A5051359788- Microstructure and mechanical properties
- High-Velocity Impact and Material Behavior
- Metal and Thin Film Mechanics
- Metallurgy and Material Forming
- Microstructure and Mechanical Properties of Steels
- Advanced Surface Polishing Techniques
- Force Microscopy Techniques and Applications
- Additive Manufacturing Materials and Processes
- Copper Interconnects and Reliability
- Welding Techniques and Residual Stresses
- Laser-Plasma Interactions and Diagnostics
- Advanced Materials Characterization Techniques
- Electronic Packaging and Soldering Technologies
- Advanced materials and composites
- High-pressure geophysics and materials
- Ion-surface interactions and analysis
- X-ray Diffraction in Crystallography
- Nuclear Materials and Properties
- Laser-induced spectroscopy and plasma
- Aluminum Alloy Microstructure Properties
- Hydrogen embrittlement and corrosion behaviors in metals
- Non-Destructive Testing Techniques
- Probabilistic and Robust Engineering Design
- High Temperature Alloys and Creep
- Laser Material Processing Techniques
Lawrence Livermore National Laboratory
2012-2021
Los Alamos National Laboratory
2016
Brown University
2009
DEVCOM Army Research Laboratory
2009
Stanford University
1999-2004
Wright-Patterson Air Force Base
2004
When a crystal deforms plastically, phenomena such as dislocation storage, multiplication, motion, pinning, and nucleation occur over the submicron-to-nanometer scale. Here we report measurements of plastic yielding for single crystals micrometer-sized dimensions three different types metals. We find that within tests, overall sample artificially limit length scales available processes. The results show dramatic size effects at surprisingly large dimensions. These emphasize micrometer scale,...
A basic tenet of material science is that the flow stress a metal increases as its grain size decreases, an effect described by Hall-Petch relation. This relation used extensively in design to optimize hardness, durability, survivability, and ductility structural metals. Letter reports experimental results new regime high pressures strain rates challenge this mechanical metallurgy. We report measurements plastic model body-centered-cubic tantalum made under conditions pressure (>100 GPa)...
The competition between dislocation slip and twinning in tantalum single crystals has been investigated utilizing a crystal level model the results from gas gun recovery experiments conducted at peak normal stresses of 25 55 GPa. recovered samples were characterized using electron back scattered diffraction, observed fractions compared with model. experimental show very low twin all orientations GPa, that among (100), (110), (111), (123) crystals, (110) had largest amount analysis shows...
We present a study on the spall strength of additive manufactured (AM) Ti-6Al-4V. Samples were obtained from two pieces selective laser melted (SLM, powder bed fusion technique) Ti-6Al-4V such that response to dynamic tensile loading could be investigated as function orientation between build layers and direction. A sample wrought bar-stock was also tested act baseline representing traditionally material response. single-stage light gas-gun used launch thin flyer plate into samples,...
The conditions which affect twinning in tantalum have been investigated across a range of strain rates and initial dislocation densities. Tantalum samples were subjected to rates, from 10−4/s 103/s under uniaxial stress conditions, laser-induced shock-loading conditions. In this study, was observed at 77K 1/s 103/s, during shock experiments. effect the density, imparted by deforming material different amounts pre-strain, also studied, it shown that is suppressed after given amount even as...
A 3D model is developed to simulate remote laser penetration of a 1mm Aluminum metal sheet with large spot size (∼ 3x3cm2), using the ALE3D multi-physics code. The deals laser-induced melting plate and mechanical interaction between solid melted part through elastic-plastic response. effect oscillations other forces on rupture, droplet formation mechanism influence gravity high power in further breaking single melt into many more fragments are analyzed. In limit low power, numerical results...
Part of a 'multiscale characterization' study heterogeneous deformation patterns in metals is reported. A copper single crystal was oriented for slip the (111)[] system and tested to ∼10% strain roughly uniaxial compression. The macroscopic field monitored during test by optical 'image correlation'. measured on orthogonal surfaces, one which (the x-face) perpendicular [] contained direction preferred system. developed an inhomogeneous pattern broad, crossed shear bands x-face. One, primary...
Abstract Mapping of residual stresses at the mesoscale is increasingly practical thanks to technological developments in electron backscatter diffraction (EBSD) and X-ray microdiffraction using high brilliance synchrotron sources. An analysis presented a Cu single crystal deformed compression about 10% macroscopic strain. Local orientation measurements were made on sectioned polished specimens EBSD microdiffraction. In broad strokes, results are similar each other with orientations being...
We present a set of high explosive driven Rayleigh-Taylor strength experiments for beryllium to produce data distinguish predictions by various models. Design simulations using existing model parameterizations from Steinberg-Lund and Preston-Tonks-Wallace (PTW) suggested an optimal design that would delineate between not just different models, but parameters sets the PTW model. Application models post-shot results, however, suggests growth consistent with little material strength. focus...
Abstract A 3-D image correlation system, which measures the full-field displacements in three dimensions, has been used to experimentally determine full deformation gradient matrix for two zinc single crystals. Based on data, slip system activity crystals calculated. The results of calculation show that, one crystal, only primary is active, consistent with traditional theory. other however, shows appreciable systems than primary. An analysis was conducted verifying experimental observation...