Center for Computing Research (CCR)
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Probing off-Hugoniot states in Ta, Cu, and Al to 1000 GPa compression with magnetically driven liner implosions

Journal of Applied Physics

Lemke, Raymond W.; Bays, Nathan R.; Dalton, Devon; Brown, Justin L.; Tomlinson, K.; Robertson, G.R.; Knudson, Marcus D.; Harding, Eric; Wills, Ann E.; Carpenter, John H.; Drake, Richard R.; Cochrane, Kyle; Blue, B.E.; Robinson, Allen C.; Mattsson, Thomas

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as it implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ∼1000 GPa is achieved in all cases. These experiments exhibit unexpectedly softer behavior above 200 GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum.

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TYPE Journal Article YEAR 2016
DOIOSTIScopus

Edge Remap for Solids

Love, Edward; Robinson, Allen C.; Ridzal, Denis

We review the edge element formulation for describing the kinematics of hyperelastic solids. This approach is used to frame the problem of remapping the inverse deformation gradient for Arbitrary Lagrangian-Eulerian (ALE) simulations of solid dynamics. For hyperelastic materials, the stress state is completely determined by the deformation gradient, so remapping this quantity effectively updates the stress state of the material. A method, inspired by the constrained transport remap in electromagnetics, is reviewed, according to which the zero-curl constraint on the inverse deformation gradient is implicitly satisfied. Open issues related to the accuracy of this approach are identified. An optimization-based approach is implemented to enforce positivity of the determinant of the deformation gradient. The efficacy of this approach is illustrated with numerical examples.

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TYPE SAND Report YEAR 2013
DOIOSTI

ALEGRA Update: Modernization and Resilience Progress

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

Abstract not provided.

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TYPE Conference YEAR 2013
OSTI
Results 26–50 of 85
Results 26–50 of 85
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