The Fragmentation of Al-W Granular Composites Under Explosive Loading

2013 ◽  
Vol 1521 ◽  
Author(s):  
Karl L. Olney ◽  
Po-Hsun Chiu ◽  
Vitali F. Nesterenko ◽  
David J. Benson ◽  
Chris Braithwaite ◽  
...  
Keyword(s):  
Fragment Size ◽  
Maximum Size ◽  
Explosive Loading ◽  
Small Scale ◽  
Homogeneous Material ◽  
Detonation Pressure ◽  
Dramatic Reduction ◽  
Size Scales ◽  
Isostatic Compression ◽  
Granular Composites

ABSTRACTSmall scale explosively driven fragmentation experiments have been performed on Aluminum (Al)-Tungsten (W) granular composite rings processed using cold isostatic compression of Al and W powders with a particle size of 4-30 microns. Fragments collected from the experiments had a maximum size of the order of a few hundred micrometers. This is a dramatic reduction in the fragment size when compared to the 1-10 mm typical for a homogeneous material such as solid aluminum under similar loading conditions. Numerical simulations of the experiment were performed to elucidate the mechanisms of fragmentation that were responsible for this shift in fragmentation size scales. Simulations were performed with a significantly stronger explosive driver to examine how the mechanisms of fragmentation change when the detonation pressure increases.

Imaging Polarimetry of Eta Carinae with the Hubble Space Telescope

1999 ◽  
Vol 169 ◽  
pp. 255-259
Author(s):  
Regina E. Schulte-Ladbeck ◽  
Anna Pasquali ◽  
Mark Clampin ◽  
Antonella Nota ◽  
John Hillier ◽  
...  
Keyword(s):  
Hubble Space Telescope ◽  
Three Dimensional ◽  
Position Angle ◽  
Small Scale ◽  
Eta Carinae ◽  
V Band ◽  
Dimensional Distribution ◽  
Imaging Polarimetry ◽  
Insight Into ◽  
Size Scales

AbstractWe have taken advantage of the high spatial resolution attainable with the HST to map the linear polarization in the V band across the nebulosity surrounding Eta Car. There are several new results related to polarization variations on different size scales. First, we present a two-dimensional map of the amount and position angle of the polarization across the Homunculus. Second, we provide measurements of the polarization within prominent features such as the “jet”, the “paddle”, the “skirt”, and the “spot” in the south-eastern lobe. Third, we comment on polarization variations associated with the small-scale structure that can be seen in HST images (and which gives the lobes their cauliflower-like appearance). The new data provide insight into the three-dimensional distribution of dust about Eta Car.

1-Amino-3-nitroguanidine (ANQ) in High-performance Ionic Energetic Materials

2012 ◽  
Vol 67 (6) ◽  
pp. 573-588 ◽  
Author(s):  
Niko Fischer ◽  
Thomas M. Klapötke ◽  
Jörg Stierstorfer
Keyword(s):  
Nitric Acid ◽  
Energetic Materials ◽  
Electrical Discharge ◽  
High Performance ◽  
Small Scale ◽  
Detonation Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dsc Measurements ◽  
Explosive Performance

1-Amino-3-nitroguanidine (ANQ, 2) was synthesized via hydrazinolysis of nitroguanidine (1). An appropriate Lewis structure of ANQ is drawn based on VB calculations. Due to its basicity, it can be protonated by strong mineral acids or acidic heterocycles. In order to synthesize new energetic materials the nitrate (3) and perchlorate (4) salts of 1-amino-3-nitroguanidine were synthesized by protonation of 2 with 40% nitric acid and 60% perchloric acid, respectively. 5-Nitrimino-1,4H-tetrazole obtained by reacting 5-amino-1H-tetrazole with 100% HNO3 was used to synthesize the nitriminotetrazolate salt 5. Furthermore, the dinitramide salt 6 of 1-amino-3-nitroguanidine was synthesized by metathesis reaction of silver dinitramide and 1-amino-3-nitroguanidinium chloride. The dinitroguanidinate salt 7 was synthesized by protonation of 2 with 1,3-dinitroguanidine, which was prepared from nitroguanidine in anhydrous nitric acid/N2O5. All compounds were fully characterized by singlecrystal X-ray diffraction, vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, and DSC measurements. The heats of formation of 2 - 7 were calculated using the atomization method based on CBS-4M enthalpies. With these values and the experimental (X-ray) densities several detonation parameters such as the detonation pressure, velocity, energy, and temperature were computed using the EXPLO5 code. In addition, the sensitivities towards impact, friction and electrical discharge were tested using the BAM drophammer, friction tester as well as a small-scale electrical discharge device. A Koenen test with 1-amino-3-nitroguanidinium nitrate (3) was carried out in order to evaluate its explosive performance and shipping classification.

Fluorodinitroethyl Ortho-carbonate and -formate as Potential High Energy Dense Oxidizers

2014 ◽  
Vol 69 (1) ◽  
pp. 8-16 ◽  
Author(s):  
Thomas M. Klapötke ◽  
Burkhard Krumm ◽  
Richard Moll ◽  
Sebastian F. Rest ◽  
Muhamed Sućeska
Keyword(s):  
Electrostatic Discharge ◽  
High Energy ◽  
Small Scale ◽  
Detonation Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dsc Measurements ◽  
Multinuclear Nmr Spectroscopy ◽  
Ray Density ◽  
Ir And Raman

Tetrakis(2-fluoro-2,2-dinitroethyl) ortho-carbonate (1) and tris(2-fluoro-2,2-dinitroethyl) orthoformate (2) were synthesized by the reaction of carbon tetrachloride, respectively chloroform, with 2-fluoro-2,2-dinitroethanol and catalytic amounts of anhydrous iron(III) chloride. The compounds were characterized by single-crystal X-ray diffraction, vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, elemental analysis, and multi-temperature DSC measurements. The suitability of the compounds as potential oxidizers in energetic formulations has been investigated and discussed. The heats of formation of the products were determined experimentally using bomb calorimetric methods. With this value and the experimental (X-ray) density, several detonation parameters such as the detonation pressure, velocity, energy, and temperature were computed using the EXPLO5 code. The sensitivity towards impact, friction and electrostatic discharge was tested using the BAM drop hammer, a friction tester and a small-scale electrostatic discharge device.

Elastic-Plastic Analysis of Cracks on Bimaterial Interfaces: Part III—Large-Scale Yielding

1991 ◽  
Vol 58 (2) ◽  
pp. 450-463 ◽  
Author(s):  
C. F. Shih ◽  
R. J. Asaro ◽  
N. P. O’Dowd
Keyword(s):  
Large Scale ◽  
Crack Tip ◽  
Field Analysis ◽  
Small Scale ◽  
Homogeneous Material ◽  
Full Account ◽  
Full Field ◽  
Bimaterial Interfaces ◽  
Homogeneous Materials ◽  
Scale Yielding

In Parts I and II, the structure of small-scale yielding fields of interface cracks were described in the context of small strain plasticity and J2 deformation theory. These fields are members of a family parameterized by the plastic phase angle ξ which also determines the shape or phase of the plastic zone. Through full-field analysis, we showed the resemblance between the plane-strain interface crack-tip fields and mixed-mode HRR fields in homogeneous material. This connection was exploited, to the extent possible, inasmuch as the interface fields do not appear to have a separable form. The present investigation is focused on “opening” dominated load states (| ξ | ≤ π/6) and the scope is broadened to include finite ligament plasticity and finite deformation effects on near-tip fields. We adopt a geometrically rigorous formulation of J2 flow theory taking full account of crack-tip blunting. Our results reveal several surprising effects, that have important implications for fracture, associated with finite ligament plasticity and finite strains. For one thing the fields that develop near bimaterial interfaces are more intense than those in homogeneous material when compared at the same value of J or remote load. For example, the plastic zones, plastic strains, and the crack-tip openings, δt, that evolve near bimaterial interfaces are considerably larger than those that develop in homogeneous materials. The stresses within the finite strain zone are also higher. In addition, a localized zone of high hydrostatic stresses develops near the crack tip but then expands rapidly within the weaker material as the plasticity spreads across the ligament. These stresses can be as much as 30 percent higher than those in homogeneous materials. Thus, the weaker material is subjected to large stresses as well as strains—states which promote ductile fracture processes. At the same time, the accompanying high interfacial stresses can promote interfacial fracture.

scholarly journals Structure and fragmentation of a high line-mass filament: Nessie

2018 ◽  
Vol 616 ◽  
pp. A78 ◽  
Author(s):  
M. Mattern ◽  
J. Kainulainen ◽  
M. Zhang ◽  
H. Beuther
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Solar Neighborhood ◽  
Small Scale ◽  
Star Forming ◽  
High Line ◽  
Line Mass ◽  
The Mean ◽  
The Relationship ◽  
Size Scales

Context. An increasing number of hundred-parsec-scale, high line-mass filaments are being detected in the Galaxy. Their evolutionary path, including fragmentation towards star formation, is virtually unknown. Aims. We characterize the fragmentation within the hundred-parsec-scale, high line-mass Nessie filament, covering size-scales in the range ~0.1–100 pc. We also connect the small-scale fragments to the star-forming potential of the cloud. Methods. We combine near-infrared data from the VISTA Variables in the Via Lactea (VVV) survey with mid-infrared Spitzer/GLIMPSE data to derive a high-resolution dust extinction map for Nessie. We then apply a wavelet decomposition technique on the map to analyze the fragmentation characteristics of the cloud. The characteristics are then compared with predictions from gravitational fragmentation models. We compare the detected objects to those identified at a resolution approximately ten times lower from ATLASGAL 870 μm dust emission data. Results. We present a high-resolution extinction map of Nessie (2″ full-width-half-max, FWHM, corresponding to 0.03 pc). We estimate the mean line mass of Nessie to be ~627 M⊙ pc−1 and the distance to be ~3.5 kpc. We find that Nessie shows fragmentation at multiple size scales. The median nearest-neighbor separations of the fragments at all scales are within a factor of two of the Jeans’ length at that scale. However, the relationship between the mean densities of the fragments and their separations is significantly shallower than expected for Jeans’ fragmentation. The relationship is similar to the one predicted for a filament that exhibits a Larson-like scaling between size-scale and velocity dispersion; such a scaling may result from turbulent support. Based on the number of young stellar objects (YSOs) in the cloud, we estimate that the star formation rate (SFR) of Nessie is ~371 M⊙ Myr−1; similar values result if using the number of dense cores, or the amount of dense gas, as the proxy of star formation. The star formation efficiency is 0.017. These numbers indicate that by its star-forming content, Nessie is comparable to the Solar neighborhood giant molecular clouds like Orion A.

scholarly journals Structure Formation and Characterization in Supernova Explosions

2011 ◽  
Vol 7 (S279) ◽  
pp. 429-430
Author(s):  
Patrick A. Young ◽  
Carola Ellinger ◽  
Chris Fryer ◽  
Gabe Rockefeller
Keyword(s):  
Structure Formation ◽  
Supernova Remnants ◽  
Surrounding Medium ◽  
Small Scale ◽  
Unstable Region ◽  
Supernova Explosions ◽  
Scale Structures ◽  
Size Scales ◽  
Small Scale Structures

AbstractObservations of supernova remnants show that large- and small scale structures form at various points in the explosion. We present a case study of structure formation in 3D in a 15 M⊙ supernova for different parameters. We investigate the structure formation and morphology of the Rayleigh-Taylor unstable region. We also propose a method of characterizing the sizes of overdense clumps that can be compared directly with observations. The RT instabilities result in clumps that are overdense by 1-2 orders of magnitude with respect to the ambient gas, have size scales on the level of a few% of the remnant diameter, and are not diffused after the first ~30 yrs of the remnant evolution, in the absence of a surrounding medium.

Subfeature patterning of organic and inorganic materials using robotic assembly

2007 ◽  
Vol 22 (6) ◽  
pp. 1601-1608 ◽  
Author(s):  
Afshin Tafazzoli ◽  
Chao-Min Cheng ◽  
Chytra Pawashe ◽  
Emily K. Sabo ◽  
Lacramioara Trofin ◽  
...  
Keyword(s):  
Inorganic Materials ◽  
Robotic Assembly ◽  
Small Scale ◽  
Automated Assembly ◽  
Potential Applications ◽  
Biological Pattern Formation ◽  
Patterning Technique ◽  
Novel Method ◽  
Pyramid Structures ◽  
Size Scales

The ability to create small-scale material patterns using lithography has been limited by the feature sizes and assembly of the master stamping system. Developing a simple and robust robotically automated patterning technique for both organic and inorganic materials, which is able to be actively controlled down to scales smaller than the operating features, would enable new capabilities and directions in research. Here, a novel method is presented to form patterns of defined shape and distribution via automated assembly along with force-controlled microstamping. Robotic assembly based particle templates and pyramid structures were used to create controlled distributions of materials. Systems including quantum dots and biomolecules were patterned, demonstrating our ability to create repeatable geometries with size scales smaller than the master stamping system. These patterns were also utilized for constraining cell adhesion and spreading. This work has potential applications in diverse areas from building molecular circuits to probing biological pattern formation.

scholarly journals The biology and ecology of tropical marine sardines and herrings in Indo-West Pacific fisheries: a review

2021 ◽  
Author(s):  
Kimberley Hunnam
Keyword(s):  
Population Dynamics ◽  
Maximum Size ◽  
Early Life History ◽  
Habitat Associations ◽  
Small Scale ◽  
Tropical Species ◽  
Similar Species ◽  
West Pacific ◽  
Fisheries Resources ◽  
Species Groups

AbstractTropical sardines and herrings (Family Clupeidae) form important fisheries resources in the Indo-West Pacific region. However knowledge of their biology and ecology is largely scattered across diverse localised studies. In addition, their challenging taxonomy due to numerous, morphologically similar species, coupled with data collected from dispersed, often small-scale and mixed species fisheries, creates difficulties for comparing species-level research and fisheries statistics across the region. This review considers four main groups of tropical marine clupeid species important for Indo-West Pacific fisheries—Sardinella (subg. Sardinella) species (‘Round-bodied Sardinellas’), Sardinella (subg. Clupeonia) species (‘Flat-bodied Sardinellas’), Amblygaster species (‘Tropical Pilchards’), and Herklotsichthys and Escualosa species (‘Tropical Herrings’)—and collates and synthesises existing knowledge on early life history, reproduction, trophic biology, habitat associations and population dynamics. Most research on tropical clupeid biology and ecology in the Indo-West Pacific is concentrated on the Round-bodied Sardinellas (S. longiceps and S. lemuru) from a few major fishery locations; other species-groups have been studied sporadically across their distributions. Characteristics such as maximum size, life span, size at first maturity and some habitat associations are generally similar within species-groups and differ between groups. However differences within the same reported species highlight the importance of continued work to improve taxonomic identification. There remain substantial gaps in knowledge on all species-groups. Regular critical review of specific research topics, such as reproductive parameters and population dynamics, would assist to standardise methods and terminology used, enable consolidation and comparison of findings, identify local research agenda, and help build and improve research on these important tropical species.

scholarly journals The seismo-hydromechanical behavior during deep geothermal reservoir stimulations: open questions tackled in a decameter-scale in situ stimulation experiment

Solid Earth ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 115-137 ◽  
Author(s):  
Florian Amann ◽  
Valentin Gischig ◽  
Keith Evans ◽  
Joseph Doetsch ◽  
Reza Jalali ◽  
...  
Keyword(s):  
Rock Mass ◽  
Geothermal Energy ◽  
Numerical Models ◽  
Test Site ◽  
Crystalline Rock ◽  
Coupled Processes ◽  
Small Scale ◽  
Homogeneous Material ◽  
Grimsel Test Site

Abstract. In this contribution, we present a review of scientific research results that address seismo-hydromechanically coupled processes relevant for the development of a sustainable heat exchanger in low-permeability crystalline rock and introduce the design of the In situ Stimulation and Circulation (ISC) experiment at the Grimsel Test Site dedicated to studying such processes under controlled conditions. The review shows that research on reservoir stimulation for deep geothermal energy exploitation has been largely based on laboratory observations, large-scale projects and numerical models. Observations of full-scale reservoir stimulations have yielded important results. However, the limited access to the reservoir and limitations in the control on the experimental conditions during deep reservoir stimulations is insufficient to resolve the details of the hydromechanical processes that would enhance process understanding in a way that aids future stimulation design. Small-scale laboratory experiments provide fundamental insights into various processes relevant for enhanced geothermal energy, but suffer from (1) difficulties and uncertainties in upscaling the results to the field scale and (2) relatively homogeneous material and stress conditions that lead to an oversimplistic fracture flow and/or hydraulic fracture propagation behavior that is not representative of a heterogeneous reservoir. Thus, there is a need for intermediate-scale hydraulic stimulation experiments with high experimental control that bridge the various scales and for which access to the target rock mass with a comprehensive monitoring system is possible. The ISC experiment is designed to address open research questions in a naturally fractured and faulted crystalline rock mass at the Grimsel Test Site (Switzerland). Two hydraulic injection phases were executed to enhance the permeability of the rock mass. During the injection phases the rock mass deformation across fractures and within intact rock, the pore pressure distribution and propagation, and the microseismic response were monitored at a high spatial and temporal resolution.

On Homogenization-Based Methods for Large-Eddy Simulation

2002 ◽  
Vol 124 (4) ◽  
pp. 892-903 ◽  
Author(s):  
L. Persson ◽  
C. Fureby ◽  
N. Svanstedt
Keyword(s):  
Large Eddy Simulation ◽  
Large Scale ◽  
Stokes Equations ◽  
Multiple Scales ◽  
Practical Importance ◽  
Small Scale ◽  
Homogeneous Material ◽  
Mean Flow ◽  
Eddy Simulation ◽  
Large Eddy

The ability to predict complex engineering flows is limited by the available turbulence models and the present-day computer capacity. In Reynolds averaged numerical simulations (RANS), which is the most prevalent approach today, equations for the mean flow are solved in conjunction with a model for the statistical properties of the turbulence. Considering the limitations of RANS and the desire to study more complex flows, more sophisticated methods are called for. An approach that fulfills these requirements is large-eddy simulation (LES) which attempts to resolve the dynamics of the large-scale flow, while modeling only the effects of the small-scale fluctuations. The limitations of LES are, however, closely tied to the subgrid model, which invariably relies on the use of eddy-viscosity models. Turbulent flows of practical importance involve inherently three-dimensional unsteady features, often subjected to strong inhomogeneous effects and rapid deformation that cannot be captured by isotropic models. As an alternative to the filtering approach fundamental to LES, we here consider the homogenization method, which consists of finding a so-called homogenized problem, i.e. finding a homogeneous “material” whose overall response is close to that of the heterogeneous “material” when the size of the inhomogeneity is small. Here, we develop a homogenization-based LES-model using a multiple-scales expansion technique and taking advantage of the scaling properties of the Navier-Stokes equations. To study the model simulations of forced homogeneous isotropic turbulence and channel flow are carried out, and comparisons are made with LES, direct numerical simulation and experimental data.

Sign in / Sign up

Export Citation Format

Share Document