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Hill Yield Criterion
The Hill yield criterion developed by Rodney Hill, is one of several yield criteria for describing anisotropic plastic deformations. The earliest version was a straightforward extension of the von Mises yield criterion and had a quadratic form. This model was later generalized by allowing for an exponent ''m''. Variations of these criteria are in wide use for metals, polymers, and certain composites. Quadratic Hill yield criterion The quadratic Hill yield criterion has the form : F(\sigma_-\sigma_)^2 + G(\sigma_-\sigma_)^2 + H(\sigma_-\sigma_)^2 + 2L\sigma_^2 + 2M\sigma_^2 + 2N\sigma_^2 = 1 ~. Here ''F, G, H, L, M, N'' are constants that have to be determined experimentally and \sigma_ are the stresses. The quadratic Hill yield criterion depends only on the deviatoric stresses and is pressure independent. It predicts the same yield stress in tension and in compression. Expressions for ''F'', ''G'', ''H'', ''L'', ''M'', ''N'' If the axes of material anisotropy are assum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hosford Yield Criterion
The Hosford yield criterion is a function that is used to determine whether a material has undergone plastic yielding under the action of stress. Hosford yield criterion for isotropic plasticity The Hosford yield criterion for isotropic materials is a generalization of the von Mises yield criterion. It has the form : \tfrac, \sigma_2-\sigma_3, ^n + \tfrac, \sigma_3-\sigma_1, ^n + \tfrac, \sigma_1-\sigma_2, ^n = \sigma_y^n \, where \sigma_i, i=1,2,3 are the principal stresses, n is a material-dependent exponent and \sigma_y is the yield stress in uniaxial tension/compression. Alternatively, the yield criterion may be written as : \sigma_y = \left(\tfrac, \sigma_2-\sigma_3, ^n + \tfrac, \sigma_3-\sigma_1, ^n + \tfrac, \sigma_1-\sigma_2, ^n\right)^ \,. This expression has the form of an ''L''''p'' norm which is defined as :\ \, x\, _p=\left(, x_1, ^p+, x_2, ^p+\cdots+, x_n, ^p\right)^ \,. When p = \infty, the we get the ''L''∞ norm, :\ \, x\, _\infty=\max \left\. Compar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rodney Hill
Rodney Hill FRS (11 June 1921 – 2 February 2011) was an applied mathematician and a former Professor of Mechanics of Solids at Gonville and Caius College, Cambridge. Career In 1953 he was appointed Professor of Applied Mathematics at the University of Nottingham. His 1950 ''The Mathematical Theory of Plasticity'' workHill R., ''The Mathematical Theory of Plasticity'', Oxford University Press, 1950. forms the foundation of plasticity theory. Hill is widely regarded as among the foremost contributors to the foundations of solid mechanics over the second half of the 20th century. His early work was central to founding the mathematical theory of plasticity. This deep interest led eventually to general studies of uniqueness and stability in nonlinear continuum mechanics, work which has had a profound influence on the field of solid mechanics—theoretical, computational and experimental alike—over the past decades. Hill was the founding editor of the ''Journal of the Mechanics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Von Mises Yield Criterion
The maximum distortion criterion (also von Mises yield criterion) states that yielding of a ductile material begins when the second invariant of deviatoric stress J_2 reaches a critical value. It is a part of plasticity theory that mostly applies to ductile materials, such as some metals. Prior to yield, material response can be assumed to be of a nonlinear elastic, viscoelastic, or linear elastic behavior. In materials science and engineering von Mises yield criterion is also formulated in terms of the von Mises stress or equivalent tensile stress, \sigma_\text. This is a scalar value of stress that can be computed from the Cauchy stress tensor. In this case, a material is said to start yielding when the von Mises stress reaches a value known as yield strength, \sigma_\text. The von Mises stress is used to predict yielding of materials under complex loading from the results of uniaxial tensile tests. The von Mises stress satisfies the property where two stress states with equa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lankford Coefficient
The Lankford coefficient (also called Lankford value, R-value, or plastic strain ratio) is a measure of the plastic anisotropy of a rolled sheet metal. This scalar quantity is used extensively as an indicator of the formability of recrystallized low-carbon steel sheets.Ken-ichiro Mori, ''Simulation of Materials Processing: Theory, Methods and Applications'', (), p. 436 Definition If x and y are the coordinate directions in the plane of rolling and z is the thickness direction, then the R-value is given by : R = \cfrac where \epsilon^p_ is the in-plane plastic strain, transverse to the loading direction, and \epsilon^p_ is the plastic strain through-the-thickness. ISO 10113:202/ref> More recent studies have shown that the R-value of a material can depend strongly on the strain even at small strains . In practice, the R value is usually measured at 20% elongation in a tensile test. For sheet metals, the R values are usually determined for three different directions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
R-value (plasticity) , a plasmid that cod ...
R-value or rvalue may refer to: * R-value (insulation) in building engineering, the efficiency of insulation of a house * R-value (soils) in geotechnical engineering, the stability of soils and aggregates for pavement construction * R-factor (crystallography), a measure of the agreement between the crystallographic model and the diffraction data * ''R''0 or ''R'' number, the basic reproduction number in epidemiology * In computer science, a pure value which cannot be assigned to * In statistics, the Pearson product-moment correlation coefficient, or simply ''correlation coefficient'' * In solid mechanics, the Lankford coefficient See also * L-value (other) * R rating (other) * R-factor Plasmid-mediated resistance is the transfer of antibiotic resistance genes which are carried on plasmids. Plasmids possess mechanisms that ensure their independent replication as well as those that regulate their replication number and guarantee st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plane Stress
In continuum mechanics, a material is said to be under plane stress if the stress vector is zero across a particular plane. When that situation occurs over an entire element of a structure, as is often the case for thin plates, the stress analysis is considerably simplified, as the stress state can be represented by a tensor of dimension 2 (representable as a 2×2 matrix rather than 3×3). A related notion, plane strain, is often applicable to very thick members. Plane stress typically occurs in thin flat plates that are acted upon only by load forces that are parallel to them. In certain situations, a gently curved thin plate may also be assumed to have plane stress for the purpose of stress analysis. This is the case, for example, of a thin-walled cylinder filled with a fluid under pressure. In such cases, stress components perpendicular to the plate are negligible compared to those parallel to it. In other situations, however, the bending stress of a thin plate cannot be ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymer
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'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foam
Foams are materials formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas. Soap foams are also known as suds. Solid foams can be closed-cell or open-cell. In closed-cell foam, the gas forms discrete pockets, each completely surrounded by the solid material. In open-cell foam, gas pockets connect to each other. A bath sponge is an example of an open-cell foam: water easily flows through the entire structure, displacing the air. A sleeping mat is an example of a closed-cell foam: gas pockets are sealed from each other so the mat cannot soak up water. Foams are examples of dispersed media. In general, gas is present, so it divides into gas bubbles of different sizes (i.e., the material is polydisperse)—separated by liquid regions that may form films, thinner and thinner when the liquid phase drain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bresler Pister Yield Criterion
Bresler is a surname. Notable people with the surname include: * Anton Bresler (born 1988), South African rugby union player *Jerry Bresler (1914–2000), American songwriter, conductor *Jerry Bresler (1908–1977), American film producer See also *Bresler Pister yield criterion *Bresler's Ice Cream Bresler's 33 Flavors was an American ice cream chain founded in 1927. Its founder was Polish immigrant William J. Bresler, who died in 1985. In 1954, Bresler's began a fast food hamburger chain called Henry's Hamburgers. The Bresler's chain w ..., American ice cream chain * Bressler, a surname {{surname, Bresler ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Honeycomb Structures
Honeycomb structures are natural or man-made structures that have the geometry of a honeycomb to allow the minimization of the amount of used material to reach minimal weight and minimal material cost. The geometry of honeycomb structures can vary widely but the common feature of all such structures is an array of hollow cells formed between thin vertical walls. The cells are often columnar and hexagonal in shape. A honeycomb shaped structure provides a material with minimal density and relative high out-of-plane compression properties and out-of-plane shear properties. Man-made honeycomb structural materials are commonly made by layering a honeycomb material between two thin layers that provide strength in tension. This forms a plate-like assembly. Honeycomb materials are widely used where flat or slightly curved surfaces are needed and their high specific strength is valuable. They are widely used in the aerospace industry for this reason, and honeycomb materials in aluminu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sandwich Structured Composite
A sandwich-structured composite is a special class of composite materials that is fabricated by attaching two thin but stiff skins to a lightweight but thick core. The core material is normally low strength material, but its higher thickness provides the sandwich composite with high bending stiffness with overall low density. Open- and closed-cell-structured foams like polyethersulfone polyvinylchloride, polyurethane, polyethylene or polystyrene foams, balsa wood, syntactic foams, and honeycombs are commonly used core materials. Sometimes, the honeycomb structure is filled with other foams for added strength. Open- and closed-cell metal foam can also be used as core materials. Laminates of glass or carbon fiber-reinforced thermoplastics or mainly thermoset polymers ( unsaturated polyesters, epoxies...) are widely used as skin materials. Sheet metal is also used as skin material in some cases. The core is bonded to the skins with an adhesive or with metal components by brazing to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasticity (physics)
In physics and materials science, plasticity, also known as plastic deformation, is the ability of a solid material to undergo permanent Deformation (engineering), deformation, a non-reversible change of shape in response to applied forces. For example, a solid 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 Elasticity (physics), elastic behavior to plastic behavior is known as Yield (engineering), yielding. Plastic deformation is observed in most materials, particularly metals, soils, Rock (geology), rocks, concrete, and foams. However, the physical 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 res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
