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définition - Fracture

fracture (n.)

1.the act of cracking something

2.(geology) a crack in the earth's crust resulting from the displacement of one side with respect to the other"they built it right over a geological fault" "he studied the faulting of the earth's crust"

3.breaking of hard tissue such as bone"it was a nasty fracture" "the break seems to have been caused by a fall"

fracture (v.)

1.fracture a bone of"I broke my foot while playing hockey"

2.break (a bone)"She broke her clavicle"

3.become fractured"The tibia fractured from the blow of the iron pipe"

4.violate or abuse"This writer really fractures the language"

5.break into pieces"The pothole fractured a bolt on the axle"

6.interrupt, break, or destroy"fracture the balance of power"

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Merriam Webster

FractureFrac"ture (?; 135), n. [L. fractura, fr. frangere, fractum, to break: cf. F. fracture. See Fraction.]
1. The act of breaking or snapping asunder; rupture; breach.

2. (Surg.) The breaking of a bone.

3. (Min.) The texture of a freshly broken surface; as, a compact fracture; an even, hackly, or conchoidal fracture.

Comminuted fracture (Surg.), a fracture in which the bone is broken into several parts. -- Complicated fracture (Surg.), a fracture of the bone combined with the lesion of some artery, nervous trunk, or joint. -- Compound fracture (Surg.), a fracture in which there is an open wound from the surface down to the fracture. -- Simple fracture (Surg.), a fracture in which the bone only is ruptured. It does not communicate with the surface by an open wound.

Syn. -- Fracture, Rupture. These words denote different kinds of breaking, according to the objects to which they are applied. Fracture is applied to hard substances; as, the fracture of a bone. Rupture is oftener applied to soft substances; as, the rupture of a blood vessel. It is also used figuratively. “To be an enemy and once to have been a friend, does it not embitter the rupture?” South.

FractureFrac"ture (?; 135), v. t. [imp. & p. p. Fractured (#; 135); p. pr. & vb. n.. Fracturing.] [Cf. F. fracturer.] To cause a fracture or fractures in; to break; to burst asunder; to crack; to separate the continuous parts of; as, to fracture a bone; to fracture the skull.

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définition (complément)

voir la définition de Wikipedia

synonymes - Fracture

locutions

-Ankle fracture • Avulsion fracture • Barton's fracture • Basilar skull fracture • Bennett's fracture • Blanco Fracture Zone • Blowout fracture • Bone fracture • Bosworth fracture • Boxer fracture • Boxer's fracture • Brittle fracture • Bumper fracture • Burst fracture • Calcaneal fracture • Cervical fracture • Chalkstick fracture • Chance fracture • Chauffeur's fracture • Child bone fracture • Chopart's fracture-dislocation • Clavicle fracture • Clay-shoveler fracture • Closed fracture • Colles' fracture • Comminuted fracture • Comminuted skull fracture • Compound fracture • Compression fracture • Conchoidal fracture • Depressed skull fracture • Diamantina Fracture Zone • Diastatic fracture • Diastatic skull fracture • Distal radius fracture • Don Juan fracture • Ductile fracture • Dupuytren's fracture • Duverney fracture • Easter Fracture Zone • Environmental stress fracture • Essex-Lopresti fracture • Fast fracture • Flexion teardrop fracture • Fracture (2004 film) • Fracture (2007 film) • Fracture (Transformers) • Fracture (bone) • Fracture (disambiguation) • Fracture (fanzine) • Fracture (geology) • Fracture (mineralogy) • Fracture (video game) • Fracture blister • Fracture mechanics • Fracture of the scapula • Fracture of the shoulder blade • Fracture toughening mechanisms • Fracture toughness • Fracture zone • Galeazzi fracture • Gibbs Fracture Zone Water • Gosselin fracture • Greenstick fracture • Growing fracture • Hangman's fracture • Hip fracture • Hip fracture treatment • Holdsworth fracture • Holstein Lewis fracture • Holstein-Lewis fracture • Hume fracture • Humerus fracture • Intergranular fracture • International Journal of Fracture • Jefferson fracture • Jones fracture • Le Fort's fracture of the ankle • LeFort fracture • Linear skull fracture • Lisfranc fracture • Lover's fracture • Lovers fracture • Maisonneuve fracture • Mandibular fracture • March fracture • Mendocino Fracture Zone • Metatarsal stress fracture • Monteggia fracture • Nasal fracture • Oblique fracture • Of Fracture and Failure • Open fracture • Owen Fracture Zone • Panama Fracture Zone • Patella fracture • Pathologic fracture • Pelvic fracture • Penetrating skull fracture • Penial fracture • Penile fracture • Pott's fracture • Rib fracture • Rolando fracture • Scaphoid fracture • Scapula fracture • Scapular fracture • Segond fracture • Shackleton Fracture Zone • Shoulder blade fracture • Skull base fracture • Skull fracture • Smith's fracture • Sovanco Fracture Zone • Spiral fracture • Sternal fracture • Stress fracture • Supersonic fracture • Supracondylar fracture • Tasman Fracture • The Ocean Fracture • Toddler's fracture • Tooth Interior Fatigue Fracture • Transgranular fracture • Trimalleolar fracture • Tripod fracture • Vertebral fracture • Vertical root fracture • Wedge fracture

dictionnaire analogique

 

MESH root[Thème]

fracture [MeSH]









 

factotum[Domaine]

IntentionalProcess[Domaine]

expend, use[Hyper.]

perversion - abuse, misuse[Dérivé]

fracture (v.)




Wikipedia

Fracture

                   

A fracture is the (local) separation of an object or material into two, or more, pieces under the action of stress.

The word fracture is often applied to bones of living creatures (that is, a bone fracture), or to crystals or crystalline materials, such as gemstones or metal. Sometimes, in crystalline materials, individual crystals fracture without the body actually separating into two or more pieces. Depending on the substance which is fractured, a fracture reduces strength (most substances) or inhibits transmission of light (optical crystals).

A detailed understanding of how fracture occurs in materials may be assisted by the study of fracture mechanics.

A fracture is also the term used for a particular mask data preparation procedure within the realm of integrated circuit design that involves transposing complex polygons into simpler shapes such as trapezoids and rectangles.

Contents

  Fracture strength

  Stress vs. strain curve typical of aluminum
1. Ultimate tensile strength
2. Yield strength
3. Proportional limit stress
4. Fracture
5. Offset strain (typically 0.2%)

Fracture strength, also known as breaking strength, is the stress at which a specimen fails via fracture.[1] This is usually determined for a given specimen by a tensile test, which charts the stress-strain curve (see image). The final recorded point is the fracture strength.

Ductile materials have a fracture strength lower than the ultimate tensile strength (UTS), whereas in brittle materials the fracture strength is equivalent to the UTS.[1] If a ductile material reaches its ultimate tensile strength in a load-controlled situation,[Note 1] it will continue to deform, with no additional load application, until it ruptures. However, if the loading is displacement-controlled,[Note 2] the deformation of the material may relieve the load, preventing rupture.

If the stress-strain curve is plotted in terms of true stress and true strain the curve will always slope upwards and never reverse, as true stress is corrected for the decrease in cross-sectional area. The true stress on the material at the time of rupture is known as the breaking strength. This is the maximum stress on the true stress-strain curve, given by point 3 on curve B.

  Types

  Brittle fracture

  Brittle fracture in glass.
  Fracture of an Aluminum Crank Arm. Bright: Brittle fracture. Dark: Fatigue fracture.

In brittle fracture, no apparent plastic deformation takes place before fracture. In brittle crystalline materials, fracture can occur by cleavage as the result of tensile stress acting normal to crystallographic planes with low bonding (cleavage planes). In amorphous solids, by contrast, the lack of a crystalline structure results in a conchoidal fracture, with cracks proceeding normal to the applied tension.

The theoretical strength of a crystalline material is (roughly)

\sigma_\mathrm{theoretical} = \sqrt{ \frac{E \gamma}{r_o} }

where: -

E is the Young's modulus of the material,
\gamma is the surface energy, and
r_o is the equilibrium distance between atomic centers.

On the other hand, a crack introduces a stress concentration modeled by

\sigma_\mathrm{elliptical\ crack} = \sigma_\mathrm{applied}\left(1 + 2 \sqrt{ \frac{a}{\rho}}\right) = 2 \sigma_\mathrm{applied} \sqrt{\frac{a}{\rho}} (For sharp cracks)

where: -

\sigma_\mathrm{applied} is the loading stress,
a is half the length of the crack, and
\rho is the radius of curvature at the crack tip.

Putting these two equations together, we get

\sigma_\mathrm{fracture} = \sqrt{ \frac{E \gamma \rho}{4 a r_o}}.

Looking closely, we can see that sharp cracks (small \rho) and large defects (large a) both lower the fracture strength of the material.

Recently, scientists have discovered supersonic fracture, the phenomenon of crack motion faster than the speed of sound in a material [2]. This phenomenon was recently also verified by experiment of fracture in rubber-like materials.

  Ductile fracture

  Ductile failure of a specimen strained axially.
  Schematic representation of the steps in ductile fracture (in pure tension).

In ductile fracture, extensive plastic deformation (necking) takes place before fracture. The terms rupture or ductile rupture describe the ultimate failure of tough ductile materials loaded in tension. Rather than cracking, the material "pulls apart," generally leaving a rough surface. In this case there is slow propagation and an absorption of a large amount energy before fracture.[citation needed]

Many ductile metals, especially materials with high purity, can sustain very large deformation of 50–100% or more strain before fracture under favorable loading condition and environmental condition. The strain at which the fracture happens is controlled by the purity of the materials. At room temperature, pure iron can undergo deformation up to 100% strain before breaking, while cast iron or high-carbon steels can barely sustain 3% of strain.[citation needed]

Because ductile rupture involves a high degree of plastic deformation, the fracture behavior of a propagating crack as modeled above changes fundamentally. Some of the energy from stress concentrations at the crack tips is dissipated by plastic deformation before the crack actually propagates.

The basic steps are: void formation, void coalescence (also known as crack formation), crack propagation, and failure, often resulting in a cup-and-cone shaped failure surface.

  Crack separation modes

  The three fracture modes.

There are three ways of applying a force to enable a crack to propagate:

  • Mode I crack – Opening mode (a tensile stress normal to the plane of the crack)
  • Mode II crack – Sliding mode (a shear stress acting parallel to the plane of the crack and perpendicular to the crack front)
  • Mode III crack – Tearing mode (a shear stress acting parallel to the plane of the crack and parallel to the crack front)

For more information, see fracture mechanics.

Crack initiation and propagation accompany fracture. The manner through which the crack propagates through the material gives great insight into the mode of fracture. In ductile materials (ductile fracture), the crack moves slowly and is accompanied by a large amount of plastic deformation. The crack will usually not extend unless an increased stress is applied. On the other hand, in dealing with brittle fracture, cracks spread very rapidly with little or no plastic deformation. The cracks that propagate in a brittle material will continue to grow and increase in magnitude once they are initiated. Another important mannerism of crack propagation is the way in which the advancing crack travels through the material. A crack that passes through the grains within the material is undergoing transgranular fracture. However, a crack that propagates along the grain boundaries is termed an intergranular fracture.

  See also

  Notes

  1. ^ A simple load-controlled tensile situation would be to support a specimen from above, and hang a weight from the bottom end. The load on the specimen is then independent of its deformation.
  2. ^ A simple displacement-controlled tensile situation would be to attach a very stiff jack to the ends of a specimen. As the jack extends, it controls the displacement of the specimen; the load on the specimen is dependent on the deformation.

  References

  1. ^ a b Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, p. 32, ISBN 0-471-65653-4. 
  2. ^ C. H. Chen, H. P. Zhang, J. Niemczura, K. Ravi-Chandar and M. Marder (November 2011). "Scaling of crack propagation in rubber sheets". Europhysics Letters 96 (3): 36009. DOI:10.1209/0295-5075/96/36009. http://iopscience.iop.org/0295-5075/96/3/36009/. 

  Further reading

  • Dieter, G. E. (1988) Mechanical Metallurgy ISBN 0-07-100406-8
  • A. Garcimartin, A. Guarino, L. Bellon and S. Cilberto (1997) " Statistical Properties of Fracture Precursors ". Physical Review Letters, 79, 3202 (1997)
  • Callister, Jr., William D. (2002) Materials Science and Engineering: An Introduction. ISBN 0-471-13576-3
  • Peter Rhys Lewis, Colin Gagg, Ken Reynolds, CRC Press (2004), Forensic Materials Engineering: Case Studies.

  External links

   
               

 

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