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

In continuum mechanics, stress is a measure of the average amount of force exerted per unit area. It is a measure of the intensity of the total internal forces acting within a body across imaginary internal surfaces, as a reaction to external applied forces and body forces....
.

The word fracture is often applied to bone
Bone

Bones are rigid organ that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red blood cell and white blood cells and store minerals....
s of living creatures, or to crystal
Crystal

A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions....
s or crystalline materials, such as gemstone
Gemstone

A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which — when cut and polished — is used to make jewellery or other adornments....
s or metal
Metal

In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions , and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....
. 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
Strength of materials

In materials science, the strength of a material refers to the material's ability to withstand an applied stress without failure. Yield strength refers to the point on the engineering stress-strain curve beyond which the material begins deformation that cannot be reversed upon removal of the loading....
 (most substances) or inhibits transmission
Transmission (telecommunications)

In telecommunications, transmission is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired or wireless....
 of light
Light

Light, or visible light, is electromagnetic radiation of a wavelength that is Visible spectrum to the human eye , or up to 380?750 nm. In the broader field of physics, light is sometimes used to refer to electromagnetic radiation of all wavelengths, whether visible or not....
 (optical crystals).

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

Fracture mechanics is the field of mechanics concerned with the study of the formation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material's resistance to fracture....
.

Types of fracture
Brittle fracture
In brittle
Brittle

A material is brittle if it is liable to fracture when subjected to stress . That is, it has little tendency to deform before fracture. This fracture absorbs relatively little energy, even in materials of high Strength of materials, and usually makes a snapping sound....
 fracture, no apparent plastic deformation
Plasticity (physics)

In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces....
 takes place before fracture.






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

In continuum mechanics, stress is a measure of the average amount of force exerted per unit area. It is a measure of the intensity of the total internal forces acting within a body across imaginary internal surfaces, as a reaction to external applied forces and body forces....
.

The word fracture is often applied to bone
Bone

Bones are rigid organ that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red blood cell and white blood cells and store minerals....
s of living creatures, or to crystal
Crystal

A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions....
s or crystalline materials, such as gemstone
Gemstone

A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which — when cut and polished — is used to make jewellery or other adornments....
s or metal
Metal

In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions , and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....
. 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
Strength of materials

In materials science, the strength of a material refers to the material's ability to withstand an applied stress without failure. Yield strength refers to the point on the engineering stress-strain curve beyond which the material begins deformation that cannot be reversed upon removal of the loading....
 (most substances) or inhibits transmission
Transmission (telecommunications)

In telecommunications, transmission is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired or wireless....
 of light
Light

Light, or visible light, is electromagnetic radiation of a wavelength that is Visible spectrum to the human eye , or up to 380?750 nm. In the broader field of physics, light is sometimes used to refer to electromagnetic radiation of all wavelengths, whether visible or not....
 (optical crystals).

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

Fracture mechanics is the field of mechanics concerned with the study of the formation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material's resistance to fracture....
.

Types of fracture


Brittle fracture


In brittle
Brittle

A material is brittle if it is liable to fracture when subjected to stress . That is, it has little tendency to deform before fracture. This fracture absorbs relatively little energy, even in materials of high Strength of materials, and usually makes a snapping sound....
 fracture, no apparent plastic deformation
Plasticity (physics)

In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces....
 takes place before fracture. In brittle crystalline materials, fracture can occur by cleavage
Cleavage (crystal)

Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite Crystallography structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the microscope and to the naked eye....
 as the result of tensile stress acting normal to crystallographic planes with low bonding (cleavage planes). In amorphous solid
Amorphous solid

An amorphous solid is a solid in which there is no long-range order of the positions of the atoms. . Most classes of solid materials can be found or prepared in an amorphous form....
s, by contrast, the lack of a crystalline structure results in a conchoidal fracture
Conchoidal fracture

Conchoidal fracture describes the way that brittle materials break when they do not follow any natural cleavage . Materials that break in this way include flint and other fine-crystalliteed minerals, as well as most amorphous solids, such as obsidian and other types of glass....
, with cracks proceeding normal to the applied tension.

The theoretical strength of a crystalline material is (roughly) where: - is the Young's modulus
Young's modulus

In solid mechanics, Young's modulus is a measure of the stiffness of an isotropic elastic material. It is also known as the Young modulus, modulus of elasticity, elastic modulus or tensile modulus....
 of the material, is the surface energy
Surface energy

Surface energy quantifies the disruption of intermolecular bonds that occurs when a surface is created. In the physics of solids, surfaces must be intrinsically less energetically favourable than the bulk of a material; otherwise there would be a driving force for surfaces to be created, and surface is all there would be ....
, and is the equilibrium distance between atomic centers.

On the other hand, a crack introduces a stress concentration modeled by (For sharp cracks) where: - is the loading stress, is half the length of the crack, and is the radius of curvature at the crack tip.

Putting these two equations together, we get

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

Recently, scientists have discovered supersonic fracture
Supersonic fracture

Supersonic fractures are fractures where the fracture velocity moves faster than the speed of sound in the material. This phenomenon was first discovered by scientists from the Max Planck Institute for Metals Research in Stuttgart and IBM Almaden Research Center in San Jose, California ....
, the phenomenon of crack motion faster than the speed of sound in a material. This phenomenon was recently also verified by experiment of fracture in rubber
Rubber

Natural rubber is an elastomer?an Elasticity_ hydrocarbon polymer?that was originally derived from a milky colloidal suspension, or latex , found in the sap of some plants....
-like materials.

Ductile fracture

In ductile fracture, extensive plastic deformation takes place before fracture. Many ductile metals, especially materials with high purity, can sustain very large deformation of 50–100% or more strain
Strain (materials science)

In continuum mechanics, the infinitesimal strain theory, sometimes called small deformation theory, small displacement theory, or small displacement-gradient theory, deals with infinitesimal Deformation s of a Continuum mechanics....
 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
Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
 can undergo deformation up to 100% strain before breaking, while cast iron
Cast iron

Cast iron usually refers to Gray iron, but also identifies a large group of ferrous alloys, which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy....
 or high-carbon steels
Plain-carbon steel

Carbon steel, also called plain carbon steel, is steel where the main alloying constituent is carbon. The AISI defines carbon steel as: "Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium [niobium], molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any...
 can barely sustain 3% of strain..

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 sample of smallest cross-sectional area), 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

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
    Shear stress

    File:Shear stress.JPGA shear stress, denoted , is defined as a stress which is applied parallel or tangent to a face of a material, as opposed to a normal stress which is applied perpendicularly....
     acting parallel to the plane of the crack and perpendicular to the crack front)
  • Mode III crack – Tearing mode (a shear stress
    Shear stress

    File:Shear stress.JPGA shear stress, denoted , is defined as a stress which is applied parallel or tangent to a face of a material, as opposed to a normal stress which is applied perpendicularly....
     acting parallel to the plane of the crack and parallel to the crack front)


For more information, see fracture mechanics
Fracture mechanics

Fracture mechanics is the field of mechanics concerned with the study of the formation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material's resistance to fracture....
.

See also

  • Bone fracture
    Bone fracture

    A bone fracture is a medical condition in which a bone is cracked or broken. It is a break in the continuity of the bone. While many fractures are the result of high force impact force or Stress fracture, bone fracture can also occur as a result of certain medical conditions that weaken the bones, such as osteoporosis, certain types of cance...
  • Brittle-ductile transition zone
    Brittle-ductile transition zone

    The brittle-ductile transition zone is the strongest part of the Crust . For quartz and feldspar rich rocks in continental crust this occurs at an approximate depth of 13-18 km ....
  • Environmental stress fracture
    Environmental stress fracture

    In materials science, environmental stress fracture or environment assisted fracture is the generic name given to premature structural failure under the influence of tensile stresses and harmful environments of materials such as metals and alloys, composite material, plastics and ceramics....
  • Fracture mechanics
    Fracture mechanics

    Fracture mechanics is the field of mechanics concerned with the study of the formation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material's resistance to fracture....
  • Fracture (mineralogy)
    Fracture (mineralogy)

    In the field of mineralogy, fracture is a term used to describe the shape and texture of the surface formed when a mineral is broken. Minerals often have a highly distinctive fracture, making it a principal feature used in their identification....
  • Fracture (geology)
  • Fracture toughness
    Fracture toughness

    In materials science, fracture toughness is a property which describes the ability of a material containing a crack to resist fracture, and is one of the most important properties of any material for virtually all design applications....
  • Fractography
    Fractography

    Fractography is the study of fracture surfaces of materials. Fractographic methods are routinely used to determine the cause of failure in engineering structures, especially in product failure and the practice of forensic engineering or failure analysis....
  • Forensic engineering
    Forensic engineering

    Forensics engineering is the investigation of material science, product , structures or components that fail or do not operate/function as intended, causing personal injury or damage to property....
  • Forensic materials engineering
    Forensic materials engineering

    A branch of Forensic engineering, the subject focuses on the material evidence from crime or accident scenes, seeking defects in those materials which might explain why an accident occurred, or the source of a specific material to identify a criminal....
  • Rupture (engineering)
    Rupture (engineering)

    Rupture, or ductile rupture describes the ultimate failure of toughness ductility materials loaded in tension. Rupture describes a failure mode in which, rather than cracking, the material "pulls apart", generally leaving a rough surface....
  • Structural failure
    Structural failure

    Structural failure refers to loss of the Structural load-carrying capacity of a component or member within a Architectural structure or of the structure itself....


Bibliography

  • Dieter, G. E. (1988) Mechanical Metallurgy ISBN 0-07-100406-8
  • A. Garcimartin, A. Guarino
    Alessio Guarino

    Alessio Guarino is an Italian physicist, born in Florence, Italy in 1970....
    , 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

Web postings at http://www.jwave.vt.edu/crcd/farkas/lectures/Fract1/tsld006.htm Virtual museum of failed products at http://materials.open.ac.uk/mem/index.html