shear

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shear

pruning and pinking shears (Academy Artworks)

(shîr)

1. To remove (fleece or hair) by cutting or clipping.
2. To remove the hair or fleece from.
3. To cut with or as if with shears: shearing a hedge.
4. To divest or deprive as if by cutting: The prisoners were shorn of their dignity.

1. To use a cutting tool such as shears.
2. To move or proceed by or as if by cutting: shear through the wheat.
3. Physics. To become deformed by forces tending to produce a shearing strain.

1. 1. A pair of scissors. Often used in the plural.
   2. Any of various implements or machines that cut with a scissorlike action. Often used in the plural.
2. The act, process, or result of shearing.
3. Something cut off by shearing.
4. The act, process, or fact of shearing. Used to indicate a sheep's age: a two-shear ram.
5. also sheers (shîrz) (used with a sing. or pl. verb) An apparatus used to lift heavy weights, consisting of two or more spars joined at the top and spread at the base, the tackle being suspended from the top.
6. Physics.
   1. An applied force or system of forces that tends to produce a shearing strain. Also called shearing stress, shear stress.
   2. A shearing strain.

[Middle English scheren, from Old English sceran. N., from Middle English shere, from Old English scēar.]

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A straining action wherein applied forces produce a sliding or skewing type of deformation. A shearing force acts parallel to a plane as distinguished from tensile or compressive forces, which act normal to a plane. Examples of force systems producing shearing action are forces transmitted from one plate to another by a rivet that tend to shear the rivet, forces in a beam that tend to displace adjacent segments by transverse shear, and forces acting on the cross section of a bar that tend to twist it by torsional shear (see illustration). Shear forces are usually accompanied by normal forces produced by tension, thrust, or bending. Shearing stress is the intensity of distributed force expressed as force per unit area. See also Stress and strain.

Shearing actions. (a) Single shear on rivet. (b) Transverse shear in beam. (c) Torsion.

verb

To decrease, as in length or amount, by or as if by severing or excising: chop¹, clip¹, crop, cut, cut back, cut down, lop¹, lower², pare, prune, slash, trim, truncate. See increase/decrease.

1. A deformation (e.g., in a beam or flexural member) in which parallel planes slide relative to each other so as to remain parallel.
2. To cut a metal with a pair of moving blades or with one moving blade and one fixed edge.
3. See shears.

An angular deformation of an object without a change in its volume.

To prune with long-bladed shears, cutting back all the stems, sometimes severely, to a uniform level or plane.

LearnThatWord.com is a free vocabulary and spelling program where you only pay for results!

1. to disrupt or fracture (an entity) using forces acting parallel to a plane, rather than perpendicularly, as with tensile or compressive forces. For example, shear forces can be used to disrupt DNA or other macromolecules by enclosing the molecules between two closely applied plane surfaces moving rapidly in opposite directions. Homogenization techniques depend on shear forces.
2. the deformation or fracture produced by such forces.

Person whose occupation is shearing sheep.

• Fabrication and Manufacturing Processes - shear: (vb) stamp or cut into forms
• Carpentry - shear: force producing opposite but parallel sliding motion in each of the contacting planes in a structural member
• Building Construction and Design - shear: force that produces opposite but parallel sliding motion on contacting planes in a structural member

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (July 2008)

Shear stress
SI symbol:	τ
SI unit:	pascal
Derivations from other quantities:	τ = F / A

A shear stress, is applied to the top of the square while the bottom is held in place. This stress results in a strain, or deformation, changing the square into a parallelogram. The area involved would be the top of the parallelogram.

A shear stress, denoted (Greek: tau), is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section. Normal stress, on the other hand, arises from the force vector component perpendicular or antiparallel to the material cross section on which it acts.

Contents 1 General shear stress 2 Other forms of shear stress 2.1 Pure shear 2.2 Beam shear 2.3 Semi-monocoque shear 2.4 Impact shear 2.5 Shear stress in fluids 3 Measurement by shear stress sensors 3.1 Diverging fringe shear stress sensor 3.2 Micro-pillar shear-stress sensor 4 See also 5 References 6 External links

General shear stress

The formula to calculate average shear stress is^{[citation needed]}:

where

τ = the shear stress;

F = the force applied;

A = the cross-sectional area of material with area parallel to the applied force vector.

Other forms of shear stress

Pure shear

Pure shear stress is related to pure shear strain, denoted γ, by the following equation:^[1]

where G is the shear modulus of the material, given by

Here E is Young's modulus and ν is Poisson's ratio.

Beam shear

Beam shear is defined as the internal shear stress of a beam caused by the shear force applied to the beam.

where

V = total shear force at the location in question;

Q = statical moment of area;

t = thickness in the material perpendicular to the shear;

I = Moment of Inertia of the entire cross sectional area.

This formula is also known as the Jourawski formula.^[2]

Semi-monocoque shear

Shear stresses within a semi-monocoque structure may be calculated by idealizing the cross-section of the structure into a set of stringers (carrying only axial loads) and webs (carrying only shear flows). Dividing the shear flow by the thickness of a given portion of the semi-monocoque structure yields the shear stress. Thus, the maximum shear stress will occur either in the web of maximum shear flow or minimum thickness.

Also constructions in soil can fail due to shear; e.g., the weight of an earth-filled dam or dike may cause the subsoil to collapse, like a small landslide.

Impact shear

The maximum shear stress created in a solid round bar subject to impact is given as the equation:

where

U = change in kinetic energy;

G = shear modulus;

V = volume of rod;

and

= mass moment of inertia;

= angular speed.

Shear stress in fluids

See also: Viscosity, Couette flow, Hagen-Poiseuille equation, Depth-slope product, and Simple shear

Any real fluids (liquids and gases included) moving along solid boundary will incur a shear stress on that boundary. The no-slip condition^[3] dictates that the speed of the fluid at the boundary (relative to the boundary) is zero, but at some height from the boundary the flow speed must equal that of the fluid. The region between these two points is aptly named the boundary layer. For all Newtonian fluids in laminar flow the shear stress is proportional to the strain rate in the fluid where the viscosity is the constant of proportionality. However for Non Newtonian fluids, this is no longer the case as for these fluids the viscosity is not constant. The shear stress is imparted onto the boundary as a result of this loss of velocity. The shear stress, for a Newtonian fluid, at a surface element parallel to a flat plate, at the point y, is given by:

where

μ is the dynamic viscosity of the fluid;

u is the velocity of the fluid along the boundary;

y is the height above the boundary.

Specifically, the wall shear stress is defined as:

In case of wind, the shear stress at the boundary is called wind stress.

Measurement by shear stress sensors

Diverging fringe shear stress sensor

This relationship can be exploited to measure the wall shear stress. If a sensor could directly measure the gradient of the velocity profile at the wall, then multiplying by the dynamic viscosity would yield the shear stress. Such a sensor was demonstrated by A. A. Naqwi and W. C. Reynolds.^[4] The interference pattern generated by sending a beam of light through two parallel slits forms a network of linearly diverging fringes that seem to originate from the plane of the two slits (see double-slit experiment). As a particle in a fluid passes through the fringes, a receiver detects the reflection of the fringe pattern. The signal can be processed, and knowing the fringe angle, the height and velocity of the particle can be extrapolated. The measured value of wall velocity gradient is independent of the fluid properties and as a result does not require calibration. Recent advancements in the micro-optic fabrication technologies have made it possible to use integrated diffractive optical element to fabricate diverging fringe shear stress sensors usable both in air and liquid.

Micro-pillar shear-stress sensor

A further technique recently proposed is that of slender wall-mounted micro-pillars made of the flexible polymer PDMS, which bend in reaction to the applying drag forces in the vicinity of the wall. The deflection of the pillar tips from a reference position is detected optically and serves as a representative of the wall-shear stress. It allows the instantaneous detection of the streamwise and spanwise wall-shear stress distribution in turbulent flow up to high Reynolds numbers.^[5][6]

See also

• Direct shear test
• Shear rate
• Shear strain
• Shear strength
• Shear and moment diagrams
• Tensile stress
• Triaxial shear test
• Critical resolved shear stress

References

1. ^ "Strength of Materials". Eformulae.com. http://www.eformulae.com/engineering/strength_materials.php#pureshear. Retrieved 24 December 2011. 
2. ^ Timoshenko, Stephen P. (1983), History of Strength of Material, Courier Dover Publications, p. 141, ISBN 0486611876, http://books.google.com/?id=tkScQmyhsb8C .
3. ^ Day, Michael A. (2004), The no-slip condition of fluid dynamics, Springer Netherlands, pp. 285–296, ISSN (Print) 1572-8420 (Online) 0165-0106 (Print) 1572-8420 (Online), http://www.springerlink.com/content/k1m4t1p02m778u88/ .
4. ^ Naqwi, A. A.; Reynolds, W. C. (jan 1987), "Dual cylindrical wave laser-Doppler method for measurement of skin friction in fluid flow", NASA STI/Recon Technical Report N 87 
5. ^ Große, S.; Schröder, W. (2009), "Two-Dimensional Visualization of Turbulent Wall Shear Stress Using Micropillars", AIAA Journal 47 (2): 314–321, Bibcode 2009AIAAJ..47..314G, doi:10.2514/1.36892 
6. ^ Große, S.; Schröder, W. (2008), "Dynamic Wall-Shear Stress Measurements in Turbulent Pipe Flow using the Micro-Pillar Sensor MPS³", International Journal of Heat and Fluid Flow 29 (3): 830–840, doi:10.1016/j.ijheatfluidflow.2008.01.008 

External links

• The second page of this brochure explains the concept of the diverging fringe shear stress sensor mentioned above.

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
v. tr. - klippe, overskære, afklippe, beskære
v. intr. - undergå forskydning
n. - skæreblad, klippet dyr, klippemaskine, afklippet uld, forskydning

Nederlands (Dutch)
blad (schaar), scheerbeurt, kloof, spleet, scheren, (door) klieven, splijten

Français (French)
v. tr. - tondre
v. intr. - tondre
n. - tonte

Deutsch (German)
n. - Scherung
v. - scheren

Ελληνική (Greek)
n. - κοπή, μηχανικό ψαλίδι, απόκομμα, (πληθ.) κλαδευτήρι
v. - κουρεύω, ψαλιδίζω, κόβω, ξακρίζω

Italiano (Italian)
cesoia, taglio, tranciare

Português (Portuguese)
n. - tosquia (f), corte (m)
v. - tosquiar, cortar, arredondar

Русский (Russian)
ножницы, стрижка, настриг, стричь, резать

Español (Spanish)
v. tr. - esquilar, podar, rapar, privar, despojar, privar de, (mec) romper por esfuerzo cortante
v. intr. - (mec) romperse obedeciendo a un esfuerzo cortante
n. - cizallas, tijeras de jardinero, esquila, (mec) esfuerzo cortante, cortadura

Svenska (Swedish)
n. - avklippt bit
v. - klippa, klippa av, hugga med svärd

中文（简体）(Chinese (Simplified))
修剪, 剥夺, 割, 剪, 剪羊毛, 切断, 切, 大剪刀

中文（繁體）(Chinese (Traditional))
v. tr. - 修剪, 剝奪, 割
v. intr. - 剪, 剪羊毛, 修剪, 切斷
n. - 剪, 修剪, 切, 大剪刀

한국어 (Korean)
v. tr. - 자르다, 보풀을 베어 내다, (권력 따위를) ~에게서 빼앗다
v. intr. - 가위질하다, 돌파하다, (배, 비행기 따위가) 헤치고 나아가다
n. - 큰 가위, (양털) 깎기, 전단 변형

日本語 (Japanese)
v. - 刈る, 毛を刈る, 刈り込む, 切る, から奪う

العربيه (Arabic)
‏(الاسم) مجزة, مقص كبير (فعل) يقص, يجز‏

עברית (Hebrew)
v. tr. - ‮גזז, סיפר, חתך, הוליך שולל, הטעה, מנע מ-, עשה לעירום‬
v. intr. - ‮הולך שולל, הוטעה, נשבר בשל מתח מבני‬
n. - ‮מתח במבנה חומר כששכבותיו מוטות זו ביחס לזו (גיאולוגיה)‬

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