[Caractérisation et modélisation 3D des fissures courtes de fatigue de coin dans des alliages dʼaluminium à haute résistance]
La croissance des fissures courtes de fatigue est fortement influencée par un grand nombre de facteurs tels que la microstructure environnante, lʼétat de contrainte local, la forme des fissures. La tomographie haute résolution permet dʼimager la propagation des fissures dans des éprouvettes de fatigue au cours dʼessais in situ avec une résolution spatiale sub micronique et permet ainsi de visualiser les processus de propagation le long de la totalité du front de fissure (en surface et en volume). Dans ce travail, la croissance des fissures de fatigue a été caractérisée dans un alliage dʼaluminium à haute résistance élaboré par coulée continue ainsi que dans un alliage à grain fins élaboré par métallurgie des poudres. Ce dernier matériau constitue un matériau modèle qui présente des formes de fissures considérablement plus simples que dans lʼalliage à gros grains ce qui permet de séparer les effets purement mécaniques (variation de lʼétat de contrainte le long du front et fermeture induite par la plasticité) des effets purement microstructuraux (tels que les déflexions locales et la fermeture par rugosité). Pour les deux alliages, la croissance des fissures a été étudiée lors dʼessais cycliques à amplitude de contrainte constante, ponctués par des essais de surcharge (sur un cycle unique). Nous présentons ici un résumé des principaux résultats obtenus du point de vue expérimental. Une modélisation de la propagation 3D des fissures est également décrite ainsi que certains des résultats que cette approche simplifiée a permis dʼobtenir.
The growth of fatigue cracks at small length scales is known to be influenced by a variety of factors, including local microstructure, varying stress states and crack shape. High resolution computed tomography allows for sub-micron resolution imaging of failure processes in small test coupons undergoing in situ cyclic loading, providing detailed three-dimensional (3D) assessment of propagation processes across the entire crack front (surface and depth). In this work fatigue crack growth has been examined in an advanced Direct Chill (DC) cast aluminium alloy, along with a fine grained powder-metallurgy alloy. The latter is identified as a model material, offering considerably simpler microscopic crack paths than the DC cast alloy, and hence a means of separating bulk mechanical effects (such as stress state variations across a crack front and plasticity induced closure) from microstructural effects (such as crystallographic deflection and roughness induced crack closure). Crack growth has been studied in both materials under both constant amplitude (CA) and single peak overload (OL) conditions. Experimental results are presented in the present paper, particularly in relation to micromechanical understanding of failure. A modelling approach based on those results, and some typical results, is also presented.
Mot clés : Fatigue, Tomographie, Rayonnement synchrotron, Fermeture des fissures, Alliages dʼaluminium
@article{CRPHYS_2012__13_3_316_0,
author = {Henry Proudhon and A. Moffat and Ian Sinclair and Jean-Yves Buffiere},
title = {Three-dimensional characterisation and modelling of small fatigue corner cracks in high strength {Al-alloys}},
journal = {Comptes Rendus. Physique},
pages = {316--327},
publisher = {Elsevier},
volume = {13},
number = {3},
year = {2012},
doi = {10.1016/j.crhy.2011.12.005},
language = {en},
}
TY - JOUR AU - Henry Proudhon AU - A. Moffat AU - Ian Sinclair AU - Jean-Yves Buffiere TI - Three-dimensional characterisation and modelling of small fatigue corner cracks in high strength Al-alloys JO - Comptes Rendus. Physique PY - 2012 SP - 316 EP - 327 VL - 13 IS - 3 PB - Elsevier DO - 10.1016/j.crhy.2011.12.005 LA - en ID - CRPHYS_2012__13_3_316_0 ER -
%0 Journal Article %A Henry Proudhon %A A. Moffat %A Ian Sinclair %A Jean-Yves Buffiere %T Three-dimensional characterisation and modelling of small fatigue corner cracks in high strength Al-alloys %J Comptes Rendus. Physique %D 2012 %P 316-327 %V 13 %N 3 %I Elsevier %R 10.1016/j.crhy.2011.12.005 %G en %F CRPHYS_2012__13_3_316_0
Henry Proudhon; A. Moffat; Ian Sinclair; Jean-Yves Buffiere. Three-dimensional characterisation and modelling of small fatigue corner cracks in high strength Al-alloys. Comptes Rendus. Physique, Volume 13 (2012) no. 3, pp. 316-327. doi : 10.1016/j.crhy.2011.12.005. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2011.12.005/
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