1.
Glass
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Glass is a non-crystalline amorphous solid that is often transparent and has widespread practical, technological, and decorative usage in, for example, window panes, tableware, and optoelectronics. The most familiar, and historically the oldest, types of glass are silicate glasses based on the chemical compound silica, the primary constituent of sand. The term glass, in usage, is often used to refer only to this type of material. Many applications of silicate glasses derive from their optical transparency, giving rise to their use as window panes. Glass can be coloured by adding metallic salts, and can also be painted and printed with vitreous enamels and these qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows. Although brittle, silicate glass is extremely durable, and many examples of glass fragments exist from early glass-making cultures, because glass can be formed or moulded into any shape, it has been traditionally used for vessels, bowls, vases, bottles, jars and drinking glasses. In its most solid forms it has also used for paperweights, marbles. Some objects historically were so commonly made of glass that they are simply called by the name of the material, such as drinking glasses. Porcelains and many polymer thermoplastics familiar from everyday use are glasses and these sorts of glasses can be made of quite different kinds of materials than silica, metallic alloys, ionic melts, aqueous solutions, molecular liquids, and polymers. For many applications, like glass bottles or eyewear, polymer glasses are a lighter alternative than traditional glass, silica is a common fundamental constituent of glass. In nature, vitrification of quartz occurs when lightning strikes sand, forming hollow, fused quartz is a glass made from chemically-pure SiO2. It has excellent resistance to shock, being able to survive immersion in water while red hot. However, its high melting-temperature and viscosity make it difficult to work with, normally, other substances are added to simplify processing. One is sodium carbonate, which lowers the transition temperature. The soda makes the glass water-soluble, which is undesirable, so lime, some magnesium oxide. The resulting glass contains about 70 to 74% silica by weight and is called a soda-lime glass, soda-lime glasses account for about 90% of manufactured glass. Most common glass contains other ingredients to change its properties, lead glass or flint glass is more brilliant because the increased refractive index causes noticeably more specular reflection and increased optical dispersion. Adding barium also increases the refractive index, iron can be incorporated into glass to absorb infrared energy, for example in heat absorbing filters for movie projectors, while cerium oxide can be used for glass that absorbs UV wavelengths
2.
Cast iron
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Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. Its usefulness derives from its low melting temperature. Carbon ranging from 1. 8–4 wt%, and silicon 1–3 wt% are the main alloying elements of cast iron, Iron alloys with less carbon content are known as steel. While this technically makes the Fe–C–Si system ternary, the principle of cast iron solidification can be understood from the simpler binary iron–carbon phase diagram, cast iron tends to be brittle, except for malleable cast irons. It is resistant to destruction and weakening by oxidation, the earliest cast iron artefacts date to the 5th century BC, and were discovered by archaeologists in what is now Jiangsu in China. Cast iron was used in ancient China for warfare, agriculture, during the 15th century, cast iron became utilized for artillery in Burgundy, France, and in England during the Reformation. The first cast iron bridge was built during the 1770s by Abraham Darby III, cast iron is also used in the construction of buildings. Cast iron is made by re-melting pig iron, often along with quantities of iron, steel, limestone, carbon. Phosphorus and sulfur may be burnt out of the iron, but this also burns out the carbon. Depending on the application, carbon and silicon content are adjusted to the desired levels, other elements are then added to the melt before the final form is produced by casting. Cast iron is melted in a special type of blast furnace known as a cupola. After melting is complete, the molten cast iron is poured into a furnace or ladle. Cast irons properties are changed by adding various alloying elements, or alloyants, next to carbon, silicon is the most important alloyant because it forces carbon out of solution. A low percentage of silicon allows carbon to remain in solution forming iron carbide, a high percentage of silicon forces carbon out of solution forming graphite and the production of grey cast iron. Other alloying agents, manganese, chromium, molybdenum, titanium and vanadium counteracts silicon, promotes the retention of carbon, nickel and copper increase strength, and machinability, but do not change the amount of graphite formed. The carbon in the form of graphite results in an iron, reduces shrinkage, lowers strength. Sulfur, largely a contaminant when present, forms iron sulfide, the problem with sulfur is that it makes molten cast iron viscous, which causes defects. To counter the effects of sulfur, manganese is added because the two form into manganese sulfide instead of iron sulfide, the manganese sulfide is lighter than the melt so it tends to float out of the melt and into the slag
3.
Stress (physics)
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For example, when a solid vertical bar is supporting a weight, each particle in the bar pushes on the particles immediately below it. When a liquid is in a container under pressure, each particle gets pushed against by all the surrounding particles. The container walls and the pressure-inducing surface push against them in reaction and these macroscopic forces are actually the net result of a very large number of intermolecular forces and collisions between the particles in those molecules. Strain inside a material may arise by various mechanisms, such as stress as applied by external forces to the material or to its surface. Any strain of a material generates an internal elastic stress, analogous to the reaction force of a spring. In liquids and gases, only deformations that change the volume generate persistent elastic stress, however, if the deformation is gradually changing with time, even in fluids there will usually be some viscous stress, opposing that change. Elastic and viscous stresses are usually combined under the mechanical stress. Significant stress may exist even when deformation is negligible or non-existent, stress may exist in the absence of external forces, such built-in stress is important, for example, in prestressed concrete and tempered glass. Stress may also be imposed on a material without the application of net forces, for example by changes in temperature or chemical composition, stress that exceeds certain strength limits of the material will result in permanent deformation or even change its crystal structure and chemical composition. In some branches of engineering, the stress is occasionally used in a looser sense as a synonym of internal force. For example, in the analysis of trusses, it may refer to the total traction or compression force acting on a beam, since ancient times humans have been consciously aware of stress inside materials. Until the 17th century the understanding of stress was largely intuitive and empirical, with those tools, Augustin-Louis Cauchy was able to give the first rigorous and general mathematical model for stress in a homogeneous medium. Cauchy observed that the force across a surface was a linear function of its normal vector, and, moreover. The understanding of stress in liquids started with Newton, who provided a formula for friction forces in parallel laminar flow. Stress is defined as the force across a small boundary per unit area of that boundary, following the basic premises of continuum mechanics, stress is a macroscopic concept. In a fluid at rest the force is perpendicular to the surface, in a solid, or in a flow of viscous liquid, the force F may not be perpendicular to S, hence the stress across a surface must be regarded a vector quantity, not a scalar. Moreover, the direction and magnitude depend on the orientation of S. Thus the stress state of the material must be described by a tensor, called the stress tensor, with respect to any chosen coordinate system, the Cauchy stress tensor can be represented as a symmetric matrix of 3×3 real numbers
4.
Energy
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In physics, energy is the property that must be transferred to an object in order to perform work on – or to heat – the object, and can be converted in form, but not created or destroyed. The SI unit of energy is the joule, which is the transferred to an object by the mechanical work of moving it a distance of 1 metre against a force of 1 newton. Mass and energy are closely related, for example, with a sensitive enough scale, one could measure an increase in mass after heating an object. Living organisms require available energy to stay alive, such as the humans get from food. Civilisation gets the energy it needs from energy resources such as fuels, nuclear fuel. The processes of Earths climate and ecosystem are driven by the radiant energy Earth receives from the sun, the total energy of a system can be subdivided and classified in various ways. It may also be convenient to distinguish gravitational energy, thermal energy, several types of energy, electric energy. Many of these overlap, for instance, thermal energy usually consists partly of kinetic. Some types of energy are a mix of both potential and kinetic energy. An example is energy which is the sum of kinetic. Whenever physical scientists discover that a phenomenon appears to violate the law of energy conservation. Heat and work are special cases in that they are not properties of systems, in general we cannot measure how much heat or work are present in an object, but rather only how much energy is transferred among objects in certain ways during the occurrence of a given process. Heat and work are measured as positive or negative depending on which side of the transfer we view them from, the distinctions between different kinds of energy is not always clear-cut. In contrast to the definition, energeia was a qualitative philosophical concept, broad enough to include ideas such as happiness. The modern analog of this property, kinetic energy, differs from vis viva only by a factor of two, in 1807, Thomas Young was possibly the first to use the term energy instead of vis viva, in its modern sense. Gustave-Gaspard Coriolis described kinetic energy in 1829 in its modern sense, the law of conservation of energy was also first postulated in the early 19th century, and applies to any isolated system. It was argued for years whether heat was a physical substance, dubbed the caloric, or merely a physical quantity. In 1845 James Prescott Joule discovered the link between mechanical work and the generation of heat and these developments led to the theory of conservation of energy, formalized largely by William Thomson as the field of thermodynamics
5.
Strength of materials
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Strength of materials, also called mechanics of materials, is a subject which deals with the behavior of solid objects subject to stresses and strains. An important founding pioneer in mechanics of materials was Stephen Timoshenko, the study of strength of materials often refers to various methods of calculating the stresses and strains in structural members, such as beams, columns, and shafts. In materials science, the strength of a material is its ability to withstand a load without failure or plastic deformation. The field of strength of materials deals with forces and deformations that result from their acting on a material, a load applied to a mechanical member will induce internal forces within the member called stresses when those forces are expressed on a unit basis. The stresses acting on the material cause deformation of the material in various manners, deformation of the material is called strain when those deformations too are placed on a unit basis. The applied loads may be axial, or rotational, the stresses and strains that develop within a mechanical member must be calculated in order to assess the load capacity of that member. This requires a description of the geometry of the member, its constraints, the loads applied to the member. With a complete description of the loading and the geometry of the member, once the state of stress and strain within the member is known, the strength of that member, its deformations, and its stability can be calculated. The calculated stresses may then be compared to some measure of the strength of the such as its material yield or ultimate strength. The calculated deflection of the member may be compared to a deflection criteria that is based on the members use, the calculated buckling load of the member may be compared to the applied load. The calculated stiffness and mass distribution of the member may be used to calculate the dynamic response. The ultimate strength refers to the point on the engineering stress–strain curve corresponding to the stress that produces fracture, transverse loading - Forces applied perpendicular to the longitudinal axis of a member. Transverse loading causes the member to bend and deflect from its position, with internal tensile. Transverse loading also induces shear forces that cause shear deformation of the material, axial loading - The applied forces are collinear with the longitudinal axis of the member. The forces cause the member to either stretch or shorten, uniaxial stress is expressed by σ = F A where F is the force acting on an area A. The area can be the area or the deformed area. A simple case of compression is the uniaxial compression induced by the action of opposite, compressive strength for materials is generally higher than their tensile strength. However, structures loaded in compression are subject to additional failure modes, such as buckling, that are dependent on the members geometry
6.
Ceramic
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A ceramic is an inorganic, non-metallic, solid material comprising metal, non-metal or metalloid atoms primarily held in ionic and covalent bonds. This article gives an overview of ceramic materials from the point of view of materials science, the crystallinity of ceramic materials ranges from highly oriented to semi-crystalline, vitrified, and often completely amorphous. Most often, fired ceramics are either vitrified or semi-vitrified as is the case with earthenware, stoneware, varying crystallinity and electron consumption in the ionic and covalent bonds cause most ceramic materials to be good thermal and electrical insulators. With such a range of possible options for the composition/structure of a ceramic, the breadth of the subject is vast. Many composites, such as fiberglass and carbon fiber, while containing ceramic materials, are not considered to be part of the ceramic family. The earliest ceramics made by humans were pottery objects or figurines made from clay, either by itself or mixed with materials like silica, hardened, sintered. Later ceramics were glazed and fired to create smooth, colored surfaces, decreasing porosity through the use of glassy, ceramics now include domestic, industrial and building products, as well as a wide range of ceramic art. In the 20th century, new materials were developed for use in advanced ceramic engineering. The word ceramic comes from the Greek word κεραμικός, of pottery or for pottery, from κέραμος, potters clay, tile, the earliest known mention of the root ceram- is the Mycenaean Greek ke-ra-me-we, workers of ceramics, written in Linear B syllabic script. The word ceramic may be used as an adjective to describe a material, product or process, or it may be used as a noun, either singular, or, more commonly, as the plural noun ceramics. A ceramic material is an inorganic, non-metallic, often crystalline oxide, nitride or carbide material, some elements, such as carbon or silicon, may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, weak in shearing and they withstand chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics generally can withstand high temperatures, such as temperatures that range from 1,000 °C to 1,600 °C. Glass is often not considered a ceramic because of its amorphous character. However, glassmaking involves several steps of the process and its mechanical properties are similar to ceramic materials. Traditional ceramic raw materials include minerals such as kaolinite, whereas more recent materials include aluminium oxide. The modern ceramic materials, which are classified as advanced ceramics, include silicon carbide, both are valued for their abrasion resistance, and hence find use in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are used in the medicine, electrical, electronics industries. Crystalline ceramic materials are not amenable to a range of processing
7.
Polymer
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A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Because of their range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure, Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. The units composing polymers derive, actually or conceptually, from molecules of low molecular mass. The term was coined in 1833 by Jöns Jacob Berzelius, though with a distinct from the modern IUPAC definition. The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger, Polymers are studied in the fields of biophysics and macromolecular science, and polymer science. Polyisoprene of latex rubber is an example of a polymer. In biological contexts, essentially all biological macromolecules—i. e, proteins, nucleic acids, and polysaccharides—are purely polymeric, or are composed in large part of polymeric components—e. g. Isoprenylated/lipid-modified glycoproteins, where small molecules and oligosaccharide modifications occur on the polyamide backbone of the protein. The simplest theoretical models for polymers are ideal chains, Polymers are of two types, Natural polymeric materials such as shellac, amber, wool, silk and natural rubber have been used for centuries. A variety of natural polymers exist, such as cellulose. Most commonly, the continuously linked backbone of a used for the preparation of plastics consists mainly of carbon atoms. A simple example is polyethylene, whose repeating unit is based on ethylene monomer, however, other structures do exist, for example, elements such as silicon form familiar materials such as silicones, examples being Silly Putty and waterproof plumbing sealant. Oxygen is also present in polymer backbones, such as those of polyethylene glycol, polysaccharides. Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network, during the polymerization process, some chemical groups may be lost from each monomer. This is the case, for example, in the polymerization of PET polyester, the distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue. Laboratory synthetic methods are divided into two categories, step-growth polymerization and chain-growth polymerization. However, some methods such as plasma polymerization do not fit neatly into either category
8.
Poly(methyl methacrylate)
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The same material can be utilised as a casting resin, in inks and coatings, and has many other uses. Chemically, it is the polymer of methyl methacrylate. PMMA is an alternative to polycarbonate when extreme strength is not necessary. Additionally, PMMA does not contain the potentially harmful bisphenol-A subunits found in polycarbonate and it is often preferred because of its moderate properties, easy handling and processing, and low cost. The first acrylic acid was created in 1843, methacrylic acid, derived from acrylic acid, was formulated in 1865. The reaction between acid and methanol results in the ester methyl methacrylate. In 1877 the German chemist Wilhelm Rudolph Fittig discovered the process that turns methyl methacrylate into polymethyl methacrylate. In 1933, the brand name Plexiglas was patented and registered by another German chemist, in 1936 Imperial Chemical Industries began the first commercially viable production of acrylic safety glass. During World War II both Allied and Axis forces used acrylic glass for submarine periscopes and aircraft windshields, canopies, common orthographic stylings include polymethyl methacrylate and polymethylmethacrylate. The full chemical name is poly, although often called simply acrylic, acrylic can also refer to other polymers or copolymers containing polyacrylonitrile. The other notable names include, Acrylite, a trademark of Evonik Cyro since 1976 Lucite, a trademark of DuPont, first registered in 1937 R-Cast. Founded in 1987 after spinning off from Reynolds & Taylor and they specialize in large scale and thick monolithic acrylic. Plexiglas, a trademark of ELF Atochem, now a subsidiary of Arkema in the US, generally, radical initiation is used, but anionic polymerization of PMMA can also be performed. To produce 1 kg of PMMA, about 2 kg of petroleum is needed, PMMA produced by radical polymerization is atactic and completely amorphous. The glass transition temperature of atactic PMMA is 105 °C, PMMA is thus an organic glass at room temperature, i. e. it is below its Tg. The forming temperature starts at the transition temperature and goes up from there. All common molding processes may be used, including molding, compression molding. The highest quality PMMA sheets are produced by casting, but in this case
9.
Polystyrene
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Polystyrene /ˌpɒliˈstaɪriːn/ is a synthetic aromatic polymer made from the monomer styrene. Polystyrene can be solid or foamed, general-purpose polystyrene is clear, hard, and rather brittle. It is an inexpensive resin per unit weight and it is a rather poor barrier to oxygen and water vapor and has a relatively low melting point. Polystyrene is one of the most widely used plastics, the scale of its production being several million tonnes per year, Polystyrene can be naturally transparent, but can be colored with colorants. Uses include protective packaging, containers, lids, bottles, trays, tumblers, as a thermoplastic polymer, polystyrene is in a solid state at room temperature but flows if heated above about 100 °C, its glass transition temperature. It becomes rigid again when cooled and this temperature behavior is exploited for extrusion and also for molding and vacuum forming, since it can be cast into molds with fine detail. Polystyrene is very slow to biodegrade and is therefore a focus of controversy among environmentalists, Polystyrene was discovered in 1839 by Eduard Simon, an apothecary from Berlin. From storax, the resin of the American sweetgum tree Liquidambar styraciflua, he distilled an oily substance, several days later, Simon found that the styrol had thickened into a jelly he dubbed styrol oxide because he presumed an oxidation. By 1845 Jamaican-born chemist John Buddle Blyth and German chemist August Wilhelm von Hofmann showed that the transformation of styrol took place in the absence of oxygen. They called the product metastyrol, analysis showed that it was identical to Simons Styroloxyd. In 1866 Marcelin Berthelot correctly identified the formation of metastyrol/Styroloxyd from styrol as a polymerization process, about 80 years later it was realized that heating of styrol starts a chain reaction that produces macromolecules, following the thesis of German organic chemist Hermann Staudinger. This eventually led to the substance receiving its present name, polystyrene, the company I. G. Farben began manufacturing polystyrene in Ludwigshafen, about 1931, hoping it would be a suitable replacement for die-cast zinc in many applications. Success was achieved when they developed a reactor vessel that extruded polystyrene through a tube and cutter. In 1941, Dow Chemical invented a Styrofoam process, before 1949, the chemical engineer Fritz Stastny developed pre-expanded PS beads by incorporating aliphatic hydrocarbons, such as pentane. These beads are the raw material for moulding parts or extruding sheets, BASF and Stastny applied for a patent that was issued in 1949. The moulding process was demonstrated at the Kunststoff Messe 1952 in Düsseldorf, the crystal structure of isotactic polystyrene was reported by Giulio Natta. In 1954, the Koppers Company in Pittsburgh, Pennsylvania, developed expanded polystyrene foam under the trade name Dylite, in 1960, Dart Container, the largest manufacturer of foam cups, shipped their first order. In 1988, the first U. S. ban of general polystyrene foam was enacted in Berkeley, in chemical terms, polystyrene is a long chain hydrocarbon wherein alternating carbon centers are attached to phenyl groups
10.
Steel
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Steel is an alloy of iron and other elements, primarily carbon, that is widely used in construction and other applications because of its high tensile strength and low cost. Steels base metal is iron, which is able to take on two forms, body centered cubic and face centered cubic, depending on its temperature. It is the interaction of those allotropes with the elements, primarily carbon. In the body-centred cubic arrangement, there is an atom in the centre of each cube. Carbon, other elements, and inclusions within iron act as hardening agents that prevent the movement of dislocations that otherwise occur in the lattices of iron atoms. The carbon in steel alloys may contribute up to 2. 1% of its weight. Steels strength compared to pure iron is possible at the expense of irons ductility. With the invention of the Bessemer process in the mid-19th century and this was followed by Siemens-Martin process and then Gilchrist-Thomas process that refined the quality of steel. With their introductions, mild steel replaced wrought iron, further refinements in the process, such as basic oxygen steelmaking, largely replaced earlier methods by further lowering the cost of production and increasing the quality of the product. Today, steel is one of the most common materials in the world and it is a major component in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades defined by assorted standards organizations, the noun steel originates from the Proto-Germanic adjective stakhlijan, which is related to stakhla. The carbon content of steel is between 0. 002% and 2. 1% by weight for plain iron–carbon alloys and these values vary depending on alloying elements such as manganese, chromium, nickel, iron, tungsten, carbon and so on. Basically, steel is an alloy that does not undergo eutectic reaction. In contrast, cast iron does undergo eutectic reaction, too little carbon content leaves iron quite soft, ductile, and weak. Carbon contents higher than those of steel make an alloy, commonly called pig iron, while iron alloyed with carbon is called carbon steel, alloy steel is steel to which other alloying elements have been intentionally added to modify the characteristics of steel. Common alloying elements include, manganese, nickel, chromium, molybdenum, boron, titanium, vanadium, tungsten, cobalt, and niobium. Additional elements are important in steel, phosphorus, sulfur, silicon, and traces of oxygen, nitrogen, and copper. Alloys with a higher than 2. 1% carbon content, depending on other element content, cast iron is not malleable even when hot, but it can be formed by casting as it has a lower melting point than steel and good castability properties
11.
Ductility
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In materials science, ductility is a solid materials ability to deform under tensile stress, this is often characterized by the materials ability to be stretched into a wire. Malleability, a property, is a materials ability to deform under compressive stress. Both of these properties are aspects of plasticity, the extent to which a solid material can be plastically deformed without fracture. Also, these properties are dependent on temperature and pressure. Ductility and malleability are not always coextensive – for instance, while gold has high ductility and malleability, lead has low ductility, the word ductility is sometimes used to encompass both types of plasticity. Ductility is especially important in metalworking, as materials that crack, break or shatter under stress cannot be manipulated using metal-forming processes such as hammering, rolling, malleable materials can be formed cold using stamping or pressing, whereas brittle materials may be cast or thermoformed. High degrees of ductility occur due to bonds, which are found predominantly in metals. In metallic bonds valence shell electrons are delocalized and shared between many atoms, the delocalized electrons allow metal atoms to slide past one another without being subjected to strong repulsive forces that would cause other materials to shatter. Ductility can be quantified by the fracture strain ε f, which is the strain at which a test specimen fractures during a uniaxial tensile test. Another commonly used measure is the reduction of area at fracture q, the ductility of steel varies depending on the alloying constituents. Increasing levels of carbon decrease ductility, many plastics and amorphous solids, such as Play-Doh, are also malleable. The most ductile metal is platinum and the most malleable metal is gold, DBTT is important since, once a material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending or deforming. For example, zamak 3 exhibits good ductility at room temperature, DBTT is a very important consideration in selecting materials that are subjected to mechanical stresses. A similar phenomenon, the transition temperature, occurs with glasses and polymers. In some materials the transition is sharper than others and typically requires a temperature-sensitive deformation mechanism and this can be problematic for steels with a high ferrite content. This famously resulted in serious hull cracking in Liberty ships in colder waters during World War II, DBTT can also be influenced by external factors such as neutron radiation, which leads to an increase in internal lattice defects and a corresponding decrease in ductility and increase in DBTT. The most accurate method of measuring the DBTT of a material is by fracture testing, typically four point bend testing at a range of temperatures is performed on pre-cracked bars of polished material. For experiments conducted at higher temperatures, dislocation activity increases, the temperature at which this occurs is the ductile–brittle transition temperature
12.
Materials science
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The interdisciplinary field of materials science, also commonly termed materials science and engineering, involves the discovery and design of new materials, with an emphasis on solids. Materials science still incorporates elements of physics, chemistry, and engineering, as such, the field was long considered by academic institutions as a sub-field of these related fields. Materials science is a syncretic discipline hybridizing metallurgy, ceramics, solid-state physics and it is the first example of a new academic discipline emerging by fusion rather than fission. Many of the most pressing scientific problems humans currently face are due to the limits of the materials that are available, thus, breakthroughs in materials science are likely to affect the future of technology significantly. Materials scientists emphasize understanding how the history of a material influences its structure, the understanding of processing-structure-properties relationships is called the § materials paradigm. This paradigm is used to advance understanding in a variety of areas, including nanotechnology, biomaterials. Such investigations are key to understanding, for example, the causes of various accidents and incidents. The material of choice of a given era is often a defining point, phrases such as Stone Age, Bronze Age, Iron Age, and Steel Age are great examples. Originally deriving from the manufacture of ceramics and its putative derivative metallurgy, materials science is one of the oldest forms of engineering, modern materials science evolved directly from metallurgy, which itself evolved from mining and ceramics and the use of fire. Materials science has driven, and been driven by, the development of technologies such as rubbers, plastics, semiconductors. Before the 1960s, many materials science departments were named metallurgy departments, reflecting the 19th, a material is defined as a substance that is intended to be used for certain applications. There are a myriad of materials around us—they can be found in anything from buildings to spacecraft, Materials can generally be divided into two classes, crystalline and non-crystalline. The traditional examples of materials are metals, semiconductors, ceramics, New and advanced materials that are being developed include nanomaterials and biomaterials, etc. The basis of science involves studying the structure of materials. Once a materials scientist knows about this structure-property correlation, they can go on to study the relative performance of a material in a given application. The major determinants of the structure of a material and thus of its properties are its constituent chemical elements and these characteristics, taken together and related through the laws of thermodynamics and kinetics, govern a materials microstructure, and thus its properties. As mentioned above, structure is one of the most important components of the field of materials science, Materials science examines the structure of materials from the atomic scale, all the way up to the macro scale. Characterization is the way materials scientists examine the structure of a material, structure is studied at various levels, as detailed below
13.
Plasticity (physics)
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In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a piece of metal being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself. In engineering, the transition from elastic behavior to plastic behavior is called yield, plastic deformation is observed in most materials, particularly metals, soils, rocks, concrete, foams, bone and skin. However, the mechanisms that cause plastic deformation can vary widely. At a crystalline scale, plasticity in metals is usually a consequence of dislocations, such defects are relatively rare in most crystalline materials, but are numerous in some and part of their crystal structure, in such cases, plastic crystallinity can result. In brittle materials such as rock, concrete and bone, plasticity is caused predominantly by slip at microcracks, for many ductile metals, tensile loading applied to a sample will cause it to behave in an elastic manner. Each increment of load is accompanied by an increment in extension. When the load is removed, the returns to its original size. However, once the load exceeds a threshold – the yield strength – the extension increases more rapidly than in the region, now when the load is removed. Elastic deformation, however, is an approximation and its quality depends on the time frame considered, if, as indicated in the graph opposite, the deformation includes elastic deformation, it is also often referred to as elasto-plastic deformation or elastic-plastic deformation. Perfect plasticity is a property of materials to undergo irreversible deformation without any increase in stresses or loads, plastic materials with hardening necessitate increasingly higher stresses to result in further plastic deformation. Generally, plastic deformation is dependent on the deformation speed. Such materials are said to deform visco-plastically, the plasticity of a material is directly proportional to the ductility and malleability of the material. Plasticity in a crystal of pure metal is primarily caused by two modes of deformation in the lattice, slip and twinning. Slip is a deformation which moves the atoms through many interatomic distances relative to their initial positions. Twinning is the plastic deformation takes place along two planes due to a set of forces applied to a given metal piece. Most metals show more plasticity when hot than when cold, lead shows sufficient plasticity at room temperature, while cast iron does not possess sufficient plasticity for any forging operation even when hot. This property is of importance in forming, shaping and extruding operations on metals, most metals are rendered plastic by heating and hence shaped hot
14.
Grain size
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Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials and this is different from the crystallite size, which refers to the size of a single crystal inside a particle or grain. A single grain can be composed of several crystals, granular material can range from very small colloidal particles, through clay, silt, sand, gravel, and cobbles, to boulders. Size ranges define limits of classes that are given names in the Wentworth scale used in the United States, the Krumbein phi scale, a modification of the Wentworth scale created by W. C. This equation can be rearranged to find diameter using φ, D = D0 ×2 − ϕ In some schemes, ISO 14688-1 is applicable to natural soils in situ, similar man-made materials in situ and soils redeposited by people. An accumulation of sediment can also be characterized by the size distribution. A sediment deposit can undergo sorting when a particle size range is removed by an agency such as a river or the wind, a Scale of Grade and Class Terms for Clastic Sediments
15.
Precipitation hardening
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In superalloys, it is known to cause yield strength anomaly providing excellent high-temperature strength. Since dislocations are often the dominant carriers of plasticity, this serves to harden the material, the impurities play the same role as the particle substances in particle-reinforced composite materials. Unlike ordinary tempering, alloys must be kept at elevated temperature for hours to allow precipitation to take place and this time delay is called aging. Solution treatment and aging is sometimes abbreviated STA in metals specs, note that two different heat treatments involving precipitates can alter the strength of a material, solution heat treating and precipitation heat treating. Solid solution strengthening involves formation of a solid solution via quenching. Precipitation heat treating involves the addition of impurity particles to increase a materials strength, precipitation hardening via precipitation heat treatment is the main topic of discussion in this article. Nucleation occurs at a high temperature so that the kinetic barrier of surface energy can be more easily overcome. These particles are allowed to grow at lower temperature in a process called aging. This is carried out under conditions of low solubility so that thermodynamics drive a total volume of precipitate formation. Diffusions exponential dependence upon temperature makes precipitation strengthening, like all heat treatments, too little diffusion, and the particles will be too small to impede dislocations effectively, too much, and they will be too large and dispersed to interact with the majority of dislocations. Precipitation strengthening is possible if the line of solid solubility slopes strongly toward the center of a phase diagram, while a large volume of precipitate particles is desirable, a small enough amount of the alloying element should be added that it remains easily soluble at some reasonable annealing temperature. Elements used for strengthening in typical aluminum and titanium alloys make up about 10% of their composition. While binary alloys are easily understood as an academic exercise. A large number of other constituents may be unintentional, but benign, in some cases, such as many aluminum alloys, an increase in strength is achieved at the expense of corrosion resistance. The addition of large amounts of nickel and chromium needed for corrosion resistance in stainless steels means that traditional hardening and tempering methods are not effective, however, precipitates of chromium, copper, or other elements can strengthen the steel by similar amounts in comparison to hardening and tempering. The strength can be tailored by adjusting the annealing process, with lower initial temperatures resulting in higher strengths, the lower initial temperatures increase the driving force of nucleation. More driving force means more nucleation sites, and more sites means more places for dislocations to be disrupted while the part is in use. Many alloy systems allow the temperature to be adjusted
16.
Work hardening
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Work hardening, also known as strain hardening or cold working, is the strengthening of a metal by plastic deformation. This strengthening occurs because of dislocation movements and dislocation generation within the structure of the material. Many non-brittle metals with a high melting point as well as several polymers can be strengthened in this fashion. Alloys not amenable to treatment, including low-carbon steel, are often work-hardened. Some materials cannot be work-hardened at low temperatures, such as indium, however others can only be strengthened via work hardening, such as pure copper, Work hardening may be desirable or undesirable depending on the context. An example of work hardening is during machining when early passes of a cutter inadvertently work-harden the workpiece surface. Certain alloys are prone to this than others, superalloys such as Inconel require machining strategies that take it into account. An example of work hardening is that which occurs in metalworking processes that intentionally induce plastic deformation to exact a shape change. These processes are known as working or cold forming processes. They are characterized by shaping the workpiece at a temperature below its recrystallization temperature, cold forming techniques are usually classified into four major groups, squeezing, bending, drawing, and shearing. Applications include the heading of bolts and cap screws and the finishing of cold rolled steel, in cold forming, metal is formed at high speed and high pressure using tool steel or carbide dies. The cold working of the increasing the hardness, yield strength. Copper was the first metal in use for tools and containers since it is one of the few metals available in non-oxidized form. Copper is easily softened by heating and then cooling, in this annealed state it may then be hammered, stretched and otherwise formed, progressing toward the desired final shape, but becoming harder and less ductile as work progresses. If work continues beyond a certain hardness the metal will tend to fracture when worked, annealing is stopped when the workpiece is near its final desired shape, and so the final product will have a desired stiffness and hardness. The technique of repoussé exploits these properties of copper, enabling the construction of durable jewelry articles and sculptures, for this reason modern aluminum aircraft will have an imposed working lifetime, after which the aircraft must be retired. Before work hardening, the lattice of the material exhibits a regular, the defect-free lattice can be created or restored at any time by annealing. As the material is work hardened it becomes saturated with new dislocations
17.
Laminated glass
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Laminated glass is a type of safety glass that holds together when shattered. In the event of breaking, it is held in place by an interlayer, typically of polyvinyl butyral or ethylene-vinyl acetate, the interlayer keeps the layers of glass bonded even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. This produces a characteristic spider web cracking pattern when the impact is not enough to pierce the glass. In the case of the EVA, the thermoset EVA, offers a complete bounding with the material whether it is glass, polycarbonate, PET, or other types products. Laminated glass is used when there is a possibility of human impact or where the glass could fall if shattered. Skylight glazing and automobile windshields typically use laminated glass, in geographical areas requiring hurricane-resistant construction, laminated glass is often used in exterior storefronts, curtain walls and windows. Laminated glass is used to increase the sound insulation rating of a window. For this purpose a special acoustic PVB compound is used for the interlayer, in the case of the EVA material, no additional acoustic material is required, since the EVA provides sound insulation. An additional property of laminated glass for windows is that a PVB, a thermoset EVA could block up to 99. 9% of the UV rays. In 1902, the French Le Carbone corporation obtained a patent for coating glass objects with celluloid in order to render them susceptible to cracking or breaking. Laminated glass was invented in 1903 by the French chemist Édouard Bénédictus, a glass flask had become coated with the plastic cellulose nitrate and when dropped shattered but did not break into pieces. However, it was not until 1909 that Benedictus filed a patent, in 1911, he formed the Société du Verre Triplex, which fabricated a glass-plastic composite to reduce injuries in car accidents. Production of Triplex glass was slow and painstaking, making it expensive and it was not immediately widely adopted by automobile manufacturers, but laminated glass was widely used in the eyepieces of gas masks during World War I. In 1912, the process was licensed to The English Triplex Safety Glass Company, subsequently, in the United States, both Libbey Owens-Ford and Du Pont de Nemours with Pittsburg Plate Glass produced Triplex. Meanwhile, in 1905, John Crewe Wood, a solicitor in Swindon, Wiltshire, England, the layers of glass were bonded together by Canada balsam. In 1906 he founded the Safety Motor Screen Co. to produce, in 1927, the Canadian chemists Howard W. Matheson and Frederick W. Skirrow invented the plastic polyvinyl butyral. Within five years, the new safety glass had replaced its predecessor. In the Road Traffic Act of 1930, the British parliament required new cars to use windscreens of safety glass
18.
Polyvinyl butyral
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Polyvinyl butyral is a resin mostly used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. It is prepared from polyvinyl alcohol by reaction with butyraldehyde, the major application is laminated safety glass for automobile windshields. Tradenames for PVB-films include KB PVB, Saflex, GlasNovations, Butacite, WINLITE, S-Lec, Trosifol, laminated glass, commonly used in the automotive and architectural fields, comprises a protective interlayer, usually polyvinyl butyral, bonded between two panels of glass. The bonding process takes place under heat and pressure, when laminated under these conditions, the PVB interlayer becomes optically clear and binds the two panes of glass together. Once sealed together, the glass sandwich behaves as a single unit, the polymer interlayer of PVB is tough and ductile, so brittle cracks will not pass from one side of the laminate to the other. PVB interlayer can be purchased in colored sheets, such as for the blue or green shade band at the top edge of many automobile windshields. PVB interlayers can also be purchased in different colors for architectural laminated glass manufacture ranging from Bronze, Gray, Green, Brown, White, discovered in the late 1990s it was found that PVB degraded over time within laminated windows. PVB has gained acceptance among manufacturers of photovoltaic thin film solar modules, the photovoltaic circuit is formed on a sheet of glass using thin film deposition and patterning techniques. PVB and a sheet of glass are then placed directly on the circuit. The lamination of this sandwich encapsulates the circuit, protecting it from the environment, current is extracted from the module at a sealed terminal box that is attached to the circuit through a hole in the back glass. Another common laminant used in the industry is ethylene-vinyl acetate. PVB resin is particularly useful at bonding to metals, ceramics, annealed glass, heat-strengthened or tempered glass can be used to produce laminated glass. While laminated glass will crack if struck with sufficient force, the glass fragments tend to adhere to the interlayer rather than falling free. A passenger in a car crash, thus, the benefits of laminated glass include safety and security. Laminated glass also has decorative applications, the interlayer can be colored or patterned. In 1927, the Canadian chemists Howard W. Matheson and Frederick W. Skirrow invented the plastic polyvinyl butyral, PVB has been the dominant interlayer material since the late 1930s. It is currently manufactured and marketed by a number of worldwide, including Eastman, Sekisui, Kuraray Europe GmbH. The market for laminated glass products is mature, with only minor modifications, the PVB interlayer sold today is essentially identical to the PVB sold 30 years ago
19.
Viscoelasticity
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Viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Viscous materials, like honey, resist shear flow and strain linearly with time when a stress is applied, elastic materials strain when stretched and quickly return to their original state once the stress is removed. Viscoelastic materials have elements of both of properties and, as such, exhibit time-dependent strain. In the nineteenth century, physicists such as Maxwell, Boltzmann, and Kelvin researched and experimented with creep and recovery of glasses, metals, viscoelasticity was further examined in the late twentieth century when synthetic polymers were engineered and used in a variety of applications. Viscoelasticity calculations depend heavily on the viscosity variable, η, the inverse of η is also known as fluidity, φ. The value of either can be derived as a function of temperature or as a given value, depending on the change of strain rate versus stress inside a material the viscosity can be categorized as having a linear, non-linear, or plastic response. When a material exhibits a linear response it is categorized as a Newtonian material, in this case the stress is linearly proportional to the strain rate. If the material exhibits a non-linear response to the strain rate, there is also an interesting case where the viscosity decreases as the shear/strain rate remains constant. A material which exhibits this type of behavior is known as thixotropic, in addition, when the stress is independent of this strain rate, the material exhibits plastic deformation. Many viscoelastic materials exhibit rubber like behavior explained by the theory of polymer elasticity. Some examples of materials include amorphous polymers, semicrystalline polymers, biopolymers, metals at very high temperatures. Cracking occurs when the strain is applied quickly and outside of the elastic limit, ligaments and tendons are viscoelastic, so the extent of the potential damage to them depends both on the rate of the change of their length as well as on the force applied. The viscosity of a viscoelastic substance gives the substance a strain rate dependence on time, purely elastic materials do not dissipate energy when a load is applied, then removed. However, a viscoelastic substance loses energy when a load is applied, hysteresis is observed in the stress–strain curve, with the area of the loop being equal to the energy lost during the loading cycle. Since viscosity is the resistance to thermally activated plastic deformation, a material will lose energy through a loading cycle. Plastic deformation results in lost energy, which is uncharacteristic of a purely elastic materials reaction to a loading cycle, specifically, viscoelasticity is a molecular rearrangement. When a stress is applied to a material such as a polymer. This movement or rearrangement is called creep, polymers remain a solid material even when these parts of their chains are rearranging in order to accompany the stress, and as this occurs, it creates a back stress in the material
20.
Toughened glass
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Toughened or tempered glass is a type of safety glass processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. Tempering puts the outer surfaces into compression and the inner surfaces into tension, such stresses cause the glass, when broken, to crumble into small granular chunks instead of splintering into jagged shards as plate glass creates. The granular chunks are less likely to cause injury, toughened glass is physically and thermally stronger than regular glass. The greater contraction of the inner layer during manufacturing induces compressive stresses in the surface of the glass balanced by tensile stresses in the body of the glass. For glass to be considered toughened, this stress on the surface of the glass should be a minimum of 69 megapascals. For it to be considered safety glass, the compressive stress should exceed 100 megapascals. The greater the stress, the smaller the glass particles will be when broken. It is this compressive stress that gives the toughened glass increased strength and this is because any surface flaws tend to be pressed closed by the retained compressive forces, while the core layer remains relatively free of the defects which could cause a crack to begin. Any cutting or grinding must be prior to tempering. Cutting, grinding, and sharp impacts after tempering will cause the glass to fracture, the strain pattern resulting from tempering can be observed with polarized light or by using a pair of polarizing sun glasses. Toughened glass is used when strength, thermal resistance, and safety are important considerations, the most commonly encountered tempered glass is that used for side and rear windows in automobiles. It is used for its characteristic of shattering into small cubes rather than large shards and is referred to as safety glass in this context. Toughened glass is used in buildings for unframed assemblies, structurally loaded applications. Tempered and heat strengthened glass can be three to seven times stronger than annealed glass, rim-tempered indicates that a limited area, such as the rim of the glass or plate, is tempered and is popular in food service. However, there are also specialist manufacturers that offer a fully tempered/toughened drinkware solution that can bring increased benefits in the form of strength, in some countries these products are specified in venues that require increased performance levels or have a requirement for a safer glass due to intense usage. Tempered glass has also increased usage in bars and pubs, particularly in the United Kingdom and Australia. Some forms of tempered glass are used for cooking and baking, manufacturers and brands include Glasslock, Pyrex, Corelle, and Arc International. Most touchscreen mobile devices use some form of toughened glass, as do some aftermarket screen protectors for these devices, toughened glass can be made from annealed glass via a thermal tempering process
21.
Prestressed concrete
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Prestressed concrete is a concrete construction material which is placed under compression prior to it supporting any applied loads. A more technical definition is Structural concrete in which stresses have been introduced to reduce potential tensile stresses in the concrete resulting from loads. This compression is produced by the tensioning of high-strength tendons located within or adjacent to the concrete volume, tendons may consist of single wires, multi-wire strands or threaded bars, and are most commonly made from high-tensile steels, carbon fibre or aramid fibre. This can result in improved structural capacity and/or serviceability compared to reinforced concrete in many situations. Typical applications range through high-rise buildings, residential slabs, foundation systems, bridge and dam structures, silos and tanks, industrial pavements, first used in the late-nineteenth century, prestressed concrete has developed to encompass a wide range of technologies. Tensioning of the tendons may be undertaken either before or after the concrete itself is cast, tendons may be located either within the concrete volume, or wholly outside of it. Whereas pre-tensioned concrete by definition uses tendons directly bonded to the concrete, pre-tensioned concrete is a variant of prestressed concrete where the tendons are tensioned prior to the concrete being cast. Pre-tensioning is a common technique, where the resulting concrete element is manufactured remotely from the final structure location. It requires strong, stable end-anchorage points between which the tendons are stretched and these anchorages form the ends of a casting bed which may be many times the length of the concrete element being fabricated. Higher bond strength in early-age concrete allows more economical fabrication as it speeds production, to promote this, pre-tensioned tendons are usually composed of isolated single wires or strands, as this provides a greater surface area for bond action than bundled strand tendons. Unlike those of post-tensioned concrete, the tendons of pre-tensioned concrete elements generally form straight lines between end-anchorages, where profiled or harped tendons are required, one or more intermediate deviators are located between the ends of the tendon to hold the tendon to the desired non-linear alignment during tensioning. Such deviators usually act against substantial forces, and hence require a robust casting bed foundation system, pre-tensioned concrete is most commonly used for the fabrication of structural beams, floor slabs, hollow-core planks, balconies, lintels, driven piles, water tanks and concrete pipes. Post-tensioned concrete is a variant of prestressed concrete where the tendons are tensioned after the concrete structure has been cast. The tendons are not placed in contact with the concrete. At each end of a tendon is an anchorage assembly firmly fixed to the surrounding concrete, once the concrete has been cast and set, the tendons are tensioned by pulling the tendon ends through the anchorages while pressing against the concrete. The large forces required to tension the tendons result in a significant permanent compression being applied to the once the tendon is locked-off at the anchorage. Casting the tendon ducts/sleeves into the concrete before any tensioning occurs allows them to be profiled to any desired shape including incorporating vertical and/or horizontal curvature. Bonded post-tensioning has prestressing tendons permanently bonded to the concrete by the in situ grouting of their encapsulating ducting following tendon tensioning
22.
Prince Rupert's Drop
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Prince Ruperts Drops are toughened glass beads created by dripping molten glass into cold water, which causes it to solidify into a tadpole-shaped droplet with a long, thin tail. In nature, similar structures are produced under conditions in volcanic lava. Prince Ruperts drops are produced by dripping molten glass into cold water, the water rapidly cools and solidifies the glass on the outside of the drop, while the inner core remains molten. When the glass on the inside eventually cools it contracts inwards, because of the transparency of glass, the internal stress within these objects can be demonstrated by viewing them through polarizing filters, a technique used in the study of photoelasticity. A scholarly account of the history of Prince Rupert’s Drops is given in the Notes. Most of the scientific study of the drops was performed at the Royal Society. The drops are reliably reported to have made in Mecklenburg in North Germany. However, it has claimed that they were invented in the Netherlands. The secret of how to make them remained in the Mecklenburg area for some time, although the drops were disseminated across Europe from there, for sale as toys or curiosities. It seems clear that Prince Rupert did not discover the drops and he gave them to King Charles II, who in turn delivered them in 1661 to the Royal Society for scientific study. Several early publications from the Royal Society give accounts of the drops, among these publications was Micrographia of 1665 by Robert Hooke, who later would discover Hooke’s Law. A fuller understanding of crack propagation had to wait until the work of A. A. Griffith in 1920. de Luynes had published accounts of his experiments with them. It has been known since at least the 19th century that formations similar to Prince Ruperts Drops are produced under conditions in volcanic lava. Because of their use as a party piece, Prince Rupert’s Drops became widely known in the late 17th century — far more than today and it can be seen that educated people were expected to be familiar with them, from their use in the literature of the day. Samuel Butler used them as a metaphor in his poem Hudibras in 1663, in his 1943 novella Conjure Wife, Fritz Leiber uses Prince Rupert Drops as a metaphor for the volatility of several characters personalities. These small-town college faculty people seem to be placid and impervious, peter Carey devotes a chapter to the drops in his 1988 novel Oscar and Lucinda. Prince Ruperts Drop Video demonstrating the creation, strength, and explosive fragility of a Prince Rupert Drop, Video showing the making and the breaking of Prince Ruperts Drops from the Museum of Glass Popular Science article with video detailing Prince Rupert’s Drops Corning Inc. The Glass Age, Part 2, Strong, Durable Glass, adam Savage and Jamie Hyneman demonstrate Ruperts Drops, including diagram of internal stresses
23.
Zirconium dioxide
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Zirconium dioxide, sometimes known as zirconia, is a white crystalline oxide of zirconium. Its most naturally occurring form, with a crystalline structure, is the mineral baddeleyite. A dopant stabilized cubic structured zirconia, cubic zirconia, is synthesized in various colours for use as a gemstone, Zirconia is produced by calcining zirconium compounds, exploiting its high thermal stability. Three phases are known, monoclinic <1,170 °C, tetragonal 1, 170–2,370 °C, the trend is for higher symmetry at higher temperatures, as is usually the case. A few percentage of the oxides of calcium or yttrium stabilize the cubic phase, the very rare mineral tazheranite O2 is cubic. Unlike TiO2, which features six-coordinate Ti in all phases, monoclinic zirconia consists of seven-coordinate zirconium centres and this difference is attributed to the larger size of Zr atom relative to the Ti atom. It is slowly attacked by concentrated hydrofluoric acid and sulfuric acid, when heated with carbon, it converts to zirconium carbide. When heated with carbon in the presence of chlorine, it converts to zirconium tetrachloride and this conversion is the basis for the purification of zirconium metal and is analogous to the Kroll process. Zirconium dioxide is one of the most studied ceramic materials, ZrO2 adopts a monoclinic crystal structure at room temperature and transitions to tetragonal and cubic at higher temperatures. The change of volume caused by the structure transitions from to tetragonal to monoclinic to cubic induces large stresses, when the zirconia is blended with some other oxides, the tetragonal and/or cubic phases are stabilized. Effective dopants include magnesium oxide, yttrium oxide, calcium oxide, Zirconia is often more useful in its phase stabilized state. Upon heating, zirconia undergoes disruptive phase changes, by adding small percentages of yttria, these phase changes are eliminated, and the resulting material has superior thermal, mechanical, and electrical properties. In some cases, the phase can be metastable. This phase transformation can then put the crack into compression, retarding its growth and this mechanism is known as transformation toughening, and significantly extends the reliability and lifetime of products made with stabilized zirconia. The ZrO2 band gap is dependent on the phase and preparation methods, a special case of zirconia is that of tetragonal zirconia polycrystal, or TZP, which is indicative of polycrystalline zirconia composed of only the metastable tetragonal phase. Stabilized zirconia is used in sensors and fuel cell membranes because it has the ability to allow oxygen ions to move freely through the crystal structure at high temperatures. This high ionic conductivity makes it one of the most useful electroceramics, zirconium dioxide is also used as the solid electrolyte in electrochromic devices. Zirconia is a precursor to the electroceramic lead zirconate titanate, which is a high-K dielectric, which is found in myriad components
24.
Composite material
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The individual components remain separate and distinct within the finished structure. The new material may be preferred for reasons, common examples include materials which are stronger, lighter. More recently, researchers have begun to actively include sensing, actuation, computation and communication into composites. The most advanced examples perform routinely on spacecraft and aircraft in demanding environments, the earliest man-made composite materials were straw and mud combined to form bricks for building construction. Ancient brick-making was documented by Egyptian tomb paintings, wattle and daub is one of the oldest man-made composite materials, at over 6000 years old. Concrete is also a material, and is used more than any other man-made material in the world. As of 2006, about 7.5 billion cubic metres of concrete are made each year—more than one metre for every person on Earth. 2181–2055 BC and was used for death masks Cob Mud Bricks, concrete was described by Vitruvius, writing around 25 BC in his Ten Books on Architecture, distinguished types of aggregate appropriate for the preparation of lime mortars. For structural mortars, he recommended pozzolana, which were volcanic sands from the beds of Pozzuoli brownish-yellow-gray in colour near Naples. Natural cement-stones, after burning, produced cements used in concretes from post-Roman times into the 20th century, the glass fiber is relatively strong and stiff, whereas the polymer is ductile. Thus the resulting fiberglass is relatively stiff, strong, flexible, concrete is the most common artificial composite material of all and typically consists of loose stones held with a matrix of cement. Concrete is a material, and will not compress or shatter even under quite a large compressive force. However, concrete cannot survive tensile loading, therefore, to give concrete the ability to resist being stretched, steel bars, which can resist high stretching forces, are often added to concrete to form reinforced concrete. Fibre-reinforced polymers or FRPs include carbon-fiber-reinforced polymer or CFRP, and glass-reinforced plastic or GRP, if classified by matrix then there are thermoplastic composites, short fiber thermoplastics, long fibre thermoplastics or long fibre-reinforced thermoplastics. There are numerous thermoset composites, including paper composite panels, many advanced thermoset polymer matrix systems usually incorporate aramid fibre and carbon fibre in an epoxy resin matrix. Shape memory polymer composites are high-performance composites, formulated using fibre or fabric reinforcement and they can also be reheated and reshaped repeatedly without losing their material properties. These composites are ideal for such as lightweight, rigid, deployable structures, rapid manufacturing. Although high strain composites exhibit many similarities to shape memory polymers, Composites can also use metal fibres reinforcing other metals, as in metal matrix composites or ceramic matrix composites, which includes bone, cermet and concrete
25.
Glass fiber
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Glass fiber is a material consisting of numerous extremely fine fibers of glass. Glassmakers throughout history have experimented with glass fibers, but mass manufacture of fiber was only made possible with the invention of finer machine tooling. In 1893, Edward Drummond Libbey exhibited a dress at the Worlds Columbian Exposition incorporating glass fibers with the diameter and this was first worn by the popular stage actress of the time Georgia Cayvan. Glass fibers can also occur naturally, as Peles hair, Glass wool, which is one product called fiberglass today, was invented in 1932–1933 by Russell Games Slayter of Owens-Corning, as a material to be used as thermal building insulation. It is marketed under the trade name Fiberglas, which has become a genericized trademark, Glass fiber has roughly comparable mechanical properties to other fibers such as polymers and carbon fiber. Although not as strong or as rigid as carbon fiber, it is much cheaper and this structural material product contains little or no air or gas, is more dense, and is a much poorer thermal insulator than is glass wool. Glass fiber is formed when thin strands of silica-based or other formulation glass are extruded into fibers with small diameters suitable for textile processing. The technique of heating and drawing glass into fine fibers has been known for millennia, however, until this time, all glass fiber had been manufactured as staple. The modern method for producing glass wool is the invention of Games Slayter working at the Owens-Illinois Glass Co and he first applied for a patent for a new process to make glass wool in 1933. The first commercial production of fiber was in 1936. In 1938 Owens-Illinois Glass Company and Corning Glass Works joined to form the Owens-Corning Fiberglas Corporation, when the two companies joined to produce and promote glass fiber, they introduced continuous filament glass fibers. Owens-Corning is still the major producer in the market today. The most common types of fiber used in fiberglass is E-glass. Other types of glass used are A-glass, E-CR-glass, C-glass, D-glass, R-glass, and S-glass. Pure silica, when cooled as fused quartz into a glass with no true melting point, can be used as a fiber for fiberglass. In order to lower the necessary temperature, other materials are introduced as fluxing agents. Ordinary A-glass or soda lime glass, crushed and ready to be remelted, E-glass, is alkali free, and was the first glass formulation used for continuous filament formation. It now makes up most of the production in the world
26.
Pressure
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Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the relative to the ambient pressure. Various units are used to express pressure, Pressure may also be expressed in terms of standard atmospheric pressure, the atmosphere is equal to this pressure and the torr is defined as 1⁄760 of this. Manometric units such as the centimetre of water, millimetre of mercury, Pressure is the amount of force acting per unit area. The symbol for it is p or P, the IUPAC recommendation for pressure is a lower-case p. However, upper-case P is widely used. The usage of P vs p depends upon the field in one is working, on the nearby presence of other symbols for quantities such as power and momentum. Mathematically, p = F A where, p is the pressure, F is the normal force and it relates the vector surface element with the normal force acting on it. It is incorrect to say the pressure is directed in such or such direction, the pressure, as a scalar, has no direction. The force given by the relationship to the quantity has a direction. If we change the orientation of the element, the direction of the normal force changes accordingly. Pressure is distributed to solid boundaries or across arbitrary sections of normal to these boundaries or sections at every point. It is a parameter in thermodynamics, and it is conjugate to volume. The SI unit for pressure is the pascal, equal to one newton per square metre and this name for the unit was added in 1971, before that, pressure in SI was expressed simply in newtons per square metre. Other units of pressure, such as pounds per square inch, the CGS unit of pressure is the barye, equal to 1 dyn·cm−2 or 0.1 Pa. Pressure is sometimes expressed in grams-force or kilograms-force per square centimetre, but using the names kilogram, gram, kilogram-force, or gram-force as units of force is expressly forbidden in SI. The technical atmosphere is 1 kgf/cm2, since a system under pressure has potential to perform work on its surroundings, pressure is a measure of potential energy stored per unit volume. It is therefore related to density and may be expressed in units such as joules per cubic metre. Similar pressures are given in kilopascals in most other fields, where the prefix is rarely used
27.
Crust (geology)
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In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle. The crust of the Earth is composed of a variety of igneous, metamorphic. The crust is underlain by the mantle, the upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust. The boundary between the crust and mantle is conventionally placed at the Mohorovičić discontinuity, a boundary defined by a contrast in seismic velocity, the crust occupies less than 1% of Earths volume. The crust of the Earth is of two types, oceanic and continental. The oceanic crust is 5 km to 10 km thick and is composed primarily of basalt, diabase, the continental crust is typically from 30 km to 50 km thick and is mostly composed of slightly less dense rocks than those of the oceanic crust. Some of these less dense rocks, such as granite, are common in the continental crust, both the continental and oceanic crust float on the mantle. Because the continental crust is thicker, it both to greater elevations and greater depth than the oceanic crust. The slightly lower density of continental rock compared to basaltic oceanic rock contributes to the higher relative elevation of the top of the continental crust. As the top of the continental crust reaches elevations higher than that of the oceanic, the temperature of the crust increases with depth, reaching values typically in the range from about 200 °C to 400 °C at the boundary with the underlying mantle. The crust and underlying relatively rigid uppermost mantle make up the lithosphere, because of convection in the underlying plastic upper mantle and asthenosphere, the lithosphere is broken into tectonic plates that move. The temperature increases by as much as 30 °C for every kilometer locally in the part of the crust. Earth has probably always had some form of basaltic crust, in contrast, the bulk of the continental crust is much older. The oldest continental crustal rocks on Earth have ages in the range from about 3.7 to 4, some zircon with age as great as 4.3 billion years has been found in the Narryer Gneiss Terrane. The average age of the current Earths continental crust has been estimated to be about 2.0 billion years, most crustal rocks formed before 2.5 billion years ago are located in cratons. Such old continental crust and the underlying mantle asthenosphere are less dense than elsewhere in Earth, formation of new continental crust is linked to periods of intense orogeny, these periods coincide with the formation of the supercontinents such as Rodinia, Pangaea and Gondwana. The continental crust has a composition similar to that of andesite. The most abundant minerals in Earths continental crust are feldspars, which make up about 41% of the crust by weight, followed by quartz at 12%, Continental crust is enriched in incompatible elements compared to the basaltic ocean crust and much enriched compared to the underlying mantle
28.
Max Planck Institute for Intelligent Systems
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The Max Planck Institute for Intelligent Systems exists since March 18,2011. Its Stuttgart location is in the process of scientific reorientation, a new institute location arises in Tübingen, the MPI for Intelligent Systems belongs to the Max Planck Society, a German research institution strong in basic research. The institute focuses on establishing the foundations of perception, action and learning through interdisciplinary and collaborative research across scales. An organizing principle for the institute is the concept of a perception-action loop, Learning the structure and optimized functionality of such feedback loops is critical for all autonomous systems. Thus, understanding the principles of perception-action loops in diverse instantiations of autonomous systems will be one common theme across the groups of the institute. While pursuing research at both the macro and micro scales, a key focus of the institute is the integration of ideas across scales. To help them do so, the Max Planck Society and the ETH Zürich opened on November 30,2015 the Max Planck ETH Center for Learning Systems, the Center’s scientists want to understand what the principles of learning are, both in theory and in real machines. Among other goals they hope to develop robots which can act autonomously in an unknown, the Center is an essential building block for the further development of the research area involving learning and intelligent systems in Baden-Württemberg. Through their cooperation the MPS and the ETH are creating scientific and personal synergies, the Center for Learning Systems organizes joint events as summer schools, workshops, retreats etc. Moreover there are joint PhD- and Postdoc projects, the CLS is headed by the two Co-Directors Prof. Dr. Thomas Hofmann, ETH Zürich und Prof. Dr. Bernhard Schölkopf, MPI for Intelligent Systems. Further members of the center are Professors and Scientists of both institutions, the Max Planck Institute for Metals Research was founded in Berlin-Neubabelsberg in 1920 as one of the first Kaiser Wilhelm Institutes. In 1934 it moved to Stuttgart and in 1949 it was renamed Max-Planck-Institut für Metallforschung, in the early days of the MPI-MF its main research areas were physical metallurgy and metal physics. In the 70s, new areas like engineering ceramics, intermetallics, at last the name Metals Research was only half the story. The limits between the classical physics, chemistry and engineering sciences became blurred. International Journal of Materials Research 1027, Carl Hanser Verlag GmbH & Co
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Stuttgart
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Stuttgart is the capital and largest city of the German state of Baden-Württemberg. It is located on the Neckar river in a fertile valley known as the Stuttgart Cauldron an hour from the Swabian Jura. Stuttgarts urban area has a population of 623,738, making it the sixth largest city in Germany. 2.7 million people live in the administrative region and another 5.3 million people in its metropolitan area. Since the 6th millennium BC, the Stuttgart area has been an important agricultural area and has been host to a number of cultures seeking to utilize the rich soil of the Neckar valley. The Roman Empire conquered the area in 83 AD and built a massive Castrum near Bad Cannstatt, Stuttgarts roots were truly laid in the 10th century with its founding by Liudolf, Duke of Swabia as a stud farm for his warhorses. Overshadowed by nearby Cannstatt, the town grew steadily and was granted a charter in 1320, the fortunes of Stuttgart turned with those of the House of Württemberg, and they made it the capital of their County, Duchy, and Kingdom from the 15th Century to 1918. Stuttgart prospered despite setbacks in the forms of the Thirty Years War and devastating air raids by the Allies on the city, however, by 1952, the city had bounced back and became the major economic, industrial, tourism and publishing center it is today. Stuttgart is also an important transport junction, and possesses the sixth largest airport in Germany. Such companies as Porsche, Mercedes-Benz, Daimler AG, Dinkelacker, Stuttgart is unusual in the scheme of German cities. It is spread across a variety of hills, valleys and parks and this is often a source of surprise to visitors who associate the city with its reputation as the Cradle of the Automobile. The citys tourism slogan is Stuttgart offers more, under current plans to improve transport links to the international infrastructure, the city unveiled a new logo and slogan in March 2008 describing itself as Das neue Herz Europas. For business, it describes itself as Where business meets the future, in July 2010, Stuttgart unveiled a new city logo, designed to entice more business people to stay in the city and enjoy breaks in the area. Stuttgart is a city of mostly immigrants, according to Dorling Kindersley Publishings Eyewitness Travel Guide to Germany, In the city of Stuttgart, every third inhabitant is a foreigner. 40% of Stuttgarts residents, and 64% of the population below the age of five are of immigrant background, the reason for this being that the city was founded in 950 AD by Duke Liudolf of Swabia to breed warhorses. Originally, the most important location in the Neckar river valley as the rim of the Stuttgart basin at what is today Bad Cannstatt. As with many military installations, a settlement sprang up nearby, when they did, the town was left in the capable hands of a local brickworks that produced sophisticated architectural ceramics and pottery. When the Romans were driven back past the Rhine and Danube rivers in the 3rd Century by the Alamanni, in 700, Duke Gotfrid mentions a Chan Stada in a document regarding property
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Markus J. Buehler
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Markus J. Buehler is an American materials scientist and engineer at the Massachusetts Institute of Technology. He is a professor at MITs Department of Civil and Environmental Engineering, since 2013, he serves as the Head of the Department of Civil and Environmental Engineering at MIT. Buehler has a background in science, engineering science and applied mechanics. He is best known for the use of computational models to explain complex materials phenomena in biology. He collaborates broadly with experimental researchers in the United States, Europe and his teaching at MIT focus on engineering mechanics and modeling and simulation, and on introducing undergraduate and graduate students to computational research. He is also participating in MITs Undergraduate Research Opportunities Program. He is a faculty advisor in the MIT Summer Research Program, since 2011 he serves as a co-Editor in Chief of BioNanoScience, a journal he co-founded. He was elected to the Editorial Board of the Journal of the Royal Society Interface in 2012. S, National Committee on Biomechanics, and participates in several other committees at ASME including the Committee on Mechanics in Biology and Medicine. He is also active in the Materials Research Society as volunteer writer for the MRS Bulletin, organizer of MRS symposiums, since 2010 he serves as the Director of the MIT-Germany Program. Buehler received the National Science Foundation CAREER Award, the United States Air Force Young Investigator Award, the Navy Young Investigator Award, in 2011 he received the inaugural Leonardo da Vinci Award from EMI. His work was recognized with other awards including the Alfred Noble Prize. Going nature one better M. J. Buehler, Tuning weakness to strength, Nano Today, Vol.5, pp. 379–383,2010
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IBM Research - Almaden
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IBM Research - Almaden is in Almaden Valley, San Jose, California, and is one of IBMs twelve worldwide research labs that form IBM Research. Its scientists perform basic and applied research in science, services, storage systems, physical sciences. The center opened in 1986, and continues the research started in San Jose more than fifty years ago, nearly all of Almaden’s approximately 500 research employees are in technical functions and more than half of these hold Ph. D. s. The lab is home to ten IBM Fellows, ten IBM Distinguished Engineers, nine IBM Master Inventors, Almaden occupies part of a site owned by IBM at 650 Harry Road on nearly 700 acres of land in the hills above Silicon Valley. The site, built in 1985 for the center, was chosen because of its close proximity to Stanford University, UC Santa Cruz, UC Berkeley. Today, the division is still the largest tenant of the site. IBM opened its first West Coast research centre, the San Jose Research Laboratory in 1952, amongst its first developments was the IBM350, the first commercial moving head hard disk drive. Launched in 1956, this saw use in the IBM305 RAMAC computer system, subdivisions included the Advanced Systems Development Division. Directors of the center include hard disc drive developer Jack Harker, prompted by a need for additional space, the center moved to its present Almaden location in 1986. Scientists at IBM Almaden have contributed to scientific discoveries such as the development of photoresists. Johnson, Maria Klawe, Jaishankar Menon, Dharmendra Modha, William E. Moerner, mohan, Stuart Parkin, Nick Pippenger, Patricia Selinger, Ted Selker, Barbara Simons, Ramakrishnan Srikant, Larry Stockmeyer, Moshe Vardi, Jennifer Widom
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San Jose, California
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San Jose, officially the City of San José, is the economic, cultural, and political center of Silicon Valley and the largest city in Northern California. With an estimated 2015 population of 1,026,908, it is the third most populous city in California and the tenth most populous in United States. Located in the center of the Santa Clara Valley, on the shore of San Francisco Bay. San Jose is the county seat of Santa Clara County, the most affluent county in California. San Jose is the largest city in both the San Francisco Bay Area and the San Jose-San Francisco-Oakland Combined Statistical Area, which contain 7.7 million and 8.7 million people respectively. Before the arrival of the Spanish, the area around San Jose was inhabited by the Ohlone people, San Jose was founded on November 29,1777, as the Pueblo of San José de Guadalupe, the first civilian town founded in Spanish Alta California. When California gained statehood in 1850, San Jose became the states first capital, following World War II, San Jose experienced an economic boom, with a rapid population growth and aggressive annexation of nearby cities and communities carried out in the 1950s and 60s. The rapid growth of the high-technology and electronics industries further accelerated the transition from a center to an urbanized metropolitan area. Results of the 1990 U. S. Census indicated that San Jose had officially surpassed San Francisco as the most populous city in Northern California, by the 1990s, San Jose and the rest of Silicon Valley had become the global center for the high tech and internet industries. San Jose is considered to be a city, notable for its affluence. San Joses location within the high tech industry, as a cultural, political. San Jose is one of the wealthiest major cities in the United States and the world, and has the third highest GDP per capita in the world, according to the Brookings Institute. Major global tech companies including Cisco Systems, eBay, Adobe Systems, PayPal, Brocade, Samsung, Acer, Prior to European settlement, the area was inhabited by several groups of Ohlone Native Americans. The first lasting European presence began with a series of Franciscan missions established from 1769 by Junípero Serra, San Jose came under Mexican rule in 1821 after Mexico broke with the Spanish crown. It then became part of the United States, after it capitulated in 1846, on March 27,1850, San Jose became the second incorporated city in the state, with Josiah Belden its first mayor. San Jose was Californias first state capital, and hosted the first, today the Circle of Palms Plaza in downtown is the historical marker for the first state capital. The city was a station on the Butterfield Overland Mail route, in the period 1900 through 1910, San Jose served as a center for pioneering invention, innovation, and impact in both lighter-than-air and heavier-than-air flight. These activities were led principally by John Montgomery and his peers, the City of San Jose has established Montgomery Park, a Monument at San Felipe and Yerba Buena Roads, and John J. Montgomery Elementary School in his honor
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Russian language
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Russian is an East Slavic language and an official language in Russia, Belarus, Kazakhstan, Kyrgyzstan and many minor or unrecognised territories. Russian belongs to the family of Indo-European languages and is one of the four living members of the East Slavic languages, written examples of Old East Slavonic are attested from the 10th century and beyond. It is the most geographically widespread language of Eurasia and the most widely spoken of the Slavic languages and it is also the largest native language in Europe, with 144 million native speakers in Russia, Ukraine and Belarus. Russian is the eighth most spoken language in the world by number of native speakers, the language is one of the six official languages of the United Nations. Russian is also the second most widespread language on the Internet after English, Russian distinguishes between consonant phonemes with palatal secondary articulation and those without, the so-called soft and hard sounds. This distinction is found between pairs of almost all consonants and is one of the most distinguishing features of the language, another important aspect is the reduction of unstressed vowels. Russian is a Slavic language of the Indo-European family and it is a lineal descendant of the language used in Kievan Rus. From the point of view of the language, its closest relatives are Ukrainian, Belarusian, and Rusyn. An East Slavic Old Novgorod dialect, although vanished during the 15th or 16th century, is considered to have played a significant role in the formation of modern Russian. In the 19th century, the language was often called Great Russian to distinguish it from Belarusian, then called White Russian and Ukrainian, however, the East Slavic forms have tended to be used exclusively in the various dialects that are experiencing a rapid decline. In some cases, both the East Slavic and the Church Slavonic forms are in use, with different meanings. For details, see Russian phonology and History of the Russian language and it is also regarded by the United States Intelligence Community as a hard target language, due to both its difficulty to master for English speakers and its critical role in American world policy. The standard form of Russian is generally regarded as the modern Russian literary language, mikhail Lomonosov first compiled a normalizing grammar book in 1755, in 1783 the Russian Academys first explanatory Russian dictionary appeared. By the mid-20th century, such dialects were forced out with the introduction of the education system that was established by the Soviet government. Despite the formalization of Standard Russian, some nonstandard dialectal features are observed in colloquial speech. Thus, the Russian language is the 6th largest in the world by number of speakers, after English, Mandarin, Hindi/Urdu, Spanish, Russian is one of the six official languages of the United Nations. Education in Russian is still a choice for both Russian as a second language and native speakers in Russia as well as many of the former Soviet republics. Russian is still seen as an important language for children to learn in most of the former Soviet republics, samuel P. Huntington wrote in the Clash of Civilizations, During the heyday of the Soviet Union, Russian was the lingua franca from Prague to Hanoi
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Charpy impact test
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The Charpy impact test, also known as the Charpy V-notch test, is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given materials notch toughness and it is widely applied in industry, since it is easy to prepare and conduct and results can be obtained quickly and cheaply. A disadvantage is that results are only comparative. The test was developed around 1900 by S. B, the test became known as the Charpy test in the early 1900s due to the technical contributions and standardization efforts by Charpy. The test was pivotal in understanding the problems of ships during World War II. Today it is utilized in many industries for testing materials, for example the construction of pressure vessels, in 1896 S. B. Russell introduced the idea of residual fracture energy and devised a pendulum fracture test. Russells initial tests measured un-notched samples, in 1897 Frémont introduced a test trying to measure the same phenomenon using a spring-loaded machine. In 1901 Georges Charpy proposed a standardized method improving Russells by introducing a redesigned pendulum, notched sample, the apparatus consists of a pendulum of known mass and length that is dropped from a known height to impact a notched specimen of material. The energy transferred to the material can be inferred by comparing the difference in the height of the hammer before, the notch in the sample affects the results of the impact test, thus it is necessary for the notch to be of regular dimensions and geometry. The size of the sample can also affect results, since the dimensions determine whether or not the material is in plane strain and this difference can greatly affect conclusions made. The quantitative result of the tests the energy needed to fracture a material. There is a connection to the yield strength but it cannot be expressed by a standard formula, also, the strain rate may be studied and analyzed for its effect on fracture. The ductile-brittle transition temperature may be derived from the temperature where the energy needed to fracture the material drastically changes, however, in practice there is no sharp transition and it is difficult to obtain a precise transition temperature. An exact DBTT may be derived in many ways, a specific absorbed energy, change in aspect of fracture. The qualitative results of the impact test can be used to determine the ductility of a material, if the material breaks on a flat plane, the fracture was brittle, and if the material breaks with jagged edges or shear lips, then the fracture was ductile. According to ASTM A370, the standard size for Charpy impact testing is 10 mm × 10mm × 55mm. Details of specimens as per ASTM A370, according to EN 10045-1, standard specimen sizes are 10 mm ×10 mm ×55 mm. Subsize specimens are,10 mm ×7.5 mm ×55 mm and 10 mm ×5 mm ×55 mm
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Fractography
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Fractography is the study of the fracture surfaces of materials. Fractographic methods are used to determine the cause of failure in engineering structures, especially in product failure. In material science research, fractography is used to develop and evaluate theoretical models of growth behavior. One of the aims of fractographic examination is to determine the cause of failure by studying the characteristics of a fractured surface, different types of crack growth produce characteristic features on the surface, which can be used to help identify the failure mode. The overall pattern of cracking can be more important than a crack, however, especially in the case of brittle materials like ceramics. An important aim of fractography is to establish and examine the origin of cracking, optical microscopy or macrophotography are often enough to pinpoint the nature of the failure and the causes of crack initiation and growth if the loading pattern is known. Common features that may cause crack initiation are inclusions, voids or empty holes in the material, contamination, hachures, are the lines on fracture surfaces which show crack direction. The broken crankshaft shown at right failed from a surface defect near the bulb at lower centre, the single crack growing up into the bulk material by small steps. The crankshaft also shows hachures which point back to the origin of the fracture, some modes of crack growth can leave characteristic marks on the surface that identify the mode of crack growth and origin on a macro scale e. g. beachmarks or striations on fatigue cracks. The areas of the product can also be revealing, especially if there are traces of sub-critical cracks. They can indicate that the material was faulty when loaded, or alternatively, a cusp is formed where brittle cracks meet, as shown on the picture of a failed catheter. The cusp was formed by brittle failure of the catheter on a breast implant in silicone rubber, the origin of the cracks is at the shoulder at the left-hand side. Identifying such features will allow a fracture surface map to be made of the surface being studied, the implant failed because of overload, all the imposed loads being concentrated at the connection between the catheter and the bag holding salt solution. As a result, the patient reported loss of fluid from the implant, USB microscopes are especially useful for examining fracture surface features since they are small enough to be hand-held. A variety of sizes and resolution are available commercially at low cost. The camera cable plugs into the computer via a USB plug, a schematic fracture surface map is a valuable result of visual or microscopic examination. It seeks to isolate and identify the features on the surface which show how the product failed, such a map can be a valuable way of presenting information which shows clearly how a crack was initiated and grew with time. In the case of the failed breast implant catheter, the path was very simple
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Forensic engineering
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Forensic engineering is the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property. The consequences of failure are dealt with by the law of product liability, the field also deals with retracing processes and procedures leading to accidents in operation of vehicles or machinery. The subject is applied most commonly in civil law cases, although it may be of use in law cases. It can also involve investigation of intellectual property claims, especially patents, as the field of engineering has evolved over time, so has the field of forensic engineering. Early examples include investigation of bridge failures such as the Tay rail bridge disaster of 1879, many early rail accidents prompted the invention of tensile testing of samples and fractography of failed components. Vital to the field of engineering is the process of investigating and collecting data related to the materials, products. This involves inspections, collecting evidence, measurements, developing models, obtaining exemplar products, often testing and measurements are conducted in an Independent testing laboratory or other reputable unbiased laboratory. Failure mode and effects analysis and fault tree analysis methods also examine product or process failure in a structured and systematic way, however, all such techniques rely on accurate reporting of failure rates, and precise identification, of the failure modes involved. There is some common ground between forensic science and forensic engineering, such as scene of crime and scene of accident analysis, integrity of the evidence, both disciplines make extensive use of optical and scanning electron microscopes, for example. They also share use of spectroscopy to examine critical evidence. Radiography using X-rays, or neutrons is also useful in examining thick products for their internal defects before destructive examination is attempted. Often, however, a hand lens may reveal the cause of a particular problem. Trace evidence is sometimes an important factor in reconstructing the sequence of events in an accident, for example, tire burn marks on a road surface can enable vehicle speeds to be estimated, when the brakes were applied and so on. Ladder feet often leave a trace of movement of the ladder during a slipaway, thus an acetal resin water pipe joint suddenly failed and caused substantial damages to a building in which it was situated. Analysis of the joint showed traces of chlorine, indicating a stress corrosion cracking failure mode, the failed fuel pipe junction mentioned above showed traces of sulfur on the fracture surface from the sulfuric acid, which had initiated the crack. Extracting physical evidence from digital photography is a technique used in forensic accident reconstruction. Camera matching, photogrammetry, and photo rectification techniques are used to create three-dimensional, overlooked or undocumented evidence for accident reconstruction can be retrieved and quantified as long as photographs of such evidence are available. By using photographs of the accident scene including the vehicle, lost evidence can be recovered, Forensic materials engineering involves methods applied to specific materials, such as metals, glasses, ceramics, composites and polymers
