Application du modèle d'écrouissage cinématique à la mise en forme : influence de la température sur limite de formage

Abstract : A great number of parameter may influence the formability of sheets. Among the most important are the strain-hardening, the strain rate sensitivity, damage, initial and induced anisotropy. For some materials with low thermal conductivity or high rate conditions, thermal effects are not negligible. Influence of such effects on formability has received little attention. In the first part of this work, we are concerned in anisotropic induced hardening. We use a formulation of kinematic hardening with memory effect. This formulation leads to a VOCE-type stress-strain law. So the powedr law with constant strain hardening coefficient may not be the best description of materials like brass or stainless steel that seem to exhibit a VOCE stress-strain law. The effect of the objective derivative used in the kinematic hardening model is discussed. Two objective derivatives are tested leading to different behavior in simple shear. We study the influence of this behavior on the forming limit diagrams and compare with experimental results. We are also interested in the influence of strain rate sensitivity and thermomechanical coupling on formability. Finally, we consider a material which the shear stress depends upon temperature, strain, strain rate through a power law. Shear localization is studied and combined influence of strain rate sensitivity, strain hardening and thermal softening in formability is discussed
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Daniel Dudzinski. Application du modèle d'écrouissage cinématique à la mise en forme : influence de la température sur limite de formage. Matériaux. Université Paul Verlaine - Metz, 1986. Français. ⟨NNT : 1986METZ019S⟩. ⟨tel-01775524⟩

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