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Golden record (informatics)

Master data

Golden_record_(informatics) > Master data

In master data management (MDM), the golden copy refers to the master data (master version) of the reference data which works as an authoritative source for the "truth" for all applications in a given IT landscape.

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Key relevance

Summary

Key_relevance

In master locksmithing, key relevance is the measurable difference between an original key and a copy made of that key, either from a wax impression or directly from the original, and how similar the two keys are in size and shape. It can also refer to the measurable difference between a key and the size required to fit and operate the keyway of its paired lock. No two copies of keys are exactly the same, even if they were both made from key blanks that are struck from the same mould or cut from the same duplicating/milling machine with no changes to the bitting settings in between. Even under these favorable circumstances, there will be minute differences between the two key shapes, though their key relevance is extremely high.

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Key relevance

Summary

Key_relevance

In all machining work, there are measurable amounts of difference between the design specification of an object, and its actual manufactured size. In locksmithing, the allowable tolerance is decided by the range of minute differences between a key's size and shape in comparison to the size and shape required to turn the tumblers within the lock.

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Key relevance

Summary

Key_relevance

Key relevance is the measure of similarity between the key and the optimal size needed to fit the lock, or it is the similarity between a duplicate key and the original it is seeking to replicate. Key relevance cannot be deduced from a key code, since the key code merely refers to a central authoritative source for designed shapes and sizes of keys. Typical modern keys require a key relevance of approximately 0.03 millimetres (0.0012 in) to 0.07 millimetres (0.0028 in) (accuracy within 0.75% to 1.75%) in order to operate.

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Stroke Index

Detail

Stroke_Index > Detail

In match play the stroke index is used to evenly spread the handicap allowances across the course. This is done by allocating the odd stroke index numbers to the more difficult half (9 holes, Out or In) of the course, which is usually the longer half, and the even stroke index numbers to the easier half of the course. Holes 1 and 18 are usually not included in the first 8 of the stroke index. The first and second stroke index holes should be placed close to the middle of each nine and the first six strokes should not be allocated to adjacent holes.

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Stroke Index

Detail

Stroke_Index > Detail

The 7th to the 10th stroke index holes should be allocated so that a player receiving 10 strokes does not receive strokes on three consecutive holes.In Stableford, par and bogey competitions using stroke play, where an even distribution of strokes is not so important, if the club uses a different stroke index for these competitions then generally the most difficult hole to play is given the index of 1 and the easiest is indexed as 18 (there being 18 holes on a standard golf course). Technicality and hole length are factors contributing to difficulty. Some clubs allocate different indexes for match play and Stableford/par/bogey matches.Handicap strokes are deducted from a player's score in the order of stroke index from indexed hole 1 to 18 recurring.

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Stroke Index

Detail

Stroke_Index > Detail

For example, a player with a handicap of 12 would be given a stroke deduction only on the holes with stroke index 1 to 12. A player with a handicap of 24 would receive a stroke at all 18 holes plus an extra stroke at holes 1 to 6 (18 + 6 = 24) so they would receive two strokes on holes 1 to 6 and one stroke for holes 7 to 18.

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Stroke Index

Detail

Stroke_Index > Detail

In a handicap match play competition where the one player has a handicap 8 shots higher than their opponent then that player will receive a handicap stroke on the holes with stroke index 1 to 8. The stroke index is usually printed on a golf club's scorecard listed alongside each hole. == References ==

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Shooting target

International Practical Shooting Confederation

Shooting_target > Firearm sports > International Practical Shooting Confederation

In matches organized by the International Practical Shooting Confederation, both steel and paper targets are used. Currently the only paper targets used for handgun is the IPSC Target (formerly Classic Target) and the 2/3 scaled down IPSC Mini Target (formerly IPSC Mini Classic Target). The center of these paper targets is called the A-zone. Additionally, for rifle and shotgun "A3" and "A4" paper targets and the "Universal Target" is used. For steel targets, standardized knock down targets called "poppers" are used. The two approved designs are the full size "IPSC Popper" (formerly IPSC Classic Popper) and the 2/3 scaled down version "IPSC Mini Popper" (formerly "IPSC Classic Mini Popper"), while the Pepper Popper and Mini Pepper Popper is now obsolete.

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Net Run Rate

7. Interrupted game with revised D/L target

Net_Run_Rate > Permutations > 7. Interrupted game with revised D/L target

In matches where Duckworth-Lewis revised targets are set due to interruptions which reduce the number of overs bowled, those revised targets and revised overs are used to calculate the NRR for both teams. For example, Team A are dismissed for 165 in 33.5 overs. Team B progresses to 120–0, but play is halted after 18 overs due to rain. Six overs are lost, and the target is reset to 150 from 44 overs, which Team B reach comfortably after 26.2 overs.

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Net Run Rate

7. Interrupted game with revised D/L target

Net_Run_Rate > Permutations > 7. Interrupted game with revised D/L target

Because the target was revised to 150 runs from 44 overs, Team A's total is reset to 149 from 44 overs, thus their RR = 149 44 ≈ 3.39 {\displaystyle ={\frac {149}{44}}\approx 3.39} . Team B's RR, however, is computed as normal: 150 26.33 ≈ 5.70 {\displaystyle {\frac {150}{26.33}}\approx 5.70} . Computing the match NRR for Team A gives us 3.39 – 5.70 = –2.31. Team B's NRR is: 5.70 – 3.39 = +2.31.

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Orthotropic material

Summary

Orthotropic_material

In material science and solid mechanics, orthotropic materials have material properties at a particular point which differ along three orthogonal axes, where each axis has twofold rotational symmetry. These directional differences in strength can be quantified with Hankinson's equation. They are a subset of anisotropic materials, because their properties change when measured from different directions.

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Orthotropic material

Summary

Orthotropic_material

A familiar example of an orthotropic material is wood. In wood, one can define three mutually perpendicular directions at each point in which the properties are different. It is most stiff (and strong) along the grain (axial direction), because most cellulose fibrils are aligned that way.

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Orthotropic material

Summary

Orthotropic_material

It is usually least stiff in the radial direction (between the growth rings), and is intermediate in the circumferential direction. This anisotropy was provided by evolution, as it best enables the tree to remain upright.

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Orthotropic material

Summary

Orthotropic_material

Because the preferred coordinate system is cylindrical-polar, this type of orthotropy is also called polar orthotropy. Another example of an orthotropic material is sheet metal formed by squeezing thick sections of metal between heavy rollers.

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Orthotropic material

Summary

Orthotropic_material

This flattens and stretches its grain structure. As a result, the material becomes anisotropic — its properties differ between the direction it was rolled in and each of the two transverse directions. This method is used to advantage in structural steel beams, and in aluminium aircraft skins.

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Orthotropic material

Summary

Orthotropic_material

If orthotropic properties vary between points inside an object, it possesses both orthotropy and inhomogeneity. This suggests that orthotropy is the property of a point within an object rather than for the object as a whole (unless the object is homogeneous). The associated planes of symmetry are also defined for a small region around a point and do not necessarily have to be identical to the planes of symmetry of the whole object.

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Orthotropic material

Summary

Orthotropic_material

Orthotropic materials are a subset of anisotropic materials; their properties depend on the direction in which they are measured. Orthotropic materials have three planes/axes of symmetry. An isotropic material, in contrast, has the same properties in every direction.

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Orthotropic material

Summary

Orthotropic_material

It can be proved that a material having two planes of symmetry must have a third one. Isotropic materials have an infinite number of planes of symmetry. Transversely isotropic materials are special orthotropic materials that have one axis of symmetry (any other pair of axes that are perpendicular to the main one and orthogonal among themselves are also axes of symmetry).

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Orthotropic material

Summary

Orthotropic_material

One common example of transversely isotropic material with one axis of symmetry is a polymer reinforced by parallel glass or graphite fibers. The strength and stiffness of such a composite material will usually be greater in a direction parallel to the fibers than in the transverse direction, and the thickness direction usually has properties similar to the transverse direction. Another example would be a biological membrane, in which the properties in the plane of the membrane will be different from those in the perpendicular direction.

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Orthotropic material

Summary

Orthotropic_material

Orthotropic material properties have been shown to provide a more accurate representation of bone's elastic symmetry and can also give information about the three-dimensional directionality of bone's tissue-level material properties.It is important to keep in mind that a material which is anisotropic on one length scale may be isotropic on another (usually larger) length scale. For instance, most metals are polycrystalline with very small grains. Each of the individual grains may be anisotropic, but if the material as a whole comprises many randomly oriented grains, then its measured mechanical properties will be an average of the properties over all possible orientations of the individual grains.

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Glutaraldehyde

Material Science

Glutaraldehyde > Uses > Material Science

In material science glutaraldehyde application areas range from polymers to metals and biomaterials. Glutaraldehyde is commonly used as fixing agent before characterization of biomaterials for microscopy. Glutaraldehyde is a powerful crosslinking agent for many polymers containing primary amine groups.. Glutaraldehdye also can be used for an interlinking agent to improve the adhesion force between two polymeric coatings. Glutaraldehyde is also used to protect against corrosion of undersea pipes.

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Layered materials

Summary

Layered_materials

In material science, layered materials are solids with highly anisotropic bonding, in which two-dimensional sheets are internally strongly bonded, but only weakly bonded to adjacent layers. Owing to their distinctive structures, layered materials are often suitable for intercalation reactions.One large family of layered materials are metal dichalcogenides. In such materials, the M-chalcogen bonding is strong and covalent. These materials exhibit anisotropic electronic properties such as thermal and electrical conductivity.

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Resilience (materials science)

Summary

Resilience_(materials_science)

In material science, resilience is the ability of a material to absorb energy when it is deformed elastically, and release that energy upon unloading. Proof resilience is defined as the maximum energy that can be absorbed up to the elastic limit, without creating a permanent distortion. The modulus of resilience is defined as the maximum energy that can be absorbed per unit volume without creating a permanent distortion.

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Resilience (materials science)

Summary

Resilience_(materials_science)

It can be calculated by integrating the stress–strain curve from zero to the elastic limit. In uniaxial tension, under the assumptions of linear elasticity, U r = σ y 2 2 E = σ y ε y 2 {\displaystyle U_{r}={\frac {\sigma _{y}^{2}}{2E}}={\frac {\sigma _{y}\varepsilon _{y}}{2}}} where Ur is the modulus of resilience, σy is the yield strength, εy is the yield strain, and E is the Young's modulus. This analysis is not valid for non-linear elastic materials like rubber, for which the approach of area under the curve until elastic limit must be used.

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Rubber toughening

Rubber selection and miscibility with continuous phase

Rubber_toughening > Relationship between the secondary phase properties and toughening effect > Rubber selection and miscibility with continuous phase

In material selection it is important to look at the interaction between the matrix and the secondary phase. For example, crosslinking within the rubber phase promotes high strength fibril formation that toughens the rubber, preventing particle fracture.Carboxyl-terminated butadiene-acrylonitrile (CTBN) is often used to toughen epoxies, but using CTBN alone increases the toughness at the cost of stiffness and heat resistance. Amine-terminated butadiene acrylonitrile (ATBN) is also used. Using ultra-fine full-vulcanized powdered rubber (UFPR) researchers have been able to improve all three, toughness, stiffness, and heat resistance simultaneously, resetting the stage for rubber toughening with particles smaller than previously thought to be effective.In applications where high optical transparency is necessary, examples being poly(methyl methacrylate) and polycarbonate it is important to find a secondary phase that does not scatter light.

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Rubber toughening

Rubber selection and miscibility with continuous phase

Rubber_toughening > Relationship between the secondary phase properties and toughening effect > Rubber selection and miscibility with continuous phase

To do so it is important to match refractive indices of both phases. Traditional rubber particles do not offer this quality. Modifying the surface of nanoparticles with polymers of comparable refractive indices is an interest of current research.

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Cobalt oxide nanoparticles

Summary

Cobalt_oxide_nanoparticle

In materials and electric battery research, cobalt oxide nanoparticles usually refers to particles of cobalt(II,III) oxide Co3O4 of nanometer size, with various shapes and crystal structures. Cobalt oxide nanoparticles have potential applications in lithium-ion batteries and electronic gas sensors.

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Binary phase

Summary

Binary_compound

In materials chemistry, a binary phase or binary compound is a chemical compound containing two different elements. Some binary phase compounds are molecular, e.g. carbon tetrachloride (CCl4). More typically binary phase refers to extended solids. Famous examples zinc sulfide, which contains zinc and sulfur, and tungsten carbide, which contains tungsten and carbon.Phases with higher degrees of complexity feature more elements, e.g. three elements in ternary phases, four elements in quaternary phases. == References ==

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Quaternary phase

Summary

Quaternary_phase

In materials chemistry, a quaternary phase is a chemical compound containing four elements. Some compounds can be molecular or ionic, examples being chlorodifluoromethane (CHClF2) sodium bicarbonate (NaCO3H). More typically quaternary phase refers to extended solids. A famous example are the yttrium barium copper oxide superconductors.

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Hot hardness

Summary

Hot_hardness

In materials engineering and metallurgy, hot hardness or red hardness (when a metal glows a dull red from the heat) corresponds to hardness of a material at high temperatures. As the temperature of the material increases, hardness decreases and at some point a drastic change in hardness occurs. The hardness at this point is termed the hot or red hardness of that material. Such changes can be seen in materials such as heat treated alloys. == References ==

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Suspension Plasma Spray

Summary

Suspension_Plasma_Spray

In materials engineering, suspension plasma spray (SPS) is a form of plasma spraying where the ceramic feedstock is dispersed in a liquid suspension before being injected into the plasma jet.By suspending powder in a fluid, normal feeding problems are circumvented, allowing the deposition of finer microstructures through the use of finer powders. == References ==

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ABC analysis

Summary

ABC_analysis

In materials management, ABC analysis is an inventory categorisation technique. ABC analysis divides an inventory into three categories—"A items" with very tight control and accurate records, "B items" with less tightly controlled and good records, and "C items" with the simplest controls possible and minimal records. The ABC analysis provides a mechanism for identifying items that will have a significant impact on overall inventory cost, while also providing a mechanism for identifying different categories of stock that will require different management and controls. The ABC analysis suggests that inventories of an organization are not of equal value.

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ABC analysis

Summary

ABC_analysis

Thus, the inventory is grouped into three categories (A, B, and C) in order of their estimated importance. 'A' items are very important for an organization.

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ABC analysis

Summary

ABC_analysis

Because of the high value of these 'A' items, frequent value analysis is required. In addition to that, an organization needs to choose an appropriate order pattern (e.g. 'just-in-time') to avoid excess capacity. 'B' items are important, but of course less important than 'A' items and more important than 'C' items. Therefore, 'B' items are intergroup items. 'C' items are marginally important.

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Crack growth resistance curve

Summary

Crack_growth_resistance_curve

In materials modeled by linear elastic fracture mechanics (LEFM), crack extension occurs when the applied energy release rate G {\displaystyle G} exceeds G R {\displaystyle G_{R}} , where G R {\displaystyle G_{R}} is the material's resistance to crack extension. Conceptually G {\displaystyle G} can be thought of as the energetic gain associated with an additional infinitesimal increment of crack extension, while G R {\displaystyle G_{R}} can be thought of as the energetic penalty of an additional infinitesimal increment of crack extension. At any moment in time, if G ≥ G R {\displaystyle G\geq G_{R}} then crack extension is energetically favorable.

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Crack growth resistance curve

Summary

Crack_growth_resistance_curve

A complication to this process is that in some materials, G R {\displaystyle G_{R}} is not a constant value during the crack extension process. A plot of crack growth resistance G R {\displaystyle G_{R}} versus crack extension Δ a {\displaystyle \Delta a} is called a crack growth resistance curve, or R-curve. A plot of energy release rate G {\displaystyle G} versus crack extension Δ a {\displaystyle \Delta a} for a particular loading configuration is called the driving force curve.

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Crack growth resistance curve

Summary

Crack_growth_resistance_curve

The nature of the applied driving force curve relative to the material's R-curve determines the stability of a given crack. The usage of R-curves in fracture analysis is a more complex, but more comprehensive failure criteria compared to the common failure criteria that fracture occurs when G ≥ G c {\displaystyle G\geq G_{c}} where G c {\displaystyle G_{c}} is simply a constant value called the critical energy release rate. An R-curve based failure analysis takes into account the notion that a material's resistance to fracture is not necessarily constant during crack growth. R-curves can alternatively be discussed in terms of stress intensity factors ( K ) {\displaystyle (K)} rather than energy release rates ( G ) {\displaystyle (G)} , where the R-curves can be expressed as the fracture toughness ( K I c {\displaystyle K_{Ic}} , sometimes referred to as K R {\displaystyle K_{R}} ) as a function of crack length a {\displaystyle a} .

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Radiation length

Definition

Radiation_length > Definition

In materials of high atomic number (e.g. tungsten, uranium, plutonium) the electrons of energies >~10 MeV predominantly lose energy by bremsstrahlung, and high-energy photons by e+e− pair production. The characteristic amount of matter traversed for these related interactions is called the radiation length X0, usually measured in g·cm−2. It is both the mean distance over which a high-energy electron loses all but 1⁄e of its energy by bremsstrahlung, and 7⁄9 of the mean free path for pair production by a high-energy photon. It is also the appropriate length scale for describing high-energy electromagnetic cascades.

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Radiation length

Definition

Radiation_length > Definition

The radiation length for a given material consisting of a single type of nucleus can be approximated by the following expression: where Z is the atomic number and A is mass number of the nucleus. For Z > 4, a good approximation is where na is the number density of the nucleus, ℏ {\displaystyle \hbar } denotes the reduced Planck constant, me is the electron rest mass, c is the speed of light, α is the fine-structure constant.For electrons at lower energies (below few tens of MeV), the energy loss by ionization is predominant. While this definition may also be used for other electromagnetic interacting particles beyond leptons and photons, the presence of the stronger hadronic and nuclear interaction makes it a far less interesting characterisation of the material; the nuclear collision length and nuclear interaction length are more relevant. Comprehensive tables for radiation lengths and other properties of materials are available from the Particle Data Group.

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Rod mill

Grinding machines

Mill_(grinding) > Grinding machines

In materials processing a grinder is a machine for producing fine particle size reduction through attrition and compressive forces at the grain size level. See also crusher for mechanisms producing larger particles. In general, grinding processes require a relatively large amount of energy; for this reason, an experimental method to measure the energy used locally during milling with different machines was recently proposed.

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Cocrystal

Summary

Cocrystal

In materials science (specifically crystallography), cocrystals are "solids that are crystalline, single-phase materials composed of two or more different molecular or ionic compounds generally in a stoichiometric ratio which are neither solvates nor simple salts." A broader definition is that cocrystals "consist of two or more components that form a unique crystalline structure having unique properties." Several subclassifications of cocrystals exist.Cocrystals can encompass many types of compounds, including hydrates, solvates and clathrates, which represent the basic principle of host–guest chemistry. Hundreds of examples of cocrystallization are reported annually.

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Functionally graded material

Summary

Functionally_graded_material

In materials science Functionally Graded Materials (FGMs) may be characterized by the variation in composition and structure gradually over volume, resulting in corresponding changes in the properties of the material. The materials can be designed for specific function and applications. Various approaches based on the bulk (particulate processing), preform processing, layer processing and melt processing are used to fabricate the functionally graded materials.

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Giant magnetoimpedance

Summary

Giant_magnetoimpedance

In materials science Giant Magnetoimpedance (GMI) is the effect that occurs in some materials where an external magnetic field causes a large variation in the electrical impedance of the material. It should not be confused with the separate physical phenomenon of Giant Magnetoresistance.

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Particle size

Colloidal particle

Colloidal_particle > International conventions > Colloidal particle

In materials science and colloidal chemistry, the term colloidal particle refers to a small amount of matter having a size typical for colloids and with a clear phase boundary. The dispersed-phase particles have a diameter between approximately 1 and 1000 nanometers. Colloids are heterogeneous in nature, invisible to the naked eye, and always move in a random zig-zag-like motion known as Brownian motion. The scattering of light by colloidal particles is known as Tyndall effect.

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Viscoelasticity

Summary

Viscoelasticity

In materials science and continuum mechanics, viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Viscous materials, like water, resist shear flow and strain linearly with time when a stress is applied. Elastic materials strain when stretched and immediately return to their original state once the stress is removed. Viscoelastic materials have elements of both of these properties and, as such, exhibit time-dependent strain. Whereas elasticity is usually the result of bond stretching along crystallographic planes in an ordered solid, viscosity is the result of the diffusion of atoms or molecules inside an amorphous material.

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Viscous forces

Dynamic viscosity

Inviscid_fluids > Definitions > Dynamic viscosity

In materials science and engineering, one is often interested in understanding the forces or stresses involved in the deformation of a material. For instance, if the material were a simple spring, the answer would be given by Hooke's law, which says that the force experienced by a spring is proportional to the distance displaced from equilibrium. Stresses which can be attributed to the deformation of a material from some rest state are called elastic stresses. In other materials, stresses are present which can be attributed to the deformation rate over time.

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Viscous forces

Dynamic viscosity

Inviscid_fluids > Definitions > Dynamic viscosity

These are called viscous stresses. For instance, in a fluid such as water the stresses which arise from shearing the fluid do not depend on the distance the fluid has been sheared; rather, they depend on how quickly the shearing occurs. Viscosity is the material property which relates the viscous stresses in a material to the rate of change of a deformation (the strain rate).

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Viscous forces

Dynamic viscosity

Inviscid_fluids > Definitions > Dynamic viscosity

Although it applies to general flows, it is easy to visualize and define in a simple shearing flow, such as a planar Couette flow. In the Couette flow, a fluid is trapped between two infinitely large plates, one fixed and one in parallel motion at constant speed u {\displaystyle u} (see illustration to the right). If the speed of the top plate is low enough (to avoid turbulence), then in steady state the fluid particles move parallel to it, and their speed varies from 0 {\displaystyle 0} at the bottom to u {\displaystyle u} at the top.

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Viscous forces

Dynamic viscosity

Inviscid_fluids > Definitions > Dynamic viscosity

Each layer of fluid moves faster than the one just below it, and friction between them gives rise to a force resisting their relative motion. In particular, the fluid applies on the top plate a force in the direction opposite to its motion, and an equal but opposite force on the bottom plate. An external force is therefore required in order to keep the top plate moving at constant speed.

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Viscous forces

Dynamic viscosity

Inviscid_fluids > Definitions > Dynamic viscosity

In many fluids, the flow velocity is observed to vary linearly from zero at the bottom to u {\displaystyle u} at the top. Moreover, the magnitude of the force, F {\displaystyle F} , acting on the top plate is found to be proportional to the speed u {\displaystyle u} and the area A {\displaystyle A} of each plate, and inversely proportional to their separation y {\displaystyle y}: F = μ A u y . {\displaystyle F=\mu A{\frac {u}{y}}.}

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Viscous forces

Dynamic viscosity

Inviscid_fluids > Definitions > Dynamic viscosity

The proportionality factor is the dynamic viscosity of the fluid, often simply referred to as the viscosity. It is denoted by the Greek letter mu (μ). The dynamic viscosity has the dimensions ( m a s s / l e n g t h ) / t i m e {\displaystyle \mathrm {(mass/length)/time} } , therefore resulting in the SI units and the derived units: = k g m ⋅ s = N m 2 ⋅ s = P a ⋅ s = {\displaystyle ={\frac {\rm {kg}}{\rm {m{\cdot }s}}}={\frac {\rm {N}}{\rm {m^{2}}}}{\cdot }{\rm {s}}={\rm {Pa{\cdot }s}}=} pressure multiplied by time.The aforementioned ratio u / y {\displaystyle u/y} is called the rate of shear deformation or shear velocity, and is the derivative of the fluid speed in the direction perpendicular to the normal vector of the plates (see illustrations to the right).

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Viscous forces

Dynamic viscosity

Inviscid_fluids > Definitions > Dynamic viscosity

If the velocity does not vary linearly with y {\displaystyle y} , then the appropriate generalization is: τ = μ ∂ u ∂ y , {\displaystyle \tau =\mu {\frac {\partial u}{\partial y}},} where τ = F / A {\displaystyle \tau =F/A} , and ∂ u / ∂ y {\displaystyle \partial u/\partial y} is the local shear velocity. This expression is referred to as Newton's law of viscosity.

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Viscous forces

Dynamic viscosity

Inviscid_fluids > Definitions > Dynamic viscosity

In shearing flows with planar symmetry, it is what defines μ {\displaystyle \mu } . It is a special case of the general definition of viscosity (see below), which can be expressed in coordinate-free form. Use of the Greek letter mu ( μ {\displaystyle \mu } ) for the dynamic viscosity (sometimes also called the absolute viscosity) is common among mechanical and chemical engineers, as well as mathematicians and physicists.

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Viscous forces

Dynamic viscosity

Inviscid_fluids > Definitions > Dynamic viscosity

However, the Greek letter eta ( η {\displaystyle \eta } ) is also used by chemists, physicists, and the IUPAC. The viscosity μ {\displaystyle \mu } is sometimes also called the shear viscosity. However, at least one author discourages the use of this terminology, noting that μ {\displaystyle \mu } can appear in non-shearing flows in addition to shearing flows.

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Yield (engineering)

Summary

Yield_Stress

In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed, some fraction of the deformation will be permanent and non-reversible and is known as plastic deformation. The yield strength or yield stress is a material property and is the stress corresponding to the yield point at which the material begins to deform plastically.

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Yield (engineering)

Summary

Yield_Stress

The yield strength is often used to determine the maximum allowable load in a mechanical component, since it represents the upper limit to forces that can be applied without producing permanent deformation. In some materials, such as aluminium, there is a gradual onset of non-linear behavior, and no precise yield point. In such a case, the offset yield point (or proof stress) is taken as the stress at which 0.2% plastic deformation occurs.

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Yield (engineering)

Summary

Yield_Stress

Yielding is a gradual failure mode which is normally not catastrophic, unlike ultimate failure. In solid mechanics, the yield point can be specified in terms of the three-dimensional principal stresses ( σ 1 , σ 2 , σ 3 {\displaystyle \sigma _{1},\sigma _{2},\sigma _{3}} ) with a yield surface or a yield criterion. A variety of yield criteria have been developed for different materials.

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Uranium metallurgy

Summary

Uranium_metallurgy

In materials science and materials engineering, uranium metallurgy is the study of the physical and chemical behavior of uranium and its alloys.Commercial-grade uranium can be produced through the reduction of uranium halides with alkali or alkaline earth metals. Uranium metal can also be made through electrolysis of KUF5 or UF4, dissolved in a molten CaCl2 and NaCl. Very pure uranium can be produced through the thermal decomposition of uranium halides on a hot filament.

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Uranium metallurgy

Summary

Uranium_metallurgy

The uranium isotope 235U is used as the fuel for nuclear reactors and nuclear weapons. It is the only isotope existing in nature to any appreciable extent that is fissile, that is, fissionable by thermal neutrons. The isotope 238U is also important because it absorbs neutrons to produce a radioactive isotope that subsequently decays to the isotope 239Pu (plutonium), which also is fissile. Uranium in its natural state comprises just 0.71% 235U and 99.3% 238U, and the main focus of uranium metallurgy is the enrichment of uranium through isotope separation.

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Functionally graded element

Summary

Functionally_graded_element

In materials science and mathematics, functionally graded elements are elements used in finite element analysis. They can be used to describe a functionally graded material.

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Toughness

Summary

Shock_resistance

In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing. Toughness is the strength with which the material opposes rupture. One definition of material toughness is the amount of energy per unit volume that a material can absorb before rupturing. This measure of toughness is different from that used for fracture toughness, which describes the capacity of materials to resist fracture. Toughness requires a balance of strength and ductility.

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Thermostability

Summary

Heat_stability

In materials science and molecular biology, thermostability is the ability of a substance to resist irreversible change in its chemical or physical structure, often by resisting decomposition or polymerization, at a high relative temperature. Thermostable materials may be used industrially as fire retardants. A thermostable plastic, an uncommon and unconventional term, is likely to refer to a thermosetting plastic that cannot be reshaped when heated, than to a thermoplastic that can be remelted and recast. Thermostability is also a property of some proteins. To be a thermostable protein means to be resistant to changes in protein structure due to applied heat.

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Slip line field

Summary

Slip_line_field

In materials science and soil mechanics, a slip line field or slip line field theory is a technique often used to analyze the stresses and forces involved in the major deformation of metals or soils. In essence, in some problems including plane strain and plane stress elastic-plastic problems, elastic part of the material prevent unrestrained plastic flow but in many metal-forming processes, such as rolling, drawing, gorging, etc., large unrestricted plastic flows occur except for many small elastic zones. In effect we are concerned with a rigid-plastic material under condition of plane strain. it turns out that the simplest way of solving stress equations is to express them in terms of a coordinate system that is along potential slip (or failure) surfaces. It is for this reason that this type of analysis is termed slip line analysis or the theory of slip line fields in the literature.

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Poisson's Ratio

Summary

Poisson’s_ratio

In materials science and solid mechanics, Poisson's ratio ν {\displaystyle \nu } (nu) is a measure of the Poisson effect, the deformation (expansion or contraction) of a material in directions perpendicular to the specific direction of loading. The value of Poisson's ratio is the negative of the ratio of transverse strain to axial strain. For small values of these changes, ν {\displaystyle \nu } is the amount of transversal elongation divided by the amount of axial compression. Most materials have Poisson's ratio values ranging between 0.0 and 0.5.

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Poisson's Ratio

Summary

Poisson’s_ratio

For soft materials, such as rubber, where the bulk modulus is much higher than the shear modulus, Poisson's ratio is near 0.5. For open-cell polymer foams, Poisson's ratio is near zero, since the cells tend to collapse in compression. Many typical solids have Poisson's ratios in the range of 0.2–0.3. The ratio is named after the French mathematician and physicist Siméon Poisson.

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Biaxial tensile testing

Summary

Biaxial_tensile_testing

In materials science and solid mechanics, biaxial tensile testing is a versatile technique to address the mechanical characterization of planar materials. It is a generalized form of tensile testing in which the material sample is simultaneously stressed along two perpendicular axes. Typical materials tested in biaxial configuration include metal sheets,silicone elastomers,composites,thin films,textiles and biological soft tissues.

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Residual stress

Summary

Residual_stress

In materials science and solid mechanics, residual stresses are stresses that remain in a solid material after the original cause of the stresses has been removed. Residual stress may be desirable or undesirable. For example, laser peening imparts deep beneficial compressive residual stresses into metal components such as turbine engine fan blades, and it is used in toughened glass to allow for large, thin, crack- and scratch-resistant glass displays on smartphones. However, unintended residual stress in a designed structure may cause it to fail prematurely.

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Residual stress

Summary

Residual_stress

Residual stresses can result from a variety of mechanisms including inelastic (plastic) deformations, temperature gradients (during thermal cycle) or structural changes (phase transformation). Heat from welding may cause localized expansion, which is taken up during welding by either the molten metal or the placement of parts being welded. When the finished weldment cools, some areas cool and contract more than others, leaving residual stresses. Another example occurs during semiconductor fabrication and microsystem fabrication when thin film materials with different thermal and crystalline properties are deposited sequentially under different process conditions. The stress variation through a stack of thin film materials can be very complex and can vary between compressive and tensile stresses from layer to layer.

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Work hardened

Dislocations and lattice strain fields

Work_hardened > Theory > Dislocations and lattice strain fields

In materials science parlance, dislocations are defined as line defects in a material's crystal structure. The bonds surrounding the dislocation are already elastically strained by the defect compared to the bonds between the constituents of the regular crystal lattice. Therefore, these bonds break at relatively lower stresses, leading to plastic deformation. The strained bonds around a dislocation are characterized by lattice strain fields.

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Work hardened

Dislocations and lattice strain fields

Work_hardened > Theory > Dislocations and lattice strain fields

For example, there are compressively strained bonds directly next to an edge dislocation and tensilely strained bonds beyond the end of an edge dislocation. These form compressive strain fields and tensile strain fields, respectively. Strain fields are analogous to electric fields in certain ways.

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Work hardened

Dislocations and lattice strain fields

Work_hardened > Theory > Dislocations and lattice strain fields

Specifically, the strain fields of dislocations obey similar laws of attraction and repulsion; in order to reduce overall strain, compressive strains are attracted to tensile strains, and vice versa. The visible (macroscopic) results of plastic deformation are the result of microscopic dislocation motion. For example, the stretching of a steel rod in a tensile tester is accommodated through dislocation motion on the atomic scale.

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Flow stress

Summary

Flow_stress

In materials science the flow stress, typically denoted as Yf (or σ f {\displaystyle \sigma _{\text{f}}} ), is defined as the instantaneous value of stress required to continue plastically deforming a material - to keep it flowing. It is most commonly, though not exclusively, used in reference to metals. On a stress-strain curve, the flow stress can be found anywhere within the plastic regime; more explicitly, a flow stress can be found for any value of strain between and including yield point ( σ y {\displaystyle \sigma _{\text{y}}} ) and excluding fracture ( σ F {\displaystyle \sigma _{\text{F}}} ): σ y ≤ Y f < σ F {\displaystyle \sigma _{\text{y}}\leq Y_{\text{f}}<\sigma _{\text{F}}} . The flow stress changes as deformation proceeds and usually increases as strain accumulates due to work hardening, although the flow stress could decrease due to any recovery process.

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Flow stress

Summary

Flow_stress

In continuum mechanics, the flow stress for a given material will vary with changes in temperature, T {\displaystyle T} , strain, ε {\displaystyle \varepsilon } , and strain-rate, ε ˙ {\displaystyle {\dot {\varepsilon }}} ; therefore it can be written as some function of those properties: Y f = f ( ε , ε ˙ , T ) {\displaystyle Y_{\text{f}}=f(\varepsilon ,{\dot {\varepsilon }},T)} The exact equation to represent flow stress depends on the particular material and plasticity model being used. Hollomon's equation is commonly used to represent the behavior seen in a stress-strain plot during work hardening: Y f = K ε p n {\displaystyle Y_{\text{f}}=K\varepsilon _{\text{p}}^{\text{n}}} Where Y f {\displaystyle Y_{\text{f}}} is flow stress, K {\displaystyle K} is a strength coefficient, ε p {\displaystyle \varepsilon _{\text{p}}} is the plastic strain, and n {\displaystyle n} is the strain hardening exponent. Note that this is an empirical relation and does not model the relation at other temperatures or strain-rates (though the behavior may be similar).

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Flow stress

Summary

Flow_stress

Generally, raising the temperature of an alloy above 0.5 Tm results in the plastic deformation mechanisms being controlled by strain-rate sensitivity, whereas at room temperature metals are generally strain-dependent. Other models may also include the effects of strain gradients. Independent of test conditions, the flow stress is also affected by: chemical composition, purity, crystal structure, phase constitution, microstructure, grain size, and prior strain.The flow stress is an important parameter in the fatigue failure of ductile materials.

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Flow stress

Summary

Flow_stress

Fatigue failure is caused by crack propagation in materials under a varying load, typically a cyclically varying load. The rate of crack propagation is inversely proportional to the flow stress of the material. == References ==

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MXenes

Summary

MXenes

In materials science, MXenes are a class of two-dimensional inorganic compounds , that consist of atomically thin layers of transition metal carbides, nitrides, or carbonitrides. MXenes accept a variety of hydrophilic terminations. MXenes were first reported in 2012.

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Ostwald's step rule

Summary

Ostwald's_rule

In materials science, Ostwald's rule or Ostwald's step rule, conceived by Wilhelm Ostwald, describes the formation of polymorphs. The rule states that usually the less stable polymorph crystallizes first. Ostwald's rule is not a universal law but a common tendency observed in nature.This can be explained on the basis of irreversible thermodynamics, structural relationships, or a combined consideration of statistical thermodynamics and structural variation with temperature.

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Ostwald's step rule

Summary

Ostwald's_rule

Unstable polymorphs more closely resemble the state in solution, and thus are kinetically advantaged. For example, out of hot water, metastable, fibrous crystals of benzamide appear first, only later to spontaneously convert to the more stable rhombic polymorph. Another example is magnesium carbonate, which more readily forms dolomite.

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Ostwald's step rule

Summary

Ostwald's_rule

A dramatic example is phosphorus, which upon sublimation first forms the less stable white phosphorus, which only slowly polymerizes to the red allotrope. This is notably the case for the anatase polymorph of titanium dioxide, which having a lower surface energy is commonly the first phase to form by crystallisation from amorphous precursors or solutions despite being metastable, with rutile being the equilibrium phase at all temperatures and pressures. == References ==

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Schmid's law

Summary

Schmid's_law

In materials science, Schmid's law (also Schmid factor) describes the slip plane and the slip direction of a stressed material, which can resolve the most shear stress. Schmid's Law states that the critically resolved shear stress (τ) is equal to the stress applied to the material (σ) multiplied by the cosine of the angle with the vector normal to the glide plane (φ) and the cosine of the angle with the glide direction (λ). Which can be expressed as: τ = m σ {\displaystyle \tau =m\sigma } where m is known as the Schmid factor m = cos ⁡ ( ϕ ) cos ⁡ ( λ ) {\displaystyle m=\cos(\phi )\cos(\lambda )} Both factors τ and σ are measured in stress units, which is calculated the same way as pressure (force divided by area). φ and λ are angles. The factor is named after Erich Schmid who coauthored a book with Walter Boas introducing the concept in 1935.

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Bingham fluid

Summary

Bingham_plastic

In materials science, a Bingham plastic is a viscoplastic material that behaves as a rigid body at low stresses but flows as a viscous fluid at high stress. It is named after Eugene C. Bingham who proposed its mathematical form.It is used as a common mathematical model of mud flow in drilling engineering, and in the handling of slurries. A common example is toothpaste, which will not be extruded until a certain pressure is applied to the tube. It is then pushed out as a relatively coherent plug.

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Frank-Read source

Summary

Frank-Read_source

In materials science, a Frank–Read source is a mechanism explaining the generation of multiple dislocations in specific well-spaced slip planes in crystals when they are deformed. When a crystal is deformed, in order for slip to occur, dislocations must be generated in the material. This implies that, during deformation, dislocations must be primarily generated in these planes.

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Frank-Read source

Summary

Frank-Read_source

Cold working of metal increases the number of dislocations by the Frank–Read mechanism. Higher dislocation density increases yield strength and causes work hardening of metals. The mechanism of dislocation generation was proposed by and named after British physicist Charles Frank and Thornton Read.

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Lomer–Cottrell junction

Summary

Lomer–Cottrell_junction

In materials science, a Lomer–Cottrell junction is a particular configuration of dislocations. When two perfect dislocations encounter along a slip plane, each perfect dislocation can split into two Shockley partial dislocations: a leading dislocation and a trailing dislocation. When the two leading Shockley partials combine, they form a separate dislocation with a burgers vector that is not in the slip plane. This is the Lomer–Cottrell dislocation.

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Lomer–Cottrell junction

Summary

Lomer–Cottrell_junction

It is sessile and immobile in the slip plane, acting as a barrier against other dislocations in the plane. The trailing dislocations pile up behind the Lomer–Cottrell dislocation, and an ever greater force is required to push additional dislocations into the pile-up. ex. FCC lattice along {111} slip planes |leading| |trailing| a 2 → a 6 + a 6 {\displaystyle {\frac {a}{2}}\rightarrow {\frac {a}{6}}+{\frac {a}{6}}} a 2 → a 6 + a 6 {\displaystyle {\frac {a}{2}}\rightarrow {\frac {a}{6}}+{\frac {a}{6}}} Combination of leading dislocations: a 6 + a 6 → a 3 {\displaystyle {\frac {a}{6}}+{\frac {a}{6}}\rightarrow {\frac {a}{3}}} The resulting dislocation is along the crystal face, which is not a slip plane in FCC at room temperature. Lomer–Cottrell dislocation == References ==

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Composite laminate

Summary

Composite_laminate

In materials science, a composite laminate is an assembly of layers of fibrous composite materials which can be joined to provide required engineering properties, including in-plane stiffness, bending stiffness, strength, and coefficient of thermal expansion. The individual layers consist of high-modulus, high-strength fibers in a polymeric, metallic, or ceramic matrix material. Typical fibers used include cellulose, graphite, glass, boron, and silicon carbide, and some matrix materials are epoxies, polyimides, aluminium, titanium, and alumina.

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Composite laminate

Summary

Composite_laminate

Layers of different materials may be used, resulting in a hybrid laminate. The individual layers generally are orthotropic (that is, with principal properties in orthogonal directions) or transversely isotropic (with isotropic properties in the transverse plane) with the laminate then exhibiting anisotropic (with variable direction of principal properties), orthotropic, or quasi-isotropic properties. Quasi-isotropic laminates exhibit isotropic (that is, independent of direction) inplane response but are not restricted to isotropic out-of-plane (bending) response. Depending upon the stacking sequence of the individual layers, the laminate may exhibit coupling between inplane and out-of-plane response. An example of bending-stretching coupling is the presence of curvature developing as a result of in-plane loading.

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Dislocation

Summary

Dislocation_climb

In materials science, a dislocation or Taylor's dislocation is a linear crystallographic defect or irregularity within a crystal structure that contains an abrupt change in the arrangement of atoms. The movement of dislocations allow atoms to slide over each other at low stress levels and is known as glide or slip. The crystalline order is restored on either side of a glide dislocation but the atoms on one side have moved by one position. The crystalline order is not fully restored with a partial dislocation.

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Dislocation

Summary

Dislocation_climb

A dislocation defines the boundary between slipped and unslipped regions of material and as a result, must either form a complete loop, intersect other dislocations or defects, or extend to the edges of the crystal. A dislocation can be characterised by the distance and direction of movement it causes to atoms which is defined by the Burgers vector. Plastic deformation of a material occurs by the creation and movement of many dislocations.

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Dislocation

Summary

Dislocation_climb

The number and arrangement of dislocations influences many of the properties of materials. The two primary types of dislocations are sessile dislocations which are immobile and glissile dislocations which are mobile. Examples of sessile dislocations are the stair-rod dislocation and the Lomer–Cottrell junction.

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Dislocation

Summary

Dislocation_climb

The two main types of mobile dislocations are edge and screw dislocations. Edge dislocations can be visualized as being caused by the termination of a plane of atoms in the middle of a crystal. In such a case, the surrounding planes are not straight, but instead bend around the edge of the terminating plane so that the crystal structure is perfectly ordered on either side.

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Dislocation

Summary

Dislocation_climb

This phenomenon is analogous to half of a piece of paper inserted into a stack of paper, where the defect in the stack is noticeable only at the edge of the half sheet. The theory describing the elastic fields of the defects was originally developed by Vito Volterra in 1907. In 1934, Egon Orowan, Michael Polanyi and G. I. Taylor, proposed that the low stresses observed to produce plastic deformation compared to theoretical predictions at the time could be explained in terms of the theory of dislocations.

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Rule of mixtures

Summary

Rule_of_mixtures

In materials science, a general rule of mixtures is a weighted mean used to predict various properties of a composite material . It provides a theoretical upper- and lower-bound on properties such as the elastic modulus, ultimate tensile strength, thermal conductivity, and electrical conductivity. In general there are two models, one for axial loading (Voigt model), and one for transverse loading (Reuss model).In general, for some material property E {\displaystyle E} (often the elastic modulus), the rule of mixtures states that the overall property in the direction parallel to the fibers may be as high as E c = f E f + ( 1 − f ) E m {\displaystyle E_{c}=fE_{f}+\left(1-f\right)E_{m}} where f = V f V f + V m {\displaystyle f={\frac {V_{f}}{V_{f}+V_{m}}}} is the volume fraction of the fibers E f {\displaystyle E_{f}} is the material property of the fibers E m {\displaystyle E_{m}} is the material property of the matrixIt is a common mistake to believe that this is the upper-bound modulus for Young's modulus.

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Rule of mixtures

Summary

Rule_of_mixtures

The real upper-bound Young's modulus is larger than E c {\displaystyle E_{c}} given by this formula. Even if both constituents are isotropic, the real upper bound is E c {\displaystyle E_{c}} plus a term in the order of square of the difference of the Poisson's ratios of the two constituents.The inverse rule of mixtures states that in the direction perpendicular to the fibers, the elastic modulus of a composite can be as low as E c = ( f E f + 1 − f E m ) − 1 . {\displaystyle E_{c}=\left({\frac {f}{E_{f}}}+{\frac {1-f}{E_{m}}}\right)^{-1}.} If the property under study is the elastic modulus, this quantity is called the lower-bound modulus, and corresponds to a transverse loading.

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Grain boundary

Summary

Grain_boundary

In materials science, a grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are two-dimensional defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material. Most grain boundaries are preferred sites for the onset of corrosion and for the precipitation of new phases from the solid. They are also important to many of the mechanisms of creep. On the other hand, grain boundaries disrupt the motion of dislocations through a material, so reducing crystallite size is a common way to improve mechanical strength, as described by the Hall–Petch relationship.

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Matrix (composite)

Summary

Matrix_(composite)

In materials science, a matrix is a constituent of a composite material.

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Sponge metal

Summary

Aluminum_foam

In materials science, a metal foam is a material or structure consisting of a solid metal (frequently aluminium) with gas-filled pores comprising a large portion of the volume. The pores can be sealed (closed-cell foam) or interconnected (open-cell foam). The defining characteristic of metal foams is a high porosity: typically only 5–25% of the volume is the base metal. The strength of the material is due to the square–cube law.

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Sponge metal

Summary

Aluminum_foam

Metal foams typically retain some physical properties of their base material. Foam made from non-flammable metal remains non-flammable and can generally be recycled as the base material. Its coefficient of thermal expansion is similar while thermal conductivity is likely reduced.

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Metal matrix composite

Summary

Metal_matrix_composites

In materials science, a metal matrix composite (MMC) is a composite material with fibers or particles dispersed in a metallic matrix, such as copper, aluminum, or steel. The secondary phase is typically a ceramic (such as alumina or silicon carbide) or another metal (such as steel). They are typically classified according to the type of reinforcement: short discontinuous fibers (whiskers), continuous fibers, or particulates.