Bingham Plastic
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A viscoplastic material that behaves as a rigid body at low stresses but flows as a viscous fluid at high stress. A common example is toothpaste, which will not be extruded until a certain pressure is applied to the tube. It then is pushed out as a solid plug.
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Compression
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The result of the subjection of a material to compressive stress, resulting in reduction of volume. The opposite of compression is tension. In simple terms, compression is a pushing force.
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Conservation of Momentum
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In a closed system (one that does not exchange any matter with the outside and is not acted on by outside forces) the total momentum is constant.
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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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Elasticity
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The physical property of a material when it deforms under stress (e.g. external forces), but returns to its original shape when the stress is removed. The amount of deformation is called the strain. The elastic regime is characterized by a linear relationship between stress and strain, denoted linear elasticity.
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Electric Field
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The space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field (that can also be equated to electric flux density). This electric field exerts a force on other electrically charged objects.
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If the solid carries an electric charge.
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Electrorheological Effect
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Electrorheological (ER) fluids are suspensions of extremely fine non-conducting particles (up to 50 micrometres diameter) in an electrically insulating fluid. The apparent viscosity of ER fluids changes reversibly by an order of up to 100,000 in response to an electric field. A typical ER fluid can go from the consistency of a liquid to that of a gel, and back, with response times of the order of ms. Sometimes called the Winslow Effect.
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It has been proposed to create bullet-proof vests using an ER fluid because the ability to soak the fluid into cloth creates the potential for a very light vest that can change from a normal cloth into a hard covering almost instantaneously
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Electrostatics
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The phenomena arising from stationary or slowly moving electric charges
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For example, the leaves of a gold-leaf electroscope.
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Electrostriction
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A property of all electrical non-conductors, or dielectrics, that causes them to change their shape under the application of an electric field. All dielectrics exhibit some electrostriction, but certain engineered ceramics, known as relaxor ferroelectrics, have extraordinarily high electrostrictive constants,e.g. Lead magnesium niobate (PMN), Lead magnesium niobate-lead titanate (PMN-PT), Lead lanthanum zirconate titanate (PLZT).
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Entropic Explosion
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An explosion in which the reactants undergo a large change in volume without releasing a large amount 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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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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Fluidisation
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A process similar to liquefaction whereby a granular material is converted from a static solid-like state to a dynamic fluid-like state. This process occurs when a fluid (liquid or gas) is passed up through the granular material. When fluidized, a bed of solid particles will behave as a fluid, like a liquid or gas.
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Fluidisation allows granular solid material to be manipulated as if it were a liquid, allowing liquid processing methods to be used, such as pumping.
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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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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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Fractal Forms
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A fractal is generally 'a rough or fragmented geometric shape that can be split into parts, each of which is (at least approximately) a reduced-size copy of the whole,' a property called self-similarity. A mathematical fractal is based on an equation that undergoes iteration, a form of feedback based on recursion.
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Gravitation
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A natural phenomenon by which objects with mass attract one another. In everyday life, gravitation is most commonly thought of as the agency which lends weight to objects with mass.
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Hyperboloid
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A hyperboloid is a quadric, a type of surface in three dimensions. A hyperboloid of revolution of one sheet can be obtained by revolving a hyperbola around its semi-minor axis. A hyperboloid of revolution of two sheets can be obtained by revolving a hyperbola around its focal axis. Hyperboloid structures are used in construction - they can be built with straight steel beams. Examples include cooling towers.
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The hyperboloid is an example of a curved structure that can be constructed using straight lines - for example a power station cooling tower.
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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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Magnetic Field
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A vector field which surrounds magnets and electric currents, and is detected by the force it exerts on moving electric charges and on magnetic materials. When placed in a magnetic field, magnetic dipoles tend to align their axes parallel to the magnetic field. Magnetic fields also have their own energy with an energy density proportional to the square of the field intensity.
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Magnetism
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One of the phenomena by which materials exert attractive or repulsive forces on other materials. Some well-known materials that exhibit easily detectable magnetic properties (called magnets) are nickel, iron, cobalt, and their alloys; however, all materials are influenced to greater or lesser degree by the presence of a magnetic field.
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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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Magnetovolume Effect
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One of a group of Magnetoelastic Effects. Volume change due to magnetisation (most evident near the Curie temperature)
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By combining a materials having different susceptibilities to the magnetovolume effect.
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Mechanical Force
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A mechanical influence that causes a free body to undergo an acceleration.
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Piezoelectric Effect
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Generation of electrical charge in certain solid materials (notably crystals, certain ceramics, and biological matter such as bone, DNA and various proteins) in response to applied mechanical strain. The piezoelectric effect is a reversible process in that materials also exhibit the reverse piezoelectric effect (the internal generation of a mechanical force resulting from an applied electrical field).
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Plasticity
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The deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a solid piece of metal or plastic being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself.
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Poisson's Effect
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When a material is compressed in one direction, it usually tends to expand in the other two directions perpendicular to the direction of compression.
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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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Pressure Increase
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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.
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Pressurisation
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The application of pressure in a given situation or environment; and more specifically refers to the process by which atmospheric pressure is maintained in an isolated or semi-isolated atmospheric environment (for instance, in an aircraft, or whilst scuba diving).
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Pseudoelasticity
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(or superelasticity) An elastic (impermanent) response to relatively high stress caused by a phase transformation between the austenitic and martensitic phases of a crystal. Exhibited in Shape memory alloys. Superelastic alloys belong to the larger family of shape memory alloys. Unlike shape-memory alloys, no change in temperature is needed for the alloy to recover its initial shape.
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Shape Memory Alloy
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An alloy that 'remembers' its original, cold-forged shape: returning the pre-deformed shape by heating. This material is a lightweight, solid-state alternative to conventional actuators such as hydraulic, pneumatic, and motor-based systems.
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Shear Stress
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A stress which is applied parallel or tangential to a face of a material, as opposed to a normal stress which is applied perpendicularly.
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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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Superplasticity
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A state in which solid crystalline material is deformed well beyond its usual breaking point, usually over about 200% during tensile deformation. Such a state is usually achieved at high homologous temperature, typically half the absolute melting point. Examples of superplastic materials are some fine-grained metals and ceramics.
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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 Contraction
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The tendency of matter to reduce in volume (contract) in response to a change in temperature or when a substance is cooled.
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Thermal Expansion
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The tendency of matter to change in volume in response to a change in temperature or when a substance is heated.
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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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Viscoelasticity
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The property of exhibiting both viscous and elastic characteristics when undergoing deformation.
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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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