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M. Gonzales and N. N. Thadhani
and Engineering (ICMSE) paradigm, where physics-based models on spatially
resolved microstructures or meso-structures provide insight into the dynamic event
that experimental measurements are unable to fully capture. Naturally, experimental
validation guides highly resolved numerical simulations of impact processes, which
can capture the microstructural complexity of the material if suitable constitutive
models and equations of state exist.
1.2 ICMSE Approaches to Probing Dynamic Behavior of
Materials
The advent of distributed memory and parallelized computing has enabled massively parallel numerical computations of physical phenomena. Complex numerical
simulations using discretized forms of the conservation equations are now readily
available and make multi-material dynamic simulations a possibility. The sophistication of constitutive models and equations of state is constantly evolving, rendering
a predictive physics-based calculation tenable. However, there remain aspects of
the phenomena where deterministic calculation fails to capture the true nature of
the behavior, and stochastic methods become attractive. Meso-scale simulations of
realistic microstructural configurations under extreme dynamic loads can provide a
window into how these microstructures evolve and affect the bulk dynamic behavior
of the system.
1.2.1 Molecular Dynamics and Coarse-Grained Methods
Molecular dynamics (MD) provides a simulation methodology whereby ensembles
of atoms, treated as Newtonian bodies interacting in a field, [38] can provide bulk
and continuum-level properties through statistical mechanics considerations. MD
simulations relying on conventional thermo and barostats have been successfully
used to study shock compression phenomena, cf. [43, 55]. Jarmakani et al. [43]
studied shock propagation in both mono- and nanocrystalline Ni using the Mishin
potentials through an embedded atom method (EAM). They observed stacking faults
and partial dislocation formation consistent with experiments and found that the
stress release process was responsible for the annihilation of partial dislocation
loops formed after the shock wave traversed the crystal, which explained prior
discrepancies between post-shock observations and MD predictions. Figure 2
shows a representative output of the deformed substructure in nanocrystalline Ni
(Fig. 2a, b,) and Cu (Fig. 2c), which captures the richness in plastic deformation
mechanisms, which includes stacking fault formation and twinning. Blue areas
denote undeformed atomic configurations, green areas denote displacement by
the Burgers vector of a Shockley partial, and red areas denote displacement by
a full Burgers vector corresponding to a perfect dislocation. Perfect dislocations
M. Gonzales and N. N. Thadhani
and Engineering (ICMSE) paradigm, where physics-based models on spatially
resolved microstructures or meso-structures provide insight into the dynamic event
that experimental measurements are unable to fully capture. Naturally, experimental
validation guides highly resolved numerical simulations of impact processes, which
can capture the microstructural complexity of the material if suitable constitutive
models and equations of state exist.
1.2 ICMSE Approaches to Probing Dynamic Behavior of
Materials
The advent of distributed memory and parallelized computing has enabled massively parallel numerical computations of physical phenomena. Complex numerical
simulations using discretized forms of the conservation equations are now readily
available and make multi-material dynamic simulations a possibility. The sophistication of constitutive models and equations of state is constantly evolving, rendering
a predictive physics-based calculation tenable. However, there remain aspects of
the phenomena where deterministic calculation fails to capture the true nature of
the behavior, and stochastic methods become attractive. Meso-scale simulations of
realistic microstructural configurations under extreme dynamic loads can provide a
window into how these microstructures evolve and affect the bulk dynamic behavior
of the system.
1.2.1 Molecular Dynamics and Coarse-Grained Methods
Molecular dynamics (MD) provides a simulation methodology whereby ensembles
of atoms, treated as Newtonian bodies interacting in a field, [38] can provide bulk
and continuum-level properties through statistical mechanics considerations. MD
simulations relying on conventional thermo and barostats have been successfully
used to study shock compression phenomena, cf. [43, 55]. Jarmakani et al. [43]
studied shock propagation in both mono- and nanocrystalline Ni using the Mishin
potentials through an embedded atom method (EAM). They observed stacking faults
and partial dislocation formation consistent with experiments and found that the
stress release process was responsible for the annihilation of partial dislocation
loops formed after the shock wave traversed the crystal, which explained prior
discrepancies between post-shock observations and MD predictions. Figure 2
shows a representative output of the deformed substructure in nanocrystalline Ni
(Fig. 2a, b,) and Cu (Fig. 2c), which captures the richness in plastic deformation
mechanisms, which includes stacking fault formation and twinning. Blue areas
denote undeformed atomic configurations, green areas denote displacement by
the Burgers vector of a Shockley partial, and red areas denote displacement by
a full Burgers vector corresponding to a perfect dislocation. Perfect dislocations