Atomistic Modeling of Shock Loading in SiC Ceramics

2013 ◽  
Vol 1535 ◽  
Author(s):  
Paulo S. Branicio ◽  
Jingyun Zhang
Keyword(s):  
Shock Wave ◽  
Particle Velocity ◽  
Large Scale ◽  
Shock Loading ◽  
Structural Phase ◽  
High Strength ◽  
Plane Shock ◽  
Wide Range ◽  
Shock Impact ◽  
Dynamics Simulations

ABSTRACTLarge scale molecular-dynamics simulations of plane shock loading in SiC are performed to reveal the interplay between shock-induced compaction, structural phase transformation (SPT) and plastic deformation. The shock profile is calculated for a wide range of particle velocity from 0.1 km/s to 6.0 km/s. Single crystalline models indicate no induced plasticity or SPT for shock loading below 2.0 km/s. For intermediate particle velocity, between 2.0 km/s and 4.5 km/s the generated shock wave splits into an elastic precursor and a zinc blende to rocksalt structural transformation wave. That is induced by the increase in shock pressure to over 90 GPa and results in a steep increase of density from 3.21 g/cm3 to ∼4.65 g/cm3. For particle velocity greater than 4.5 km/s a single overdriven transformation shock wave is generated. These simulation results provide an atomistic view of the dynamic effects of shock impact on single crystal high-strength ceramics.

Efficient Prediction of Contact Behavior in a 6-High Rolling Mill With Continuously Variable Crown Intermediate Rolls

2017 ◽  
Author(s):  
Feng Zhang ◽  
Arif S. Malik
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Mixed Finite Element ◽  
Mixed Finite Element Method ◽  
High Strength ◽  
Computational Time ◽  
Ferrous Alloys ◽  
Thickness Profile ◽  
Wide Range ◽  
Contact Force Distribution

Continuously Variable Crown (CVC) shifting mechanisms represent a control technology with wide range of capability to influence the thickness profile and flatness (shape) of metal strip and sheet in rolling-type manufacturing processes. Further, because of the efficiency and extensive control capability to operate on thin-gauge, high-strength ferrous alloys, the 6-high mill with CVC profiles machined onto the intermediate rolls (IR) represents a popular mill configuration. This is because of the large control range for the strip thickness profile and flatness, which results from lateral shifting of the CVC intermediate rolls. However, together with this efficiency and capability comes very complex contact behaviors between the rolls and strip, including highly non-linear contact force distribution, loss of contact, asymmetric roll wear, unwanted strip wedge profiles, and the need to apply corrective roll tilting. Therefore, for most effective industry use of 6-high mills with intermediate roll CVC shifting, a rapid and accurate mathematical rolling model is needed to predict and account for these complex contact behaviors. This paper introduces an efficient roll-stack computational model capable of simulating such rolling mills under steady-state conditions. The model formulation applies the simplified mixed finite element method (SM-FEM), which is adapted to simulate asymmetric 6-high CVC mill contact behaviors. Results for a specific case study compare favorably to those obtained from a large-scale commercial finite element simulation, yet require a small fraction of the associated computational time and effort.

Plasticity induced by a shock wave: large scale molecular dynamics simulations

2004 ◽  
Vol 387-389 ◽  
pp. 262-265 ◽  
Author(s):  
D. Tanguy ◽  
M. Mareschal ◽  
T.C. Germann ◽  
B.L. Holian ◽  
P.S. Lomdahl ◽  
...  
Keyword(s):  
Shock Wave ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Large Scale ◽  
Dynamics Simulations

Pressure Induced Phase Transformations in Silica

1997 ◽  
Vol 492 ◽  
Author(s):  
Tahir Çağin ◽  
Ersan Demiralp ◽  
William A. Goddard
Keyword(s):  
Phase Transformations ◽  
Shock Loading ◽  
Glassy Phase ◽  
Loading Rate ◽  
Structural Phase ◽  
Interaction Force ◽  
Pressure Loading ◽  
Loading Rates ◽  
Dynamics Simulations ◽  
Structural Phase Transformations

ABSTRACTSilica, SiO2, is one of the most widely studied substance because of its complex and unusual properties. We have used a recently developed 2-body interaction force field [1] to study the structural phase transformations in silica under various pressure loading conditions. The specific transformations we studied are the a-quartz to stishovite, coesite to stishovite and fused glass to a dominantly six-coordinated dense glassy phase. Molecular dynamics simulations are performed under constant loading rates ranging from 0.1 GPa/ps to 1.0 GPa/ps, with final pressures upto 100 GPa and at temperatures of 300, 500, and 700 K. We observe the crystal to crystal transformations to occur reconstructively, whereas it occurs in a smooth and displacive manner from glass to a stishovite-like phase confirming earlier conjectures.[2] We studied the dependence of transition pressure on the loading rate and the temperature to elucidate the shock loading experiments. We also studied the unloading behavior of each transformation to assess the hysterisis effect.

Flexural Strength and Stiffness of High Strength Concrete Beams with Exposed Main Steel

2012 ◽  
Vol 446-449 ◽  
pp. 718-727
Author(s):  
Hamid Reza Azizipesteh Baglo ◽  
Mohammed Raoof
Keyword(s):  
High Strength Concrete ◽  
Large Scale ◽  
Structural Characteristics ◽  
High Strength ◽  
Design Parameters ◽  
Normal Strength Concrete ◽  
Strength Concrete ◽  
Beam Design ◽  
Wide Range ◽  
Normal Strength

In a number of previous publications, results were reported for a series of extensive and carefully conducted tests on large scale reinforced concrete (R.C.) beams with various extents of loss of concrete cover and exposure of main reinforcement along their spans, with such areas of simulated damage being located within their regions which are dominated by either shear or flexure. These tests on R.C. beams made with normal strength concrete have covered a wide range of first order beam design parameters, with their results used to verify the generality of various theoretical models. In the present paper, much attention will be devoted to various structural characteristics (such as ultimate strength, flexural stiffness, etc.) of similar damaged R.C. beams with the proviso that, instead of the previously used normal strength concrete, the beams are made with high strength concrete. No such results (for high strength R.C. beams) have previously been reported in the public domain.

scholarly journals A general aerosol-assisted biosynthesis of functional bulk nanocomposites

2018 ◽  
Vol 6 (1) ◽  
pp. 64-73 ◽  
Author(s):  
Qing-Fang Guan ◽  
Zi-Meng Han ◽  
Tong-Tong Luo ◽  
Huai-Bin Yang ◽  
Hai-Wei Liang ◽  
...  
Keyword(s):  
Electromagnetic Interference ◽  
Large Scale ◽  
Bulk Material ◽  
Cellulose Nanofibrils ◽  
High Strength ◽  
Building Blocks ◽  
Scale Production ◽  
Cellulose Nanofibril ◽  
Practical Applications ◽  
Wide Range

Abstract Although a variety of nanoparticles with better-than-bulk material performances can be synthesized, it remains a challenge to scale the extraordinary properties of individual nanoscale units to the macroscopic level for bulk nanostructured materials. Here, we report a general and scalable biosynthesis strategy that involves simultaneous growth of cellulose nanofibrils through microbial fermentation and co-deposition of various kinds of nanoscale building blocks (NBBs) through aerosol feeding on solid culture substrates. We employ this biosynthesis strategy to assemble a wide range of NBBs into cellulose nanofibril-based bulk nanocomposites. In particular, the biosynthesized carbon nanotubes/bacterial cellulose nanocomposites that consist of integrated 3D cellulose nanofibril networks simultaneously achieve an extremely high mechanical strength and electrical conductivity, and thus exhibit outstanding performance as high-strength lightweight electromagnetic interference shielding materials. The biosynthesis approach represents a general and efficient strategy for large-scale production of functional bulk nanocomposites with enhanced performances for practical applications. Industrial-scale production of these bulk nanocomposite materials for practical applications can be expected in the near future.

Ejecta Production and Transport From a Shocked Sn Coupon

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Y. Liu ◽  
B. Grieves
Keyword(s):  
Shock Wave ◽  
Surface Roughness ◽  
Shock Loading ◽  
Wave Form ◽  
Shock Strength ◽  
Transport Studies ◽  
Wide Range ◽  
Particulate Mass ◽  
The One ◽  
Micrometer Scale

When a shock interacts with a Sn coupon, micrometer-scale particulate fragments, called ejecta, are usually formed and emitted from its free surface. Understanding the characteristics of such ejecta is of great importance in many fields. The velocity distribution and amount of particulate mass are directly dependent on several physical properties of the shock wave and shocked material states. In this paper, we numerically interrogate ejecta production and its dynamics for a wide range of shock loading conditions in a supported wave form and quantify the correlation of ejecta source with shock strength as well as surface roughness, which is represented by randomly perturbed surfaces and the one with a macrofeature superimposed. Furthermore, an unsteadiness-aware drag coefficient is discussed and implemented to accomplish ejecta transport studies.

Compromising high strength and ductility in nanoglass–metallic glass nanolaminates

RSC Advances ◽  
2016 ◽  
Vol 6 (16) ◽  
pp. 13548-13553 ◽  
Author(s):  
Sara Adibi ◽  
Paulo S. Branicio ◽  
Roberto Ballarini
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Metallic Glass ◽  
Molecular Dynamics Simulations ◽  
Large Scale ◽  
High Strength ◽  
Dynamics Simulations ◽  
Thick Layers ◽  
Strength And Ductility

Large-scale molecular-dynamics simulations are used to investigate the mechanical properties of 50 nm diameter Cu64Zr36 nanolaminate nanopillars constructed from 5 nm thick layers of metallic glass (MG) or MG and 5 nm grain sized nanoglass.

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