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Convexity of yield surface with directional distortional hardening rules / Plesek, Jiri in Journal of engineering mechanics, Vol. 136 N° 4 (Avril 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 4 (Avril 2010) . - pp. 477-484 Titre : Convexity of yield surface with directional distortional hardening rules Type de document : texte imprimé Auteurs : Plesek, Jiri, Auteur ; Feigenbaum, Heidi P., Auteur ; Dafalias, Yannis F., Auteur Article en page(s) : pp. 477-484 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Plasticity  Elastoplasticity  Yield  Anisotropy. Résumé : The present paper examines the convexity of the yield surface in the directional distortional hardening models by Feigenbaum and Dafalias. In these models anisotropy develops through kinematic and directional distortional hardening, supplemented by the classical isotropic hardening, and the associative flow rule is used. However, the issue of convexity, which naturally arises due to the distortion of the yield surface, was not fully addressed. The present paper derives the necessary and sufficient conditions to ensure convexity of the yield surface for the simpler Feigenbaum and Dafalias models, but it is not as straightforward to derive corresponding conditions for convexity of the Feigenbaum and Dafalias model version which contains an evolving fourth-order tensor. In this case convexity will be addressed first in general and then at the limit state for which simple restrictions on the material constants to ensure convexity are derived. Numerical examples will show that some of the yield surfaces simulated in the original Feigenbaum and Dafalias publication will not stay convex if loaded beyond what was done in these publications. Therefore the material constants for these cases are recalibrated based on the derived relations for satisfaction of the convexity requirement, and the fitting of the yield surfaces is repeated with the new set of constants and compared with the previous case. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Convexity of yield surface with directional distortional hardening rules [texte imprimé] / Plesek, Jiri, Auteur ; Feigenbaum, Heidi P., Auteur ; Dafalias, Yannis F., Auteur . - pp. 477-484. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 4 (Avril 2010) . - pp. 477-484 Mots-clés : Plasticity  Elastoplasticity  Yield  Anisotropy. Résumé : The present paper examines the convexity of the yield surface in the directional distortional hardening models by Feigenbaum and Dafalias. In these models anisotropy develops through kinematic and directional distortional hardening, supplemented by the classical isotropic hardening, and the associative flow rule is used. However, the issue of convexity, which naturally arises due to the distortion of the yield surface, was not fully addressed. The present paper derives the necessary and sufficient conditions to ensure convexity of the yield surface for the simpler Feigenbaum and Dafalias models, but it is not as straightforward to derive corresponding conditions for convexity of the Feigenbaum and Dafalias model version which contains an evolving fourth-order tensor. In this case convexity will be addressed first in general and then at the limit state for which simple restrictions on the material constants to ensure convexity are derived. Numerical examples will show that some of the yield surfaces simulated in the original Feigenbaum and Dafalias publication will not stay convex if loaded beyond what was done in these publications. Therefore the material constants for these cases are recalibrated based on the derived relations for satisfaction of the convexity requirement, and the fitting of the yield surfaces is repeated with the new set of constants and compared with the previous case. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Simple model for directional distortional hardening in metal plasticity within thermodynamics / Feigenbaum, Heidi P. in Journal of engineering mechanics, Vol. 134 n°9 (Septembre 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°9 (Septembre 2008) . - pp.730-738 Titre : Simple model for directional distortional hardening in metal plasticity within thermodynamics Type de document : texte imprimé Auteurs : Feigenbaum, Heidi P., Auteur ; Dafalias, Yannis F., Auteur Année de publication : 2008 Article en page(s) : pp.730-738 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Plasticity  Elastoplasticity  Yield  Thermal  factors  Anisotropy Résumé : Directional distortion, observed in many experiments on various types of metals, refers to the formation of a region of high curvature (sharpening) on the yield surface approximately in the direction of loading, and a region of low curvature (flattening) approximately in the opposite direction. Constitutive modeling of directional distortion was recently presented by the writers where an evolving fourth-order tensor-valued internal variable was introduced. In the current paper a much simpler mathematical formulation describing directional distortional hardening is presented without the use of a fourth-order tensor, in conjunction with kinematic and isotropic hardening. Two versions of the model in ascending level of complexity follow similar lines of development, which include derivation of all hardening rules on the basis of conditions sufficient to satisfy the thermodynamic dissipation inequality. As a tradeoff for its simplicity the present model does not fit experimental data as well as the model with the evolving fourth-order tensor, but it still captures the salient features of directional distortion in a rather satisfactory way. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A9%2872 [...] [article] Simple model for directional distortional hardening in metal plasticity within thermodynamics [texte imprimé] / Feigenbaum, Heidi P., Auteur ; Dafalias, Yannis F., Auteur . - 2008 . - pp.730-738. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°9 (Septembre 2008) . - pp.730-738 Mots-clés : Plasticity  Elastoplasticity  Yield  Thermal  factors  Anisotropy Résumé : Directional distortion, observed in many experiments on various types of metals, refers to the formation of a region of high curvature (sharpening) on the yield surface approximately in the direction of loading, and a region of low curvature (flattening) approximately in the opposite direction. Constitutive modeling of directional distortion was recently presented by the writers where an evolving fourth-order tensor-valued internal variable was introduced. In the current paper a much simpler mathematical formulation describing directional distortional hardening is presented without the use of a fourth-order tensor, in conjunction with kinematic and isotropic hardening. Two versions of the model in ascending level of complexity follow similar lines of development, which include derivation of all hardening rules on the basis of conditions sufficient to satisfy the thermodynamic dissipation inequality. As a tradeoff for its simplicity the present model does not fit experimental data as well as the model with the evolving fourth-order tensor, but it still captures the salient features of directional distortion in a rather satisfactory way. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A9%2872 [...]