10 results on '"Tracy Vogler"'
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2. A Nonlocal Peridynamic Plasticity Model for the Dynamic Flow and Fracture of Concrete
- Author
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Christopher J. Lammi and Tracy Vogler
- Subjects
Materials science ,Flow (mathematics) ,business.industry ,Fracture (geology) ,Geotechnical engineering ,Structural engineering ,Plasticity ,business - Published
- 2014
- Full Text
- View/download PDF
Catalog
3. High-pressure shock behavior of WC and Ta2O5 powders
- Author
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William D. Reinhart, Marcus D. Knudson, Seth Root, and Tracy Vogler
- Subjects
Yield (engineering) ,Materials science ,Equation of state (cosmology) ,Metallurgy ,Analytical chemistry ,Nanoindentation ,Granular material ,Shock (mechanics) ,law.invention ,chemistry.chemical_compound ,Planar ,chemistry ,Tungsten carbide ,law ,Light-gas gun - Abstract
Planar shock experiments were conducted on granular tungsten carbide (WC) and tantalum oxide (Ta{sub 2}O{sub 5}) using the Z machine and a 2-stage gas gun. Additional shock experiments were also conducted on a nearly fully dense form of Ta{sub 2}O{sub 5}. The experiments on WC yield some of the highest pressure results for granular materials obtained to date. Because of the high distention of Ta{sub 2}O{sub 5}, the pressures obtained were significantly lower, but the very high temperatures generated led to large contributions of thermal energy to the material response. These experiments demonstrate that the Z machine can be used to obtain accurate shock data on granular materials. The data on Ta{sub 2}O{sub 5} were utilized in making improvements to the P-{lambda} model for high pressures; the model is found to capture the results not only of the Z and gas gun experiments but also those from laser experiments on low density aerogels. The results are also used to illustrate an approach for generating an equation of state using only the limited data coming from nanoindentation. Although the EOS generated in this manner is rather simplistic, for this material it gives reasonably good results. more...
- Published
- 2011
- Full Text
- View/download PDF
4. Pressure-shear experiments on granular materials
- Author
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C. Scott Alexander, William D. Reinhart, Tom F. Thornhill, and Tracy Vogler
- Subjects
Shearing (physics) ,chemistry.chemical_compound ,Materials science ,Shear (geology) ,chemistry ,Tungsten carbide ,Free surface ,Shear stress ,Comminution ,Composite material ,Granular material ,Longitudinal wave - Abstract
Pressure-shear experiments were performed on granular tungsten carbide and sand using a newly-refurbished slotted barrel gun. The sample is a thin layer of the granular material sandwiched between driver and anvil plates that remain elastic. Because of the obliquity, impact generates both a longitudinal wave, which compresses the sample, and a shear wave that probes the strength of the sample. Laser velocity interferometry is employed to measure the velocity history of the free surface of the anvil. Since the driver and anvil remain elastic, analysis of the results is, in principal, straightforward. Experiments were performed at pressures up to nearly 2 GPa using titanium plates and at higher pressure using zirconium plates. Those done with the titanium plates produced values of shear stress of 0.1-0.2 GPa, with the value increasing with pressure. On the other hand, those experiments conducted with zirconia anvils display results that may be related to slipping at an interface and shear stresses mostly at 0.1 GPa or less. Recovered samples display much greater particle fracture than is observed in planar loading, suggesting that shearing is a very effective mechanism for comminution of the grains. more...
- Published
- 2011
- Full Text
- View/download PDF
5. Expansion into vacuum of a shocked tungsten carbide-epoxy mixture
- Author
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William D. Reinhart, Tracy Vogler, C. Scott Alexander, and Tom F. Thornhill
- Subjects
Materials science ,Shock (fluid dynamics) ,Flow (psychology) ,Metallurgy ,Evaporation ,chemistry.chemical_element ,Epoxy matrix ,Epoxy ,Tungsten ,chemistry.chemical_compound ,chemistry ,Tungsten carbide ,visual_art ,Vaporization ,visual_art.visual_art_medium - Abstract
The behavior of a shocked tungsten carbide / epoxy mixture as it expands into a vacuum has been studied through a combination of experiments and simulations. X-ray radiography of the expanding material as well as the velocity measured for a stood-off witness late are used to understand the physics of the problem. The initial shock causes vaporization of the epoxy matrix, leading to a multi-phase flow situation as the epoxy expands rapidly at around 8 km/s followed by the WC particles moving around 3 km/s. There are also small amounts of WC moving at higher velocities, apparently due to jetting in the sample. These experiments provide important data about the multi-phase flow characteristics of this material. more...
- Published
- 2009
- Full Text
- View/download PDF
6. Creating bulk nanocrystalline metal
- Author
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Aaron Christopher. Hall, David Dennis Gill, D. Anthony Fredenburg, Tracy Vogler, Timothy John Roemer, Pin Yang, and Christopher Saldana
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Metal ,Fabrication ,Nanostructure ,Materials science ,Nanocrystal ,Consolidation (soil) ,Powder metallurgy ,visual_art ,visual_art.visual_art_medium ,Nanotechnology ,Microstructure ,Nanocrystalline material - Abstract
Nanocrystalline and nanostructured materials offer unique microstructure-dependent properties that are superior to coarse-grained materials. These materials have been shown to have very high hardness, strength, and wear resistance. However, most current methods of producing nanostructured materials in weapons-relevant materials create powdered metal that must be consolidated into bulk form to be useful. Conventional consolidation methods are not appropriate due to the need to maintain the nanocrystalline structure. This research investigated new ways of creating nanocrystalline material, new methods of consolidating nanocrystalline material, and an analysis of these different methods of creation and consolidation to evaluate their applicability to mesoscale weapons applications where part features are often under 100 {micro}m wide and the material's microstructure must be very small to give homogeneous properties across the feature. more...
- Published
- 2008
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7. Shock response of dry sand
- Author
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Justin Brown, Tom F. Thornhill, Lalit C. Chhabildas, Tracy Vogler, and William D. Reinhart
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Shock wave ,Interferometry ,Materials science ,Mathematical model ,Shock response spectrum ,Compaction ,Geotechnical engineering ,Mechanics ,Porous medium ,Dynamic compaction ,Shock (mechanics) - Abstract
The dynamic compaction of sand was investigated experimentally and computationally to stresses of 1.8 GPa. Experiments have been performed in the powder's partial compaction regime at impact velocities of approximately 0.25, 0.5, and 0.75 km/s. The experiments utilized multiple velocity interferometry probes on the rear surface of a stepped target for an accurate measurement of shock velocity, and an impedance matching technique was used to deduce the shock Hugoniot state. Wave profiles were further examined for estimates of reshock states. Experimental results were used to fit parameters to the P-Lambda model for porous materials. For simple 1-D simulations, the P-Lambda model seems to capture some of the physics behind the compaction process very well, typically predicting the Hugoniot state to within 3%. more...
- Published
- 2007
- Full Text
- View/download PDF
8. Exploring pulse shaping for Z using graded-density impactors on gas guns (final report for LDRD project 79879)
- Author
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Hixson, Rob (Los Alamos National Laboratory, Los Alamos, Nm), Michael D. Furnish, Tracy Vogler, William W. Anderson, William D. Reinhart, and Marlin E. Kipp
- Subjects
Diffraction ,Phase transition ,Planar ,Wavelet ,Materials science ,Isentropic process ,Dynamic data ,Nuclear engineering ,Compressibility ,Mechanical engineering ,Pulse shaping - Abstract
While isentropic compression experiment (ICE) techniques have proved useful in deducing the high-pressure compressibility of a wide range of materials, they have encountered difficulties where large-volume phase transitions exist. The present study sought to apply graded-density impactor methods for producing isentropic loading to planar impact experiments to selected such problems. Cerium was chosen due to its 20% compression between 0.7 and 1.0 GPa. A model was constructed based on limited earlier dynamic data, and applied to the design of a suite of experiments. A capability for handling this material was installed. Two experiments were executed using shock/reload techniques with available samples, loading initially to near the gamma-alpha transition, then reloading. As well, two graded-density impactor experiments were conducted with alumina. A method for interpreting ICE data was developed and validated; this uses a wavelet construction for the ramp wave and includes corrections for the ''diffraction'' of wavelets by releases or reloads reflected from the sample/window interface. Alternate methods for constructing graded-density impactors are discussed. more...
- Published
- 2005
- Full Text
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9. Dynamic compaction of tungsten carbide powder
- Author
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Jeffrey Weston Gluth, Dennis Edward Grady, Clint Hall, and Tracy Vogler
- Subjects
Shock wave ,chemistry.chemical_compound ,Work (thermodynamics) ,Materials science ,chemistry ,Tungsten carbide ,Powder metallurgy ,Metallurgy ,Compaction ,Composite material ,Edge (geometry) ,Dynamic compaction ,Shock (mechanics) - Abstract
The shock compaction behavior of a tungsten carbide powder was investigated using a new experimental design for gas-gun experiments. This design allows the Hugoniot properties to be measured with reasonably good accuracy despite the inherent difficulties involved with distended powders. The experiments also provide the first reshock state for the compacted powder. Experiments were conducted at impact velocities of 245, 500, and 711 m/s. A steady shock wave was observed for some of the sample thicknesses, but the remainder were attenuated due to release from the back of the impactor or the edge of the sample. The shock velocity for the powder was found to be quite low, and the propagating shock waves were seen to be very dispersive. The Hugoniot density for the 711 m/s experiment was close to ambient crystal density for tungsten carbide, indicating nearly complete compaction. When compared with quasi-static compaction results for the same material, the dynamic compaction data is seen to be significantly stiffer for the regime over which they overlap. Based on these initial results, recommendations are made for improving the experimental technique and for future work to improve our understanding of powder compaction. more...
- Published
- 2005
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10. HVL{_}CTH: A Simple Tool That Simulates The Hyper-Velocity Launch of a Flyer Plate
- Author
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Tracy Vogler, Lalit C. Chhabildas, and Daniel R. Blackburn
- Subjects
Shock wave ,Engineering ,Fortran ,Projectile ,business.industry ,Single shock ,Shock (mechanics) ,law.invention ,Piston ,law ,Shock physics ,Computational analysis ,Aerospace engineering ,business ,computer ,Simulation ,computer.programming_language - Abstract
Sandia National Laboratories has developed a unique method for a hyper-velocity launch (HVL), the three-stage gun. The three-stage gun is a modified two-stage light-gas gun, consisting of a piston used in the first stage, an impactor in the second stage, and a flyer plate in the third stage. The impactor is made up of different material layers that are increasing in shock impedance. The graded or pillowed layers allow the flyer to be launched at velocities up to 16 km/s without the formation of a single shock wave in the flyer plate and without it melting. Under certain experimental conditions the flyer velocity cannot be measured by standard means, X-rays and VISAR. Also, there is a need to know the flyer velocity prior to a launch in order to calibrate instruments and determine the appropriate shot configuration. The objective of HVL{_}CTH is to produce an accurate forecast of the flyer plate velocity under different launch conditions. CTH is a Eulerian shock physics computational analysis package developed at Sandia National Laboratories. Using CTH requires knowledge of its syntax and capabilities. HVL{_}CTH allows the user to easily interface with CTH, through the use of Fortran programs and batch files, in order to simulate the three-stage launch of a flyer plate. The program, HVL{_}CTH, requires little to no knowledge of the CTH program and greatly reduces the time needed to calculate the flyer velocity. Users of HVL{_}CTH are assumed to have no experience with CTH. The results from HVL{_}CTH were compared to results of X-ray and VISAR measurements obtained from HVL experiments. The comparisons show that HVL{_}CTH was within 1-2% of the X-Ray and VISAR results most of the time. more...
- Published
- 2003
- Full Text
- View/download PDF
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