A single-crystal model for the high-strain rate deformation of cyclotrimethylene trinitramine including phase transformations and plastic slip
A continuum model for the high-rate, thermo-mechanical deformation of single-crystal cyclotrimethylene trinitramine (RDX) is developed. The model includes the effects of anisotropy, large deformations, nonlinear thermo-elasticity, phase transformations, and plastic slip. A multiplicative decompositi...
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Published in | Journal of applied physics Vol. 121; no. 18 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
14.05.2017
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Online Access | Get full text |
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Summary: | A continuum model for the high-rate, thermo-mechanical deformation of
single-crystal
cyclotrimethylene trinitramine (RDX) is developed. The model includes the effects of
anisotropy,
large deformations, nonlinear thermo-elasticity, phase transformations, and
plastic slip. A multiplicative decomposition of the deformation gradient is
used. The volumetric elastic component of the deformation is accounted for through a free-energy
based equation of
state for the low- (α) and high-pressure (γ) polymorphs of RDX. Crystal
plasticity is addressed using a phenomenological thermal activation model. The
deformation gradient for the phase transformation is based on an approach that has been
applied to martensitic transformations. Simulations were conducted and compared to
high-rate, impact loading of oriented RDX single crystals. The simulations considered multiple
orientations of the crystal relative to the direction of shock loading and multiple sample
thicknesses. Thirteen slip
systems, which were inferred from indentation and x-ray topography, were
used to model the α-polymorph. It is shown that by increasing the number of slip systems from the
previously considered number of six (6) to thirteen (13) in the α-polymorph, better
comparisons with data may be obtained. Simulations of impact conditions in the vicinity of
the α- to γ-polymorph transformation (3.8 GPa) are considered. Eleven of the simulations,
which were at pressures below the transformation value (3.0 GPa), were compared to
experimental data. Comparison of the model was also made with available data for one
experiment above
the transformation pressure (4.4 GPa). Also, simulations are provided for a nominal
pressure of 7.5 GPa to demonstrate the effect of the transformation kinetics on the
deformation of a high-rate plate impact problem. |
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ISSN: | 0021-8979 1089-7550 |
DOI: | 10.1063/1.4983009 |