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<span style="font-size:1.2em;font-weight:bold;">Griffith, Alan Arnold – Pioneer of fracture mechanics</span>
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==Biography==

The British engineer Alan Arnold Griffith (1893–1963) studied mechanical engineering and also earned his doctorate at the University of Liverpool. He is considered the founder of [[Fracture Mechanics#Linear-elastic fracture mechanics|linear-elastic fracture mechanics (LEFM)]], and his name is closely associated with the [[Crack Model according to GRIFFITH|GRIFFITH crack model]]. The development of LEFM began around 1920 with his famous work in the Philosophical Transactions of the Royal Society: “The Phenomena of Rupture and Flow in Solids”. Griffith worked for the Royal Aircraft Factory (RAF) in Farnborough and, after World War I, had the necessary leisure to reflect on such fundamental problems of mechanics and [[Materials Science|materials technology]].

[[File:griffith.jpg]][[File:titleseite_grffith.jpg]]
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|width="600px" |Fracture mechanics pioneer A. A. Griffith and the title page of his famous work
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However, for several decades he was pretty much the only person working in this field until the Second World War prompted renewed interest and reflection on [[Fracture Mechanics|fracture mechanics]].  Griffith initially addressed the existing problem of the lack of explanation for the difference between theoretical and practical [[Strength|strength]] in the [[Material & Werkstoff|material]] glass. He explained the often considerable differences in strength by energetic interactions between submicroscopic order regions. The ideas developed by Griffith on this subject led to a theory of microdefects, which is now well established both theoretically and experimentally (see: [[GRIFFITH's Theory|GRIFFITH's theory]]).

Griffith assumed that [[Crack|cracks]] in the order of 5–75 µm (also inside the glass) were present in the glass. In the [[Surface|surface]] area, these “Griffith cracks” have the shape of a semi-ellipsoid and have a greater influence on the [[Strength|strength]] of the glass than those inside (after all, glass always breaks from the surface, never from the inside). The existence of such notches (see: [[Notch|notch]]) was subsequently proven using various methods (electron-optically by surface silvering, by selective etching, etc.). Griffith found that glass fibres of different thicknesses differ significantly in terms of their strength behaviour, so that, for example, when the thickness of a glass fibre is reduced from 1 mm to 0.003 mm in diameter, the strength increases from 170 to 3400 MPa. However, these high values of [[Flexural Strength|flexural strength]] decrease rapidly when the fibres lose their juvenile character through simple contact with the hand.

Griffith was also the first to discuss the energy balance in the case of [[Crack Propagation|crack propagation]]. The application of LEFM was quickly expanded when catastrophic failures occurred in other [[Material & Werkstoff|materials]] such as steel (e.g., in ships) or aluminum (e.g., window panels in jet aircraft). 

The application of LEFM in material development and [[Fracture Behaviour of Plastics Components|component monitoring of plastics]] and [[Composite Materials Testing|composites]] began a few years after Griffith's death.

==See also==

* [[GRIFFITH's Theory|GRIFFITH’s Theory for strength and fracture failure of solid bodies]]
* [[GRIFFITH's Criteria|GRIFFITH's criteria]]
* [[Crack Model according to GRIFFITH|Crack model according to GRIFFITH]]
* [[Crack]]
* [[Levels of Knowledge in Fracture Mechanics|Levels of knowledge in fracture mechanics]]

==References==

* Griffith, A. A.: The Phenomena of Rupture and Flow in Solids. Phil. Trans. Roy. Soc. London Vol. 7, A 221 (1920) 163 DOI: https://doi.org/10.1098/rsta.1921.0006
* Kühne, K.: Werkstoff Glas. Wissenschaftliche Taschenbücher Chemie. Akademie-Verlag, Berlin (1976) (see [[AMK-Library]] under Q 2)
* Spauszus, S.: Werkstoffkunde Glas. Verlag für Grundstoffindustrie Leipzig (1974) (see [[AMK-Library]] under Q 1)

==Weblinks==

&blacksquare; Wikipedia – The free Encyclopedia: [https://en.wikipedia.org/wiki/Alan_Arnold_Griffith Griffith, Alan Arnold]

' 100 Jahre Bruchmechanik: Alan Arnold Griffith. DVM-Nachrichten N 71 • Frühjahr 2020 p. 9 [https://dvm-berlin.de/sites/default/files/files/publications/field-teaser-pdfdownloads/1224620288.pdf Download as PDF]

[[Category:Material Scientists Polymer Scientists]]