Radial Stress Release Wave Induced Twinning in a Tantalum Single Crystal

2014 ◽  
Vol 46 (10) ◽  
pp. 4522-4526
Author(s):  
Bo Pang ◽  
Ian P. Jones ◽  
Jeremy C. F. Millett ◽  
Glenn Whiteman ◽  
N. Bourne ◽  
...  
Keyword(s):  
Single Crystal ◽  
Radial Stress ◽  
Stress Release ◽  
Release Wave ◽  
Wave Induced

Dynamic shock wave induced order-disorder type phase transition of sodium nitrate single crystal

2021 ◽  
pp. 114625
Author(s):  
A. Sivakumar ◽  
P. Eniya ◽  
S. Sahaya Jude Dhas ◽  
S. Joreme Dhas ◽  
J. Kalyana Sundar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Shock Wave ◽  
Single Crystal ◽  
Sodium Nitrate ◽  
Type Phase ◽  
Wave Induced ◽  
Disorder Type

AB INITIO STUDY OF NITROGEN-DOPED CARBON NANOTUBES

NANO ◽  
2007 ◽  
Vol 02 (03) ◽  
pp. 181-188 ◽  
Author(s):  
S. S. YU ◽  
Q. B. WEN ◽  
W. T. ZHENG ◽  
Q. JIANG
Keyword(s):  
Carbon Nanotubes ◽  
Ab Initio ◽  
Radial Stress ◽  
Density Functional ◽  
Stress Release ◽  
Functional Theory ◽  
Structural Stabilization ◽  
Impurity Atoms ◽  
Nitrogen Impurity ◽  
Nitrogen Doped Carbon

Calculations have been made for carbon nanotubes containing substitutional nitrogen impurity atoms using ab initio density functional theory. It is found that the distribution of N atoms depends upon the chirality and diameter of the tube. When two nitrogen atoms are introduced into the (5, 5), (6, 6) and (7, 4) tubes, nitrogen atoms prefer to be adjacent to each other along the circumference, while they tend to be far from each other in other carbon nanotubes. As more nitrogen atoms are incorporated, they prefer to be localized, leading to the broken N – N bond and the interstice is formed in the thin tubes. However, for thick tubes, nitrogen atoms tend to distribute uniformly. It is the finding in this work that the high radial stress plays an important role in nitrogen atom distribution for the thin tubes. For thin N -doped tubes, the major contribution to the structural stabilization comes from the radial stress release after the N – N bond is broken.

Radial Stress Release Phenomena in Plate Impact Experiments: Compression-Release

1972 ◽  
Vol 39 (2) ◽  
pp. 359-366 ◽  
Author(s):  
A. L. Stevens ◽  
O. E. Jones
Keyword(s):  
Radial Stress ◽  
Residual Effects ◽  
Stress Release ◽  
Plate Impact ◽  
Secondary Importance ◽  
Physical Experiments ◽  
Impact Experiment ◽  
Circular Target ◽  
The Impact ◽  
Impact Experiments

A common objective in designing a postmortem type of plate-impact experiment is to be able to attribute the observable residual effects (such as residual strain, hardness, or dislocation density) primarily to the conditions which existed while the material was in a state of uniaxial strain. In the past it has generally been assumed that effects due to radial stress release phenomena, which are always present in such an experiment, are of secondary importance. In order to test the validity of this assumption, a two-dimensional Lagrangian finite-difference computer program is used to model physical experiments representative of common practice. Target plate dimensions, the target and flyer plate material, and the impact velocity are systematically varied for circular target plates with, and without, guard rings. The results show that in many cases the effects of radial release phenomena are too large to ignore. Conclusions are presented which serve as guidelines for designing experiments to minimize radial release effects.

scholarly journals 2D Semimodel of Full-Section Anchorage in Thick Soft Rock Roadway

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xianzhou Lyu ◽  
Zenghui Zhao ◽  
Qing Ma ◽  
Xiaojie Wang ◽  
Xiaojie Gao
Keyword(s):  
Tangential Stress ◽  
Radial Stress ◽  
Coupling Effect ◽  
Superposition Principle ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Stress Release ◽  
Full Face ◽  
Soft Rock Roadway ◽  
Rock Roadway

This paper focuses on the reinforcement effect of full-face anchorage in thick soft rock roadway. A 2D semimodel of full-face anchorage in roadway with thick surrounding soft rock was proposed firstly by transforming the confinement effect of the excavation face in the longitudinal direction as the virtual internal support force at the circumferential surface. Then, based on the theory of elasticity, the theoretical model of the coupling effect between surrounding rock and anchoring system was established, and the analytical solutions of stress and displacement were obtained employing superposition principle. Finally, the theoretical solution was verified by numerical simulation, and the distribution laws of stress release-anchor stock-surrounding rock coupling were analyzed in detail considering stress release. Results demonstrated that the stress field of the surrounding rock diverse widely with different stress release coefficients. With the increasing of stress release coefficient, the radial stress of the surrounding rock decreases, while the tangential stress increases. The supporting role of the bolt is mainly reflected in improving the radial stress of the anchorage zone. However, it has little effect on the tangential stress. What is more, the anchoring effect is more significant to soft rock stress than hard rock. In addition, the prestress of rock bolt has a certain matching relation with the bolt parameters, the surrounding rock parameters, and the initial stress. This study laid a theoretical foundation for further analysis of the interaction between surrounding rock and bolt supporting in plastic zone.

A Preparation of High Resolution Standards for Electron Microscopy. Part II

1971 ◽  
Vol 29 ◽  
pp. 160-161
Author(s):  
Akira Tanaka ◽  
David F. Harling
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Carbon Black ◽  
Single Crystal ◽  
Dark Field ◽  
Graphitized Carbon Black ◽  
Graphitized Carbon ◽  
Dark Field Imaging ◽  
Crystal Films ◽  
Micro Holes

In the previous paper, the author reported on a technique for preparing vapor-deposited single crystal films as high resolution standards for electron microscopy. The present paper is intended to describe the preparation of several high resolution standards for dark field microscopy and also to mention some results obtained from these studies. Three preparations were used initially: 1.) Graphitized carbon black, 2.) Epitaxially grown particles of different metals prepared by vapor deposition, and 3.) Particles grown epitaxially on the edge of micro-holes formed in a gold single crystal film.The authors successfully obtained dark field micrographs demonstrating the 3.4Å lattice spacing of graphitized carbon black and the Au single crystal (111) lattice of 2.35Å. The latter spacing is especially suitable for dark field imaging because of its preparation, as in 3.), above. After the deposited film of Au (001) orientation is prepared at 400°C the substrate temperature is raised, resulting in the formation of many square micro-holes caused by partial evaporation of the Au film.

Structure of Palladium Single-Crystal Films Prepared by Flash Evaporation onto (001) NaCl Substrates

1970 ◽  
Vol 28 ◽  
pp. 456-457
Author(s):  
L. E. Murr ◽  
G. Wong
Keyword(s):  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Rate ◽  
Flash Evaporation ◽  
Optimum Load ◽  
Single Crystal Films ◽  
Crystal Films ◽  
A Current

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

Dislocations, Ordering and Antiferromagnetic Domains in MnO

1970 ◽  
Vol 28 ◽  
pp. 522-523
Author(s):  
D. J. Barber ◽  
R. G. Evans
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Optical Microscopy ◽  
Defect Chemistry ◽  
Magnetic Structures ◽  
Optically Transparent ◽  
Magnetic Features ◽  
Antiferromagnetic Domains

Manganese (II) oxide, MnO, in common with CoO, NiO and FeO, possesses the NaCl structure and shows antiferromagnetism below its Neel point, Tn∼ 122 K. However, the defect chemistry of the four oxides is different and the magnetic structures are not identical. The non-stoichiometry in MnO2 small (∼2%) and below the Tn the spins lie in (111) planes. Previous work reported observations of magnetic features in CoO and NiO. The aim of our work was to find explanations for certain resonance results on antiferromagnetic MnO.Foils of single crystal MnO were prepared from shaped discs by dissolution in a mixture of HCl and HNO3. Optical microscopy revealed that the etch-pitted foils contained cruciform-shaped precipitates, often thick and proud of the surface but red-colored when optically transparent (MnO is green). Electron diffraction and probe microanalysis indicated that the precipitates were Mn2O3, in contrast with recent findings of Co3O4 in CoO.

Electron Microscopy of Shock Loaded Polycrystalline Beryllium

1974 ◽  
Vol 32 ◽  
pp. 506-507 ◽  
Author(s):  
J. M. Galbraith ◽  
L. E. Murr ◽  
A. L. Stevens
Keyword(s):  
Electron Microscopy ◽  
Wave Propagation ◽  
Structural Change ◽  
Single Crystal ◽  
Diffraction Pattern ◽  
Shock Loading ◽  
Slip Systems ◽  
Compression Tests ◽  
X Ray Diffraction ◽  
X Ray

Uniaxial compression tests and hydrostatic tests at pressures up to 27 kbars have been performed to determine operating slip systems in single crystal and polycrystal1ine beryllium. A recent study has been made of wave propagation in single crystal beryllium by shock loading to selectively activate various slip systems, and this has been followed by a study of wave propagation and spallation in textured, polycrystal1ine beryllium. An alteration in the X-ray diffraction pattern has been noted after shock loading, but this alteration has not yet been correlated with any structural change occurring during shock loading of polycrystal1ine beryllium.This study is being conducted in an effort to characterize the effects of shock loading on textured, polycrystal1ine beryllium. Samples were fabricated from a billet of Kawecki-Berylco hot pressed HP-10 beryllium.

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