Détermination des déformations critiques en cisaillement adiabatique : effets matériels et effets de structure

Abstract : The attention is focused on the determination of the critical nominal shear strain, obtained during the localization of the plastix deformation in adiabatic shear bands, and on the influence of the material and structural parameters on this process. In order to complete this study, the spatial distribution of the plastic deformation and its temporal evolution have to be clarified. An unidimensional model of the adiabatic localization allows the determination of the distribution of the plastic deformation for different constitutive laws, by convergent series developments of the integrals, written with hypergeometric functions. We focus on the conditions and on the velocity of convergence of these developments. This leads to an analytical expression of the distribution of the plastic deformation in the case of the Knowles constitutive law. The critical nominal strain for the knowles' law is also determined with an analytical approach. The parametric study of the critical strain shows that it increases with the strain rate sensitivity parameter and with the hardening coefficient, and decreases when the sharpness 1/R and the size of the defect increase. These results extend to the critical nominal strain the trends obtained from the linear stability analysis nad the previous asymptotic localization analyses. We also exhibit the influence of the boundary conditions on the critical strains. According to the amount of energy, the critical strain under stress controlled boundary conditions can be less than, equal to, or greater than the critical strain under velocity controlled conditions : the lack of control of the experimental boundary conditions may thus lead to some scatter in the critical nominal strains
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Jean-Louis Minot. Détermination des déformations critiques en cisaillement adiabatique : effets matériels et effets de structure. Autre. Université Paul Verlaine - Metz, 1997. Français. ⟨NNT : 1997METZ018S⟩. ⟨tel-01777203⟩

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