Documents disponibles écrits par cet auteur

Orientation dependence of shock-induced twinning and substructures in a copper bicrystal / Fang Cao in Acta materialia, Vol. 58 N° 2 (Janvier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 2 (Janvier 2010) . - pp. 549-559 Titre : Orientation dependence of shock-induced twinning and substructures in a copper bicrystal Type de document : texte imprimé Auteurs : Fang Cao, Auteur ; Irene J. Beyerlein, Auteur ; Francis L. Addessio, Auteur Article en page(s) : pp. 549-559 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Copper  Shock  recovery  Deformation  structure  Twinning  Dislocation  structure Index. décimale : 669 Métallurgie Résumé : Shock recovery experiments have been conducted to assess the role of shock stress and orientation dependence on substructure evolution and deformation twinning of a [1 0 0]/View the MathML source copper bicrystal. Transmission electron microscopy of the post-shock specimens revealed that well-defined dislocation cell structures developed in both grains and the average cell size decreased with increasing shock pressure from 5 to 10 GPa. Twinning occurred in the [1 0 0] grain, but not the View the MathML source grain, at the 10 GPa shock pressure. The stress and orientation dependence of incipient twinning can be predicted by the stress and orientation conditions required to dissociate slip dislocations into glissile twinning dislocations. The dynamic widths between the two partials are calculated considering the three-dimensional deviatoric stress state induced by the shock as calculated using plane-strain plate impact simulations and the relativistic and drag effects on dislocations moving at high speeds. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235556%23 [...] [article] Orientation dependence of shock-induced twinning and substructures in a copper bicrystal [texte imprimé] / Fang Cao, Auteur ; Irene J. Beyerlein, Auteur ; Francis L. Addessio, Auteur . - pp. 549-559. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 2 (Janvier 2010) . - pp. 549-559 Mots-clés : Copper  Shock  recovery  Deformation  structure  Twinning  Dislocation  structure Index. décimale : 669 Métallurgie Résumé : Shock recovery experiments have been conducted to assess the role of shock stress and orientation dependence on substructure evolution and deformation twinning of a [1 0 0]/View the MathML source copper bicrystal. Transmission electron microscopy of the post-shock specimens revealed that well-defined dislocation cell structures developed in both grains and the average cell size decreased with increasing shock pressure from 5 to 10 GPa. Twinning occurred in the [1 0 0] grain, but not the View the MathML source grain, at the 10 GPa shock pressure. The stress and orientation dependence of incipient twinning can be predicted by the stress and orientation conditions required to dissociate slip dislocations into glissile twinning dislocations. The dynamic widths between the two partials are calculated considering the three-dimensional deviatoric stress state induced by the shock as calculated using plane-strain plate impact simulations and the relativistic and drag effects on dislocations moving at high speeds. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235556%23 [...]

Plastic deformation mechanisms of fcc single crystals at small scales / Caizhi Zhou in Acta materialia, Vol. 59 N° 20 (Décembre 2011) 

Public ISBD [article]  in Acta materialia > Vol. 59 N° 20 (Décembre 2011) . - pp. 7673–7682 Titre : Plastic deformation mechanisms of fcc single crystals at small scales Type de document : texte imprimé Auteurs : Caizhi Zhou, Auteur ; Irene J. Beyerlein, Auteur ; Richard LeSar, Auteur Année de publication : 2012 Article en page(s) : pp. 7673–7682 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Dislocation  dynamics  Size  effects  Small  scales  Dislocation  starvation  Cross-slip Résumé : Three-dimensional (3-D) dislocation dynamics simulations were employed to examine the fundamental mechanisms of plasticity in small-scale face-centered cubic single crystals. Guided by the simulation results, we examined two distinct modes of behavior that reflect the dominant physical mechanisms of plastic deformation at small scales. We found that the residence lifetimes of internal dislocation sources formed by cross-slip decrease as the system size decreases. Below a critical sample size (which depends on the initial density of dislocations) the dislocation loss rate exceeds the multiplication rate, leading to the loss of internal dislocation sources. In this case nucleation of surface dislocations is required to provide dislocations for deformation and the “starvation hardening” mechanism becomes the dominant deformation process. When the sample is larger than a critical size multiplication of internal dislocation sources provides the dominant mechanism for plastic flow. As the strain is increased the rising dislocation density leads to reactions that shut off these sources, creating “exhaustion hardening”. ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645411006094 [article] Plastic deformation mechanisms of fcc single crystals at small scales [texte imprimé] / Caizhi Zhou, Auteur ; Irene J. Beyerlein, Auteur ; Richard LeSar, Auteur . - 2012 . - pp. 7673–7682. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 59 N° 20 (Décembre 2011) . - pp. 7673–7682 Mots-clés : Dislocation  dynamics  Size  effects  Small  scales  Dislocation  starvation  Cross-slip Résumé : Three-dimensional (3-D) dislocation dynamics simulations were employed to examine the fundamental mechanisms of plasticity in small-scale face-centered cubic single crystals. Guided by the simulation results, we examined two distinct modes of behavior that reflect the dominant physical mechanisms of plastic deformation at small scales. We found that the residence lifetimes of internal dislocation sources formed by cross-slip decrease as the system size decreases. Below a critical sample size (which depends on the initial density of dislocations) the dislocation loss rate exceeds the multiplication rate, leading to the loss of internal dislocation sources. In this case nucleation of surface dislocations is required to provide dislocations for deformation and the “starvation hardening” mechanism becomes the dominant deformation process. When the sample is larger than a critical size multiplication of internal dislocation sources provides the dominant mechanism for plastic flow. As the strain is increased the rising dislocation density leads to reactions that shut off these sources, creating “exhaustion hardening”. ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645411006094