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SHEAR BEHAVIOR AND RELATED MECHANISMS IN MATERIALS PLASTICITY

Numerical Study of Impact Penetration Shearing Employing Finite Strain Viscoplasticity Model Incorporating Adiabatic Shear Banding

[+] Author and Article Information
Patrice Longère1

 Université Européenne de Bretagne, LIMATB-UBS (EA4250), 56321 Lorient Cedex, Francepatrice.longere@univ-ubs.fr

André Dragon

Laboratoire de Mécanique et de Physique des Matériaux, ENSMA, UMR CNRS 6617, 86961 Futuroscope-Chasseneuil Cedex, France

Xavier Deprince

 Nexter Systems, 18023 Bourges Cedex, France

1

Corresponding author.

J. Eng. Mater. Technol 131(1), 011105 (Dec 19, 2008) (14 pages) doi:10.1115/1.3030880 History: Received January 14, 2008; Revised June 03, 2008; Published December 19, 2008

This work brings forward a twofold contribution relevant to the adiabatic shear banding (ASB) process as a part of dynamic plasticity of high-strength metallic materials. The first contribution is a reassessment of a three-dimensional finite deformation model starting from a specific scale postulate and devoted to cover a wide range of dissipative phenomena, including ASB-related material instabilities (strong softening prefailure stage). The model, particularly destined to deal with impacted structures was first detailed by (Longère2003, “Modelling Adiabatic Shear Banding Via Damage Mechanics Approach  ,” Arch. Mech., 55, pp. 3–38; 2005, “Adiabatic Shear Banding Induced Degradation in a Thermo-Elastic/Viscoplastic Material Under Dynamic Loading  ,” Int. J. Impact Eng., 32, pp. 285–320). The second novel contribution concerns numerical solution of a genuine ballistic penetration problem employing the above model for a target plate material. The ASB trajectories are shown to follow a multistage history and complex distribution pattern leading finally to plugging failure mechanism. The corresponding analysis and related parametric study are intended to put to the test the pertinency of the model as an advanced predictive tool for complex shock related problems.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

“Large RVE” concept illustrated by Marchand and Duffy (12) dynamic torsion experiment and consecutive global softening corresponding to growing density d according to the present model

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Figure 2

Equivalent homogeneous volume element containing a family of band (α=1)

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Figure 3

Material element under dynamic shearing as observed by Marchand and Duffy (12): (a) Undeformed configuration; (b) homogeneous shear deformation; (c) weak localization; (d) ASB-induced strong localization

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Figure 4

Intermediate configuration and decomposition of the deformation gradient F in the presence of anisotropy; see also Ref. 24

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Figure 5

HSS dynamic shearing test device (Nexter (17)): (a) schematic representation of the test device; (b) HSS geometry

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Figure 6

Configuration with Lstriker=90 mm; Vstriker=23.7 m/s(Tnom=42.2 μs): (a) macrograph; (b) numerical deterioration map (100 μs); (c) experimental and numerical stress histories in the output bar. No visible drop in stress during the nominal time period.

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Figure 7

Configuration with Lstriker=200 mm; Vstriker=17.8 m/s(Tnom=93.8 μs). After Ref 19: (a) macrograph; (b) numerical deterioration map (150 μs); (c) experimental and numerical stress histories in the output bar. No visible drop in stress during the nominal time period

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Figure 8

Configuration with Lstriker=40 mm; Vstriker=35.6 m/s(Tnom=18.7 μs). After Ref. 19: (a) macrograph; (b) numerical deterioration map (40 μs); (c) experimental and numerical stress histories in the output bar. The drop in stress in the first signal fluctuation is typical of a crossing band.

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Figure 9

Geometry and spatial discretization of the FSP and the plate: (a) FSP geometry; (b) spatial discretization

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Figure 10

Numerical views of the deformed plate for FSP initial velocity VFSP lower and higher than the ballistic penetration limit velocity Vbpl(H=2R): (a) VFSP/Vbpl=95%. Deterioration map in deformed view; (b) VFSP/Vbpl=105% in deformed view

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Figure 11

Influence of the constant k for the prediction of ASB onset. Numerical simulation of the simple shear (dynamic torsion) test.

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Figure 12

Influence of the constant k for the prediction of crossing deteriorated FE band time. Numerical simulation of the HSS dynamic shearing test.

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Figure 13

Influence of the value of the constant k (hardening) of the TEVPD model. Numerical deterioration (Tr D) map in the configuration with H=2R at the same time for a FSP initial velocity lower than the ballistic limit. (a) k=10; (b). k=30

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Figure 14

Plastic deformation (p) map in the configuration with H=R at the same time for a FSP initial velocity lower than the ballistic limit. (a) Johnson–Cook model; (b) TEVPD model.

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Figure 15

Numerical deterioration (Tr D̃) map in the configuration with H=R at the same time for a FSP initial velocity lower than the ballistic limit. (a) a=0.5 mm; (b) a=1 mm.

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