Publications

Specht, Paul E.; Adams, David P.; Mitchell, John A.; Brown, Justin L.; Branch, Brittany A.; Silling, Stewart A.; Wise, Jack L.; Brown, Donald W.; Palmer, Todd A.

Abstract not provided.

Specht, Paul E.; Mitchell, John A.; Adams, David P.; Brown, Justin L.; Silling, Stewart A.; Wise, Jack L.; Palmer , Todd P.

This report outlines the fiscal year (FY) 2019 status of an ongoing multi-year effort to develop a general, microstructurally-aware, continuum-level model for representing the dynamic response of material with complex microstructures. This work has focused on accurately representing the response of both conventionally wrought processed and additively manufactured (AM) 304L stainless steel (SS) as a test case. Additive manufacturing, or 3D printing, is an emerging technology capable of enabling shortened design and certification cycles for stockpile components through rapid prototyping. However, there is not an understanding of how the complex and unique microstructures of AM materials affect their mechanical response at high strain rates. To achieve our project goal, an upscaling technique was developed to bridge the gap between the microstructural and continuum scales to represent AM microstructures on a Finite Element (FE) mesh. This process involves the simulations of the additive process using the Sandia developed kinetic Monte Carlo (KMC) code SPPARKS. These SPPARKS microstructures are characterized using clustering algorithms from machine learning and used to populate the quadrature points of a FE mesh. Additionally, a spall kinetic model (SKM) was developed to more accurately represent the dynamic failure of AM materials. Validation experiments were performed using both pulsed power machines and projectile launchers. These experiments have provided equation of state (EOS) and flow strength measurements of both wrought and AM 304L SS to above Mbar pressures. In some experiments, multi-point interferometry was used to quantify the variation is observed material response of the AM 304L SS. Analysis of these experiments is ongoing, but preliminary comparisons of our upscaling technique and SKM to experimental data were performed as a validation exercise. Moving forward, this project will advance and further validate our computational framework, using advanced theory and additional high-fidelity experiments. ACKNOWLEDGEMENTS The authors greatly appreciate the support of Mike Saavedra in machining the experimental samples. The authors would also like to thank the Dynamic Integrated Compression facility (DICE) staff for executing the Thor experiments: Brian Stoltzfus, Randy Hickman, Keith Hodge, Joshua Usher, Lena Pacheco, and Eric Breden. The authors would also like to thank the staff at the Shock Thermodynamics Applied Research (STAR) facility for executing the plate impact experiments: Scott Alexander, Bill Reinhart, Bernardo Farfan, Rocky Palomino, John Martinez, and Rafael Sanchez. Lastly, the authors would like to acknowledge the development support of Jason Sanchez in ALEGRA to incorporate our upscaling method and Michael Powell for helping with post processing scripts for results analysis.

Specht, Paul E.; Silling, Stewart A.; Mitchell, John A.; Battaile, Corbett C.; Brown, Justin L.; Wise, Jack L.; Adams, David P.; Brown, Donald W.; Palmer, Todd A.; Michael, Joseph R.; Saavedra, Michael P.

Abstract not provided.

Specht, Paul E.; Adams, David P.; Silling, Stewart A.; Mitchell, John A.; Battaile, Corbett C.; Brown, Justin L.; Wise, Jack L.; Brown, Donald W.; Palmer, Todd A.; Michael, Joseph R.; Saavedra, Michael P.

Abstract not provided.

Specht, Paul E.; Adams, David P.; Mitchell, John A.; Silling, Stewart A.; Brown, Justin L.; Wise, Jack L.; Brown, Donald W.; Palmer, Todd A.

Abstract not provided.

Specht, Paul E.; Wise, Jack L.; Brown, Justin L.; Furnish, Michael D.; Adams, David P.; Silling, Stewart A.; Battaile, Corbett C.; Palmer, Todd A.

Abstract not provided.

Brown, Justin L.; Seagle, Christopher T.; Carpenter, John H.

Abstract not provided.

Mattsson, Thomas M.; Lemke, Raymond W.; Dolan, Daniel H.; Dalton, Devon D.; Brown, Justin L.; Tomlinson, Kurt T.; Robertson, Grafton K.; Knudson, Marcus D.; Harding, Eric H.; Mattsson, Ann E.; Carpenter, John H.; Drake, Richard R.; Cochrane, Kyle C.; Blue, Brent B.; Robinson, Allen C.

Abstract not provided.

Journal of Applied Physics

Lemke, Raymond W.; Dolan, Daniel H.; Dalton, D.G.; Brown, Justin L.; Tomlinson, K.; Robertson, G.R.; Knudson, Marcus D.; Harding, Eric H.; Mattsson, A.E.; Carpenter, John H.; Drake, Richard R.; Cochrane, Kyle C.; Blue, B.E.; Robinson, Allen C.; Mattsson, Thomas M.

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.

Wills, Ann E.; Brown, Justin L.; Greeff, Carl W.

Abstract not provided.

Wills, Ann E.; Brown, Justin L.; Greeff, Carl W.

Abstract not provided.

Brown, Justin L.; Carpenter, John H.; Seagle, Christopher T.

Abstract not provided.