Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session T3: Grain Scale to Continuum Modeling V: Methodology II |
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Chair: Ryan Austin and Keo Springer, Lawrence Livermore National Laboratory Room: Grand G |
Thursday, June 18, 2015 11:15AM - 11:30AM |
T3.00001: The Multiscale Material Point Method for Simulating Transient Responses Zhen Chen, Yu-Chen Su, Hetao Zhang, Shan Jiang, Thomas Sewell To effectively simulate multiscale transient responses such as impact and penetration without invoking master/slave treatment, the multiscale material point method (Multi-MPM) is being developed in which molecular dynamics at nanoscale and dissipative particle dynamics at mesoscale might be concurrently handled within the framework of the original MPM at microscale (continuum level). The proposed numerical scheme for concurrently linking different scales is described in this paper with simple examples for demonstration. It is shown from the preliminary study that the mapping and re-mapping procedure used in the original MPM could coarse-grain the information at fine scale and that the proposed interfacial scheme could provide a smooth link between different scales. Since the original MPM is an extension from computational fluid dynamics to solid dynamics, the proposed Multi-MPM might also become robust for dealing with multiphase interactions involving failure evolution. [Preview Abstract] |
Thursday, June 18, 2015 11:30AM - 11:45AM |
T3.00002: Towards mechanism-based simulation of impact damage using Exascale computing Anton Shterenlikht, Lee Margetts, Samuel McDonald, Neil Bourne Over the past 60 years, the finite element method has been very successful in modelling deformation in engineering structures. However the method requires the definition of constitutive models that represent the response of the material to applied loads. There are two issues. Firstly, the models are often difficult to define. Secondly, there is often no physical connection between the models and the mechanisms that accommodate deformation. In this paper, we present a potentially disruptive two-level strategy which couples the finite element method in the macroscale with cellular automata in the mesoscale. The cellular automata are used to simulate mechanisms, such as crack propagation. The stress-strain relationship emerges as a continuum mechanics scale interpretation of changes at the micro- and meso-scales. Iterative two-way updating between the cellular automata and finite elements drives the simulation forward as the material undergoes progressive damage at high strain rates. The strategy is particularly attractive on large-scale computing platforms as both methods scale well on tens of thousands of CPUs. [Preview Abstract] |
Thursday, June 18, 2015 11:45AM - 12:00PM |
T3.00003: Modeling shocks in periodic lattice materials Mark Messner, Matthew Barham, Nathan Barton Periodic lattice materials have an excellent density-to-stiffness ratio, with the elastic stiffness of stretch dominated lattices scaling linearly with relative density. Recent developments in additive manufacturing techniques enable the use of lattice materials in situations where the response of the material to shock loading may become significant. Current continuum models do not describe the response of such lattice materials subject to shocks. This presentation details the development of continuum models suitable for representing shock propagation in periodic lattice materials, particularly focusing on the transition between elastic and plastic response. In the elastic regime, the material retains its periodic structure and equivalent continuum models of infinite, periodic truss structures accurately reproduce characteristics of stretch-dominated lattices. At higher velocities, the material tends to lose its initial lattice structure and begins to resemble a foam or a solid with dispersed voids. Capturing the transition between these regimes can be computationally challenging. [Preview Abstract] |
Thursday, June 18, 2015 12:00PM - 12:15PM |
T3.00004: Mesoscale simulations of shockwave energy dissipation via chemical reactions Edwin Antillon, Alejandro Strachan We use a particle-based mesoscale model that incorporates chemical reactions at a coarse-grained level to study the response of materials under shockwave-loading conditions. An additional implicit variable (the particle size) is used to describe volume-reducing chemical reactions using an intra-molecular potential inspired by Transition State Theory, while the dynamics of the center-of-mass motion evolves according to inter-particle forces. The equations of motion are derived from a Hamiltonian and the model captures both: total energy conservation and Galilean invariance. We demonstrate that this model captures complex thermo-mechanical-chemical processes, and we use these features to explore materials with the capabilities to dissipate shocks-wave energy due to ballistic impacts. Our results characterize how the parameters of the chemical model affect shock-wave attenuation, and we elucidate on how the coupling between the different energy-transferring mechanisms influences nucleation of chemistry for conditions away from equilibrium. [Preview Abstract] |
Thursday, June 18, 2015 12:15PM - 12:30PM |
T3.00005: A computationally efficient strength model for textured HCP metals undergoing dynamic loading conditions: Application to Magnesium Jeffrey Lloyd, Richard Becker Predicting the behavior of HCP metals presents challenges beyond those of FCC and BCC metals because several deformation mechanisms, each with their own distinct behavior, compete simultaneously. Understanding and capturing the competition of these mechanisms is essential for modeling the anisotropic and highly orientation-dependent behavior exhibited by most HCP metals, yet doing so in a computationally efficient manner has been elusive. In this work an orientation-dependent strength model is developed that captures the competition between basal slip, extension twinning, and non-basal slip at significantly lower computational cost than conventional crystal plasticity models. The model is applied to various textured Magnesium polycrystals, and where applicable, compared with experimental results. Although the model developed in this work is only applied to Magnesium, both the framework and model are applicable to other non-cubic crystal structures. [Preview Abstract] |
Thursday, June 18, 2015 12:30PM - 12:45PM |
T3.00006: Simulation texture development of polycrystalline aluminum under dynamic loading Xiaomian Hu, Hao Pan, Zihui Wu Effect of texture to dynamic response of polycrystalline metals under dynamic loading attracted much attention because of interesting phenomena and great challenges to experiment and simulation. This paper uses a crystal plasticity finite element method (CPFEM) with a dislocation based hardening law to model the texture development of polycrystalline aluminum under simple compression, uniaxial strain ramp loading and shock wave loading. Strain hardening under the three compression conditions is also compared. The simulation results show that the preferred orientation during of the polycrystalline aluminum under the three compression conditions has some different. It caused normalized stress-strain profiles of state of 1D stress and 1D strain are different when strain is over 5\% and strain rate is same [Preview Abstract] |
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