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Created page with "{{Language_sel|LANG=ger|ARTIKEL=Effektive Risslänge}} {{PSM_Infobox}} Effective crack length __FORCETOC__ ==The environment of the crack tip== In the case of macroscopically brittle fracture behaviour, plastic deformation often occurs due to stress concentration in front of the crack tip, i.e. the formation of a Plastic Zone|plastic zon..."

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{{Language_sel|LANG=ger|ARTIKEL=Effektive Risslänge}}
{{PSM_Infobox}}
Effective crack length
__FORCETOC__

==The environment of the crack tip==

In the case of macroscopically brittle [[Fracture Behaviour|fracture behaviour]], [[Deformation#Plastic deformation|plastic deformation]] often occurs due to stress concentration in front of the [[Crack Opening|crack tip]], i.e. the formation of a [[Plastic Zone|plastic zone]]. Assuming that the energy dissipated during crack growth in the region around the crack tip is proportional to the [[Surface|surface]] area (see also: [[Fracture Surface|fracture surface]]). The radius of the plastic zone is regarded as a fictitious extension of the crack. The consideration of this [[Plastic Zone|plastic zone]], which is small in comparison to the component dimensions and the ligament (cross-section before the crack), lead Irwin in 1952 to a significant extension of the [[Crack Model according to GRIFFITH|GRIFFITH crack model]] and is now referred to as the [[Crack Model according to IRWIN and Mc CLINTOCK|crack model according to IRWIN and Mc CLINTOCK]].

==LEFM with small-scale yielding==

By taking the [[Plastic Zone|plastic zone]] into account when describing [[Toughness|toughness]], the transition from linear-elastic [[Fracture Mechanics|fracture mechanics]] (LEFM) to LEFM with small-scale yielding is formally completed. If the above conditions are fulfilled, the true crack length ''a'' (or [[Initial Crack Length|initial crack length]]) and the radius of the plastic zone ''r''pl are combined to form an effective crack length ''a''eff.

{|
|-
|width="20px"|
|width="500px" | <math> a_{eff} = a + r_{pl}</math>
|(1)
|}

The [[Plastic Zone|plastic zone]] is often visible on the [[Fracture Surface|fracture surface]] in the form of a [[Fracture Mirror|fracture mirror]] as an expression of [[Crack Propagation|stable crack growth]] and can be detected using light or [[Scanning Electron Microscopy|scanning electron microscopy]] (SEM). An example is shown in the '''Figure'''.

[[file:Effective Crack Length Fig.jpg|500px]]
{|
|- valign="top"
|width="50px"|'''Figure''':
|width="600px"|Fracture survace of an ethylene/propylene random copolymer with 4 mol% ethylene (a) and schematic representation of the characteristic areas (b)
|}

==See also==

* [[Initial Crack Length|Initial crack length]]
* [[Plastic Zone|Plastic zone]]
* [[Notch]]
* [[Notching]]
* [[Fracture Surface|Fracture surface]]

'''References'''

* [[Blumenauer, Horst|Blumenauer, H.]], Pusch, G.: Technische Bruchmechanik, Deutscher Verlag für Grundstoffindustrie, Leipzig Stuttgart (1993), (ISBN 3-342-00659-5; see [[AMK-Büchersammlung|AMK-Library]] under E 29-3)
* [[Grellmann, Wolfgang|Grellmann, W.]], [[Seidler, Sabine|Seidler, S.]] (Eds.): Kunststoffprüfung. Carl Hanser Verlag, Munich (2024) 4th Edition, p. 244 (ISBN 978-3-446-44718-9; E-Book: ISBN 978-3-446-48105-3; see [[AMK-Büchersammlung|AMK-Library]] under A 23)

[[category:Fracture Mechanics]]
[[category:Instrumented Impact Test]]

Effective Crack Length - Revision history