A5006647950- Microstructure and mechanical properties
- High-pressure geophysics and materials
- High-Velocity Impact and Material Behavior
- Metal and Thin Film Mechanics
- Diamond and Carbon-based Materials Research
- Energetic Materials and Combustion
- Force Microscopy Techniques and Applications
- Laser-Plasma Interactions and Diagnostics
- Additive Manufacturing Materials and Processes
- Metallurgy and Material Forming
- Manufacturing Process and Optimization
- Additive Manufacturing and 3D Printing Technologies
- Advanced Surface Polishing Techniques
- Solidification and crystal growth phenomena
- Scientific Computing and Data Management
- Ion-surface interactions and analysis
- Metal Forming Simulation Techniques
- Advanced Chemical Physics Studies
- Aluminum Alloy Microstructure Properties
- Machine Learning in Materials Science
- Adhesion, Friction, and Surface Interactions
- Fusion materials and technologies
- Advanced Materials Characterization Techniques
- Distributed and Parallel Computing Systems
- High Temperature Alloys and Creep
Lawrence Livermore National Laboratory
2013-2024
University of California System
1996-2007
University of Nebraska–Lincoln
2002-2003
University of California, Berkeley
2003
Zimmer Biomet (United States)
2002
National Technical Information Service
2001
University of Rochester
2001
University of Oxford
2001
Office of Scientific and Technical Information
2001
Association of Research Libraries
2001
We present here a report produced by workshop on ‘Addressing failures in exascale computing’ held Park City, Utah, 4–11 August 2012. The charter of this was to establish common taxonomy about resilience across all the levels computing system, discuss existing knowledge various hardware and software layers an build those results, examining potential solutions from both perspective focusing combined approach. brought together participants with expertise applications, system software, hardware;...
In situ optical absorptivity measurements are carried out to clarify the physics of laser‐material interactions involved and validate both finite element analytical models describing laser powder bed fusion processing. Absorption energy is evaluated directly using precise calorimetry compared melt pool depths for common structural metal alloys (Ti‐6Al‐4V, Inconel 625, stainless steel 316L) as a function incident power, scan velocity beam diameter. Changes in all materials found vary strongly...
In situ x-ray diffraction studies of iron under shock conditions confirm unambiguously a phase change from the bcc (alpha) to hcp (epsilon) structure. Previous identification this transition in shock-loaded has been inferred correlation between shock-wave-profile analyses and static high-pressure measurements. This is intrinsically limited because dynamic loading can markedly affect structural modifications solids. The measurements are consistent with uniaxial collapse along [001] direction...
We have used x-ray diffraction with subnanosecond temporal resolution to measure the lattice parameters of orthogonal planes in shock compressed single crystals silicon (Si) and copper (Cu). Despite uniaxial compression along (400) direction Si reducing spacing by nearly $11%$, no observable changes occur normals propagation direction. In contrast, shocked Cu shows prompt hydrostaticlike compression. These results are consistent simple estimates plastic strain rates based on dislocation...
We present an overview of recent work on quantum-based atomistic simulation materials properties in transition metals performed the Metals and Alloys Group at Lawrence Livermore National Laboratory. Central to much this effort has been development, from fundamental quantum mechanics, robust many-body interatomic potentials for bcc via model generalized pseudopotential theory (MGPT), providing close linkage between ab initio electronic-structure calculations large-scale static dynamic...
The effect of stress triaxiality on growth a void in three-dimensional single-crystal face-centered-cubic lattice has been studied. Molecular dynamics simulations using an embedded-atom potential for copper have performed at room temperature and strain controlling with high rates ranging from ${10}^{7}/\mathrm{sec}$ to ${10}^{10}/\mathrm{sec}.$ Strain these magnitudes can be studied experimentally, e.g., shock waves induced by laser ablation. Void simulated three different conditions,...
Li-insertion-induced phase transformation in nanoscale olivine particles is studied by phase-field simulations this paper. We show that the anisotropic growth morphology observed experiments thermodynamically controlled elastic energy arising from misfit strain between Li-rich and Li-poor phases kinetically influenced Li surface-reaction kinetics. The one-dimensional diffusivity inherent to structure found stabilize boundary after insertion termintates facilitate ex-situ observation. Our...
Additive manufacturing (AM), or 3D printing, of metals is transforming the fabrication components, in part by dramatically expanding design space, allowing optimization shape and topology. However, although physical processes involved AM are similar to those welding, a field with decades experimental, modeling, simulation, characterization experience, qualification parts remains challenge. The availability exascale computational systems, particularly when combined data-driven approaches such...
Abstract The Additive Manufacturing Benchmark Test Series (AM Bench) provides rigorous measurement data for validating additive manufacturing (AM) simulations a broad range of AM technologies and material systems. Bench includes extensive in situ ex measurements, simulation challenges the modeling community, corresponding conference series. In 2022, second round challenge problems, were completed, focusing primarily upon laser powder bed fusion (LPBF) processing metals, both extrusion vat...
Molecular dynamics simulations in three-dimensional copper are performed to quantify the void coalescence process leading fracture. The correlated growth of voids during their linking is investigated both terms onset and ensuing dynamical interactions through rate reduction distance between directional voids. critical intervoid ligament marking shown be approximately one radius measures.
The equivalence of two approaches to the variational theory cell-membrane equilibria which have been proposed in literature is demonstrated. Both assume a constraint on surface area, global one formulation and local alternative, accordance with measurements reveal negligible dilation presence membrane deformation. We thus address potential controversy mathematical modeling an important problem biophysics.
Experiments show that charge-stabilized colloidal suspensions form crystals which can melt by applied shear stress. We present a molecular-dynamics simulation study of melting in colloids. The nonequilibrium phase diagram is calculated for volume fraction has an equilibrium fcc structure. mechanism flow the sheared solid found to be planes sliding over planes. find weak solids (high added salt) melt, but strong do not. Instead, produces crossover new This appears as reentrant phase. Results...
Nonequilibrium indentation simulations for two-dimensional crystals composed of up to 1036 800=720\ifmmode\times\else\texttimes\fi{}1440 atoms are described. The forces used include smoothly truncated Lennard-Jones force laws, both with and without added embedded-atom contributions typical copper or nickel. Both low intermediate temperatures considered over a wide range indentor speeds. Typical microhardness yield strengths these materials, divided by projected area, exceed 10% the shear...
Void coalescence and interaction in dynamic fracture of ductile metals have been investigated using three-dimensional strain-controlled multimillion atom molecular dynamics simulations copper. The correlated growth two voids during the process leading to is investigated, both terms its onset ensuing dynamical interactions. interactions are quantified through rate reduction distance between voids, directional shape evolution voids. critical intervoid ligament marking shown be approximately...
Thermodynamic properties of solid nitrogen are calculated over a variety isotherms and isobars using constant pressure Monte Carlo method with deformable, periodic boundary conditions. Vibron frequencies simple perturbation theory. In addition, pressure–volume relations, thermal expansion coefficients, structures, phase transition pressures temperatures determined. particular, the nature orientational disorder in plastic crystal phases is examined by calculating order parameters.