Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session G7: Continuum and Multiscale Modeling I |
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Chair: Mike Winey, Washington State University Room: Fairmont Orchid Hotel Promenade III |
Tuesday, June 26, 2007 10:30AM - 10:45AM |
G7.00001: A Two-Scale FEM formulation for Hetereogeneous Materials Axinte Ionita, Eric Mas, Bradford Clements We present a new Two-Scale Finite Element formulation, in the dynamic case, for the heterogeneous materials (for example, high explosives and other composites). The method employs two sets of finite element discretizations: one global (associated with the I$^{st}$ scale) and, for each element in the mesh at the I$^{st}$ scale, a local discretization (associated with the II$^{nd}$ scale). Using the principle of virtual work in conjunction with the localization problem the Two-Scale FEM equations are established for two cases: the case when the representative volume element (RVE) is much smaller than the finite element size of the I$^{st}$ scale, and for the case when the RVE size become comparable with the finite element of the I$^{st}$ scale. The obtained equations are decoupled in the sense that the dynamics equations are solved relative to the I$^{st}$ scale while the II$^{nd}$ scale is used to determine the material response. The proposed approach allows more flexible and a better correlation with experiments and eventually can be incorporated in a larger context analysis involving heterogeneous materials. Numerical examples are included. LA-UR-06-5889. [Preview Abstract] |
Tuesday, June 26, 2007 10:45AM - 11:00AM |
G7.00002: Multiscale Modeling of Plastic Bonded Explosives Grant Smith, Dmitry Bedrov, Oleg Borodin We have developed a multiscale modeling paradigm for the prediction of the viscoelastic properties, equation of state and yielding behavior of plastic bonded explosives (PBXs). In our multiscale modeling approach the components of the explosive (e.g., energetic material, metal and binder) are explicitly resolved and the material point method (MPM) is utilized to predict the response of the composite material to loading (isentropic, shock, etc.). This data are then utilized to develop equation-of-state and constitutive models for the PBX. The properties of the components are determined either from atomistic simulations or are taken from the literature. Force fields for the atomistic simulations in turn have been developed based upon high-level electronic structure calculations of model compounds and molecular complexes. Hence, our multiscale simulation approach systematically bridges length scales from atomistic to macroscopic. Applications of this approach to PBX-9501 and other PBXs will be considered. [Preview Abstract] |
Tuesday, June 26, 2007 11:00AM - 11:15AM |
G7.00003: Modeling the Asymmetric Burning of Agglomerate Particles Clinton Richmond A model has been developed to describe asymmetric burning effects due to oxide caps or other substances on the surface of agglomerate particles. The model accounts for the burning behavior of single particles when they are combined together in an agglomerate of particles. The model calculates the available surface area that is exposed to burning by the geometric formation of the agglomerate of the combining particles. Averaging analytic techniques are applied to the burning behavior of the agglomerate of particles so that its burning effects can be compared to the burning effects from the uncombined, single particles. [Preview Abstract] |
Tuesday, June 26, 2007 11:15AM - 11:30AM |
G7.00004: Modelling of detonation in PBX 9502 with a stiffened-gas EOS mixture model Charles Kiyanda, Mark Short An analytically tractable model of detonation in PBX 9502 is developed. It consists of a mixture of reactant and product materials, with each component represented by a stiffened-gas equation of state. The five free thermodynamic parameters in the model allow us to address some of the restrictions of simpler analytical models. We first explore generic properties of the steady ZND detonation structure under this model. Secondly, we show that fitting of the thermodynamic data to experimental data on reactant and product properties yields non-intersecting Hugoniot curves. The associated chemical kinetic scheme consists of two reaction steps. The first step has a pressure dependent rate term. It takes the reactants to an intermediate state, a mixture of effectively mostly gaseous products with some solid carbon. The second step models the clustering of solid carbon atoms. Pop-plot and detonation velocity vs. curvature data are used to fit the chemical kinetic parameters. Finally, the linear stability of PBX 9502 detonation waves modeled by the stiffened gas system is studied. [Preview Abstract] |
Tuesday, June 26, 2007 11:30AM - 11:45AM |
G7.00005: Metal Particle Heating and Acceleration in Condensed Explosives Robert Ripley, Fan Zhang, Fue-Sang Lien For condensed explosives containing metal particle additives, a characteristic parameter relating the detonation reaction zone length (L$_{r}$) to the particle size (d$_p$) can be defined as $\delta $ = d$_{p}$/L$_{r}$. The detonation reaction zone length is typically 0.01 $<$ L$_{r}<$ 100 mm, whereas metal particle sizes of 100 nm $<$ d$_{p}<$ 1 mm can be employed. This indicates a potential range of 10$^{-6} <\delta <$ 10$^{2} $. The limiting case of $\delta \ll$ 1 involves frozen shock/particle interaction; for $\delta \gg$ 1 the interaction consists of a thin-detonation-front diffraction followed by expanding products flow. The intermediate case of $\delta \approx$ 1 has been studied previously as a function of metal mass fraction and particle packing to determine momentum and heat transfer during the detonation interaction time. Results indicate a strong dependence of particle acceleration and heating rate on $\delta $ for high metal mass fraction conditions. The present study employs 3D mesoscale simulation to further conduct parametric studies in the 0.1 $\le \delta \le$ 10 range by varying the particle diameter, particle metal and explosive material. The results are quantified to determine macroscopic physical models for particle acceleration and heating. [Preview Abstract] |
Tuesday, June 26, 2007 11:45AM - 12:00PM |
G7.00006: Rate-Independent Material Model to Describe the Shock and Ramp Wave Loading Response of 6061-T6 Aluminum to 22 GPa J.M. Winey, W. Mamun, Y.M. Gupta A rate-independent phenomenological material model has been developed to describe the response of 6061-T6 aluminum for shock loading to 22 GPa and ramp wave loading to 4 GPa. To describe the mean stress response of the material, existing isothermal pressure-volume data from hydrostatic compression experiments were utilized. The elastic shear response was modeled by assuming that Poisson's ratio is constant. Material strength was described using a von Mises yield surface, together with nonlinear strain-hardening. Simulations using this material model were performed to compare with experimental wave profile data for shock and ramp wave loading. Our simulations show better agreement with the experimental results compared to previous materials models. In particular, experimental features such as the speed of the plastic wave, the ramping behavior between the elastic and plastic waves, and the speed of the release wave from the shocked state are described well by our model. Work supported by DOE. [Preview Abstract] |
Tuesday, June 26, 2007 12:00PM - 12:15PM |
G7.00007: Nickel based superalloy containment case design: constitutive modeling and computational analysis Andrew Ruggiero, Nicola Bonora, Giovanni Torrice, Marco Di Sciuva, Marco Degiovanni, Massimiliano Mattone, Marco Gherlone, Carlo Frola Quasi-static and dynamic characterization of nickel based superalloy Waspaloy{\textregistered} has been performed at the University of Cassino. Quasy-static tensile tests have been carried out on both round bar specimens, to obtain the flow stress curve at low strain rates, and hourglass specimens, to investigate damage evolution with plastic strain. The mechanical behavior at high strain rates has been obtained by means of a direct tension split Hopkinson Bar, which allows the characterization of the material up to failure. Experimental results show that when strain rates increases, the failure strain increases while the yield strength decreases, in some intervals of the range considered. This singular behavior has been modeled and implement in a Finite Element Method commercial code in order to perform numerical simulations of experimental ballistic tests carried out at the Polytechnics of Turin, using an airgun facility. Good agreement has been found between FEM simulations and experimental results.. [Preview Abstract] |
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