Ablation
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The removal of material from the surface of an object by vaporisation, chipping, or other erosive processes. The term occurs in space physics associated with atmospheric reentry, in glaciology, medicine and passive fire protection. In space vehicle design, ablation is used to both cool and protect mechanical parts and/or payloads that would otherwise be adversely affected by extremely high temperatures.
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Abrasion
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The process of scuffing, scratching, wearing down, marring, or rubbing away. It can be intentionally imposed in a controlled process using an abrasive.
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Acoustic Cavitation
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Cavitation induced by an acoustic field. Microscopic gas bubbles which are generally present in a liquid will be forced to oscillate due to an applied acoustic field. If the acoustic intensity is sufficiently high, the bubbles will first grow in size, and then rapidly collapse. High power ultrasonics usually use the inertial cavitation of microscopic vacuum bubbles for treatment of surfaces, liquids and slurries.
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Aerobic Digestion
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A series of processes in which microorganisms break down biodegradable material in the presence of oxygen
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Aeroelastic Flutter
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A self-feeding and potentially destructive vibration where aerodynamic forces on an object couple with a structure's natural mode of vibration to produce rapid periodic motion. Flutter can occur in any object within a strong fluid flow, under the conditions that a positive feedback occurs between the structure's natural vibration and the aerodynamic forces.
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Anaerobic Digestion
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A series of processes in which microorganisms break down biodegradable material in the absence of oxygen. It is widely used to treat wastewater sludges and organic wastes because it provides volume and mass reduction of the input material.
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Arc Evaporation
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A high current, low voltage electric arc on the surface of a cathode gives rise to a small highly energetic emitting area (a cathode spot) at which the high temperature results in a high velocity jet of vapourised cathode material, leaving a crater. The cathode spot is only active for a short period of time, then it self-extinguishes and re-ignites in a new area close to the previous crater causing apparent motion of the arc.
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Argon Flash
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A method for generating very short and extremely bright flashes of light using a shock wave in argon or other suitable noble gas. The device consists of a vessel filled with argon and a solid explosive charge. The explosion generates a shock wave, which heats the gas to very high temperature (over 104 K). The gas then emits a flash of intense visible and ultraviolet radiation. The amount of explosive can control the intensity of the flash.
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Avalanche Breakdown
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A phenomenon that can occur in both insulating and semiconducting materials (solids, liquids, or gases), allowing very large currents to flow within materials which are otherwise good insulators. Occurs when the electric field in the material is great enough to accelerate free electrons to the point that, when they strike atoms in the material, they can knock other electrons free: the number of free electrons is thus increased rapidly as newly generated particles become part of the process.
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Brinelling
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Surface fatigue caused by repeated impact or overloading.
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Brush
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A device with bristles, wire or other filaments, used for cleaning, grooming hair, applying liquids such as paint, sealing gaps between moving surfaces, deburring and other kinds of surface finishing, and for many other purposes.
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Catalysis
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The process in which the rate of a chemical reaction is increased by means of a chemical substance known as a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed. Catalysts work by lowering the activation energy for a reaction, thus dramatically increasing the rate of the reaction. As a result, products are formed faster and reactions reach their equilibrium state more rapidly.
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Cavitation
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The formation of vapour bubbles in a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure. Usually divided into two classes of behavior. Inertial (or transient) cavitation occurs when a void or bubble in a liquid rapidly collapses, producing a shock wave. Non-inertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to energy input, e.g. acoustic field.
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Coherent Light
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Two light waves are said to be coherent if they have a constant relative phase, which also implies that they have the same frequency.
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Combustion
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(or burning) A complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames. Direct combustion by atmospheric oxygen is a reaction mediated by radical intermediates typically produced as a result of thermal runaway, where the heat generated by combustion is necessary to maintain the high temperature necessary for radical production.
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Composting
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The aerobic decomposition of biodegradable organic matter, producing compost. The decomposition is performed primarily by facultative and obligate aerobic bacteria, yeasts and fungi, helped in the cooler initial and ending phases by a number of larger organisms, such as springtails, ants, nematodes and oligochaete worms.
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Conduction (electrical)
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The movement of electrically charged particles through a transmission medium (electrical conductor). The movement of charge constitutes an electric current. The charge transport may result as a response to an electric field, or as a result of a concentration gradient in carrier density, that is, by diffusion .
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Through heating resulting from the flow of current.
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Cooling
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The act of reducing temperature.
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Crevice Corrosion
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Corrosion occurring in spaces having limited access to working fluid from the environment, such as gaps and contact areas between parts, under gaskets or seals, inside cracks and seams. Generally occurs due to high concentration of impurities in the crevice (e.g., chlorides, acid, or base), or differential electrolyte chemistry inside and outside the crevice: a single metal part being submerged in two different environments.
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Cryolysis
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Destruction by cold (usually in a medical context)
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Decomposition (biological)
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The break down of tissue of a formerly living organism into simpler forms of matter.
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Deflagration
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A technical term describing subsonic combustion that usually propagates through thermal conductivity (hot burning material heats the next layer of cold material and ignites it). Most 'fire' found in daily life, from flames to explosions, is technically deflagration. Deflagration is different from detonation (which is supersonic and propagates through shock compression).
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Deformation
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A change in the shape or size of an object due to an applied force. This can be a result of tensile (pulling) forces, compressive (pushing) forces, shear, bending or torsion (twisting). Deformation is often described in terms of strain.
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For example, by repeated deformation.
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Depressurisation
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Reduction in pressure. Rapid depressurisation can be used to create pressure differences.
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For example, sunflower seeds are broken open by subjecting them to a high pressure followed by rapid depressurisation. The resulting pressure difference breaks open the husks.
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Detonation
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Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases.
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Eddy Currents
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An electrical phenomenon caused when a conductor is exposed to a changing magnetic field due to relative motion of the field source and conductor; or due to variations of the field with time. This can cause eddys of circulating current within the conductor which create electromagnets with magnetic fields that opposes the change of the magnetic field.
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Through inductive heating.
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Electric Arc
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An electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air
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Electrical Discharge Machining
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(also referred to as spark machining, spark eroding, burning, die sinking or wire erosion), A manufacturing process whereby a desired shape is obtained using electrical discharges (sparks). Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage.
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Electrohydrogenesis
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Electrohydrogenesis or biocatalyzed electrolysis is the name given to a process for generating hydrogen gas from organic matter being decomposed by bacteria.
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Electrolysis
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A method of separating chemically bonded elements and compounds by passing an electric current through them. Electrolysis involves the passage of an electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes.
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Through electrolytic erosion at electrodes.
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Electromagnetic Induction
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The generation of electromotive force (EMF) in a current-carrying conductor exposed to a changing magnetic field
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Through inductive heating.
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Electron Beam
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(also called Cathode Rays or e-beam) are streams of electrons observed in vacuum tubes, i.e. evacuated glass tubes that are equipped with at least two metal electrodes to which a voltage is applied, a cathode or negative electrode and an anode or positive electrode.
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Electron Impact Desorption
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Desorption arising from electron-impact induced adsorbate surface bond breaking. Molecules on surfaces may also be chemically converted to other species by electron impact
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Electrostatic Discharge
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The sudden and momentary electric current that flows between two objects at different electrical potentials
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Enzyme
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Proteins that catalyze (i.e., increase the rates of) chemical reactions. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates sufficient for life. Enzymes differ from most other catalysts in that they are highly specific for their substrates
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Erosion
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The process of weathering and transport of solids (sediment, soil, rock and other particles) in the natural environment or their source and deposits them elsewhere. It usually occurs due to transport by wind, water, or ice; by down-slope creep of soil and other material under the force of gravity; or by living organisms, such as burrowing animals, in the case of bioerosion.
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Exothermic Reaction
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An exothermic reaction is a chemical reaction accompanied by the release of heat. In other words, the energy needed for the reaction to occur is less than the total energy released. As a result of this, the extra energy is released, usually in the form of heat.
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Explosion
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A sudden increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases.
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Explosive Lens
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A device composed of several explosive charges that are shaped in such a way as to change the shape of the detonation wave passing through it; conceptually similar to the effect of an optical lens on light
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Farnsworth-Hirsch Fusor
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A relativly simple nuclear fusion device based on inertial electrostatic confinement.
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Fatigue
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The progressive and localised structural damage that occurs when a material is subjected to cyclic loading. The maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.
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Ferromagnetic Powder
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Ferromagnetic material in a powdered or finely divided form. Ferromagnetic materials (such as iron) form permanent magnets and/or exhibit strong interactions with magnets. Ferromagnetic materials lose their ferromagnetic properties above a characteristic temperature (the Curie Point).
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If a solid 'structure' is composed of ferromagnetic powder, sustained by the presence of a magnetic field, then the structure can be destroyed by removing or disturbing the sustaining magnetic field.
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Ferromagnetism
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The mechanism by which certain materials (such as iron) form permanent magnets and/or exhibit strong interactions with magnets. Responsible for commonly observed magnetism phenomena, e.g. 'fridge magnets. A material is 'ferromagnetic' only if all its magnetic ions add a positive contribution to the net magnetisation. If some of them subtract from the net magnetisation (i.e. are partially anti-aligned), then the material is 'ferrimagnetic'.
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By using a magnetic field to differentially attract material components having different ferromagnetic properties.
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Flutter
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A dynamic instability of an elastic structure in a fluid flow, caused by positive feedback between the body's deflection and the force exerted by the fluid flow.
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For example, the Tacoma Narrows suspension bridge.
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Force
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That which can cause an object with mass to accelerate. Force has both magnitude & direction, i.e. it's a vector quantity. An object with constant mass will accelerate in proportion to the net force acting upon it and in inverse proportion to its mass (or the net force on an object is equal to the rate of change of momentum it experiences). Forces acting on objects may cause them to rotate or deform, or result in a change in pressure.
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Fracture Mechanics
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Fracture mechanics is an important tool in improving the mechanical performance of materials and components. It applies the physics of stress and strain, in particular the theories of elasticity and plasticity, to the microscopic crystallographic defects found in real materials in order to predict the macroscopic mechanical failure of bodies.
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Freezing
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A phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. Colloquially it is applied to water, but technically it applies to any liquid. All known liquids, except liquid helium, freeze when the temperature is lowered enough.
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For example, frost damage in the case of water which has a negative coeficcient of thermal expansion at temperatures below 4 °C.
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Friction
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The force resisting the relative motion of two surfaces in contact or a surface in contact with a fluid (e.g. air on an aircraft or water in a pipe).
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Gear
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A gear (or more correctly a gear wheel) is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine. Geared devices can change the speed, magnitude, and direction of a power source.
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By crushing or grinding between the cogs of meshing gears.
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Heating
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The act of increasing temperature.
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Hydraulic Press
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A hydraulic mechanism for applying a large lifting or compressive force. It is the hydraulic equivalent of a mechanical lever.
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Hydrodynamic Cavitation
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The process of vaporisation, bubble generation and bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in local pressure.
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Hydrogenation
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Hydrogenation is the chemical reaction that results from the addition of hydrogen. The process is usually employed to a reduce or saturate organic compounds. The process typically constitutes the addition of pairs of hydrogen atoms to a molecule.
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Impact Force
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A high force or shock applied over a short time period. Such a force or acceleration can sometimes have a greater effect than a lower force applied over a proportionally longer time period.
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Inertia
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The resistance of any physical object to a change in its state of motion or rest. It is proportional to an object's mass.
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Infrared Radiation
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Infrared (IR) radiation is electromagnetic radiation whose wavelength is longer than that of visible light (400-700 nm), but shorter than that of terahertz radiation (3-300 µm) and microwaves (~30,000 µm). Infrared radiation spans roughly three orders of magnitude (750 nm and 1000 µm).
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From energy of incident infrared radiation.
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Interference
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The addition (superposition) of two or more waves that result in a new wave pattern. As most commonly used, the term interference usually refers to the interaction of waves which are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency.
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Through amplification of a destructive field by constructive interference.
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Intumescent Materials
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An intumescent is a substance which swells as a result of heat exposure, thus increasing in volume, and decreasing in density. Intumescents are typically used in passive fire protection.
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Ion Beam
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An ion beam is a type of particle beam consisting of ions. Ion beams have many uses in electronics manufacturing (principally ion implantation) and other industries.
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Ion Beam Sputtering can be used to polish telescope mirrors.
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Jet
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A coherent stream of fluid (e.g. gas or liquid) that is projected into a surrounding medium, usually from some kind of a nozzle or aperture. Jets can travel long distances without dissipating.
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Jet Erosion
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A method of cutting or slicing a material using a jet of liquid or gas at high velocity and pressure, or a mixture of liquid/gas and an abrasive substance.
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Joule Heating
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The process by which the passage of an electric current through a conductor releases heat. Heat generated is a function of current, resistance and time. Also known as the Joule-Lenz effect, Ohmic heating or resitive heating.
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Kármán Vortex Street
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A repeating pattern of swirling vortices caused by the unsteady separation of flow of a fluid over bluff bodies. It is responsible for such phenomena as the 'singing' of suspended telephone or power lines, the vibration of a car antenna at certain speeds.
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Vortex shedding caused the collapse of three towers at Ferrybridge power station in 1968 during high winds.
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Laser
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A device that emits light (electromagnetic radiation) through a process called stimulated emission.
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Laser Ablation
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The process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma. Usually, laser ablation refers to removing material with a pulsed laser, but it is possible to ablate material with a continuous wave laser beam if the laser intensity is high enough.
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Light
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Light is electromagnetic radiation of a wavelength that is visible to the human eye (in a range from about 380 or 400 nanometres to about 760 or 780 nm)
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Using a high-power light source or a target susceptible to light
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Magnetoelastic Effects
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A group of effects including Magnetostriction (or Joule Magnetostriction), Delta-E Effect, Wiedemann Effect, Magnetovolume Effect, and their Inverses: Villari Effect, Delta-E Effect, Matteucci Effect and the Nagaoka-Honda Effect.
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Magnetostriction
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A property of ferromagnetic materials that causes them to change their shape or dimensions during the process of magnetisation. The variation of material's magnetisation due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value. This effect can cause losses due to frictional heating in susceptible ferromagnetic cores.
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Melting
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A process that results in the phase change of a substance from a solid to a liquid. The internal energy of a solid substance is increased (typically by the absorbtion of heat) to a specific temperature (called the melting point) at which it changes to the liquid phase.
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Misznay-Schardin Effect
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A characteristic of the detonation of a broad sheet of explosive. The explosive blast expands directly away from (perpendicular to) the surface of an explosive (unlike the blast from a rounded explosive charge)
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Montmorillonite
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A very soft phyllosilicate mineral that typically forms in microscopic crystals, forming a clay. Montmorillonite's water content is variable and it increases greatly in volume when it absorbs water.
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Sodium montmorillonite has come to be used as the major constituent in non-explosive agents for splitting rock in natural stone quarries in order to limit the amount of waste, or for the demolition of concrete structures where the use of explosive charges is unacceptable.
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Nuclear Fission
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The splitting of the nucleus of an atom into parts (lighter nuclei) often producing free neutrons and other smaller nuclei, which may eventually produce photons (in the form of gamma rays). Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place).
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Oxidation
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A chemical reaction that involves the loss of electrons or an increase in the oxidation state by a molecule, atom or ion.
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Ozone
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Ozone (O3), or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope (O2).
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Photo-oxidation
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Oxidation facilitated radiant energy such as UV or artificial light. This process is often the most significant component of weather degradation of polymers.
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Photodissociation
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A chemical reaction in which a chemical compound is broken down by photons. Any photon with sufficient energy can affect the chemical bonds of a chemical compound. Since a photon's energy is inversely proportional to its wavelength, electromagnetic waves with the energy of visible light or higher, such as ultraviolet light, x-rays and gamma rays are usually involved in such reactions.
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Piezomagnetism
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A phenomenon observed in some antiferromagnetic crystals. It is characterised by a linear coupling between the system's magnetic polarisation and mechanical strain. In a piezomagnetic, one may induce a spontaneous magnetic moment by applying physical stress, or a physical deformation by applying a magnetic field. Piezomagnetism differs from the related property of magnetostriction.
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Plasma
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A partially ionized gas, in which a certain proportion of electrons are free rather than being bound to an atom or molecule. The ability of the positive and negative charges to move somewhat independently makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma therefore has properties quite unlike those of solids, liquids or gases and is considered to be a distinct state of matter.
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Pressure Drop
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Pressure is an effect which occurs when a force is applied on a surface. Pressure is transmitted to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point. Rapid pressure drop is a useful technique for applying force or breaking objects apart.
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For example, the breaking apart of sunflower seed shells by sudden pressure drop.
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Pulsed Magnet
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Pulsed magnets can generate field strengths far in excess of conventional magnets. They come in two types: destructive and non-destructive.
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Pyrolysis
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A thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. Pyrolysis typically occurs under pressure and at operating temperatures above 430 °C (800 °F). Pyrolysis is a special case of thermolysis.
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Pyrophoricity
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A pyrophoric substance ignites spontaneously in air at or below 55 degrees centigrade. The creation of sparks from metals is based on the pyrophoricity of small metal particles. The sparking mechanism in cigarette lighters is an example. Some liquids and gases are phyrophoric.
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Radiation
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A process in which energetic particles or waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing.
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Radioactive Decay
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The process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation.
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Redox Reactions
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Redox (shorthand for oxidation-reduction) reactions describe all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process, such as the oxidation of carbon to yield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), or a complex process such as the oxidation of sugar(C6H12O6) in the human body through a series of complex electron transfer processes.
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Reduction
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A chemical reaction that involves the gain of electrons or a decrease in the oxidation state by a molecule, atom or ion.
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Resonance
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The tendency of a system to oscillate with larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies. At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy.
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Shaped Charge
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An explosive charge shaped to focus the effect of the explosive's energy. Various types are used to cut and form metal, initiate nuclear weapons, in the oil and gas industry and to penetrate armour. A typical modern lined shaped charge can penetrate armor steel to a depth of 7 or more times the diameter of the charge's cone, though greater depths of 10 times and above are now feasible.
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Shock Wave
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A type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium (solid, liquid, gas or plasma) or through a field such as the electromagnetic field. Characterized by an abrupt, nearly discontinuous change in the characteristics of the medium. Associated with rapid rise in pressure, temperature and density of the flow. A shock wave travels through most media at a higher speed than an ordinary wave.
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Solvation
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(commonly called dissolution) The process of attraction and association of molecules of a solvent with molecules or ions of a solute. As ions dissolve in a solvent they spread out and become surrounded by solvent molecules. The bigger the ion, the more solvent molecules are able to surround it and the more it becomes solvated.
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Sonochemistry
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The effect of sonic waves and wave properties on chemical systems. Sonochemistry arises from acoustic cavitation: the formation, growth, and implosive collapse of bubbles in a liquid. This is demonstrated in phenomena such as ultrasound, sonication, sonoluminescence, and sonic cavitation.
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Sputtering
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A process whereby atoms are ejected from a solid target material due to bombardment of the target by energetic ions. It is commonly used for thin-film deposition, etching and analytical techniques
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Ion Beam Sputtering can be used to polish telescope mirrors.
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Steam Explosion
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A violent boiling or flashing of water into steam, occurring when water is either superheated, rapidly heated by fine hot debris produced within it, or the interaction of molten metals . The water changes from a liquid to a gas with extreme speed, increasing dramatically in volume.
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Sublimation
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The change of the physical state of aggregation (or simply state) of matter directly from solid phase to gaseous phase without passing through an intermediate liquid phase.
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Tension
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The pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression.
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Thermal Radiation
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Electromagnetic radiation emitted from the surface of an object due to the object's temperature.
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Thermal Shock
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Cracking as a result of rapid temperature change. Thermal shock occurs when a thermal gradient causes different parts of an object to expand by different amounts. This differential expansion can be understood in terms of stress or of strain, equivalently. At some point, this stress overcomes the strength of the material, causing a crack to form. If nothing stops this crack from propagating through the material, it will cause the object's structure to fail.
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Thermolysis
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(or Thermal decomposition) A chemical decomposition caused by heat. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion.
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Torque
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Torque (also called moment or moment of force) is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist. Torque is the rotational analogue of Force.
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Turbulence
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A fluid regime characterised by chaotic, stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time (flow that is not turbulent is called laminar flow).
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Ultrasonic Vibration
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Vibration at ultrasonic frequencies.
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Ultrasound
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Cyclic sound pressure with a frequency greater than the upper limit of human hearing. Although this limit varies from person to person, 20 kHz serves as a useful lower limit in describing ultrasound.
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Vibration
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Mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.
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Weak Point
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Explotation of a natural or deliberately introduced weak point in a system or structure. For example: an electrical fuse or a shear pin.
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By introducing weak point(s) into a system, either when originally manufactured, or subsequently.
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Wear
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The erosion of material from a solid surface by the action of another surface.
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Weathering
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The breaking down of Earth's rocks, soils and minerals through direct contact with the planet's atmosphere. Weathering occurs in situ, or 'with no movement', and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, wind, and gravity.
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Wedge
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A triangular shaped tool, a compound and portable inclined plane. It can be used to separate two objects, or portions of objects, lift an object, or hold an object in place. It operates by converting a force applied to the wide end into forces perpendicular to the inclined surfaces.
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By using the wedge, combined with mechanical force, to break a solid object apart.
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Wiedemann Effect
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A magnetoelastic effect. The twisting of a magnetic material when a helical magnetic field is applied to it.
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X-Ray
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A form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3 × 1016 Hz to 3 × 1019 Hz) and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma rays. In many languages, X-radiation is called Röntgen radiation.
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