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Etude des champs de température et de déformation dans les matériaux métalliques sollicités à grande vitesse de déformation

Abstract : This work concerns the study of the damage and failure mechanisms of metallic materials under dynamic loading. For high strain rates, it appears a strain localization in fine bands called adiabatic shear bands (ASB). As the solicitation duration is very short, the dissipation of the mechanical energy into heat generates strong temperature heterogeneities. To study the mechanisms of formation and propagation of ASB during a dynamic torsion test, we developed an experimental device to measure temperature by pyrometry: for the "low temperatures" ranging between 50°C and 300°C, we use a bar of 32 InSb infra-red detectors in order to study temperature heterogeneities during the ASB formation. The acquisition frequency is 1MHz and the spatial resolution is 43µm. For the "high temperatures" ranging between 800°C and 1600°C, we use an intensified camera whose spectral band is in visible range. The spatial resolution is 2µm and the aperture time is 10µs. This device showed that the temperature could exceed 1100°C with a temperature heterogeneity inside the band. To explain these results, we developed a two-dimensional thermomechanical model of the torsion specimen. A roughness defect was inserted in the center of the test-tube and a Johnson-Cook elasto-thermoviscoplastic behavior law was chosen. The parameters of this law were identified from static and dynamic tests at various temperatures. The solution obtained with the finite elements code Abaqus allows to simulate the formation and the propagation of the ASB. The comparison between the experiment and the model enabled us to propose a mechanism of multiple ASB formation followed by interactions and annihilations of the ASB.
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https://tel.archives-ouvertes.fr/tel-00010301
Contributor : Nicolas Ranc <>
Submitted on : Tuesday, September 27, 2005 - 1:47:11 PM
Last modification on : Tuesday, March 2, 2021 - 10:04:27 AM
Long-term archiving on: : Friday, April 2, 2010 - 10:29:27 PM

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  • HAL Id : tel-00010301, version 1

Citation

Nicolas Ranc. Etude des champs de température et de déformation dans les matériaux métalliques sollicités à grande vitesse de déformation. Energie électrique. Université de Nanterre - Paris X, 2004. Français. ⟨tel-00010301⟩

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