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FLEXO: Development of a Discontinuous Galerkin Multimaterial Magneto-Hydrodynamics Code for MagLIF Simulation

Beckwith, Kristian B.; Beckwith, Kristian B.; Bond, Stephen D.; Bond, Stephen D.; Granzow, Brian N.; Granzow, Brian N.; Hamlin, Nathaniel D.; Hamlin, Nathaniel D.; Martin, Matthew; Martin, Matthew; Powell, Michael P.; Powell, Michael P.; Ruggirello, Kevin P.; Ruggirello, Kevin P.; Stagg, Alan K.; Stagg, Alan K.; Voth, Thomas E.; Voth, Thomas E.

Abstract not provided.

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TYPE Conference Poster YEAR 2019
OSTI

Development of the Flexo XMHD Code

Beckwith, Kristian B.; Beckwith, Kristian B.; Beckwith, Kristian B.; Beckwith, Kristian B.; Bond, Stephen D.; Bond, Stephen D.; Bond, Stephen D.; Bond, Stephen D.; Granzow, Brian N.; Granzow, Brian N.; Granzow, Brian N.; Granzow, Brian N.; Jennings, Christopher A.; Jennings, Christopher A.; Jennings, Christopher A.; Jennings, Christopher A.; Martin, Matthew; Martin, Matthew; Martin, Matthew; Martin, Matthew; Porwitzky, Andrew J.; Porwitzky, Andrew J.; Porwitzky, Andrew J.; Porwitzky, Andrew J.; Stagg, Alan K.; Stagg, Alan K.; Stagg, Alan K.; Stagg, Alan K.; Voth, Thomas E.; Voth, Thomas E.; Voth, Thomas E.; Voth, Thomas E.

Abstract not provided.

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TYPE Conference Poster YEAR 2018
OSTI

Formulation and computation of dynamic, interface-compatible Whitney complexes in three dimensions

Journal of Computational Physics

Kramer, Richard M.; Siefert, Christopher S.; Voth, Thomas E.; Bochev, Pavel B.

A discrete De Rham complex enables compatible, structure-preserving discretizations for a broad range of partial differential equations problems. Such discretizations can correctly reproduce the physics of interface problems, provided the grid conforms to the interface. However, large deformations, complex geometries, and evolving interfaces makes generation of such grids difficult. We develop and demonstrate two formally equivalent approaches that, for a given background mesh, dynamically construct an interface-conforming discrete De Rham complex. Both approaches start by dividing cut elements into interface-conforming subelements but differ in how they build the finite element basis on these subelements. The first approach discards the existing non-conforming basis of the parent element and replaces it by a dynamic set of degrees of freedom of the same kind. The second approach defines the interface-conforming degrees of freedom on the subelements as superpositions of the basis functions of the parent element. These approaches generalize the Conformal Decomposition Finite Element Method (CDFEM) and the extended finite element method with algebraic constraints (XFEM-AC), respectively, across the De Rham complex.

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TYPE Journal Article YEAR 2018
ScopusOSTIDOI

Topology Optimization of Cellular Structure

Robbins, Joshua R.; Owen, Steven J.; Clark, Brett W.; Voth, Thomas E.

This paper presents an end-to-end design process for compliance minimization based topological optimization of cellular structures through to the realization of a final printed product. Homogenization is used to derive properties representative of these structures through direct numerical simulation of unit cell models of the underlying periodic structure. The resulting homogenized properties are then used assuming uniform distribution of the cellular structure to compute the final macro-scale structure. A new method is then presented for generating an STL representation of the final optimized part that is suitable for printing on typical industrial machines. Quite fine cellular structures are shown to be possible using this method as compared to other approaches that use nurb based CAD representations of the geometry. Finally, results are presented that illustrate the fine-scale stresses developed in the final macro-scale optimized part and suggestions are made as to incorporate these features into the overall optimization process.

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TYPE Journal Article YEAR 2015
OSTI

Electromagnetic Extended Finite Elements for High-Fidelity Multimaterial Problems LDRD Final Report

Siefert, Christopher S.; Bochev, Pavel B.; Kramer, Richard M.; Voth, Thomas E.; Cox, James C.

Surface effects are critical to the accurate simulation of electromagnetics (EM) as current tends to concentrate near material surfaces. Sandia EM applications, which include exploding bridge wires for detonator design, electromagnetic launch of flyer plates for material testing and gun design, lightning blast-through for weapon safety, electromagnetic armor, and magnetic flux compression generators, all require accurate resolution of surface effects. These applications operate in a large deformation regime, where body-fitted meshes are impractical and multimaterial elements are the only feasible option. State-of-the-art methods use various mixture models to approximate the multi-physics of these elements. The empirical nature of these models can significantly compromise the accuracy of the simulation in this very important surface region. We propose to substantially improve the predictive capability of electromagnetic simulations by removing the need for empirical mixture models at material surfaces. We do this by developing an eXtended Finite Element Method (XFEM) and an associated Conformal Decomposition Finite Element Method (CDFEM) which satisfy the physically required compatibility conditions at material interfaces. We demonstrate the effectiveness of these methods for diffusion and diffusion-like problems on node, edge and face elements in 2D and 3D. We also present preliminary work on h -hierarchical elements and remap algorithms.

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TYPE SAND Report YEAR 2014
OSTIDOI

Wave propagation and dispersion in elasto-plastic microstructured materials

International Journal of Solids and Structures

Dingreville, Rémi; Robbins, Joshua R.; Voth, Thomas E.

A Mindlin continuum model that incorporates both a dependence upon the microstructure and inelastic (nonlinear) behavior is used to study dispersive effects in elasto-plastic microstructured materials. A one-dimensional equation of motion of such material systems is derived based on a combination of the Mindlin microcontinuum model and a hardening model both at the macroscopic and microscopic level. The dispersion relation of propagating waves is established and compared to the classical linear elastic and gradient-dependent solutions. It is shown that the observed wave dispersion is the result of introducing microstructural effects and material inelasticity. The introduction of an internal characteristic length scale regularizes the ill-posedness of the set of partial differential equations governing the wave propagation. The phase speed does not necessarily become imaginary at the onset of plastic softening, as it is the case in classical continuum models and the dispersive character of such models constrains strain softening regions to localize. © 2014 Elsevier Ltd. All rights reserved.

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TYPE Conference Poster YEAR 2014
ScopusOSTI

LDRD final report : mesoscale modeling of dynamic loading of heterogeneous materials

Robbins, Joshua R.; Dingreville, Remi P.; Voth, Thomas E.; Furnish, Michael D.

Material response to dynamic loading is often dominated by microstructure (grain structure, porosity, inclusions, defects). An example critically important to Sandia's mission is dynamic strength of polycrystalline metals where heterogeneities lead to localization of deformation and loss of shear strength. Microstructural effects are of broad importance to the scientific community and several institutions within DoD and DOE; however, current models rely on inaccurate assumptions about mechanisms at the sub-continuum or mesoscale. Consequently, there is a critical need for accurate and robust methods for modeling heterogeneous material response at this lower length scale. This report summarizes work performed as part of an LDRD effort (FY11 to FY13; project number 151364) to meet these needs.

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TYPE SAND Report YEAR 2013
OSTIDOI

ALEGRA Update: Modernization and Resilience Progress

Robinson, Allen C.; Petney, Sharon P.; Drake, Richard R.; Weirs, Vincent G.; Adams, Brian M.; Vigil, Dena V.; Carpenter, John H.; Garasi, Christopher J.; Wong, Michael K.; Robbins, Joshua R.; Siefert, Christopher S.; Strack, Otto E.; Wills, Ann E.; Trucano, Timothy G.; Bochev, Pavel B.; Summers, Randall M.; Stewart, James R.; Ober, Curtis C.; Rider, William J.; Haill, Thomas A.; Lemke, Raymond W.; Cochrane, Kyle C.; Desjarlais, Michael P.; Love, Edward L.; Voth, Thomas E.; Mosso, Stewart J.; Niederhaus, John H.

Abstract not provided.

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TYPE Conference YEAR 2013
OSTI
Results 1–50 of 75
Results 1–50 of 75