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Created page with "{{Language_sel|LANG=ger|ARTIKEL=Brucharten}} {{PSM_Infobox}} Fracture types __FORCETOC__ ==Types of fracture== In fracture mechanics, macroscopic examination of fracture surfaces initially distinguishes between normal stress fracture (separating fracture) and shear fracture. Depending on the type of mechanical stress, uniaxial stress is referred to as fast (bri..."

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{{Language_sel|LANG=ger|ARTIKEL=Brucharten}}
{{PSM_Infobox}}
Fracture types
__FORCETOC__

==Types of fracture==

In [[Fracture Mechanics|fracture mechanics]], macroscopic examination of [[Fracture Surface|fracture surfaces]] initially distinguishes between normal stress fracture (separating fracture) and shear fracture. Depending on the type of mechanical [[Stress|stress]], uniaxial stress is referred to as fast (brittle) fracture and alternating stress as [[Vibration Fracture|vibration fracture]] (see also: [[Fatigue|fatigue]]).

==Macroscopic fracture features==

Macroscopic features can be either the extent of the [[Deformation#Plastic deformation|plastic deformation]] preceding the [[Fracture|fracture]] or the fracture shape (Fig. 1), which depends on the stress state (see [[Uniaxial Stress State|uniaxial]] and [[multiaxial Stress State|multiaxial]] stress state) and the component thickness [1].

[[file:Fracture Types 1.jpg|600px]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px"|Macroscopic fracture features on plate-shaped components (according to [1]) 
a) Shear fracture (shear-plane fracture) 
b) Separation fracture with shear lips 
c) Normal stress fracture (separation fracture; normal-surface fracture)
|}

Shear fracture ('''Fig. 1a''') is a consequence of the plane stress state as it occurs approximately in components of constant thickness that is significantly smaller than the other dimensions due to loading in the component plane. Failure is initiated by exceeding critical shear stresses (see example: [[Component Failure|component failure]]).

In contrast, a plane strain state can develop in thicker [[Plastic Component|components]], leading to separation failure. The separation occurs perpendicular (normal) to the tensile stress. '''Figure 1b''' corresponds to a mixed stress state (plane stress state at the edge, plane strain state or triaxial stress state inside the component; see: [[Plane Stress and Strain State|plane stress and strain state]]). With increasing component thickness, the tendency toward normal stress fracture (normal-surface separation fracture) increases ('''Fig. 1c'''), so that the width of the shear lips occurring at the edge is a measure of the plasticity reserve. The shear lips arise as [[Deformation#Plastic deformation|plastic deformation]] in the area of the plane stress state as a result of the free deformability at the [[Surface|surface]] of the [[Plastic Component|component]]. The size depends on the [[Material & Werkstoff|material]] but also on the environmental conditions, such as stress temperature and [[Deformation Rate|deformation rate]]. Under constant stress and environmental conditions, the area on the [[Fracture Surface|fracture surface]] in which the plane strain state leads to a low-deformation separation fracture increases with increasing wall thickness. The area in which shear lips form as a result of the plane stress state remains constant.

==Microscopic fracture features==

The microscopic fracture characteristics are determined by the fracture mechanism, i.e., the processes involved in [[Crack Propagation|crack propagation]]. In addition to the two basic mechanisms of splitting and shearing, trans- or intercrystalline [[Crack Propagation|crack propagation]] can also be regarded as a fracture feature in crystalline materials. Figure 2 shows the basic types of microscopic fracture features of [[Plastics|plastics]] [1].

[[file:Brucharten 2.jpg|600px]]
{|
|- valign="top"
|width="50px"|'''Fig. 2''':
|width="600px" |Selected microscopic fracture features for [[Plastics|plastics]] 
{|
|- valign="top"
|width="20px"|a)
|width="580px"|Low-deformation brittle fracture with [[Crazing|craze]] formation
|-
|b)
|Low-deformation brittle fracture with [[Ramps, Clods and Steps|ramps or clods]]
|-
|c)
|Deformation fracture with a courtyard around the inclusion
|-
|d)
|Deformation fracture (large [[Deformation#Plastic deformation|plastic deformation]] with [[Threads, Tips and Films|tip formation]])
|-
|e)
|[[Fracture|Fracture]] with [[Waves and Arrest Lines|waves or arrest lines]] as a result of different crack propagation speeds
|-
|f)
|Fracture of a [[Fibre-reinforced Plastics|fibre-reinforced plastic]] with good [[Fibre–Matrix Adhesion|fibre–matrix adhesion]]
|}
|}

==Deformation phenomena==

[[Crazing|Crazing]] is a micromechanical [[Deformation Mechanisms|deformation mechanism]] that is very commonly observed in plastics.

[[Micromechanics & Nanomechanics|Crazes]] are normal stress cracks that contain plastically stretched material parallel to the direction of stress (see [[Tensile Test|tensile test]]) under tensile stress. The areas under tensile stress are relieved by stretched fibrils. Ehrenstein [2] describes these deformation phenomena as "stabilized" fast (brittle) cracks, whose separation surfaces are bridged by stretched fibrils and fibres with a fibril diameter of 0.01 to 0.1 µm.
[[Craze-Types|Crazes]] can occur both on free [[Surface|surfaces]] (see also: [[Fracture Surface|fracture surface]]) and inside the test [[Specimen|specimen]] and are therefore semi-circular or circular in shape. In transparent [[Plastics|plastics]], the extent of the circle can be seen with the naked eye (white fracture) [2].

==See also==

* [[Fracture Formation|Fracture formation]]
* [[Fracture]]
* [[Fracture Surface|Fracture surface]]
* [[Fracture Modes|Fracture modes]]
* [[Fracture Process Zone|Fracture process zone]]
* [[Fracture Mirror|Fracture mirror]]

'''References'''

{|
|-valign="top"
|[1]
|[[Blumenauer, Horst|Blumenauer, H.]], Pusch, G.: Technische Bruchmechanik (Technical fracture mechanics). Deutscher Verlag für Grundstoffindustrie, Leipzig Stuttgart (1982); (see [[AMK-Büchersammlung|AMK-Library]] under E 29-1)
|-valign="top"
|[2]
|[[Ehrenstein,_Gottfried_W.|Ehrenstein, G. W.]], Engel, K., Klingele, H., Schaper, H.: Scanning Electron Microscopy of Plastics Failure / REM von Kunststoffschäden. Carl Hanser, Munich (2011), (ISBN 978-3-446-42242-1; see [[AMK-Büchersammlung|AMK-Library]] under D 5)
|}

[[category:Fracture Mechanics]]

Fracture Types - Revision history