Orientation of boundaries of planar shear bands in Ni3Fe single crystals

1997 ◽  
Vol 40 (8) ◽  
pp. 764-768 ◽  
Author(s):  
M. P. Kashchenko ◽  
L. A. Teplyakova ◽  
L. V. Lychagin ◽  
A. V. Paul'
Keyword(s):  
Single Crystals ◽  
Shear Bands ◽  
Planar Shear

scholarly journals Symmetric shear banding and swarming vortices in bacterial superfluids

2018 ◽  
Vol 115 (28) ◽  
pp. 7212-7217 ◽  
Author(s):  
Shuo Guo ◽  
Devranjan Samanta ◽  
Yi Peng ◽  
Xinliang Xu ◽  
Xiang Cheng
Keyword(s):  
High Speed ◽  
Shear Banding ◽  
Shear Bands ◽  
Local Stress ◽  
Transport Processes ◽  
Shear Stresses ◽  
Planar Shear ◽  
Collective Motions ◽  
Swimming Bacteria ◽  
Microscopic Origin

Bacterial suspensions—a premier example of active fluids—show an unusual response to shear stresses. Instead of increasing the viscosity of the suspending fluid, the emergent collective motions of swimming bacteria can turn a suspension into a superfluid with zero apparent viscosity. Although the existence of active superfluids has been demonstrated in bulk rheological measurements, the microscopic origin and dynamics of such an exotic phase have not been experimentally probed. Here, using high-speed confocal rheometry, we study the dynamics of concentrated bacterial suspensions under simple planar shear. We find that bacterial superfluids under shear exhibit unusual symmetric shear bands, defying the conventional wisdom on shear banding of complex fluids, where the formation of steady shear bands necessarily breaks the symmetry of unsheared samples. We propose a simple hydrodynamic model based on the local stress balance and the ergodic sampling of nonequilibrium shear configurations, which quantitatively describes the observed symmetric shear-banding structure. The model also successfully predicts various interesting features of swarming vortices in stationary bacterial suspensions. Our study provides insights into the physical properties of collective swarming in active fluids and illustrates their profound influences on transport processes.

Fatigue-induced shear bands in ferritic single crystals

1982 ◽  
Vol 30 (1) ◽  
pp. 273-278 ◽  
Author(s):  
T. Magnin ◽  
A. Fourdeux ◽  
J.H. Driver
Keyword(s):  
Single Crystals ◽  
Shear Bands

Validation of the energy-balance approach to curve-shaped shear-band propagation in soil

2010 ◽  
Vol 467 (2127) ◽  
pp. 627-652 ◽  
Author(s):  
Erich Saurer ◽  
Alexander M. Puzrin
Keyword(s):  
Energy Balance ◽  
Analytical Solution ◽  
Shear Band ◽  
Shear Bands ◽  
Silty Sand ◽  
Catastrophic Failure ◽  
Data Comparison ◽  
Balance Approach ◽  
Planar Shear ◽  
Energy Balance Approach

Progressive and catastrophic failure in soils has been commonly associated with the phenomenon of shear-band propagation. This is a challenging topic, both in terms of understanding and simulation. Most existing studies have focused on the propagation of planar shear bands. This paper is an attempt to analytically model the rate of progressive shear-band propagation in shear-blade tests, especially designed to produce curved shear bands in dense silty sand. The simplified analytical solution is based on fracture mechanics energy balance and on limiting equilibrium approaches. The analytical solution is validated against experimental data. Comparison shows that, despite the simplifications, the energy-balance approach is a useful tool in modelling the rate of non-planar shear-band propagation, both qualitatively and quantitatively.

scholarly journals The Development of Dislocation Structure and Texture in Rolled Copper (001)[110] Single Crystals

1988 ◽  
Vol 10 (1) ◽  
pp. 67-75 ◽  
Author(s):  
M. Wróbel ◽  
S. Dymek ◽  
M. Blicharski ◽  
S. Gorczyca
Keyword(s):  
Electron Microscopy ◽  
Single Crystals ◽  
Dislocation Structure ◽  
Transverse Direction ◽  
Shear Bands ◽  
Taylor Factor ◽  
Initial Orientation ◽  
Slip Systems ◽  
Deformation Bands ◽  
Pole Figures

The initial orientation has split into two equally strong symmetric orientations: (112)[111¯] and (112)[1¯1¯1]. Areas of identical orientation were band shaped and were called deformation bands. Up to 60% reduction, deformation occurs by slip on one plane (one from two possible) in two directions. This leads to the appearance of deformation bands with transition bands between them. Due to such deformation the initial orientation rotates around transverse direction towards the end-orientation {112}〈111〉. Due to rotation of the crystallographic lattice with deformation, the Taylor factor M changes as well, and it causes the activation of two not coplanar slip systems which stabilize the end-orientations {112}〈111〉. Such a sequence of the slip systems activation was concluded from the agreement of the calculated and experimental pole figures. The electron microscopy investigations showed that first shear bands formed due to the activation of these new slip systems.

Microstructure and Texture of Magnesium Single Crystals Processed by ECAP

2010 ◽  
Vol 667-669 ◽  
pp. 355-360
Author(s):  
Petra Šedá ◽  
Aleš Jäger ◽  
Pavel Lejček
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Single Crystals ◽  
Shear Bands ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Face Centered ◽  
Mechanical Twins

Equal channel angular pressing (ECAP) is a promising severe plastic deformation technique for production of ultrafine-grained bulk metals with face centered cubic (fcc) structure. However, the process is often complicated in hexagonal close packed (hcp) metals such as magnesium due to its low forming capability. In this contribution, magnesium single crystals were processed by ECAP through a single pass in order to reveal processes taking place in hcp lattice during severe plastic deformation. The microstructure and texture were investigated by SEM-EBSD. The deformed microstructure contains shear bands, recrystallized regions and mechanical twins. Activity of twinning systems and texture formation are discussed regarding different initial orientation of the single crystals.

Shear bands and microstructure of Al single crystals during rolling

1985 ◽  
Vol 19 (2) ◽  
pp. 185-188 ◽  
Author(s):  
K. Morii ◽  
Y. Nakayama
Keyword(s):  
Single Crystals ◽  
Shear Bands
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