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Created page with "{{Language_sel|LANG=ger|ARTIKEL=Bruchfläche}} {{PSM_Infobox}} Fracture surface __FORCETOC__ ==Fracture Surface== A fracture surface, i.e. a free surface area, is created by the destruction of atomic or molecular bonds and is associated with the loss of load-bearing capacity of a structural component. In plastics, this material separation occur..."

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{{Language_sel|LANG=ger|ARTIKEL=Bruchfläche}}
{{PSM_Infobox}}
Fracture surface
__FORCETOC__

==Fracture Surface==

A fracture surface, i.e. a free [[Surface|surface]] area, is created by the destruction of atomic or molecular bonds and is associated with the loss of load-bearing capacity of a [[Plastic Component|structural component]]. In [[Plastics|plastics]], this [[Material & Werkstoff|material]] separation occurs through the [[Fracture|fracture]] of molecular chains, the pulling out of molecular chains and the tearing open of [[Phase Boundary Surface|phase boundaries]].

Local [[Deformation#Plastic deformation|plastic deformations]], such as [[Crazing|crazes]] or [[Shear Band Formation|shear bands]], become microscopically visible on the fracture surface, providing information about the causes of failure on the material side (see: [[Failure Analysis ‒ Basics|failure analysis ‒ basics]]). Such micromechanical [[Deformation Mechanisms|deformation mechanisms]] are described in detail in the literature [1‒5].

==Determination of the effective crack length==

In fracture mechanics [[Polymer Testing|polymer testing]] [6], the focus is on determining [[Material Value|material values]], which requires measuring the [[Effective Crack Length|effective crack length]] on the fracture surface. The effective or fracture-mechanically effective crack length is composed of the [[Initial Crack Length|length of the initial crack]] (mechanical [[Notch|notch]]; true crack length) and the length of stable crack growth ([[Fracture Mirror|fracture mirror]]; radius of the [[Plastic Zone|plastic zone]]).

Two examples of selected fracture surfaces are shown in '''Figs. 1''' and '''2'''.

[[File:Fracture_Surface_Fig-1.jpg|600px]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px" |Fracture surface of a heterophasic copolymer of propylene with ethylene (HeCo)
|}

[[File:Fracture_Surface_Fig-2.jpg]]
{|
|- valign="top"
|width="50px"|'''Fig. 2''':
|width="600px" | Scanning electron microscope (SEM) images of the fracture surface morphology of a heterophasic PP/EPR/PE blend with 90 wt.-% RAHECO® [7] from an R-curve test (see: [[Crack Resistance Curve – Experimental Methods|crack resistance curve – experimental methods]])
|}

The [[Scanning Electron Microscopy|scanning electron microscope]] (SEM) examinations of the fracture surfaces are described in detail under the explanation of the term ‘[[Stretch Zone|stretch zone]]’. At the end of the crack propagation area ([[Crack Propagation|stable crack growth]]; [[Fracture Mirror|fracture mirror]]; see: [[Effective Crack Length|effective crack length]]), the formation of a stretch zone is observed using a scanning electron microscope.

==Determination of the stretch zone height SZH and stretch zone width SZW==

The measured stretch zone height SZH in the example of the PP/EPR/PE blend (see: [[Stretch Zone|stretch zone]]) varied slightly around the value SZH = 30 μm, but showed no systematic dependence on the RAHECO content, which can be explained by the low influence of [[Microscopic Structure|morphology]] on [[Crack Initiation|crack initiation]].

Assuming proportionality between the stretch zone height SZH and the stretch zone width SZW, and taking into account the general relationship between the stretch zone height and crack opening displacement (see: [[Extended CTOD Concept|extended CTOD concept]])

<center>''δ'' = 2 SZH</center>

it can be assumed that, with constant SZH, the [[Crack Toughness|crack toughness]] at the actual physical [[Crack Initiation|crack initiation]] ''δ''i is not significantly influenced by the morphological changes (see: [[Micromechanics & Nanomechanics|micromechanics & nanomechanics]]) in the [[Material & Werkstoff|material]] [8].

==See also==

* [[Effective Crack Length|Effective crack length]]
* [[Initial Crack Length|Initial crack length]]
* [[Notching]]
* [[Fracture Mirror|Fracture mirror]]
* [[Plastic Zone|Plastic zone]]
* [[Fracture Process Zone|Fracture process zone]]

==References==

{|
|-valign="top"
|[1]
|[[Michler,_Goerg_Hannes|Michler, G. H.]]: Kunststoff-Mikromechanik. Morphologie, Deformations- und Bruchmechanismen. Carl Hanser, Munich Vienna (1992) (ISBN 3-446-17068-5; see [[AMK-Library]] under F 4)
|-valign="top"
|[2]
|Michler, G. H.: Electron Microscopy of Polymers. Springer Verlag, Berlin (2008) (ISBN 978-3-54036350-7; see [[AMK-Library]] under F 1)
|-valign="top"
|[3]
|Michler, G. H., Balta-Calleja, F. J.: Nano- and Micromechanics of Polymers: Structure Modification and Improvement of Properties. Carl Hanser, Munich (2012) (ISBN 978-3446427679; see [[AMK-Library]] under F 13)
|-valign="top"
|[4]
|Woodward, A. E.: Understanding Polymer Morphology. Carl Hanser, Munich (1994) (ISBN 3-446-17431-1; https://doi.org/10.1002/pi.1995.210370411)
|-valign="top"
|[5]
|Michler, G. H.: Atlas of Polymer Structures. Morphology, Deformation and Fracture Structures. Carl Hanser, Munich (2016) (ISBN 978-1-56990-557-9; E-Book ISBN 978-1-56990-558-6; see AMK-Library under F 14)
|-valign="top"
|[6]
|[[Grellmann,_Wolfgang|Grellmann, W.]], [[Seidler,_Sabine|Seidler, S.]] (Eds.): Polymer Testing. Carl Hanser, Munich (2022) 3rd Edition, pp. 235–236, (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see [[AMK-Library]] under A 23)
|-valign="top"
|[7]
|Cäsar, T., Seidler, S.,[https://www.researchgate.net/profile/Wolfgang-Grellmann Grellmann, W.]: Bruchmechanische Zähigkeitsbewertung des Rißinitiierungs- und Rißausbreitungsverhaltens von Ethylen-Propylen-Random-Copolymerisaten. In: Grellmann, W., Seidler, S. (Eds.): Deformation und Bruchverhalten von Kunststoffen. Springer, Berlin, Heidelberg (1998) pp. 271–284, (ISBN 3-540-63671-4; e-Book (2014): ISBN 978-3-642-58766-5; see [[AMK-Library]] under A 6)
|-valign="top"
|[8]
|Seidler, S.: Anwendung des Risswiderstandskonzeptes zur Ermittlung strukturbezogener bruchmechanischer Werkstoffkenngrößen bei dynamischer Beanspruchung. Habilitation (1997), Martin-Luther-Universität Halle-Wittenberg, VDI-Reihe 18: Mechanik/Bruchmechanik Nr. 231, VDI-Publishing (1998), Düsseldorf (ISBN 978-3-1832-3118-8; see [[AMK-Library]] under B 2-1)
|}

[[Category:Fracture Mechanics]]
[[Category:Damage Analysis_Component Failure]]
[[Category:Surface Testing Technology]]

Fracture Surface - Revision history