Journal ArticleDOI
The role of pre-existing defects in shock-generated ejecta in copper
TLDR
In this paper, molecular dynamics simulations are used to systematically investigate the effect of size and concentration of He bubbles in Cu with planar free surfaces on ejecta production, and it is shown that the presence of defects leads to the formation of non-planarity in the shock wave itself producing ejecta as the front reaches the flat free surface.Abstract:
The interaction of shock waves with non-planar free surfaces can cause atoms to eject from the surface, leading to the formation of ejecta. These non-planarities in the free surface can occur due to machining of the free surface or can be induced in the shock wave itself due to the presence of heterogeneities in the material. Both cases lead to the formation of ejecta. While the effect of machining on ejecta has been well studied, the latter has not been a topic of significant investigations. In this work, molecular dynamics simulations are used to systematically investigate the effect of size and concentration of He bubbles in Cu with planar free surfaces on ejecta production. It is shown that the presence of defects leads to the formation of non-planarity in the shock wave itself producing ejecta as the front reaches the flat free surface. The cluster size and velocity of ejected particles greatly exceeds that of pure Cu; the radius, density, and nature of the helium-filled voids alter the mass, velocity, and size distribution of the ejected matter.read more
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Posted Content
Message-Passing Multi-Cell Molecular Dynamics on the Connection Machine 5
D. M. Beazley,Peter S. Lomdahl +1 more
TL;DR: A new scalable algorithm for short-range molecular dynamics simulations on distributed memory MIMD multicomputers based on a message-passing multi-cell approach is presented and it is demonstrated that meso-scale molecular dynamics with more than 108 particles is now possible on massively parallel MIMd computers.
Journal Article
Nonequilibrium Molecular Dynamics Simulations of Ejecta Formation in Helium-Implanted Copper
TL;DR: In this article, the effect of He concentration and morphology on ejecta production via molecular dynamics simulations was investigated by inserting identical He concentrations into Cu single crystals as interstitial atoms or bubbles near a flat free surface.
Journal ArticleDOI
Dynamic fracture characteristics of nanocrystalline Al containing He bubbles
TL;DR: In this paper , the individual and combined effects of He bubbles and grain boundaries on the spallation of aluminum at different strain rates were investigated, and a linear relationship was found between spall strength of polycrystalline Al and the fraction of He atoms when He concentration is below 0.4 at.
Journal ArticleDOI
Transition in Helium Bubble Strengthening of Copper from Quasi-static to Dynamic Deformation
Calvin R. Lear,Matthew Chancey,R. M. Flanagan,Jonathan G. Gigax,M.T. Hoang,H. Kim,Daniel T. Martinez,Benjamin M. Morrow,Nikhil Mathew,Y R Wang,N Li,J. R. Payton,Michael B. Prime,S. Fensin +13 more
TL;DR: In this article , the effects of helium bubbles on the materials strength of high-purity copper at strain rates of 0.001/s − 108/s were explored. But, the results showed that the nanoscale helium bubbles acting as dispersed barriers to dislocation motion at quasi-static strain rates collapse under shock loading and cease to be effective barriers at high strain rates.
References
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TL;DR: The Open Visualization Tool (OVITO) as discussed by the authors is a 3D visualization software designed for post-processing atomistic data obtained from molecular dynamics or Monte Carlo simulations, which is written in object-oriented C++, controllable via Python scripts and easily extendable through a plug-in interface.
Journal ArticleDOI
Computational Analysis Methods in Atomistic Modeling of Crystals
TL;DR: In this article, the authors discuss computational analysis methods typically used in atomistic modeling of crystalline materials and highlight recent developments that can provide better insights into processes at the atomic scale, including the classification of local atomic structures, the transition from atomistics to mesoscale and continuum-scale descriptions, and the automated identification of dislocations.
Journal ArticleDOI
Numerical Investigation of the Stability of a Shock‐Accelerated Interface between Two Fluids
K. A. Meyer,P. J. Blewett +1 more
TL;DR: Using a two-dimensional Lagrangian hydrodynamic code, this paper showed qualitative agreement with Meshkov's experiments, numerical calculations, and linear analysis are compared, and good agreement was obtained between numerical calculations and linear analyses.
Journal ArticleDOI
Probing the underlying physics of ejecta production from shocked Sn samples
Michael B. Zellner,W. Vogan McNeil,James E. Hammerberg,Robert Hixson,A. W. Obst,R. T. Olson,J. R. Payton,Paulo Rigg,Nathan Routley,Gerald Stevens,William Turley,L. R. Veeser,William T. Buttler +12 more
TL;DR: In this paper, the authors investigated the underlying physics of ejecta production for high explosive (HE) shocked Sn surfaces prepared with finishes typical to those roughened by tool marks left from machining processes.
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