Engineering Transactions, 59, 3, pp. 211–233, 2011

Fe Analysis on the Formation of Plastic Instabilities in Dynamically Expanded Copper Rings

C. VELA
University Carlos III of Madrid Department of Continuum Mechanics and Structural Analysis

J. A. RODRIGUEZ – MARTINEZ
University Carlos III of Madrid Department of Continuum Mechanics and Structural Analysis

A. RUSINEK
National Engineering School of Metz (ENIM) Laboratory of Mechanics, Biomechanics, Polymers and Structures (LaBPS)

In this work the influence of the constitutive description in numerical simulations of the ra-
dial expansion of annealed OFHC copper rings has been studied. For that task, three physical-
based constitutive models are implemented into the FE code ABAQUS/Explicit and applied to
define the thermo-viscoplastic behaviour of the material in the simulations. These are those due
to Rusinek et al. [A. Rusinek, J.A. Rodr´ıguez–Mart´ınez, A. Arias, A thermo-viscoplastic
constitutive model for FCC metals with application to OFHC copper, Int. J. Mech. Sci., 52,
120–135, 2010], Nemat–Nasser and Li [S. Nemat–Nasser, Y. Li, Flow stress of FCC polycrystals
with application to OFHC Copper, Acta Mater., 46, 565–577, 1998] and Voyiadjis
and Almasri [G. Z. Voyiadjis, A.H. Almasri, A physically based constitutive model for fcc
metals with applications to dynamic hardness, Mech. Mater., 40, 549–563, 2008]. The atten-
tion is primarily focussed on analyzing the influence of the material description on the strain
localization process. Notable differences are observed in the response of the specimen under
loading depending on the constitutive relation used. The numerical study indicated that the
constitutive model controls the flow localization, defines the strain of instability and determines
the number of necks formed. The causes which reside behind such decisive role played by the
constitutive relation are investigated. It has been found that the rate sensitivity definition
governs the models’ predictions for the strain localization process.
Keywords: annealed OFHC copper, Fragmentation, Ring expansion, Constitutive descrip- tion, Numerical simulation
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