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Simulation and analysis of Magnetically-Applied Pressure-Shear (MAPS) experiments

Haill, Thomas A.; Alexander, Charles S.

A new experimental technique to measure material shear strength at high pressures has been developed for use on magnetohydrodynamic (MHD) drive pulsed power platforms. The technique is referred to as Magnetically-Applied Pressure-Shear (MAPS). By applying an external static magnetic field to the sample region, the MHD drive directly induces a shear stress wave in addition to the usual longitudinal stress wave. Strength is probed by passing this shear wave through a sample material where the transmissible shear stress is limited to the sample strength. The magnitude of the transmitted shear wave is measured via a transverse velocity interferometry system (VISAR) from which the sample strength is determined. The strength of materials is defined as the ability of a material to sustain deviatoric (shear) stresses. Strength is an important aspect of the response of materials subjected to compression to high pressure. Beyond the elastic response, material strength will govern at what pressure and to what extent a material will plastically deform. The MAPS technique cleverly exploits the property that, for a von Mises yield criterion at a given longitudinal stress, the maximum amplitude shear wave that can be transmitted is limited by the strength at that stress level. Successful fielding of MAPS experiments to measure shear stresses relies upon correct numerical simulation of the experiment. Complex wave interactions among forward and reflected longitudinal and shear waves, as well as the advancing magnetic diffusion front of the MHD drive, can make the design of the experiment complicated. Careful consideration must be given to driver, sample, and anvil materials; to the thicknesses of the driver, sample and anvil layers; as well as to the timing of the interacting waves. This paper will present and analyze the 2D MHD simulations used to design the MAPS experiments. The MAPS experiments are modeled using Sandia's ALEGRA-MHD simulation code. ALEGRA-MHD is an operator-split, multi-physics, multi-material, arbitrary lagrangian-eulerian code developed to model magnetic implosion, ceramic fracture, and electromagnetic launch. We will detail the numerical investigations into MHD shear generation, longitudinal and shear stress coupling, timing of wave interactions, and transmission of shear at material interfaces.

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TYPE Conference YEAR 2011
OSTI

Magnetically applied pressure-shear : a new technique for direct strength measurement at high pressure (final report for LDRD project 117856)

Alexander, Charles S.; Haill, Thomas A.; Lamppa, Derek C.

A new experimental technique to measure material shear strength at high pressures has been developed for use on magneto-hydrodynamic (MHD) drive pulsed power platforms. By applying an external static magnetic field to the sample region, the MHD drive directly induces a shear stress wave in addition to the usual longitudinal stress wave. Strength is probed by passing this shear wave through a sample material where the transmissible shear stress is limited to the sample strength. The magnitude of the transmitted shear wave is measured via a transverse VISAR system from which the sample strength is determined.

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TYPE SAND Report YEAR 2010
DOIOSTI

Effects of mass ablation on the scaling of X-ray power with current in wire-array Z pinches

Physical Review Letters

Lemke, R.W.; Sinars, Daniel S.; Waisman, E.M.; Cuneo, M.E.; Yu, E.P.; Haill, Thomas A.; Hanshaw, Heath L.; Brunner, Thomas A.; Jennings, C.A.; Stygar, William A.; Desjarlais, Michael P.; Mehlhorn, Thomas A.; Porter, J.L.

X-ray production by imploding wire-array Z pinches is studied using radiation magnetohydrodynamics simulation. It is found that the density distribution created by ablating wire material influences both x-ray power production, and how the peak power scales with applied current. For a given array there is an optimum ablation rate that maximizes the peak x-ray power, and produces the strongest scaling of peak power with peak current. This work is consistent with trends in wire-array Z pinch x-ray power scaling experiments on the Z accelerator. © 2009 The American Physical Society.

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TYPE Journal Article YEAR 2009
ScopusOSTI

Three-dimensional effects in trailing mass in the wire-array Z pinch

Physics of Plasmas

Yu, Edmund Y.; Cuneo, M.E.; Desjarlais, Michael P.; Lemke, Raymond W.; Sinars, Daniel S.; Haill, Thomas A.; Waisman, E.M.; Bennett, G.R.; Jennings, C.A.; Mehlhorn, T.A.; Brunner, T.A.; Hanshaw, H.L.; Porter, J.L.; Stygar, W.A.; Rudakov, L.I.

The implosion phase of a wire-array Z pinch is investigated using three-dimensional (3D) simulations, which model the mass ablation phase and its associated axial instability using a mass injection boundary condition. The physical mechanisms driving the trailing mass network are explored, and it is found that in 3D the current paths though the trailing mass can reduce bubble growth on the imploding plasma sheath, relative to the 2D (r,z) equivalent. Comparison between the simulations and a high quality set of experimental radiographs is presented. © 2008 American Institute of Physics.

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TYPE Conference YEAR 2008
ScopusOSTI

Towards a predictive MHD simulation capability for designing hypervelocity magnetically-driven flyer plates and PWclass z-pinch x-ray sources on Z and ZR

Mehlhorn, Thomas A.; Yu, Edmund Y.; Vesey, Roger A.; Cuneo, M.E.; Jones, Brent M.; Knudson, Marcus D.; Sinars, Daniel S.; Robinson, Allen C.; Trucano, Timothy G.; Brunner, Thomas A.; Desjarlais, Michael P.; Garasi, Christopher J.; Haill, Thomas A.; Hanshaw, Heath L.; Lemke, Raymond W.; Oliver, Bryan V.; Peterson, Kyle J.

Abstract not provided.

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TYPE Conference YEAR 2007
OSTI
Results 26–50 of 58
Results 26–50 of 58