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Necking (engineering)
In engineering and materials science, necking is a mode of tensile deformation where relatively large amounts of strain localize disproportionately in a small region of the material. The resulting prominent decrease in local cross-sectional area provides the basis for the name "neck". Because the local strains in the neck are large, necking is often closely associated with yielding, a form of plastic deformation associated with ductile materials, often metals or polymers. Once necking has begun, the neck becomes the exclusive location of yielding in the material, as the reduced area gives the neck the largest local stress. Formation Necking results from an instability during tensile deformation when the cross-sectional area of the sample decreases by a greater proportion than the material strain hardens. Armand Considère published the basic criterion for necking in 1885, in the context of the stability of large scale structures such as bridges. Three concepts provide the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Necking Example
{{disambiguation ...
Necking can refer to: * Making out, a term for heavy kissing of the neck or petting of that area * Necking (engineering), the process by which a ductile material deforms under tension forming a thin ''neck'' * Necking (electronics), thinning of traces in PCB layouts * Necking, a behavior of giraffes * Necking up or necking down, methods of modifying a firearm cartridge to make a wildcat cartridge or a new production cartridge (e.g. the US .60 caliber T17 round being shortened and necked up to create the 20×102 mm M61 Vulcan cannon cartridge) See also * Neck (other) * Rubbernecking Rubbernecking is a derogatory term primarily used to refer to bystanders staring at accidents. More generally, it can refer to anyone staring at something of everyday interest compulsively (especially tourists). The term ''rubbernecking'' derive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Poisson's Ratio
In materials science and solid mechanics, Poisson's ratio \nu ( nu) is a measure of the Poisson effect, the deformation (expansion or contraction) of a material in directions perpendicular to the specific direction of loading. The value of Poisson's ratio is the negative of the ratio of transverse strain to axial strain. For small values of these changes, \nu is the amount of transversal elongation divided by the amount of axial compression. Most materials have Poisson's ratio values ranging between 0.0 and 0.5. For soft materials, such as rubber, where the bulk modulus is much higher than the shear modulus, Poisson's ratio is near 0.5. For open-cell polymer foams, Poisson's ratio is near zero, since the cells tend to collapse in compression. Many typical solids have Poisson's ratios in the range of 0.2–0.3. The ratio is named after the French mathematician and physicist Siméon Poisson. Origin Poisson's ratio is a measure of the Poisson effect, the phenomenon in which a ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trace Necking
In printed circuit boards, teardrops are typically drop-shaped features at the junction of vias (''teardrop vias'') or contact pads (''teardrop pads'') and traces (''teardrop traces''). The main purpose of teardrops is to enhance structural integrity in presence of thermal or mechanical stresses, for example due to vibration or flexing. Structural integrity may be compromised, e.g., by misalignment during drilling, so that too much copper may be removed by the drill hole in the area where a trace connects to the pad or via. An extra advantage is the enlarging of manufacturing tolerances, making manufacturing easier and cheaper. While a typical shape of a teardrop is straight-line tapering, they may be concave. This type of teardrop is also called ''filleting'' or ''straight''. To produce a ''snowman''-shaped teardrop, a secondary pad of smaller size is added at the junction overlapping with the primary pad (hence the nickname). Necking For similar reasons, a technique ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stress–strain Curve
In engineering and materials science, a stress–strain curve for a material gives the relationship between stress and strain. It is obtained by gradually applying load to a test coupon and measuring the deformation, from which the stress and strain can be determined (see tensile testing). These curves reveal many of the properties of a material, such as the Young's modulus, the yield strength and the ultimate tensile strength. Definition Generally speaking, curves representing the relationship between stress and strain in any form of deformation can be regarded as stress–strain curves. The stress and strain can be normal, shear, or mixture, also can be uniaxial, biaxial, or multiaxial, even change with time. The form of deformation can be compression, stretching, torsion, rotation, and so on. If not mentioned otherwise, stress–strain curve refers to the relationship between axial normal stress and axial normal strain of materials measured in a tension test. Engineer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ductility
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stress before failure. Ductility is an important consideration in engineering and manufacturing. It defines a material's suitability for certain manufacturing operations (such as cold working) and its capacity to absorb mechanical overload.. Some metals that are generally described as ductile include gold and copper. However, not all metals experience ductile failure as some can be characterized with brittle failure like cast iron. Polymers generally can be viewed as ductile materials as they typically allow for plastic deformation. Malleability, a similar mechanical property, is characterized by a material's ability to deform plastically without failure under compressive stress. Historically, materials were considered malleable if they were am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultimate Tensile Stress
Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials the ultimate tensile strength is close to the yield point, whereas in ductile materials the ultimate tensile strength can be higher. The ultimate tensile strength is usually found by performing a tensile test and recording the engineering stress versus strain. The highest point of the stress–strain curve is the ultimate tensile strength and has units of stress. The equivalent point for the case of compression, instead of tension, is called the compressive strength. Tensile strengths are rarely of any consequence in the design of ductile members, but they are important with brittle members. They are tabulated for common materials such as alloys, composite materials, ceramics, plastics, and wood. Definition The ultimate tensile streng ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DoITPoMS
Dissemination of IT for the Promotion of Materials Science (DoITPoMS) is a web-based educational software resource designed to facilitate the teaching and learning of Materials science, at the tertiary level for free. History The DoITPoMS project originated in the early 1990s, incorporating customized online sources into the curriculum of the Materials Science courses in the Natural Sciences Tripos of the University Cambridge. The initiative became formalized in 2000, with the start of a project supported by the UK national Fund for the Development of Teaching and Learning (FDTL). This was led by the Department of Materials Science and Metallurgy in Cambridge, with five partner institutions, including the University of Leeds, London Metropolitan University, the University of Manchester, Oxford Brookes University and the University of Sheffield. This period of cooperation lasted for about 10 years. The FDTL project was aimed at building on expertise concerning the use of Inf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymer Chains
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles 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 and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals. The term "polymer" derives from the Greek word πολύς (''polus'', meaning "many, much") and μέρος (''meros'', meani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
