Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session T5: TM Continuum Modeling II |
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Chair: Turab Lookman, Los Alamos National Laboratory Room: Cascade I |
Thursday, July 11, 2013 9:15AM - 9:30AM |
T5.00001: A design of experiments approach for sensitivity screening of mesoscale simulations of explosive impact George Butler, John Cox, Teresa Daily, Keith Gonthier This paper discusses a Design of Experiments (DOE) approach for planning inert mesoscale simulations to establish how microstructure and composition affect the uniaxial impact sensitivity of metalized Plastic Bonded Explosives (PBXs). Simulations are performed using an explicit, 2D, cohesive finite and discrete element code (CODEX), developed at Georgia Institute of Technology, and account for nonlinear deformation and fracture of PBXs: explosive crystals (HMX) and aluminum particles (Al) in a polymeric binder. The relative sensitivity of PBX formulations is established by critical hot-spots formed in the microstructure. The code has flexibility in prescribing material properties, but this initial screening examines five independent variables: impact speed, initial size of HMX crystals and Al particles, and initial volume fractions of HMX and Al (the binder ensures saturation). Input settings are prescribed by the DOE approach, which plans the experiments to ensure an ability to reach statistically valid, objective conclusions with minimal runs. A full factorial matrix of simulations requires 296 runs, and each run takes up to a week. DOE reduced the matrix to 101 runs, while retaining the ability to estimate dominant variable effects and the effect of variable interactions on hot spot formation. These analyses provide a qualitative validation of CODEX, and a framework for subsequent simulations. DISTRIBUTION A. Approved for public release, distribution unlimited. (96ABW-2013-0054) [Preview Abstract] |
Thursday, July 11, 2013 9:30AM - 9:45AM |
T5.00002: Modeling and analysis of high-explosive driven perturbed plate experiments at Los Alamos James Cooley, Russell Olson, David Oro Measurement and modeling of fluid instabilities has been an important part of numerical simulation verification and validation efforts from the beginning of computational fluid dynamics. The use of these same instabilities to assess the accuracy and validity of models for material strength began at least by the middle of the 1970s [1]. These techniques have been improved upon over many decades, for example recent work in Russia [2]. These techniques have proven useful in challenging various different models for material response. We have performed several experiments at the Los Alamos pRad facility for perturbation growth in both Tantalum and Depleted Uranium. These results provide excellent data images over several microseconds of growth. In this paper, we will present efforts to use these experiments to validate our numerical code and constitutive models. We will detail a systematic study of various constitutive models for the metals and evaluate the rigidity of the constraint that these experiments provide to the modeling community. We will spend some time examining the assumptions in the constitutive models and assessing the relative uncertainties of each major assumption. LA-UR 13-21276\\[4pt] [1] J. F. Barnes, P. J. Blewett, R. G. McQueen, K. A. Meyer, and D. Venable, ``Taylor Instabilities in Solids,'' \textit{Journal of Applied Physics}, 45(2):6, 1974\\[0pt] [2] V. A. Raevsky, ``Influence of dynamic material properties on perturbation growth in solids,'' Technical Report, All-Russion Research Institute of Experimental Physics, VNIIEF, 2009 [Preview Abstract] |
Thursday, July 11, 2013 9:45AM - 10:00AM |
T5.00003: Modeling of propellant flow and explosively-driven valve for the Large-Bore Powder Gun Kin Lam The Large-Bore Powder Gun, with a 3.5-inch bore, is being developed to provide dynamic experiments on physics samples at the Nevada Test Site with impact velocities exceeding 2 km/s. A confinement system is required to seal the target chamber from the gun system to keep it free of hazardous materials from the impact event. A key component of the confinement system is an explosively driven valve (EDV), which uses a small amount of explosive (PBX 9501) to drive an aluminum piston perpendicular to the barrel axis into a tapered hole. The objective of this study is to evaluate the efficacy of the EDV design via computational simulations using models validated with prototype experiments. We first established the gun performance characteristics using an interior ballistics code. Then an energy source model capable of generating the kinematics (i.e., pressure, velocity and displacement profiles) as predicted by the interior ballistic code is used in the hydrodynamics code CTH to calculate the M14 propellant gas expansion as the projectile travels down the gun barrel with the goal of obtaining the lateral (stagnation) pressure load on the EDV piston as it is inserted into the bore. A model of the EDV operation validated against stand-alone experiments is also developed. The gas flow and EDV models are combined to simulate integrated tests as well as the operating conditions specified for qualification. Results from these simulations and those involving design modifications to improve the confinement will be presented. [Preview Abstract] |
Thursday, July 11, 2013 10:00AM - 10:15AM |
T5.00004: Multiple necking during dynamic extension of round bar: linear stability approach versus finite element calculations Skander El Mai, Sebastien Mercier, Jacques Petit, Alain Molinari The fragmentation of structures has been widely investigated in the literature, with experimental, numerical or analytical works. Many authors have proposed to reproduce by FEA the experimental fragmentation process by introducing for instance a perturbation to trigger instabilities. Therefore, the authors were able to capture the distribution of fragments. Few of them are interested in the characterization of the onset time of instability. In the proposed contribution, the multiple necking of a round bar in dynamic tensile loading is analysed by the finite element method. A perturbation of the initial flow stress is introduced in the numerical model. Various levels of loading velocities and of perturbation amplitudes are considered. The onset time of localized instabilities ti and the number of necks Nn have been characterized. A logarithmic dependence of variables ti and Nn with the loading velocity is shown. The time ti is observed to depend strongly on the level of the perturbations introduced in the numerical model while the number of necks Nn evolves moderately. Besides, by defining salient criteria in terms of the growth rate of the perturbation, a comparison of linear stability analysis dedicated to multiple necking with the numerical results can be performed. A good correlation in terms of onset time of instabilities and of number of necks is shown. [Preview Abstract] |
Thursday, July 11, 2013 10:15AM - 10:30AM |
T5.00005: Dynamic Response of Viscoelastic Plates to High Pressure Induced by Bubble Collapse S.W. Gong, E. Klaseboer, J. Lou The numerical simulations of viscoelastic plates to high pressure induced by underwater explosion bubble will be presented in this paper. The boundary-element method (BEM) is used to simulate the physical process of the explosive bubble growth, contraction and collapse. The finite element method (FEM) is used to calculate the viscoelastic plates response to the high pressure induced by underwater explosion bubble. The interaction of the viscoelastic plates and the underwater explosion bubble is simulated numerically via the coupled BEM-FEM. The computational procedure for the prediction of dynamic response of the viscoelastic plates to the high pressure induced by underwater explosion bubble is demonstrated. The case studies are conducted to examine the effects of different charge weights and locations on dynamic response of the viscoelastic plate. The results from this study may provide some insights into to the problem of viscoelastic structures subjected to underwater explosion bubble, which might be useful for potential applications in biomedicine or marine industry. [Preview Abstract] |
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