Étude expérimentale et modélisation du comportement plastique du tantale : eprise en compte de la vitesse de déformation et de l'histoire du chargement

Abstract : The growing interest numerical results showing the response of structures to dynamic loading conditions implies the development of very sophisticated constitutive models. These models must take two points into account: transcribe a bunch of experimental facts and predict the behaviour of the material under specific loading conditions. Through the mechanical behaviour of tantalum, we tried to understand and describe the phenomena occuring in b.c.c. metals. Plastic strain cannot be considered as a parameter describing the physical state of the material. Klepaczko's model based on the evolution of a single state parameter (the total dislocations density) fitted already fairly well with the experimental results for f.c.c. metals. We performed quasistatic and dynamic torsion tests on high-purity polycrystalline tantalum at room temperature. Moreover, on the same type of samples, we performed jump tests in strain rate with Split Hopkinson Torsion Bars. Although Klepaczko's model can correctly fit our experimental results, the introduction of a second state parameter (the mobile dislocations density) seems necessary for a better understanding and restituion of the phenomena occuring during plastic flow. We present a proceeding to determine analytically the contributions to the flow stress of the microstructure and of the loading conditions (temperature and strain rate). Finally, we compare the results in compression and torsion. It appears that the kind of solicitation has a major role on the mechanical behaviour of tantalum which limits at present the proposed model
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François Buy. Étude expérimentale et modélisation du comportement plastique du tantale : eprise en compte de la vitesse de déformation et de l'histoire du chargement. Autre. Université Paul Verlaine - Metz, 1996. Français. ⟨NNT : 1996METZ032S⟩. ⟨tel-01777141⟩

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