anion 
A negatively charged ion. An atom or molecule that has gained excess electron(s) and is therefore attracted to an anode in an electrolyte 
Anisotropic 
A description of material proproperties that vary with direction, for example: 
Anneal 
To anneal a carbon steel is to soften it. Forged carbon steel is annealed by heating it to between 500°C and 700°C and holding it at this temperature to allow recrystallisation to occur, followed by artificial cooling. Cast carbon steel is annealed by heating it above 723°C and holding it at this temperature to allow all the material to transform to austenite, followed by artificial cooling. Artificial cooling means more slowly than it would cool in still air and is normally carried out in an oven. 
Anode 
A positively charged electrode that loses cations to a negatively charged electrolyte (corrodes) 
AntiKnocking Agent 
The antiknocking agent used in petrol in most developed countries today is AK33X (cyclopentadienylManganeseTricarbonyl) The antiknocking agent used for petrol in the past was TEL (TetraEthylLead:64%, Ethylene Bromide:25%, Ethylene Chloride:9% and Methylene Dye:2%) 
Aphelion 
The furthest point an orbiting body gets from its attracting mass Whilst this term can also be used instead of Apogee (i.e. it means the same thing), it is normally used to describe the point at which the distance between sun and its orbiting planet is greatest a = half the width of the elipse see also Perigee and Perihelion 
Apogee 
The furthest point an orbiting body gets from its attracting mass Whilst this term can also be used instead of Aphelion (i.e. it means the same thing), it is normally used to describe the point at which the distance between the earth and its orbiting moon is greatest a = half the width of the elipse see also Perigee and Perihelion 
Apparent Power (electrical) 
Apparent power is the maximum theoretical power of an alternating current (peak current multiplied by peak voltage) and is normally expressed in terms of 'VA' or 'kVA'. see also AC, True Power, Phase Angle and Power Factor 
Arc 
A curved line that forms part of the circumference of a circle 
Area Moment 
A property of the crosssectional area of any structural body that defines its ability to resist bending or torsion see also Second Moment of Area, Moment of Inertia and Polar Moment of Inertia 
Astroid (curve) 
A special case of hypocycloid curve generated by a point on the circumference of a circle rolled around the the inside of a stationary circle four times the diameter without slipping. see also Hypocycloid 
Atmospheric Pressure 
Atmospheric pressure refers to the pressure surrounding your subject or location. The units used for defining pressure above atmospheric are normally given the suffix 'a' or 'atm' Atmospheric pressure will vary according to the density of the surrounding fluid. At sealevel and on dry land, atmospheric pressure is approximately equal to 14.7psi or 0.1N/mm² When quoting or using absolute pressures you must qualify the units with 'a' or 'atm'; 
Atom 
The smallest constituent part of a substance that comprises all the same atomic elements, which possesses the same properties as the substance in bulk, sometimes referred to as an element An atom normally comprises any number of protons, neutrons and electrons in roughly equal numbers 
Atomic Element 
Defined by the number of Protons it has in its nucleus 
Atomic Mass Unit 
One 12ᵗʰ of the mass of a pure carbon atom (¹²C) One amu is the reciprocal of Avogadro's number 
Atomic Number 
The number of protons in the atom 
Austenite 
Face centre cubic iron, which occurs at temperatures higher than 723°C (also called Gamma Iron). At 723°C austenite can absorb up to 0.83% carbon within its crystal structure and hold another 0.87% in solution. see Carbon Steel 
Autoclave 
A thickwalled pressure vessel used for heating gases under pressure Autoclaves are generally used for facilitating chemical reactions that require carefully controlled heat and pressure over a period of time, such as using steam to vulcanise rubber. 
Avogadro's Number 
The number of atoms in 12 grams of pure carbon (¹²C): The mole also applies to the same number of any basic component parts; molecules, ions, electrons, etc. Avogadro's number is also the reciprocal of one atomic mass unit in grammes 
Azimuthal Quantum Number (ℓ) 
The second in a set of quantum numbers that describes the angular momentum (or shape) of an atomic orbital The azimuthal quantum number of an electron can only be a positive integer: i.e. 1, 2, 3, 4, 5, 6, 7, etc. The orbital shape options in any shell are normally identified with the letters; s, p, d, f, etc. Whereas the azimuthal quantum numbers for each shape are defined thus: s(ℓ=1), p(ℓ=2), d(ℓ=3), f(ℓ=4), etc. At least one other quantum number must be different for each electron in the same shell with the same azimuthal quantum number 
Baryon 
A family of composite particles made of three quarks which includes protons and neutrons Baryons are strongly interacting fermions and part of the hadron particle family 
Baryon Number 
One third of the number of quarks the particle contains For example: 
Basic Oxygen Process 
A steel making procedure It is essentially the same as the Bessemer Converter but blows pure oxygen instead of air through the nozzles. It produces better quality steel and has largely replaced all Bessemer 'airblowing' systems. 
Bead Wire 
A wire approximately 1mm diameter manufactured from 'Plow Steel', which is then drawn down to form the filaments used in wire ropes The term 'Bead Wire' comes from its use in untreated form to support the rim (or bead) of a tyre 
Beam 
An elongated body to which a transverse load is applied 
Bearing Strength 
The ability of a material or a body to support pressure without collapse or plastic deformation 'Bearing Stress' is the measurement designation for this property see also Stress 
Bending Moment 
A force applied at a distance that induces bending in a body 
Berm 
A heap or pile of material (soil, sand, rocks, etc.) normally positioned to protect and/or prevent movement of a structural object (e.g. pipeline) 
Bessemer Converter 
A steel making furnace It is a large steel vessel supported on pivots with one spouted opening in the top. Air is blown through a number of nozzles in the flat base to increase applied heat. Oxygen in the air is converted to carbondioxide This process is gradually being replaced by the Open Hearth furnace 
Beta Particle 
The transmutation of a neutron into a proton and an electron and the subsequent emission of the electron In this case, the atomic mass remains the same but the atomic number increases. I.e. the atom changes into a different element 
Birdcaging 
The term used to describe the unwinding and opening up of a wrapped assembly such as a wire rope or HPHT flexible pipe when it is axially compressed or twisted against the helical lay direction 
Bisector 
A line that passes through the centre of another line or object thereby dividing it exactly in two A perpendicular Bisector is a line that passes through the centre of another line or object at rightangles to it 
BlackHole 
A collapsed star with sufficient mass to generate the gravitational energy that will prevent photons from escaping its surface minimum mass: 2.7234E+38 kg see Stars & Planets see also the Sun 
Body Centre Cubic (bcc) 
Describes the lattice arrangement of atoms within a metal. The smallest crystal of this metal will contain nine closely packed atoms, eight of which are located at each corner of a cube and one in its centre. 
Boltzmann Constant 
Defines the amount of energy (Joules) in each molecule of an ideal gas for each degree of temperature (K) relative to absolute zero (K=0) see also Gas Constant and Avogadro's Number 
Bohr Radius 
The radial distance of an electron at ground state (1s) in a hydrogen atom as defined by Nils Bohr 
Boson 
Any particle that obeys BoseEinstein statistics 5 are known; Higgs, photon, gluon, W & Z Photon, gluon, W & Z are Gauge Bosons Bosons are normally associated with force and have integer spin properties: 1, 2, 3, 4, 5, etc. Several bosons with the same energy can occupy the same quantum state, i.e. several bosons can occupy the same place in space. 
Bottom Quark 
Also known as the beauty quark, it has more than four times the mass of a proton and is part of the third generation of matter The bottom quark is classified as a fermion mᵣ=7.451526101E−24g [4.18GeV/c²], lifetime≈1E12s, Q=⅓e, I_{z}=½ 
Brass 
The term used to describe a copperzinc alloy The most common ratios (Cu%:Zn%) are: 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:35 & 60:40 As zinc content rises (see note below): 60:40 Brass is known as Munz Metal Note: this relationship holds true up to about 35% zinc after which the alloy changes phase from alpha brass to alphabeta brass and strength drops slightly 
Bronze 
The term normally used to describe coppertin alloy. The most common ratios of coppertin alloys (Cu%:Sn%) are: 98.75:1.25, 95:5, 92:8 & 90:10 As tin content rises: 
Brown & Sharpe Taper 
A conical shaft and mating sleeve for machinepart selfholding applications that optimises assembly load, holding capacity and easy release (without damage). The tapered shaft is normally driven by an EndTang (or Key) or a Longitudinal Key. Different size numbers (0 to 16) relate to different engaged lengths (15/16" to 9") As each size is based upon standard fraction lengths and diameters, not all tapers will have exactly the same taper (angle ≈ 2.4°). The tapers range between 0.04167 and 0.043 inches per inch (2.39° to 2.46°) The Brown & Sharpe Taper is used for similar applications to the Morse and Jarno Tapers 
Bulk Modulus (K) 
Relationship between a 2D stress (load per unit area) and the resultant 3D strain in a body. 
Buoyancy 
The vertical (antigravity) force exerted by a body immersed in a fluid A body with a lower density than its surrounding fluid will float or rise (positive force) A body with the same density than its surrounding fluid will settle midcolumn (zero force) A body with a greater density than its surrounding fluid will sink (negative force) 
Capacitance (C) 
Capacitance (the unit of measurement is the 'Farad') is the resistance generated by the storage of Volts as current grows in an AC power supply. This voltage is slowly released as current falls. Current leads voltage C = Q/V 
Capstan 
A general term used by CalQlata to describe not only a quayside capstan but any cylindrical surface such as a tree or drum 
Carbide 
A binary compound of carbon and a metal 
Carburise 
The process of transferring carbon into the surface of a carbon steel to case harden it. It is carried out by immersing or embedding the steel in a carbon rich substance and heating it to a temperature where the transfer of carbon atoms occurs. The longer this process is maintained, the greater the depth of hardening. 
Cardioid (curve) 
A special case of epicycloid curve generated by a point on the circumference of a circle rolled around the the outside of a stationary circle exactly the same size without slipping. 
Cartesian 
The definition of a vector using its linear dimensional relationship to the origin of a set of 2D (x,y) or 3D (x,y,z) axes see also Polar CoOrdinates and Vector 
Case Harden 
A process during which only the outer skin (or case) of a carbon steel is hardened. The inner body of the material retains its original ductility/toughness. 
Cathode 
A negatively charged electrode that gains cations via a negatively charged electrolyte (gains matter) 
Cation 
A positively charged ion. An atom or molecule with a shortage of electron(s), which is therefore attracted to a cathode in an electrolyte 
Cementite (Fe₃C) 
A very hard and brittle iron carbide that forms when excess carbon cannot be held in solution in iron Pure cementite has the following physical properties: see Carbon Steel 
Central Force Motion 
Describes the movement of an orbiting body (its deviation from a straightline path); e.g. a planet towards its sun or a moon towards its planet due to their gravitational attraction. see also Force Centre 
Centre of Buoyancy (C_{of}B) 
The centre of mass of the fluid displaced by an immersed body 
Centre of Gravity (C_{of}G) 
The only point on a line, shape or object that can be supported on the end of a pin without the line, shape or object tilting (also known as the centre of area or centre of mass) 
Centrifugal Acceleration 
The positive radial (outward) acceleration of an orbiting body directed away from its centre of rotation (or force centre) (the opposite of centripetal acceleration) 
Centrifugal Force 
Centrifugal acceleration of a body multiplied by its mass (the opposite of centripetal force) see also Central Force Motion and Force 
Centripetal Acceleration 
The negative radial (inward) acceleration of an orbiting body directed towards its centre of rotation (or force centre) (the opposite of centrifugal acceleration) 
Centripetal Force 
Centripetal acceleration of a body multiplied by its mass (the opposite of centrifugal force) see also Gravitational Force, Central Force Motion and Force 
CFC 
Chlorofluorocarbon  an organic gaseous compound used as a refrigerant and as a pressuriser in aerosol cans. CFCs have mistakenly been blamed as the cause of a hole in an ozone layer 
Charge Density 
see radiation 
Charm Quark 
The third most massive of all the quarks and part of the second generation of matter The charm quark is classified as a fermion mᵣ=2.299633653E−24g [1.29GeV/c²], Q=⅔e, I_{z}=½ 
Chord 
A straight line that joins both ends of an Arc 
Circle 
The locus generated by rotating a point at a constant distance (R) around a central origin (O) Where; R² = x² + y² see Elliptical Curves 
Clamped End 
A fixed support 
Coefficient of Expansion (α) 
A factor representing the linear relationship between temperature and dimensional change in metals There are coefficients for; where see Thermodynamics 
Coefficient of Friction (μ) 
A factor representing the linear relationship between the contact force of two surfaces and their relative sliding resistance μ = the tangent of the Angle of Repose 
Column 
An elongated body onto which an axial load is applied 
Combined Stress (σₑ) 
Normally interchangeable with equivalent stress When differentiating between two different types of combined stress, CalQlata uses the following specific definitions: see also Stress 
Compressibility Factor 
Defines a gas's ability to deform under compression It is calculated as follows: See Pipe Flow+ (Fig 1) 
Concave 
A surface that deflects inwards from a flat plane 
Convex 
A surface that deflects outwards from a flat plane 
Conductor 
A material that allows free movement of its electrons when exposed to a potential difference This term is relative. You can have a good conductor and a bad conductor. The better the conductor, the easier its electrons flow see also Resistor 
Conic 
A curve generated by a plane cutting through a circular cone The curve is defined by the locus of a point, whose distance from a fixed point (called the focus) is a constant ratio to its distance from a fixed line (called the directrix). This ratio is called the eccentricity (e) If e = 0 the curve is circular The upper cone is a nappe and the lower cone is another nappe 
Corrosion 
Corrosion is the process whereby a metal is degraded and/or its atoms are removed chemically 'Rust' is a special case where oxidisation is the chemical process that occurs in iron via an electrolyte 
Coulomb (C) 
The unit of electrical charge (or work): 1 C = 1 Amp/sec One Coulomb is approximately equal to the charge of 6.24150964505573E+18 electrons The pipeline analogy for Coulomb is the volume of fluid flowing along a pipe see also Voltage 
Coulomb's Law 
The force of attraction or repulsion (F) between two charged points is proportional to the product of their charges (Q₁.Q₂) and inversely proportional to the square of their speration distance multiplied by the relative permittivity (d².ε) of the medium: Coulomb's constant of proportionality (k) changes the above relationship to: Note: the relative permittivity at atomic level is generally regarded as 1.0 
Coulomb's Constant 
CharlesAugustin de Coulomb's constant of proportionality for electrostatic force see also Coulomb's Law 
Covalent Bond 
The sharing of pairs of electrons between atoms, which can only occur between electrons in the valence shell (including subshells) of atoms I.e. there must be an electron and a gap in the valence shell of both atoms for bonding to occur. For Example: Whilst covalent bonds normally occur between nonmetal atoms (carbon, hydrogen, oxygen, nitrogen, etc.), they also occur between some metals and nonmetals, e.g. beryllium and aluminium both form covalent bonds with chloride atoms. 
Creep 
The gradual and continual movement or distortion of an object or substance under load over time. Typical substances susceptible to creep are those will little elasticity such as soils and polymers 
Critical Pressure (cp) 
The pressure at which a gas will change state to a liquid at its critical temperature. E.g.; 
Critical Temperature (ct) 
Gas: The temperature above which a gas cannot be liquefied by pressure alone. E.g; Magnets: The temperature (Curie temperature) above which magnets lose their magnetic properties. E.g; Solids: The temperature above which a solid changes state or undergoes a fundamental change of its properties 
Crucible Furnace 
A Crucible furnace is used to manufacture consistently highquality steel. It is a very hightemperature melting process that isolates the steel from the fire in order to ensure total control over the carbon content. Modern steelmaking methods can achieve almost the same level of quality but much less expensively. 
Crystal (metals) 
A crystal of any metal is a single body (of any size) containing purely its own atoms (i.e. no impurities) all of which are arranged in prisms (trihedron, quadrahedron, pentahedron, hexahedron, heptahedron, etc.) with the same orientation and spacing in a consistent lattice structure, for example: bodycentrecubic, facecentrecubic, hexagonalclosepacked, rhombic, tetrahedral, etc. As a crystal grows, each face of every prism (or cube) in the lattice structure will also form the face of a neighbouring prism (or cube). 
Cubic 
Describes the lattice arrangement of atoms within a metal. The smallest crystal of this metal will contain eight closely packed atoms, each of which are located at each corner of a cube. 
Cubic Expansivity (α") 

Curie Point 
The point at which a material changes to or from being ferromagnetic to paramagnetic or diamagnetic Some examples are provided below: 
Current (I) 
Is the electrical charge across two points with a potential difference (the unit of measurement is the Ampere). It is the flow of electricity whereby one Ampere is equal to one coulomb flowing in one second. The pipeline analogy for current is the rate of volumetric flow of the fluid along a pipe I = V.R 
Cycle 
A 'Process' that returns a heat engine to its original state 
Cycloid (curve) 
A cycloid is a curve generated by a point on the circumference of a circle that is rolled along a flat, straight surface without slipping. see also Trochoid, Epicycloid and Hypocycloid 
Dalton's Law 
The pressure of any gas in a mixture is equal to the pressure it would exert if it occupied the same volume alone at the same temperature. This means that each gas contained in a mixture behaves as though the other gases are not present. The pressure of each gas is called a 'partial pressure'. 
Damage Ratio (Ƞ) 
Also known as 'utilisation' (the reciprocal of safety factor) is a number that describes the likelihood that a mechanical component or material will survive its design life. A value of 'one' predicts that the component will fail on the last cycle of its design life with no safety factor. A number less than one reveals a component that will last longer than its design life whilst a number greater than one shows a component that will fail before the end of its design life 
Damping (vibration) 
The reduction or avoidance of harmonic excitation (resonance). 
Damping Factor 
The ratio of damping (C) to critical damping (Cc): ζ = C ÷ Cc ζ < 1.0 is considered underdamped 
de Broglie Wavelength 
The wavelength of a particle due to its momentum λ = h/p 
Deflagration 
Sudden burst into flames see also Explosion 
Deformation Energy (Uᴰ) 
Energy absorbed/dissipated in the combined deformation of an impacting mass and the impacted system or body Elastic deformation energy: Uᴰ = ½ky² = ½Fy Plastic deformation energy: Uᴰ = Fy {m.a.y} Where: 
Degrees of Freedom 
There are six degrees of freedom; three vectors (or directions) according to the righthand rule (x,y,z) and three rotations (xy,xz,yz) On a ship these six degrees of freedom are known as Surge, Sway, Heave and Yaw, Pitch, Roll respectively 
Delta Iron 
Pure iron (> 1,663 K) with a body centre cubic crystal structure 
Density (ρ) 
The mass per unit volume of a body or substance, measured in kg/m³, lb/in³ or g/cm³. e.g. 1.0 m³ of a substance with a density of 3000 kg/m³ will have a mass of 3000 kg. The ultimate (limiting) density is that of a subatomic particle: see also Specific Gravity and Specific Volume 
Design Life 
The predicted period of time until immediately before a material or mechanical component is no longer expected to comply with its original design specification 
DewPoint 
The combined temperature and pressure at which the liquid in a vapour begins to condense An increase in pressure and/or a reduction in temperature of the vapour will cause this to occur 
Dezincification 
The removal of zinc from an alloy due to corrosion or heat 
Diamagnetism 
The repulsion of a nonmagnetic material from a magnet 
Dirac's Constant (ħ) 
ħ = h ÷ 2π = 1.05457207144921E34 J.s 
Direct Current (DC) 
Direct current Steadystate current (and voltage) that does not vary in cycles (see AC). DC current is normally supplied by battery and used for lowpower applications (<100W) such as mobile phones, computers and handheld tools. DC generators are also used for DC power supply but much less frequently (than for AC power). 
Disorder 
A measure of randomness in the molecules that compirise a system (e.g. gas, liquid, solid, etc.) Randomness, and hence disorder, increases as molecules move further apart and/or move out of alignment, such as in crystaline arrangements, which occurs due to an increase in temperature and/or through decay. 
Distributed Load 
Also known as a line load, is applied (not necessarily equally) to a body along a line (not necessarily straight) and denoted as a load per unit length 
Down Quark 
One of the two types of quark that make the proton and the neutron and forms part of the first generation of matter The down quark is classified as a fermion mᵣ=8.538949767E27g [4.79MeV/c²], Q=⅓e, I_{z}=½ 
Drag Coefficient (Cd) 
A coefficient that represents the resistance between a fluid and a surface over which it is passing and with which it is in contact For example, a theoretically perfectly smooth surface will have no resistance due to drag (zero), however, this scenario is fictitious as there is no such thing as a perfectly smooth surface Relatively smooth surfaces and low profiles will have a low drag coefficient (< 0.7) whilst rougher surfaces and high profiles will exhibit higher drag coefficients (> 0.7) Whilst there are certain circumstances where a drag coefficient can exceed 1.0, it is a rare occurrence 
Draw 
The process of reducing the diameter of a filament (single or individual metal wire) by pulling it through a small die 
Duplex (stainless steel) 
A stainless steel containing approximately equal proportions of Ferrite and Martensite 
Dynamic Amplification Factor (DAF) 
A factor by which a force (or weight) is multiplied in order to account for the dynamic nature of its condition e.g. F = mass x g x DAF 
E = m.c² 
Relativistic momentum Why isn’t E = ½.m.c² ? E² = m².c⁴ + p².c² = m².c⁴ + m².v².c² = [m².c²].c² + [m².v²].c² Therefore at velocities less than that of light: see also Momentum 
Earth (properties) 
Diameter @ poles: 12713.504km The earth's principal constituent materials are: see Earth's Properties and Earth's Atmosphere 
Elastic Moduli 
Describes the two and threedimensional behaviour of materials under elastic deformation and includes: shear, bulk and Young's moduli along with Poisson's ratio 
Elastic Strain 
A material that returns to its predeformation dimensions when stress is released 
Elastic Stress 
A load per unit area that is less than the material's yield stress see also Elastic Strain 
Electric Furnace 
The Electric Furnace is a process for melting steel. It uses high current electricity to melt the steel. It can be combined with the Bessemer Converter and Open Hearth methods by dipping charged electrodes into the melt. This process is capable of very high volume production and good quality control. It is also relatively inexpensive 
Electrode 
An electrical conductor (solid metal) that can transfer ions to or from an electrolyte 
Electrolyte 
A positive or negative electrically charged liquid that conducts electricity through ionisation. Seawater is a predominantly negatively charged electrolyte that will Corrode relatively positively charged metals (e.g. aluminium and zinc) and plate (coat) relatively negatively charged metals (e.g. carbon steel and tin) if immersed together. However, because water molecules are polar (they have both positive and negative probes), immersed steel will corrode in the absence of a donor material (e.g. aluminium or zinc) 
ElectroMotive Force (emf) 
The work done to move electrons by an electrical force (emf) across a material with electrical resistance. Whilst 'emf' and potential difference ('pd') are normally differentiated, they are essentially the same, as are their units of measurement (Volt) 
Electron 
A negatively charged particle that normally orbits the nucleus of an atom 
Electron Affinity 
The energy required to remove an electron from a negative ion 
Electronegativity 
A tendency for collecting electrons These numbers (between 1 and 4), as defined by Pauling, are used to determine the contribution an element will make to an ionic or covalent bond The higher the Electronegativity, the more electrons it will collect 
Electron Shell(s) 
Shells are numbered 1 to 7 (in the periodic table) The numbers of electrons in each shell are as follows: Shell 1: s₂ = 2 In theory; after filling subshell f, shell number 5 should create another subshell but 'f' represents the limiting forcefield 
Electron Volt 
The energy received by the charge of an electron due to the potential difference of 1 Volt see also Elementary Charge Unit 
Element 
A bar, beam, plate or member that constitutes part of a larger structure but which can be analysed individually 
Elementary Charge Unit (e) 
The negative charge (Q) carried by a single electron or the positive charge (+Q) carried by a single proton 1 elementary charge unit [Coulombs] = see UniQon see also Electron Volt 
Elementary Particle 
The fundamental particles of matter. Fermions 
Ellipse 
The circumference of a flat section cut at any angle through a rightcircular cylinder where; x²/a² + y²/b² = 1 see Elliptical Curves 
End Cap (force) 
A longitudinal tensile or compressive force in a pipe wall as a result of a variation in temperature and/or pressure see also Upheaval Buckling 
Energy (U & E) 
Essentially the same as work with the same units Energy sources can be mechanical, electrical, chemical or thermal There are three principle forms of mechanical energy: There are four principle forms of thermodynamic energy: There are a number of atomicnuclear energies, four of which are: 
Enthalpy (H) 
The total energy of a system The units of measurement are J, Btu, W.s, N.m, lbf.ft, etc. see Thermodynamics 
Entropy (S) 
The measure of disorder in a system defined by energy that cannot be converted into work Entropy is only a measure of disorder;it is not a measure of temperature temperature simply affects entropy To explain ... Entropy is the basic level of energy inherent in all molecules that is defined by the following formula: Temperature increases as heat energy is added to the above basic level. The temperature of any substance is defined by its gas constant (Rₐ) and limited by its heat capacity (cv). Therefore, as a substance gains or loses temperature (heat energy) its entropy will be affected due to its molecules moving further apart, thereby increasing disorder. So: Process formulas for a change in entropy such as: see Heat Capacity and Thermodynamics 
Epicycloid (curve) 
An epicycloid is a curve generated by a point on the circumference of a circle that is rolled around the outside of another circle without slipping. Special Case: The path generated by a point on the circumference of a rolling circle with the same radius as the stationary circle will be a 'Cardioid'. see also Cycloid, Trochoid and Hypocycloid 
Epitrochoid (curve) 
see Epicycloid 
Equilateral (triangle) 
A triangle with all three sides of equal length 
Equilibrium 
A state of constancy, stability and balance Equilibrium applies to mechanical, chemical, electrical and thermal systems that may be transferring energy but the exchange is constant, i.e. unchanging 
Equilibrium Diagram 
see also Phase Diagram 
Equivalent Stress (σₑ) 
Normally interchangeable with combined stress When differentiating between two different types of combined stress, CalQlata uses the following specific definitions: see also Stress 
Escape Altitude 
The altitude at which gravitational acceleration of a body (e.g. planet, star, etc.) is equal to the centrifugal acceleration due to the orbital velocity (v²/r) of a satellite holding a constant position over the body This altitude for the earth is 35843425.4809m above sea level. see also Geosynchronous Orbit 
Euclidian Geometry 
A universal method of geometric calculation (developed by the Greek mathematician Euclid 323 BC  285 BC) based upon a few basic rules. 
Eutectic 
A mixture of two metals that are completely soluble in a molten state but completely insoluble in a solid state. As the liquid cools to form a solid, alternate layers of each pure metal will form in the crystal(s) creating a laminated structure (like plywood). 
Eutectoid 
A mixture of two metals in a solid state that are completely soluble at a high temperature but completely insoluble at a lower temperature. As the material cools to form a different lattice structure (e.g. the transition of iron with 0.83% carbon from austenite above 723°C to pearlite below 723°C), alternate layers of each pure metal (or ferrite in steel) will form in the crystal(s) creating a laminated structure (like plywood). 
Exosphere 
Stratum of the earth's atmosphere that constitutes its outer limit (Ionosphere to 1000km) Contains neutrons and protons that have been detached by the sun's electromagnetic radiation Temperature increases exponentially with increasing altitude 
Explosion 
Sudden release of energy, that is usually chemical but it can also be pressure An explosion is always accompanied by an increase in heat and sometimes by deflagration. 
Face Centre Cubic (fcc) 
Describes the lattice arrangement of atoms within a metal. The smallest crystal of this metal will contain fourteen closely packed atoms, eight of which are located at each corner of a cube and one in the middle of each face of the cube. 
Farad 
The unit of electrostatic capacitance that when charged by the potential diference of 1 volt carries a charge of 1 Coulomb 
Faraday's Constant 
The magnitude of electric charge per mole of electrons 
Fatigue 
The deterioration of a material due to repeated stress cycling 
Fatigue Life 
The total number of stress cycles (sum of all stress blocks) that represent the expected life of a material or mechanical component and above which damage or failure will occur 
Fermion 
Any particle that obeys FermiDirac statistics Fermions include subatomic particles; leptons and quarks and compound particles; neutrons and protons Fermions have half integer spin properties: ½, 1½, 2½, 3½, 4½, 5½, etc. see also Pauli's Exclusion Principle 
Ferrite 
Body centre cubic iron, which can absorb up to 0.006% carbon within its crystal structure at room temperature and up to a maximum of 0.03% carbon at 723°C (also called alpha iron) Pure ferrite has the following physical properties: see Carbon Steel 
Ferromagnetism 
The ability of a magnetic material to retain its magnetism 
Filament 
A single very thin wire or cord of any crosssectional shape that normally forms part of a multifilament construction, e.g. a strand see also Wire Rope 
FirePoint 
A temperature above which a substance will give off sufficient vapour to maintain combustion This temperature is usually higher than the FlashPoint for the same substance see also FlashPoint 
Fission 
The splitting of an atomic element into two or more smaller particles (e.g. a helium atom into two hydrogen atoms), which releases energy Fire a neutron at a nucleus. The nucleus will split apart into lighter nuclei (smaller elements), thereby releasing unnecessary Neutrons. These Neutrons will impact other nuclei, splitting them into smaller elements and releasing more Neutrons (ad infinitum), and thereby causing a chain reaction. 
Fixed Support 
A support that prevents all six degrees of freedom 
Flammable 
Having the ability to catch fire under certain conditions see also Inflammable 
FlashPoint 
A temperature above which a vapour from a substance will combust if exposed to a spark or small flame It is usual to define this value on the basis of test using a Cleveland cup or PenskeyMartens apparatus This temperature is usually lower than the FirePoint for the same substance 
Flexural Modulus 
The deformation stress behaviour associated with polymers 
Fluid 

Focal Length 
The distance along the axis of a lens between a principal plane (at its axis) and its nearest focal point. see also Power (of a lens) 
Focal Point 
The theoretical point (F) of intersection between the axis of a Lens and an exiting lightray that entered the lens parallel to its axis at a radial distance of almost zero. The primary focal point occurs at the front of a lens 
Force (F) 
A load applied by an accelerating body (mass) on another body (mass), that may be stationary or in motion, thus changing their states of motion There are a number of specially applied forces, such as: Force = mass multiplied by acceleration (F = m.a) 
Force Centre 
A mass or force maintaining an orbiting body (mass) in its orbit, e.g. the force centre of any solar system is its sun, and the force centre of a bolas is the tension it its tiecord(s). see also Central Force Motion 
Force Coupling Factor 
A universal constant that defines the ratio between gravitational force (Fg) and electrostatic force (F) φ = Fg/F = 4.40742111792333E40 See Rydberg Atom 
Free Cutting Steel 
Free cutting steel is plain carbon steel with good machinability Plain carbon steel with more than 0.2% carbon is relatively difficult to machine because of its hardness and its embedded manganese increases this hardness. Sulphur is added to plain carbon steel to improve machinability, which it does by combining with the manganese to create manganese sulphide. This compound ensures clean chip separation without brittle fracture during machining. 
Free Support 
A support that allows all six degrees of freedom 
Frequency (ƒ) 
The number of times a cyclic event is completed in a given time period. A frequency of a number of cycles each 'second' is measured in 'Hz'. The higher the frequency (i.e. the shorter the wavelength) the greater the energy in the wave The natural frequency (ƒⁿ) of an object is the frequency at which it can regenerate a complete cycle itself (free oscillation) with minimal external assistance and is dependent upon the elasticity and inertia in the system. 
Freeze 

Friction 
Friction is the resistance to relative movement between two surfaces see also Stiction and Coefficient of Friction 
Frustum 
A pyramid truncated by a flat plane normal to its axis 
Fulcrum 
The point about which a lever or moment couple rotates Also called a pivot point 
Fusion 
The conversion of a solid to a liquid, which absorbs energy (the opposite of freeze) Also used to describe the joining of elements (e.g. two hydrogen atoms to make one helium atom), which releases energy 
Galileo's 
Inertia: Every object persists in its state of rest, or uniform motion (in a straight line); unless, it is compelled to change that state, by forces impressed on it (Newton's first law) Falling Objects: The distance traveled by a falling body is directly proportional to the square of the time it takes to fall Uniform motion: d ∝ t Uniform Acceleration: v ∝ t Parabolic Curve: A projectile that with a uniform horizontal and a naturally accelerated vertical motion describes a path which is a semiparabola (i.e. half of a full parabolic curve) Terminal Velocity: A body falling from a very considerable height will reach a velocity that will remain constant due to frictional resistance from the surrounding air (see CalQlata's Fluid Forces calculator) Frame of Reference: Any two observers moving at constant speed and direction with respect to one another will obtain the same results for all mechanical experiments see Laws of Motion 
Galvanic Corrosion 
Describes the form of corrosion whereby a sacrificial metal (anode) will lose material (protons) to another metal (cathode) Whilst this phenomenon normally occurs due to both metals being immersed (or wetted) by a common liquid (an electrolyte) facilitating the electrical transfer of positively charged ions from one to the another, it can occur if both metals are joined by any similarly capable medium. The electrical property responsible for this phenomenon in metals is Electronegativity, which indicates their relative nobility 
Gamma Iron 
Pure iron (> 1,183 K) with a face centre cubic crystal structure holds up to 2% carbon in solution 
Gamma Radiation 
The emission of very shortwave electromagnetic energy from the atom's nucleus Gamma radiation often occurs during the production of alpha or beta radiation λ < 1.0E11m (ʄ > 2.99792459E+19Hz), Q=1.2483E+05eV 
Gas 
A substance in a state whereby all of its atoms (or molecules) repel each other The natural state for a gas is to fill its container, within the constraints of gravitational attraction This state occurs at high relative temperatures for all substances 
Gas Constant (R) 
The energy required to raise the temperature of an ideal gas by one degree Universal (ideal) constant for all gases {per mole}: Specific (mass) gas constant {per unit mass}: Gas constant {for total mass of gas}: see Heat Capacity, Thermodynamics and Steam (properties) 
Gas:Oil Ratio 
The volumetric (e.g. ft³ or m³) ratio of oil to gas at 1 atmosphere and 60°F 
Gauge Boson 
Bosonic particles that act as carriers of the fundamental forces of nature 
General Relativity 
Newtonial physics ... see also Special Relativity 
Generator 
A generator is a motor that acts in reverse Copper wire coils are rotated within the field of magnets. This rotation (which is applied externally) produces an electrical current in the wire coils, which feeds AC or DC electrical power supplies. 
Geosynchronous Orbit 
The altitude where the gravitational acceleration of a planet/star equals the centrifugal acceleration on an orbitting satellite that remains continuously over exactly the same spot on the planet. R = ³√(G.m/ω²) Increased speed at this altitude will result in the centrifugal acceleration being greater than gravitational acceleration causing the satellite to drift out into space. see also Escape Altitude 
Gluon 
A strong forcecarrying gauge boson or messenger particle Gluons are elementary expressions of quark interaction and indirectly involved with the binding of protons and neutrons together in atomic nuclei There are 8 types (or colour) of gluon, any combination of two from the following colours: A gluon is a Gauge Boson m=0g, Ø≈10ˉ¹⁵m, lifetime>10²⁹yrs, Q=0, I_{z}=1 
Golden Ratio 
A universal ratio found in nature and mathematics which was first used by Phidias (500 BC  432 BC; after whom the value is named) Φ1 = 1/Φ 
Grain (crystal) 
A complete single crystal of similar atoms in the form of a naturally occurring lattice structure A grain of any material can also contain atoms of a different type but these atoms must be small enough to fit into the gaps (spaces) within the crystalline lattice structure of the granulated material Grain growth produces in large (coarse) grain structures resulting brittle metals 
Gravitational Acceleration (g) 
Where it is necessary for CalQlata to impose a default value for 'g' in any of its calculators (e.g. UniQon), the value used at sealevel is; 9.80663139027614 m/s² (which happens to be at latitude 45.5° {Milan or Minneapolis}). a) ISO states that; 1lb (force) = 4.448222N (exact) b) ISO also states that; 1lb (mass) = 0.45359327kg (exact) c) The above defaulted value for 'g' appears if you d) CalQlata default's to the above value for consistency between its calculators and this website The imperial equivalent for the above 'exact' value for 'g' is 32.173987500906ft/s² CalQlata's UniQontechnical help includes a facility for calculating an accurate value for 'g' (at your latitude) should you require one. 
Gravitational Constant (G) 
A universal constant that defines the gravitational attraction (force) between two or more bodies G = aₒ.c² / mN = 6.67359232004332E11 m³/kg/s² © G = φ.k.e² / mₑ.mp The Imperial equivalent of which is; see Laws of Motion see also Gravitational Constant 
Gravitational Constant (gc) 
A dimensionless conversion constant for gravitational acceleration used in calculations dependent upon their units 
Gravitational Energy) 
The energy in a mass that attracts other masses towards it E = m.g.R CalQlata refers to the limiting gravitational energy as that in which; 
Gravitational Force (Fg) 
A centripetal force acting between two or more bodies that is a function of their combined mass and the distance(s) between them according to the following relationship: 
Graviton 
Is a hypothetical gravitational force carrying gauge boson It is not yet known if it exists m=0g (at rest), Ø≈0m, lifetime=∞, Q=0, I_{z}=2 
Guided Support 
A support that allows four degrees of freedom; lateral movement in both planes, axial movement and axial twist 
Hadron 
Is a bound state of quarks, which includes protons and neutrons 
Half Life 
The time required for half the radioactive material to decay Example: 
Head (liquids) 
The height of the surface of a liquid above a specified datum 
Heat Capacity 
The quantity of heat energy that can be absorbed by a given mass of substance per degree (temperature) Cp = m.cp The units of measurement are J/K, Btu/°R, W.s/K, N.m/K, lbf.ft/°R, etc. see Heat Capacity 
Heat Energy (Q) 
The quantity of heat (energy) in a system at atmospheric pressure Q = Ṯ.Cp The units of measurement are J, Btu, W.s, N.m, lbf.ft, etc. see Heat Capacity and Thermodynamics 
Heat Transfer Coefficient 
The rate at which heat flows through a material or substance of specified thickness. 
Heat Transfer Rate (q) 
The rate at which heat flows from a material or substance of unit volume. 
Heave (vessels) 
The linear movement of a vessel in the direction of the vertical ('z') axis Whilst this term generally applies to the movement of ships, it is also used to define the movement of any object subject to the same degrees of freedom; e.g. aircraft and spacecraft see RightHand Rule for positive and negative directions of this movement 
Helical Gear 
A gear wheel, with teeth cut into its circumference in the form of a helix, that mates with another helical gear wheel The tooth profile is similar to that of a spur gear tooth The centres of rotation of two mating helical gear wheels are not necessarily parallel 
Henry 
The unit of mutual inductance such that... 
Hexagonal Close Packed (hcp) 
Describes the lattice arrangement of atoms within a metal. The smallest crystal of this metal will contain twelve closely packed atoms, all of which are located at each corner of an hexagonal prism. This is the most closely packed of all the lattice structures. 
Heisenberg's Uncertainty Principle 

Higgs Particle 
The Higgs particle is a very unstable boson with no spin, electric charge or color charge that almost immediately decays into other particles. It is a carrier of the Higgs field, which is supposed to give everything a mass component and without which all particles would simply be energy packets flying about at the speed of light. m≈2.246153801E25g [≈126GeV/c²], I_{z}=0 
Hooke's Law 
States that stress and consequent strain obey a linear relationship and that dimensional recovery is total when the material is relaxed This law applies to any elastically deforming body (e.g. a spring, a steel body, rubber band, etc.) all of which have a unique spring constant ('k') that defines the force needed to deform the body by one unit of length see also Young's modulus 
Hoop Stress 
Primary circumferential stress in a pipe or cylinder 
Hydrocarbons 
Molecules comprising only hydrogen and carbon atoms Predominantly organic fluids (liquids and gases) originating from degraded and compressed animal and/or vegetable matter Includes; glycol, glycerine, benzene, propane, methane, ethylene, toluene, etc. 
Hyperbola 
The perimeter of any vertical plane through two inverted rightcircular cones where; x²/a²  y²/b² = 1 see Elliptical Curves 
HyperEutectoid 
A mixture of two metals that exist above their eutectoid state For example, an hypereutectoid steel is a mixture of pearlite and cementite; i.e. solid iron with > 0.83% carbon below 723°C 
Hypocycloid (curve) 
A hypocycloid is a curve generated by a point on the circumference of a circle that is rolled around the inside of another circle without slipping. Special Cases: see also Trochoid, Epicycloid and Cycloid 
HypoEutectoid 
A mixture of two metals that exist below their eutectoid state For example, an hypoeutectoid steel is a mixture of pearlite and ferrite; i.e. solid iron with < 0.83% carbon below 723°C 
Hypotenuse 
The side opposite the 90° angle of a rightangle triangle 
Hypotrochoid (curve) 
see Hypocycloid 
Hysteresis 
A loop showing a delay in the recovery of one property that varies as a result of varying another. A complete hysteresis loop is one where recovery catches up in each cycle (as shown in diagram). 
Ideal Gas 
A gas, the molecules of which, are of negligible size and do not interact chemically with each other For example: nitrogen, argon, carbon dioxide, oxygen (O₂) and air are all ideal gases Also called a perfect gas 
Impedance (Z) 
Impedance is the total electrical resistance in a conductor Impedance² = Reactance² + Resistance² 
Inductance (L) 
Inductance (the unit of measurement is the 'henry') is the resistance generated by the induced (or 'back') emf (electromotive force), which opposes the applied emf and therefore retards the growth of an AC current Current lags voltage 
Inertia 
A body's resistance to a change in state of motion, which is a function of its mass 
Inertia Coefficient (Ci) 
A coefficient that represents the 'Added Mass' plus the mass of fluid displaced by the body itself Also known as Virtual Mass 
Inflammable 
In its strictest sense this means the inability to catch fire under any conditions, however, it is frequently used as an alternative for 'Flammable' see also Flammable 
Internal Energy (U) 
The energy in a system that has not been supplied from its surroundings In a static system: U = Ṯ.Cv The units of measurement are J, Btu, etc. see Heat Capacity and Thermodynamics 
Involute (curve) 
An involute is the curve generated by unwinding (straightening out) the arc (or circumference) of a curved shape such as a circle. For example: the end of a cotton thread unwound from a reel and pulled tight (straight) will describe a curve of everincreasing radius as the unwound length of thread gets longer. The figure shows the involute of a circle, which can, for example, be represented by the path generated by the end of the a thread as it is unwound from a reel. The circumferencial length of arc ('AO') is equal to the straightened out (unwound and tightened) length 'AP'. The radius of the involute curve at any point is equal to the arc length of the circumference unwound. For example in the figure, the radius of the curve at 'P' is equal to the straight length 'AP', which is also equal to the curved length 'AO'. Involute curves are almost always used for the profile of gear teeth for the following reasons: 
Ion 
The number of orbiting electrons in an atomic element relative to the number of protons in its nucleus A positive Ion has fewer electrons than protons. A negative Ion has more electrons than protons 
Ionic Bond 
Ionic bonding [only] involves the complete transfer of valence electron(s) between metal and nonmetal atoms. The greater the electrical polarity of each atom the greater the strength of the bond. Ionic bonds are generally stronger than covalent bonds. But bonds such as those in diamond (carbon) prove the exception is also true. 
Ionisation Energy 
This term is used to describe the various energies required to isolate and attach subatomic particles, atoms and molecules The term in CalQlata's Elements database refers specifically to the energy(ies) required to remove an electron(s) from an atom 
Ionosphere 
Stratum of the earth's atmosphere that contains only atoms and light ions of nitrogen and oxygen (Mesosphere to 600km) Temperature increases with increasing altitude 
Isentropic 
A process during which no change in entropy occurs see Thermodynamics 
Isobaric 
A process during which there is no change in pressure Isobaric refers only to the pressure properties of a process, it is therefore possible for a process to be isobaric and isochoric and/or isothermal see Thermodynamics 
Isochoric 
A process during which there is no change in volume Isochoric refers only to the volume properties of a process, it is therefore possible for a process to be isochoric and isobaric and/or isothermal see Thermodynamics 
Isosceles (triangle) 
A triangle with two of its sides of equal length and therefore, two equal angles 
Isothermal 
A process during which there is no change in temperature Isothermal refers only to the temperature properties of a process, it is therefore possible for a process to be isothermal and isobaric and/or isochoric see Thermodynamics 
Isotope 
Defined by the number of neutrons, relative to the number of protons, in the nucleus of an atomic element For example: Uranium 238 (U²³⁸) is an Isotope of Uranium (there are also 235, 236, etc. Isotopes of Uranium) but U²³⁸ is the most common 
Isotropic 
A description of material proproperties that do not vary with direction, for example; 
Independent Wire Rope Centre 
A multistranded wire rope in which the core is an individual strand and not a fiber or polymer or single filament 
Jarno Taper 
A conical shaft and mating sleeve for machinepart selfholding applications that optimises assembly load, holding capacity and easy release (without damage). The tapered shaft is normally driven by an EndTang (or Key) or a Longitudinal Key. You can have any size you like, but each taper is described dimensionally as follows, for example: Taper No. 7 Taper No. 12.35 All tapers have a slope of 0.6 inches per foot (2.86419236832929°) The Jarno Taper is almost a direct alternative to the Morse Taper and used for similar applications to the Brown & Sharpe Taper 
Joule 
A measure of energy named after James Prescott Joule, who developed the theory of heat 1 Joule is the amount of energy expended by moving ... 
Kepler's 
1ˢᵗ An orbiting body follows the path of an ellipse 2ⁿᵈ Any two (or more) equal areas of elliptical orbits will be swept by equal periods of time 3ʳᵈ The square of the period of motion is proportional to the cube of the orbital semimajor axis see CalQlata's elliptical curves calculator and Laws of Motion 
Kinetic Energy 
Energy possessed by a moving body Linear: Uᴷ = ½mv² ÷ gc Rotational: Uᴷ = ½Iω² ÷ gc Where: 
Laminar Flow 
A fluid that flows perfectly smoothly generating no disturbance or mixing of adjacent layers 
Lang Lay 
A particular type of helical lay pattern in a wire rope where the filaments are wrapped within each strand in the same helical direction as the strands are wrapped within the wire rope. In a manufactured wire rope, the filaments run at an angle (diagonal) to the long axis of the wire rope (see image). You can have 'right Lang lay' or 'left Lang lay' configurations: Lang lay wire ropes provide excellent wear resistance when used with a sheave (or pulley) due to their smoother (flatter) surface and high bending fatigue resistance but suffer from birdcaging if ill used. They are generally used for specialist applications where repeated bending and wear resistance is an issue but structural stability is not. see also Regular Lay 
Latent Heat 
The heat required to change a substance from one state to another with no resultant change in temperature For example; latent heat of vaporisation is the heat required to convert a liquid into a gas 
Lateral Stress 
Primary stress at rightangles to the axis of a component 
Latitude (Lat) 
The horizontal gridlines that divide the surface of the earth into 180 unequal spherical segment zones (slices) The vertical distance between each gridline at the equator = 111319.8922m 
Lattice Structure 
General term encompassing various specialised patterned structures of metal atoms in a crystal in their lowest energy state. see also Body Centre Cubic, Face Centre Cubic, Hexagonal Close Packed and TetraHedra 
Latus Rectum 
The width of an elliptical curve (2p) at its focus (F) Also called the parameter of the curve 
Lens 
A device that converges electromagnetic waves (radiation) at a focal point# A lens may converge or diverge the radiation dependent upon the path of the lightray in relation to the convex or concave nature of the lens faces. The front of the lens is the face at which the radiation enters the lens # The generally accepted position of the focal point of a spherical lens is theoretical (see Focal Length). 
Lepton 
A family of subatomic particles within the fermion group There are 6 leptons (I_{z} isospin quantum number); 
Lift Coefficient (Cʟ) 
A coefficient used to define the lateral force (or lift) developed in a beam or structure as a result of a fluid passing along or across it at 90° to the direction of lift This coefficient varies between 0 and 4, and is dependent upon the KeuleganCarpenter number, 
Light (visible) 
That which is visible to mankind Ranges from: ultraviolet > infrared The speed of light (c) in freespace (a vacuum) is defined as: 
Linear Expansivity (α) 

Liquid 
A substance in a state whereby attraction due to gravity is greater than attraction between the atoms (or molecules) A liquid will always occupy the lowest possible space in a container This state occurs between the gas and solid states for all substances 
Locus 
The path generated by a point following a mathematical equation. for example: the locus of a point 'x,y' following the equation: 
Logarithm 
The logarithm value of a number see Logs and Trigtechnical help 
Longitude (Lon) 
The vertical (pole to pole) gridlines that divide the surface of the earth into 360 equal spherical wedges (1°) The horizontal distance between each gridline at the equator = 111319.8922m 
Longitudinal Stress 
Primary stress parallel with the axis of a component 
Magnetic Constant 
The permeability of free space (a vacuum) This value was fixed by convention and is therefore considered to be exact. 
Magnetism 
The attraction between metals due to electron spin and alignment Some magnetic materials are listed below: 
Magnetic Quantum Number (m) 
The third in a set of quantum numbers that describes the energy level of the electron The magnetic quantum number of an electron can be a positive or negative integer: i.e. 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 5, etc. The magnetic quantum number must be different for each electron in the same shell with the same azimuthal and spin quantum numbers 
Marageing 
An ageing heat treatment procedure used to harden, strengthen & toughen certain alloys (most alloys do not respond to this process). The age hardening process is performed as follows: A marageing alloy can therefore be machined or formed easily and subsequently strengthened with age over a very short period. The word originates from 'mar' for martensite (the steel structure) and 'ageing' to describe the process see Stainless Steels 
Martensite 
Super saturated austenite created by rapid cooling (quenching). Carbon exists in sharp clumps between the grains of iron making it hard and brittle. Tempering after quenching allows the excess carbon to form smaller spheroids and redistribute itself reducing hardness and brittleness 
Mass 
The quantity of matter in a body equivalent to its inertia and is measured in kg, lbs, etc. The mass of a body is equal to: This property for any given body remains the same irrespective of liquifaction, dissection and location (in the iniverse) 
Maximum Metal Condition 
The condition of at least two assembled components that when machined within required dimensional tolerances results in the removal of the least material Whilst convention does not differentiate between minimum and maximum metal conditions when using the symbol 'MMC', CalQlata always uses MMC+ for this condition see Symbols 
Mechanical Equivalent of Heat (J) 
A conversion factor for heat energy and work energy Calculations using metric units; Calculations using Imperial units; 
Median 
A straight line that joins a vertex with the centre of the opposite side 
Member 
A longitudinal component such as a structural element, rod, bar or beam 
Membrane 
A large plate or sheet of relatively thin wall than can comprise any natural or manufactured material 
Membrane Stress 
Tensile or bending stress in the flat plane of a membrane see also Membrane 
Meson 
A pair of subatomic particles comprising one quark and one antiquark (part of the Hadron particle family) 
Mesosphere 
The ceiling for 99.95% of nitrogen, the earth's most abundant atmospheric gas (Stratosphere to 80km) Stratum of the earth's atmosphere that comprises the ceiling of normal atmospheric gases (see Ionosphere) Temperature reduces with increasing altitude 
Metacentre 
The point at which a vertical line passing through the centre of buoyancy of a slightly tilted vessel meets a line through its centre of gravity (see image). Metacentric height: The vessel is stable if the metacentre is above the centre of gravity and unstable if it is below. A vessel's stability is defined by the metacentric height. 
Metallic Bonds 
Metallic elements lose electrons freely generating a cloud or sea of electrons in which positively charged metal atoms (cations) are held together. Metallic bonds tend to be the easiest to form and also the easiest to break, making metals the most versatile of the elements. 
Microwaves 
Long wave electromagnetic radiation that falls between infrared light and radiowaves Ranges from: 
Minimum Metal Condition 
The condition of at least two assembled components that when machined within required dimensional tolerances results in the removal of the most material Whilst convention does not differentiate between minimum and maximum metal conditions when using the symbol 'MMC', CalQlata always uses MMC for this condition 
Mode 
The beam length deflected between two nodes see also Amplitude 
Molarity 

Mole 
The mass of a material that contains Avogadro's number (6.0221415E+023) of units (e.g. atoms, molecules, etc.) For example; 
Molecular Density 
The mass density (g/m³) of a substance divided by its relative atomic mass (g/mole) ρᴹ = ρ ÷ RAM (moles/m³) see also Molecular Weight 
Molecular Weight 
The sum of relative atomic masses comprising a molecule This calculation can also be applied to a mixure of gases (i.e. not a molecule) in order to specify its molecular weight 
Molecule 
The smallest part of a substance that still exhibits the chemical properties of the substance A molecule is at least two electrically charged ions joined together by sharing electrons/valences/energy in order to reduce their collective electrical charge 
Moment (M) 
An applied load or centre of area a given distance from a datum Also known as torque or rotational moment or bending moment or area moment 
Moment Couple 
Two parallel opposing forces applied a specified distance from each other 
Moment of Inertia (I) 
Also (incorrectly) known as second moment of area, describes the mass of a body about its neutral axis That is, the sum of all the particle masses multiplied by the square of their distances from the neutral axis (radii of gyration) I = A.ɍ² 
Moment of Inertia (I̊) 
Inertia possessed by a body rotating about a central axis I̊ = m.ɍ² 
Momentum (p) 
A quantity of straightline motion of a body equal to its mass multiplied by its velocity; Also a measure of force (m.a) multiplied by its period of application (in seconds); 
Monoclinic 
The arrangement of atoms within the shape of a single metal crystal. This crystal shape is a single atom located as close as possible to its neighbour. 
Morse Taper 
A conical shaft and mating sleeve for machinepart selfholding applications that optimises assembly load, holding capacity and easy release (without damage). The tapered shaft is normally driven by an EndTang (or Key) or a Longitudinal Key. Different size numbers (0 to 7) relate to different engaged lengths (115/16" to 91/2") Morse's nominal included angle is 2.86419236832929° The optimum angle for a coefficient of friction of 0.8 for clean, dry, ground, carbon steel surfaces is 2.9745503204919° The Morse Taper is a direct alternative to the Jarno Taper and used for similar applications to the Brown & Sharpe Taper 
Most Damaging StressBlock 
The stressblock that lies closest to the SN curve, within a group of stressblocks that together constitute the fatigue life of a material or mechanical component 
Motor 
A motor is a generator that acts in reverse (see MotAtors). Copper wire coils are rotated within the field of magnets. A current applied to the wire coils induces relative rotation of the magnets. This rotation of a central shaft or outer body is used to do physical work. 
Muon 
An elementary particle similar to the electron (also with a negative electric charge) but much heavier A muon is classified as a lepton m=1.884273466E25g [105.7MeV/c²], lifetime=2.2μs 
Natural Frequency (ƒⁿ) 
see Frequency 
Natural Period 
see Frequency 
Nappe (conic) 
One of two sheets on either side of the vertex forming a cone 
Natural Logarithm 
The logarithm value of a number, the base of which is 2.71828182845905 see Logs & Trigtechnical help see also Logarithm 
Necking 
The reduction in crosssectional area of a metal object exposed to a tensile stress greater than UTS but less than breaking stress 
Neutral Axis 
The plane through a bending body in which no tension or compression occurs Note: tension occurs in the material on convex side of the neutral axis and compression occurs in the material on concave side 
Neutrino 
An elementary particle with minuscule but nonzero mass that often travels close to the speed of light, that lacks an electric charge and is able to pass through ordinary matter almost undisturbed and are thus extremely difficult to detect A neutrino is classified as a lepton Neutrinos are created as a result of certain types of radioactive decay or nuclear reactions such as those that take place in the Sun, in nuclear reactors, or when cosmic rays hit atoms. There are three types, or "flavours", of neutrinos: electron neutrinos, muon neutrinos and tauon neutrinos; each type also has an antimatter partner, called an antineutrino. Interactions involving neutrinos are generally mediated by the weak force 
Neutron 
An electrically neutral particle in the nucleus of an atom that contains 1 up quark and 2 down quarks (along with other elementary particles e.g. bosons, gluons, etc.) m=1.6475621480E27kg [924.2146756MeV/c²], 
Newton's Atom © 
Newton's atomic values are calculated below: see Laws of Motion 
Newton's 
1ˢᵗ Every mass retains its momentum (including rest) until a force acts upon it (Galileo's law of inertia) 2ⁿᵈ A change in momentum is proportional to, and acts in the direction of, the applied force 3ʳᵈ To every action there is an equal and opposite reaction see Laws of Motion 
Newton's Mass 
1m³ of subatomic particle matter mN = aₒ.c² / G = 7.12660796350452E+16 kg see Laws of Motion 
Nobility 
Describes the chemical stability of a metal. The more noble a metal (e.g. gold, silver, platinum, etc.) the less chemically active it is. The least noble metals, which include caesium, sodium and magnesium are all highly reactive. A noble metal is electrically positive; i.e. it has a high affinity for electrons (see electronegativity). As a rule, the higher the electronegativity of a metal, the more noble it is. Therefore, whilst electronegativity cannot be used as a measure of nobility it may be used as a guide. 
Nodal Points 
Two points on the axis of a Lens such that an entering ray of light would theoretically project through to one nodal point (ignoring refraction) and appear to exit the lens from the other nodal point, parallel to the entering ray. The angle at which a such a lightray must enter the lens varies with its radial distance from the lens axis and only occurs at radii close to it. The primary nodal point refers to the point at the front of the lens As the radial distance (from the lens axis) of the entering lightray tends towards zero, the nodal point (primary or secondary) of a lens will coincide with the associated principal point if the refractive index of the environments are identical both sides of the lens. 
Node 
The points of intersection at each end of a mode 
Normal 
'Normal to' is an expression used to describe the relationship of one direction being at right angles to another 
Normalise 
To normalise a steel alloy is to optimise its strength by heat treatment without making the material hard (brittle). Carbon steel is normalised by heating it above 723°C, holding it there to allow all the material to transform to austenite and allowing it to cool naturally in still air, i.e. more quickly than annealing. 
Oblique (triangle) 
A triangle in which none of the angles equal 90° 
Oblong 
A threedimensional, sixsided figure, each side of which is 90° to its adjacent sides see also Rectangle 
Obtuse (angle) 
An angle between 90° and 180° 
Open Hearth 
The Open Hearth is a process for making steel (it is also called the SiemensMartin process). It directs the waste heat given off by the furnace through an open firebrick lining, heating the brickwork to a very high temperature. The same pathway is also used for introducing preheated air into the furnace significantly increasing the melt temperature. This process is gradually replacing the Bessemer Converter. 
Orbit 
A curved (e.g. elliptical) path generated by a body travelling around a central point that is maintained by equal and opposite centripetal and centrifugal forces Fᵖ = m.g = ½.m.v² / r 
Order 
see Disorder 
Overpressure 
A pressure higher than ambient It is normally measured in multiples of unit ambient pressure such as bar or atmospheres, e.g... 
Ozone 
Oxygen molecules (O₂) are split apart by the sun's ultraviolet light radiation and the two resultant oxygen atoms then bond to other oxygen molecules to produce ozone (O₃). Ozone is unstable and converts back to oxygen molecules as it falls into the troposphere where it reacts with other gases. see Ozone Layer for an explanation of the 'hole'. 
Pappus theorum 
The calculation of volumes by rotating an area about a central axis E.g. V = 2πRA 
Parabola 
The perimeter of any plane cut through a rightcircular cone parallel to its slope where; y² = 2.p.x see Elliptical Curves 
Parallelepiped 
Any threedimensional figure with six faces, four of which are dimensionally equal and parallel and the two ends are also parallel and dimensionally equal. Also described as a three dimensional rectangle of constant thickness. A special Parallelepiped is a cube where all 6 faces are dimensionally equal. 
Parallel Lay 
All strands are wrapped parallel to each other, i.e. in the same helical direction 
Paramagnetism 
The attraction of a nonmagnetic material towards a magnet 
Paraxial 
A ray of light travelling towards the front face of a lens very close to its axis and parallel to it. 
Partial Pressure 
The pressure of each gas occupying a space or container in a mixture of fluids see Partial Pressuretechnical help 
Particle 
The smallest constituent part (atom or molecule) of a substance that possesses the same properties as the substance in bulk 
Pauli's Exclusion Principle 
Only one fermion can occupy a quantum state at a given time 
Pearlite 
Alternate layers of cementite and ferrite generated as austenite containing 0.83% carbon cools below 723°C Pearlite contains the same amount of carbon as the maximum carbon carrying capacity austenite (0.83%) 
Perigee 
The nearest point an orbiting body gets to its attracting mass Whilst this term can also be used instead of Perihelion (i.e. it means the same thing), it is normally used to describe the point at which the distance between earth and its orbiting moon is smallest a = half the width of the elipse 
Perihelion 
The nearest point an orbiting body gets to its attracting mass Whilst this term can also be used instead of Perigee (i.e. it means the same thing), it is normally used to describe the point at which the distance between sun and its orbiting planet is smallest a = half the width of the elipse 
Permeability 
The ratio of magnetic flux density in a medium to the magnetising force producing it. The permeability of free space (i.e. in a vacuum) is the Magnetic Constant 
Permittivity 
The ratio of electric displacement in a medium to electric field intensity producing it. The permittivity of free space (i.e. a vacuum): Because the speed of light in a vacuum and the magnetic constant are both considered to be exact values, this too is considered to be an exact value. 
Perpendicular 
At 'a right angle' or '90°' or 'normal' to a line or surface 
Phase Angle (electrical) 
The angle of shift between the alternating current and the voltage in an AC power supply. As the current in an inductive AC power supply will peak after the voltage, it is said that the current 'lags' the voltage. As the current in a capacitive AC power supply will peak before the voltage, it is said that the current 'leads' the voltage. If there is only inductive or capacitive resistance in an AC power supply, i.e. there is zero resistance in the conductor, the phase angle will be 90°. If there is no inductive or capacitive resistance in an AC power supply the phase angle will be 0°. Electrical resistance in the conductor will shift the phase angle between 0° and 90°. The Arccosine of this 'Phase Angle' is the Power Factor of the supply. see also Apparent Power and True Power 
Phase Diagram 
An equibrium diagram of an alloy metal that defines the natural crystal structure of specific alloy compositions at specific temperatures. see Copper Alloys, Metal Properties and Carbon Steels 
Photon 
An elementary particle that emits electromagnetic radiation (light) equal to Planck's constant multiplied by its frequency A photon is a Gauge Boson m=0g, Ø≈0m, lifetime<10¹⁸yrs, Q=0, I_{z}=1 
pi (π) 
The ratio between a circle's circumference and its diameter π is an infinitely long number that can be calculated from the series formula: π² = 6/1² + 6/2² + 6/3² + 6/4² + ..... CalQlata uses the value of 3.14159265358979 in all its calculators. 
Pinned Support 
A simple support on a beam 
Pipe 
An enlosed cylinder of any diameter or length Thinwall pipe (general): t < R÷10 
Pitch (vessels) 
The rotational movement of a vessel about the lateral ('y') axis Whilst this term generally applies to the movement of ships, it is also used to define the movement of any object subject to the same degrees of freedom; e.g. aircraft and spacecraft see RightHand Rule for positive and negative directions of this movement 
Planck's Constant (h) 
Planck's law states that the energy of an electromagnetic wave is confined to indivisible packets (quanta) each of which has to be radiated or absorbed as a whole and the magnitude of this energy is proproportional to its frequency. If E is the energy (J) and ƒ is the frequency of the electromagnetic radiation (/s) then: Planck's values are calculated below: 
Plastic Strain 
A material that does not return to its predeformation dimensions when stress is released 
Plow Steel 
A high quality, high strength carbon steel (0.5% to 0.95%) used to manufacture 'Bead Wire' 
Point Load 
An applied force that is concentrated at a single point 
Poisson's Ratio (v) 
The relationship between axial stress and the lateral deformation when applied to a body that obeys Hooke's Law; Poisson's ratio varies in magnitude between 0 for a totally brittle body (no deformation whatsoever) and 0.5 for a perfect elastomer (same deformation in all three directions). 0.3 is normally used for carbon steel 
Polar 
The directional definition of a vector using its angular relationship to 2D (α,r) or 3D (α,β,r) axes see also Cartesian CoOrdinates and Vector 
Polar Moment of Inertia (J) 
Describes the structural strength of a crosssectional area, or a numerical representation of its resistance to torsional deformation The polar moment of inertia of any shape is the sum of any two second moments of area (of the same shape) at 90° to each other 
Polygon 
A 2D shape with three or more sides A Regular polygon has equal sides and an irregular polygon has unequal sides 
Polytropic 
A process in which the relationship between pressure, volume and ratio of specific heats of an ideal gas in a system remain constant and can be defined thus: p.Vn = K Where: see Thermodynamics 
Positron 
A positive electron of the same mass and electrical charge (but opposite sign) as an electron Positrons are produced in the decay of radioisotopes and Xrays of energy greater than 1MeV 
PotentialDifference (PD) 
The electrical difference between two discrete points generated by an electromotive force The unit of measurement is a Volt which equals one Joule of work done by one coulomb moving between them 
Potential Energy 
The energy stored in a system or body It could be stored in a compressed (or stretched) spring: Where: 
PotentialHydrogen 
Potential Hydrogen (sometimes referred to as the 'power of hydrogen') defines the positive hydrogen ion activity in a solution pH can be calculated using the following formula: 
Power 
Work carried out over a given period of time or the rate of doing work The faster work is done, the more power is expended The units of measurement are; Btu/h, W, J/s, cal/min, N.m/s, lbf.ft/min etc. 
Power 
The reciprocal of the focal length (ƒ) of a lens 
Power Factor (electrical) 
The factor applied to the Apparent Power of an alternating circuit in order to convert it into True Power It is calculated thus: p.f. = Resistance ÷ Impedance and is the cosine of the Phase Angle between the alternating current and the alternating voltage. 
Pressure Vessel 
An enclosure of any shape that will contain or resist a fluid under pressure without leakage Thinwall vessel: t < Ø÷10 
Pressure Welding 
Press two or more metals together with sufficient presssure to cause metal fusion between them. 
Primary Stress 
The three unidirectional tensile stresses oriented along the 3D axes (see RightHand Rule) of a mechanical component 
Principal Planes 
The curved planes that trace the principal points of lightrays entering a lens parallel to its axis. The primary principal plane refers to the plane at the front of the lens 
Principal Points 
The theoretical points of intersection of lightray projections after entering and before exiting a lens. The primary principal points refers to those at the front of the lens see also Principal Planes and Nodal Points 
Principal Quantum Number (n) 
The first in a set of numbers that uniquely describes the quantum state of an electron The principal quantum number of an electron can only be a positive integer and identifies the shell number it occupies: All other electrons in the same shell will have the same principal quantum number but at least one of its other quantum numbers must be different 
Principal Stress 
A primary stress reoriented (in space) and altered in magnitude as a result of simultaneous shear stresses 
Prism 
A longitudinal body with sides of equal width and constant crosssection. The term for a prism usually ends with '....hedron'. For example: 
Process 
Any alteration in the energy of a system Any change in the physical properties of a system will require a change in its energy, either by addition or removal Reversible Process: Irreversible Process: 
Prograde 
The same direction of rotation as the spin (rotation) of a force centre For example, the sun in our solar system spins in a clockwise direction looking down on top of it see also Sidereal and Retrograde 
Proton 
A positively charged particle in the nucleus of an atom that contains 2 up quarks and 1 down quarks (along with other elementary particles e.g. Bosons, Gluons, etc.) m=1.67262163783E27kg [938.27201984MeV/c²], 
Pyramid 
A regular or irregular threedimensional prism or cone with a pointed cap see also Frustum 
Quadrangle 
An irregularly shaped four sided figure 
Quadrilateral 
A regularly shaped four sided figure CalQlata consider all quadrilaterals to be foursided figures with all internal angles equal to 90° 
Quantum Number 
One of a set of numbers that uniquely describe the quantum state of an electron 
Quark 
The family of subatomic particles within the fermion group that constitute the constituents of matter Quarks combine to form composite particles called hadrons, the most wellknown of which are protons and neutrons 
Quench 
The rapid cooling of a heated steel alloy to lock in an unnatural crystal structure to harden and strengthen it. 
Radial 
At rightangles to a central axis 
Radial Stress 
Primary stress at rightangles to (outofplane with) both longitudinal and lateral (or hoop) stresses 
Radian 
An angle expressed in terms of π π radians = 180° 
Radiation (r) 
The emittance of energy from a source, the intensity of which declines at the square of the distance from the source in the absence of an absorption resource. 1 Roentgen corresponds to the production of CalQlata has discovered a radiation constant that it has yet to explain: 
Radioactivity 
The product of changing one isotope into another isotope 
Radio Waves 
Very longwave electromagnetic radiation used for the transmission of sound λ > 0.1m (ʄ < 2.99792459E+08Hz) 
Radius of Gyration (ɍ) 
The distance from an axis of rotation to the centre of area (or mass) ɍ = √(I/A) and ɍ = √(I/m) 
Ratio of Specific Heats 
γ = cp ÷ cv monatomic gases (i.e. gases comprising one element): γ ≈ 1.67 diatomic gases (i.e. gases comprising two elements): γ ≈ 1.4 polyatomic gases (i.e. gases comprising more than two elements): 1.0 < γ < 1.4 see also Specific Heat(s) 
Reactance (electrical) 
Reactance ('X') of inductance ('L') or capacitance ('C') is their resistance equivalent in an AC current. where: ƒ = frequency 
Recrystallisation 
The movement of atoms in a metal lattice structure towards a low energy position. After cold working or heat treatment, a residual stress is generated in a metal by atoms having been forced away from their natural position within the lattice structure. 
Rectangle 
A twodimensional, foursided figure, each side of which is 90° to its adjacent sides see also Oblong 
Refractive Index 
The ratio of the phase velocity of electromagnetic radiation in a vacuum and its phase velocity in a medium For example: see also Snell's Law 
Refraction 
The bending of light (or any electromagnetic wave) by altering its velocity; e,g, as it passes between media of different densities. see also Refractive Index 
Regular Lay 
A particular type of helical lay pattern in a wire rope where the filaments are wrapped within each strand in the opposite helical direction as the strands are wrapped within the wire rope. In a manufactured wire rope, the filaments run parallel with the long axis of the wire rope (see image). You can have 'right lay' or 'left lay' configurations: Whilst these wire ropes provide less wear resistance than 'Lang lay' constructions due to their undulating (peaky) surface and lower bending fatigue resistance, the structure is much more stable and resistant to abuse. Regular lay wire ropes are generally used for all nonspecialist applications. see also Lang Lay 
Relative Atomic Mass 
The mass number of the most stable isotope of an element For example, if Iron (Fe), which has an atomic number of 26, had the same number of protons and neutrons, its RAM would be 52 yet its actual value is 55.847. This means that in its most stable condition Iron's atoms contain more neutrons that protons and that this excess varies in any bulk of its material. 
Resistance (R) 
The static resistance (the unit of measurement is the Ohm) in a conductor due to its material resistivity, its crosssectional area, its length and its temperature. The pipeline analogy for resistance is an internal restriction such as a helical vane or venturi both of which restrict flow but provide work and generates the pressure drop across the inlet and outlet of the pipe. 
Resistor 
A material that prevents movement of its electrons when exposed to a potential difference This term is relative (see Conductor). You can have a good resistor and a bad resistor. The better the resistor, the harder it is for its electrons to flow 
Resonance 
A vibration that occurs in a sprung system at or close to its natural frequency during which deflections are amplified 
Response Amplitude (RA) 
The amount of movement in a vessel at sea (linear and rotary) generated by a passing hydrodynamic wave in six degrees of freedom 
Response Amplitude Operator (RAO) 
A factor that must be multiplied by a wave height or slope (wave or water) in order to define a resposnse amplitude Also called a 'transfer function', which refers to the transfer of motion in a specified wave to the motion of the body (e.g. ship) 
Rest Mass 
The mass of a body immediately prior to annihilation at lightspeed as originally defined by Henri Poincaré 
Retrograde 
The opposte direction of rotation as the spin (rotation) of a force centre For example, the sun in our solar system spins in a clockwise direction looking down on top of it 
Rhombic 
Describes the lattice arrangement of atoms within a metal. The smallest crystal of this metal will contain eight closely packed atoms, each of which are located at each corner of a cube that has slipped to form a rhomboid prism. 
RightAngle 
An angle of exactly 90° 
RightHand Rule 
The thumb, index and middle fingers of the right hand are projected at 90° to each other in three dimensions, where the index finger represents the xaxis (Surge), the middle finger represents the yaxis (Sway) and the thumb represents the zaxis (Heave) This definition also refers to the direction of rotational twist about the vector axes; the thumb of the right hand is projected in the direction of the axes defined above and the four fingers naturally curled in towards the palm of the hand. The positive direction of rotation {xy(Yaw), xz(Pitch), yz(Roll} are in the direction of the four fingers 
RightAngle Triangle 
A triangle with one of its angles at exactly 90° 
Roentgen [Röntgen] 
The unit of radiation exposure, dedicated to the discoverer of xrays (Wilhelm C Röntgen). Also described as the charge per unit mass (of air), equal to 2.58E04 C/kg, generated by ionisation from x or γradiation 
Roll (vessels) 
The rotational movement of a vessel about the longitudinal ('x') axis Whilst this term generally applies to the movement of ships, it is also used to define the movement of any object subject to the same degrees of freedom; e.g. aircraft and spacecraft see RightHand Rule for positive and negative directions of this movement 
Rydberg Formula 
Johannes Rydberg developed his formula to calculate the wavelength of a photon that would be emitted when an electron drops from a high initial energy state (shell nᵒ: n₁) to a low final energy state (shell nᵒ: n₂), which can be calculated thus: Rydberg's universal constants for the limiting conditions are provided below: Maximum wave number: Electron energy at ground state: Where: Nils Bohr developed alternative values for R∞ and Rᵧ based upon 
Safety Factor 
The proportion of additional stress (or use) that can be applied to a material (or component) before it fails. For example: if you design a component to experience less than or equal to 200 N/m² of stress and the material from which it has been manufactured has a minimum specified yield stress of 400 N/m², the component has a safety factor of 2 Safety factor is the inverse of utilisation 
Satellite 
A mass orbiting a force centre under the influence of gravitational force. For example: 
Saturation 
The ability of a fluid to hold another substance (gas, liquid or solid) in suspension that varies with pressure and temperature High temperatures low pressures raise the saturation level 
Scalar 
A quantity (magnitude) that has no direction, such as; see also Vector 
Schwartzschild 
Karl Schwartzschild's formula to determine the radius of a mass that would prevent the escape of photons from its surface: Schwartzschild derived his formula from Newton's formula for escape velocity: v² = 2.G.m/R 
Seafastening 
Welds, padeyes, lugs and other deck attachment facilities used to fix a mass to any part of a ship or vessel in order to prevent unwanted movement whilst in transit at sea 
Seastate 
The properties of a sequence of following waves defining representative conditions used for equipment design and/or operational conditions. Seastates are usually compiled from actual data collected from anchored 'buoys' installed in various regions around the world and subsequently sorted seasonally, monthly or daily. Representative seastates are used for operational, design (e.g. fatigue calculations), extreme, etc. wave sequences for specified weather windows. 
Second Moment of Area (I) 
Describes the structural strength of a crosssectional area, or a numerical representation of its resistance to bending deformation see also Moment of Inertia and Polar Moment of Inertia 
Section Modulus (Z) 
Describes the ratio of the second moment of area to the distance from the neutral axis of the stressed plane (I/y) 
Sector 
A shape enclosed by two radii and an arc of the same circle 
Segment 

SelfHolding 
When referring to Tapers (Morse, Jarno, Brown & Sharpe, etc.), "Selfholding" describes a condition whereby the assembly (insertion) force is the same as the disassembly (extraction) force and the coefficient of friction between tapered shaft and mating sleeve materials holds them together during use. 
Shear Force 
Equal and opposite forces induced in a material or substance immediately adjacent to each other, the physical manifestation of which is to cut or tear the material, e.g. as in a pair of scissors. 
Shear Modulus (G) 
Also known as modulus of Rigidity, is the relationship between shear stress and angular deformation for materials that obey Hooke's law 
Shear Stress 
Stress induced in a material or substance due to a shear force 
Sidreal 
The actual rotation of a body, e.g. a planet, with respect to a fixed point in space This is not the same as the rotation of an orbiting body with respect to its force centre see also Prograde and Retrograde 
Simple Support 
A support that prevents only one degree of freedom, which is at rightangles to the load 
Simpson's Rule 
An algebraic solution for integrals that are dificult or impossible to solve by integration 
Sinter 
The coalescing (conglomeration) of solid particles using heat but without actually melting (liquifying) the material. 
Sinusoidal 
A continuous curve with the same x,y relationship as the Sine of an angle 
Slag 
The unwanted (remnant) material left over after extracting a material from an ore. Slag contains commercially valueless material and an amalgamation flux. 
Slugging 
The thickening or solidification of a heavy liquid in a pipe or constricted passage that prevents freeflow conditions. 
Smelt 
The extraction of a metal from an ore by melting. During melting, the ore will seperate into two layers: a lower layer of molten metal and an upper layer of slag. 
SN Curve 
The graphical representation (normally a straightline Log_{10}Log_{10} plot) of maximum allowable stress range plotted against the maximum possible number of cycles (for this stress range), above which, damage to the material or mechanical component is expected (SN = stress number, i.e. the number of stress cycles) 
Snell's Law 
Willebrord Snellius: Dutch Proffessor of mathematics at the University of Leiden Snell's law (1621) states that after passing from one medium of refractive index 'n₁' into a medium of refractive index 'n₂' a ray of light will refract according to the following relationship: 
Solid 
A substance in a state where attraction between all of its atoms (or molecules) is greater than gravitational attraction This state occurs at low relative temperatures for all substances 
Solubility 
The ability of one substance (the solute) to dissolve onto another substance (the solvent) This ability may be measured in terms of moles per cube (e.g. moles/cm³) 
Spar 
A principal structural member of an aircraft wing or aerofoil 
Special Relativity 
Newtonial physics ... see also General Relativity 
Specific Enthalpy (h) 
The enthalpy per unit mass of a system h = u + Rₐ.Ṯ The units of measurement are J/g, Btu/lb, etc. see Heat Capacity 
Specific Entropy (s) 
The entropy per unit mass of a system s = KB.ln(N) = cp.ln(Ṯ) {per molecule} The units of measurement are J/K/mol or J/K/g, Btu/°R/lbmol or Btu/°R/lb, etc. see Heat Capacity and Thermodynamics 
Specific Gravity (SG) 
Also called 'Relative density', is the density of a liquid or a solid relative to pure water (1000 kg/m³). For example, the SG of steel is 7.85 (7850 kg/m³ divided by 1000 kg/m³) The specific gravity of a gas is quoted relative to the density of air (1.297 kg/m³). For example, the SG of helium is 0.1365 (0.177 kg/m³ ÷ 1.297 kg/m³) 
Specific Heat(s) 
Two specific heat capacities are used in thermodynamic calculations, dependent upon the process (constant pressure or constant volume): cp is the specific heat capacity of a gas that is heated and allowed to expand whilst maintaining at constant pressure cv is the specific heat capacity of a gas that is heated in an unchanging volume but where pressure is allowed to vary see also Heat Capacity and Ratio of Specific Heats 
Specific Heat Capacity (cp & cv) 
The quantity of heat energy that can be absorbed by a specific substance per unit mass, which varies with temperature The units of measurement are J/g/K, W.s/g/K, BTu/lb/R, etc. see also Specific Heat(s) and Heat Capacity 
Specific Internal Energy (u) 
The internal energy per unit mass of a system u = Ṯ.cv The units of measurement are J/kg, Btu/lb, etc. see Thermodynamics 
Specific Volume 
Volume per unit mass, or... 
Specified Minimum Yield Stress (SMYS) 
The minimum yield strength (maximum allowable yield stress) for a material as specified by a recognised authority 
Spheroidising 
The balling up of the cementite in pearlite during the annealing process 
Spin Quantum Number (s) 
The fourth in a set of quantum numbers that describes the spin direction of the electron The spin quantum number of an electron can be a positive or negative half integer: i.e. ½ or +½ The spin quantum number must be different for each electron in the same shell with the same azimuthal and magnetic quantum numbers 
Spring Coefficient (k) 
The proportional relationship between force and movement for an elastic material or a spring Also referred to as a spring constant and spring rate Measured in e.g. N/m (lbf/in) see also Stiffness 
Spring Constant (k) 

Sprung System 
Any machine or structure, or part thereof, that obeys Hooke's Law, which includes most metals, elastomers (rubber), ceramics, hardwoods, etc. 
Spur Gear 
A gear wheel, with teeth cut into its circumference at 90° to the plane of the wheel, that normally (but not necessarily) mates with another spur gear Also referred to as straightcut gear The centres of rotation of two mating spur gear wheels are always parallel 
Stanchion 
A vertical structural member 
Steady Flow 
A fluid flowing through a system the conditions and properties of which do not change with time. 
Stiction 
Stiction (static friction) is the resistance to initiate relative movement between two surfaces when forced together Stiction is always greater than friction 
Stiffness 
The resistance any material or structure exhibits to deformation Stiffness can be applied to bending, torsional and axial deformaton and describes the rate of dimensional change for a specified force see also Spring Coefficient 
Strain (e) 
The elongation in a material as a result of stress see also Elastic Strain and Plastic Strain 
Strand 
More than one filament wound together see also Wire Rope 
Strange Quark 
The third lightest of all the quarks and part of the second generation of matter The strange quark is classified as a fermion mᵣ=1.693528659E−25g [95.0MeV/c²], Q=⅓e, I_{z}=½ 
Stratosphere 
The ceiling for 99% of nitrogen, the earth's most abundant atmospheric gas Altitude @ equator: 15km to 60km Stratum of the earth's atmosphere that comprises mainly nitrogen and oxygen and is considered to be the upper limit of the atmosphere that contains anything of substance Temperature increases with increasing altitude 
Stress (σ, s) 
Force per unit area in a material Tensile stress: induced in a material as a result of a positive axial load Failure in materials due to elastic stress is predicted using various theories: Principal stress (Rankine), Principal strain (e.g. St Venant) or strain energy (Beltrami and Haigh), shear (e.g. Tresca) or shear strain energy (Henckey & Von Mises) 
Stress Amplitude (S_{a}) 
Half the stress range (S_{a} = δS÷2) 
Stress Block 
A collection of characteristic identical stress ranges that represent a defined period of time in the fatigue life of a material or component 
Stress Corrosion Cracking 
The cracking or 'crazing' of a metal surface due to galvanic corrosion whereby the cracks generate stressconcentrations in the material weaking its ability to deform elastically Hydrogen emrittlement is a typical example of this problem (see Cathodic Protection) NACE MR0175/ISO 1515461:2001(E) are internationally recognised standards that offer advice as to the control of this problem 
Stress Cycle 
One stress cycle is twice the stress range (e.g. maximum to minimum and back to maximum again) 
Stress (mean) 
Middle of the the stress range (S_{m} = (Ṡ+Ṣ)÷2) 
Stress Range (δS) 
The difference between the maximum stress and the minimum stress in a single stress cycle (δS = ṠṢ) 
Subduction 
The passing of planet's crust under a tectonic plate and down into its mantle Regions where this occurs are called Subduction Zones, and they are usually active with volcanoes and earthquakes 
Substance 
The bulk quantity of particles 
(the) Sun 
Diameter: 1.3914E+06 km Principal constituent elements (99.998%): The above figures are provided in NASA's Sun Fact Sheet 
Surface Energy (US) 
The free energy per unit area in a substance US = surface tension x surface area 
Surface Tension 
A property of liquids whereby their surface appears to have an elastic membrane in a state of tension This phenomenon occurs at the surface of liquids due to unbalanced cohesive forces between surface molecules that do not occur in the bulk of the liquid where molecular cohesive forces are able to act in all directions. 
Surge (vessels) 
The linear movement of a vessel in the direction of the longitudinal ('x') axis Whilst this term generally applies to the movement of ships, it is also used to define the movement of any object subject to the same degrees of freedom; e.g. aircraft and spacecraft see RightHand Rule for positive and negative directions of this movement 
Sway (vessels) 
The linear movement of a vessel in the direction of the lateral ('y') axis Whilst this term generally applies to the movement of ships, it is also used to define the movement of any object subject to the same degrees of freedom; e.g. aircraft and spacecraft see RightHand Rule for positive and negative directions of this movement 
Sweating 
Line (or coat) the surfaces of two metals with melted solder or braze and allow to cool. 
System 
Thermodynamic: A quantity of matter subjected to a process, everthing else is its surroundings Mechanical: The components that together create a particular action Chemical: The molecules, atoms, subatomic particles and electromagnetic radiation that are responsible for a chemical reaction see Thermodynamics and Subatomic Physics 
Tauon 
A negatively charged elementary particle also referred to as a tau particle The tauon and its antiparticle carry the same electric charges as the electron and positron respectively A tauon is classified as a lepton m=3.167469045E24g [1.77682GeV/c²], lifetime≈2.9E13s 
Techtonic Plate 
An area of planet crust that changes size and shape over time due to mantle activity Normally, a length of the tectonic plate's perimeter (edge) grows through new rock generation from volcanic emissions and the remaining perimeter is subject to subduction 
Temper 
Tempering is carried out to increase toughness and ductility in a material that has been previously hardened. The tempering process is carried out by heating the material to a temperature below its transformation temperature (1330°F or 723°C) and cooling in a controlled environment/manner to allow some recrystallisation to occur. 
Temperature 
The degree of heat measured relative a particular scale The two most commonly used 'absolute' scales are: The two most commonly used 'nonabsolute' scales are: To convert between scales: 0K = 0°R = 273.15°C = 459.67°F 
Tensile Modulus 
A general term that applies collectively to the resistance to axial deformation for all materials (e.g. metals, polymers, woods, etc.) including; Young's, flexural and elastic moduli. 
Tetrahedra 
Describes the lattice arrangement of atoms within a metal. The smallest crystal of this metal will contain four closely packed atoms, each of which are located at each corner of a tetrahedron. 
Thermal Conductivity (k) 
The rate at which heat flows through a material or substance of unit thickness. 
Thermal Resistance (R) 
The temperature difference across a barrier of a specified thickness when a unit of heat flows through it in unit time. 
Thermodynamics 
The theory of the transfer of energy between systems or its conversion into work In other words ... see Thermodynamics 
Thermosphere 
Stratum of the earth's atmosphere that contains the Ionosphere (Lower Thermosphere) and the Exosphere (Upper Thermosphere) Thermosphere means 'hot region'. The temperature of this region increases exponentially with altitude but the density of material in this stratum is so thin that the heat generated cannot be readily transferred. 
Through Harden 
A process whereby the entire body of a steel alloy is hardened to the same extent and is normally achieved by the addition of alloying elements. 
Top Quark 
The most massive of all the quarks and part of the third generation of matter The top quark is classified as a fermion mᵣ=3.085252685E−22g [173.07GeV/c²], lifetime≈5E−25s, Q=⅔e, I_{z}=½ 
Torque 
A rotational moment This is a tangential force applied to a structural element at a given radial distance from the axis of twist. 
Transfer Function 

Transformation Temperature 
The temperature range during which austenite occurs during heating. It is also a different temperature range during which Austenite disappears during cooling. These temperature ranges may overlap but they are never the same. 
Transformer (electrical) 
A transformer is a single central magnet around which are wound two or more separate copper wire coils with a different number of turns. The voltage in each coil will vary thus: V_{2} / V_{1} = n_{2} / n_{1} 
Transom 
An horizontal (or transverse) structural member 
Triangle 
A twodimensional, threestraightsided closed shape the 3 angles of which add up to 180° (πᶜ) 
TriplePoint of Water 
273.16K, 0.01°C, 32.018°F & 491.688°R The temperature at which pure water can exist in all of its phases (solid, liquid and gas) simultaneously at 1 atmosphere (pressure) 
Trochoid (curve) 
A trochoid is a curve generated by a point inside or outside the circumference of a circle that is rolled along a flat, straight surface. see also Cycloid, Epicycloid and Hypocycloid 
Troposphere 
The ceiling for 75% of nitrogen, the earth's most abundant atmospheric gas Altitude @ equator: 0km to 15km Weather generating stratum of the earth's atmosphere that contains all of the earth's gases Temperature reduces with increasing altitude 
True Power (electrical) 
True power is the apparent power multiplied by the power factor and is normally expressed in terms of 'W' or 'kW'. see also Alternating Current and Phase Angle 
Turbulent Flow 
A flowing fluid that disturbs and mixes adjacent layers 
Uncertainty Principle 
Any pair of dimensional variables (e.g. time and energy) describing a subatomic particle cannot be determined to an accuracy whereby the product (multiplication) of the errors (of each variable) is less than Dirac's constant E.g.: the more precisely the position of a particle is determined the less precisely its momentum can be known, and viceversa 
Upheaval Buckling (pipeline) 
Lateral displacement of a pipeline due to uncontrolled longitudinal compression. 
Up Quark 
One of the two types of quark that make the proton and the neutron and forms part of the first generation of matter The up quark is classified as a fermion mᵣ=3.565323494E27g [2.01MeV/c²], Q=⅔e, I_{z}=½ 
Ultimate Tensile Stress 
The maximum stress a material will support before it begins to suffer internal fracturing Resistance to deformation (strength) is increased between yield stress and ultimate tensile stress through work hardening The gradual reduction in strength after reaching UTS is due to increasing internal fracturing which will continue to reduce until the material breaks 
Utilisation 
The proportion of limiting stress (or use) you design into a component before its material fails. For example: if you design a component to experience a maximum design stress of 200 N/m² and the material from which it has been manufactured has a minimum specified yield stress of 400 N/m², the component has a utilisation of 0.5 Utilisation is the inverse of safety factor 
Vacuum 
A volume greater than zero that contains no matter 
Valence Shell 
The outermost shell of an atom in which an electron exists and includes all subshells The valence shell represents an atom's bonding capacity and hence defines its chemical properties. 
Vapour 

Vector (V) 
A straight line action (e.g. force) that has both magnitude and direction see also Polar CoOrdinates and Cartesian CoOrdinates 
Velocity (v) 
Constant rate of change in distance (distance ÷ time) 
Vertex (Vertices) 
The point at which one end of each of two lines connect 
Vibration 
The elastic reponse of a sprung system to repeated loads of similar magintude and frequency 
Virtual Mass 
A shape coefficient that represents the sum of the fluid displaced by the body and the added mass of the surrounding fluid dispursed by the body and its displaced mass 
Viscosity 
Viscosity is the measurement of a fluid's resistance to shear, and therefore to flow. It is the tangential force per unit area necessary to maintain a unit relative velocity between two parallel planes. Kinematic viscosity (ν) is measured in units of m²/s, although it is most commonly measured in Stokes (St) or centiStokes (cSt) where 1m²/s = 1000St Dynamic (or absolute) viscosity (μ) is the kinematic viscosity multiplied by the mass density (ρ) of the fluid and has the units of kg/s/m (or N.s/m²), although it is more commonly measured in Poise (P) or centipoise (cP) where 1N.s/m² = 10P 
Voltage (V) 
The potential difference between two sources of electrical energy (the unit of measurement is the Volt). Also known as potential difference (pd) and electromotive force (emf) The pipeline analogy for voltage is the pressure drop across the inlet and outluet of a pipe with a fluid flowing through it. 
Vortex Shedding 
The generation of 'vortices' (rotating fluid) in the wake of a fluid passing over an object 
W Boson 
A weak force carrier There are two types of W Boson Wˉ is the antiparticle of W⁺ m=1.4332244E−22g [80.398GeV/c²], lifetime≈3E25s, Q=±1e, I_{z}=1 
Wavelength 
The speed of a wave divided by its frequency 
Wave Number 
The reciprocal of wavelength 
Weak Force 
An interaction between elementary particles that is responsible for certain decay processes (such as beta radiation) and acts upon all known fermions Particles interact through the weak force by exchanging W & Z Bosons, which are heavy (≈100 times that of a proton). Their mass defines the shortrange (≈1E17m or ≈100 times less than the diameter of a typical atomic nucleus) nature of the weak force and that makes the weak force appear weak at the low energies associated with radioactivity. 
Weather Window 
A period of time during which limiting weather conditions will not be exceeded i.e.; A large weather window means a long period of time over which these limiting conditions are not expected to be exceeded conversely; A small weather window means a short period of time over which these limiting conditions are not expected to be exceeded 
Weight 
The resultant force between two bodies as a result of gravitational acceleration and is measured in N, pdl, etc. The weight of a body is equal to its mass multiplied by the gravitational acceleration. This property varies with gravitational acceleration. That is, any given mass will weigh differently on the Earth and the Moon, both of which have different gravitational accelerations. Out in deep space, away from all gravitational effects, a mass of 1 tonne will weigh nothing! 
Weld Joint Factor (WJF) 
A utilisation factor for the strength of a welded joint A weld joint factor of 1.0 is usual for coded welders using certified procedures and materials The lowest WJF for a weld completed by an experienced, but uncoded welder using uncertified procedures and materials is ≈0.6 
Wire Rope 
A rope comprising at least one strand, which comprises more than one filament made from metal Also recognised generically as: wire, steel rope, multistrand wire, flexible wire, cable, cord and steelcord 
Work 
A quantity synonymous with energy Mechanical: a force applied over a distance greater than zero The greater the force or the further the distance the more work has been done The units of measurement are; Btu, W.h, J, cal, N.m, lbf.ft etc. 
Work Harden 
The process of throughhardening a steel or a steel alloy by repeated deformation at stresses greater than yield stress However, if the steel/alloy is subsequently held at a sufficiently high temperature for a long enough period it will eventually revert to its original properties 
Wrap 
The longitudinal helical coiling of filaments into strands or strands into wire rope during the manufacturing process 
XRays 
Shortwave electromagnetic radiation that falls between ultraviolet light and gamma radiation Ranges from: 
Yaw (vessels) 
The rotational movement of a vessel about the vertical ('z') axis Whilst this term generally applies to the movement of ships, it is also used to define the movement of any object subject to the same degrees of freedom; e.g. aircraft and spacecraft see RightHand Rule for positive and negative directions of this movement 
Yield Stress 
The maximum stress that can be applied to a metal whilst that continues to obey Hooke's Law The release of stress above yield stress will result in permanent deformation of the material see also Specified Minimum Yield Stress 
Young's Modulus (E) 
The linear relationship (the slope of the curve) between purely elastic stress and strain in a material 
Z Boson 
A weak force carrier There is one type of Z Boson, which only changes spin and momentum but cannot change either electric charge nor any other charges (like strangeness, charm, etc.), so it never changes the generation or flavour of the particle emitting it. The Z boson (or 'Z') is electrically neutral and is its own antiparticle m=1.62556647E−22g [91.1876GeV/c²], lifetime≈1E25s, Q=0, I_{z}=1 