Fracture
From Wikipedia, the free encyclopedia
- For fractures in bones, see Bone fracture.
- For fractures in geologic formations, see Rock fracture.
| Mechanical failure modes |
|---|
| Buckling |
| Corrosion |
| Creep |
| Fatigue |
| Fracture |
| Melting |
| Thermal shock |
| Wear |
A fracture is the separation of a body into two, or more, pieces under the action of stress.
The word fracture is often applied to bones of living creatures, 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 requires the study of fracture mechanics.
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[edit] Types of fracture
[edit] Brittle 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.
Recently, scientists have discovered supersonic fracture , the phenomenon of crack motion faster than any speed of sound in a material.[citation needed] This phenomenon was recently also verified by experiment of fracture in rubber-like materials.
[edit] Ductile fracture
In ductile fracture, extensive plastic deformation takes place before fracture. In metallic materials, the plastic deformation is a well understood mechanism that stems from the atomic structure in crystalline structures. However, such mechanism only provides explanation for the material deformation, but not for material separation that constitutes fracture. No satisfactory atomic level model has been agreed on to explain the occurrence of the material separation in a pure material without inclusion. 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 obviously 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].
[edit] See also
- Rupture
- Ductile
- Brittle
- Structural failure
- Fracture toughness
- Environmental stress fracture
- Brittle-ductile transition zone
- Fracture mechanics
[edit] Bibliography
- 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)de:Bruch
es:Fractura fr:Rupture (matériau) io:Rupto nl:Breuk (mechanica) pl:Przełam ro:Fractură zh:骨折
