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Created page with "{{Language_sel|LANG=ger|ARTIKEL=Risszähigkeit}} {{PSM_Infobox}} Crack toughness __FORCETOC__ ==Explanation of terms== In fracture mechanics, crack toughness or fracture toughness describes the resistance of a component or material to crack propagation of any kind. Cracks are undesirable material discontinuities that..."

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{{Language_sel|LANG=ger|ARTIKEL=Risszähigkeit}}
{{PSM_Infobox}}
Crack toughness
__FORCETOC__

==Explanation of terms==

In [[Fracture Mechanics|fracture mechanics]], [[Crack Toughness|crack toughness]] or fracture toughness describes the resistance of a [[Plastic Component|component]] or [[Material & Werkstoff|material]] to crack propagation of any kind. [[Crack|Cracks]] are undesirable material discontinuities that arise as a result of manufacturing and/or post-treatment and processing, but often also due to external (forces and moments) or internal ([[Tensile Test Residual Stresses Orientations|residual stresses and orientations]]) [[Stress|stresses]] [1, 2].

In the case of unstable [[Crack Propagation|crack propagation]], the [[Material Parameter|characteristic parameter]] of fracture toughness is the critical stress intensity factor ''K''Ic. Crack toughness is calculated from the load stress or force acting perpendicular to the crack flanks (see: [[Crack Opening Modes|crack opening modes]]). [[Fracture]] is the most dangerous cause of failure on the material side, as it occurs without warning, i.e. without prior plastic [[Deformation|deformation]], in the case of unstable crack propagation. Once a critical stress is reached, [[Fracture Types|brittle fracture]] is triggered. In [[Plastics|plastics]], fracture is accompanied by the tearing of molecular chains, the pulling out of molecular chains (see also: [[Fibre-reinforced Plastics Fracture Model|fibre-reinforced plastics fracture model]] and [[Fracture Behaviour|fracture behaviour]]) and the tearing of [[Phase Boundary Surface|phase boundaries]] [3].

==Practical Application examples==

A number of measures are used in the design and dimensioning of [[Plastic Component|plastic components]] to increase their crack toughness and improve their [[Fracture Behaviour of Plastics Components|fracture behaviour]] [4].

* Radial ribbing on bucket bottoms,
* Ribs and stringers on structural elements in aircraft construction
* Radial and tangential ribs in [[Bend Test – Specimen Preparation#Bending test specimen made of plastic components|washing machine lye tubs]] ('''Fig. 1'''),
* Special ribs with a defined degree of freedom of deformation ('''Fig. 2a'''),
* Avoiding wall thickness variations in injection-moulded ropes ('''Fig. 2b'''),
* Setting defined [[Tensile Test Residual Stresses Orientations|orientations]] in injection-moulded parts through the design of the gate and flow path obstacles,
* Avoiding geometric heterogeneities such as edges and corners or cavities ('''Fig. 2c''').

[[File:Risszaehigkeit-1.jpg|300px]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px"|Radial and tangential ribbing of a lye tub in washing machines
|}

[[File:Risszaehigkeit-2.jpg]]
{|
|- valign="top"
|width="50px"|'''Fig. 2''':
|width="600px"|(a) Ribs with and without degrees of freedom of deformation, 
(b) wall thickness variation, and 
(c) external and internal inhomogeneities in injection-moulded parts
|}

==See also==

* [[Toughness]]
* [[Thoughness Temperature Dependence|Toughness temperature dependence]]
* [[Brittle-Tough Transition|Brittle-tough transition]]
* [[Levels of Knowledge in Fracture Mechanics|Levels of knowledge in fracture mechanics]]
* [[Crack Tip Opening Displacement Concept (CTOD)|Crack tip opening displacement concept (CTOD)]]
* [[Crack Propagation Energy|Crack propagation energy]]

'''References'''

{|
|-valign="top"
|[1]
|[[Blumenauer, Horst|Blumenauer, H.]], Pusch, G.: Technische Bruchmechanik. Deutscher Verlag für Grundstoffindustrie, Leipzig (1993) 3rd Edition p. 15, (ISBN 3-342-00659-5; see [[AMK-Büchersammlung|AMK-Library]] under E 29-3)
|-valign="top"
|[2]
|Schwalbe, K.-H.: Bruchmechanik metallischer Werkstoffe. Carl Hanser, Munich Vienna (1980), (ISBN 3-446-12983-9; see [[AMK-Büchersammlung|AMK-Library]] under E 15)
|-valign="top"
|[3]
|[[Grellmann, Wolfgang|Grellmann, W.]]: Fracture Toughness Measurements in Engineering Plastics. In: [https://www.researchgate.net/profile/Wolfgang-Grellmann Grellmann, W.], [[Seidler, Sabine|Seidler, S.]] (Eds.): Polymer Testing. Carl Hanser, Munich (2025) 3rd Edition, pp. 229–281 (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see [[AMK-Büchersammlung|AMK-Library]] under A 22)
|-valign="top"
|[4]
|[[Bierögel, Christian|Bierögel, C.]], Langer, B., Müller, H., [https://de.wikipedia.org/wiki/Wolfgang_Grellmann Grellmann, W.]: Schadensfallanalyse an Kunststoffbauteilen. In: [https://de.wikipedia.org/wiki/Michael_Pohl_(Metallurg) Pohl, M.] (Ed.): Konstruktion, Qualitätssicherung und Schadensanalyse. Tagung Werkstoffprüfung 2004, Neu-Ulm, 25.–26. November 2004, Werkstoff-Verlag Informationsgesellschaft mbH Frankfurt (ISBN 3-88355-337-9; see [[AMK-Büchersammlung|AMK-Library]] under M 12), Proceedings pp. 231–236 Download as [https://www.polymerservice-merseburg.de/fileadmin/inhalte/psm/veroeffentlichungen/Schadensfallanalyse_an_Kunststoffbauteilen_WP2004.pdf pdf-file]
|}

[[Category:Fracture Mechanics]]

Crack Toughness - Revision history