A flow visualization and superposition rheology study of shear-banding wormlike micelle solutions

Soft Matter ◽  
2016 ◽  
Vol 12 (4) ◽  
pp. 1051-1061 ◽  
Author(s):  
Hadi Mohammadigoushki ◽  
Susan J. Muller
Keyword(s):  
Diffusion Coefficient ◽  
Flow Visualization ◽  
Correlation Length ◽  
Micellar Solution ◽  
Shear Banding ◽  
Shear Bands ◽  
Wormlike Micelle ◽  
Concentric Cylinders ◽  
Stress Diffusion ◽  
Taylor Couette

In this paper, we use rheometry and flow visualization to study the dynamics of the interface between shear bands in a wormlike micellar solution sheared between concentric cylinders, i.e., in a Taylor–Couette (TC) cell, and to evaluate the stress diffusion coefficient and the stress correlation length in the Johnson–Segalman model.

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.

scholarly journals Non-trivial avalanches triggered by shear banding in compression of metallic glass foams

2020 ◽  
Vol 476 (2240) ◽  
pp. 20200186
Author(s):  
H. Lin ◽  
C. lu ◽  
H. Y. Wang ◽  
L. H. Dai
Keyword(s):  
Metallic Glass ◽  
Scaling Laws ◽  
Waiting Times ◽  
Shear Banding ◽  
Shear Bands ◽  
Mean Field ◽  
Structural Disorder ◽  
Aftershock Sequence ◽  
Atomic Scale ◽  
Characteristic Time Scale

Ductile metallic glass foams (DMGFs) are a new type of structural material with a perfect combination of high strength and toughness. Owing to their disordered atomic-scale microstructures and randomly distributed macroscopic voids, the compressive deformation of DMGFs proceeds through multiple nanoscale shear bands accompanied by local fracture of cellular structures, which induces avalanche-like intermittences in stress–strain curves. In this paper, we present a statistical analysis, including distributions of avalanche size, energy dissipation, waiting times and aftershock sequence, on such a complex dynamic process, which is dominated by shear banding. After eliminating the influence of structural disorder, we demonstrate that, in contrast to the mean-field results of their brittle counterparts, scaling laws in DMGFs are characterized by different exponents. It is shown that the occurrence of non-trivial scaling behaviours is attributed to the localized plastic yielding, which effectively prevents the system from building up a long-range correlation. This accounts for the high structural stability and energy absorption performance of DMGFs. Furthermore, our results suggest that such shear banding dynamics introduce an additional characteristic time scale, which leads to a universal gamma distribution of waiting times.

Time-dependent shear rate inhomogeneities and shear bands in a thixotropic yield-stress fluid under transient shear

Soft Matter ◽  
2019 ◽  
Vol 15 (39) ◽  
pp. 7956-7967 ◽  
Author(s):  
Yufei Wei ◽  
Michael J. Solomon ◽  
Ronald G. Larson
Keyword(s):  
Shear Rate ◽  
Yield Stress ◽  
Fumed Silica ◽  
Shear Banding ◽  
Shear Bands ◽  
Flow Reversal ◽  
Time Dependent ◽  
Yield Stress Fluid ◽  
Silica Suspension

We study the rheological responses and shear-rate inhomogeneities and shear banding behaviors of a thixotropic fumed silica suspension in shear startup tests and flow reversal tests.

The influence of material non-uniformity preceding shear-band formation in a model for granular flow

1997 ◽  
Vol 8 (5) ◽  
pp. 457-483 ◽  
Author(s):  
DAVID G. SCHAEFFER ◽  
MICHAEL SHEARER
Keyword(s):  
Shear Band ◽  
Material Properties ◽  
Shear Banding ◽  
Shear Bands ◽  
Small Variation ◽  
Band Formation ◽  
Time Period ◽  
Single Location ◽  
Change Of Type ◽  
Short Time

The onset of shear-banding in a deforming elastoplastic solid has been linked to change of type of the governing partial differential equations. If uniform material properties are assumed, then (i) deformations prior to shear-banding are uniform, and (ii) the onset of shear-banding occurs simultaneously at all points in the sample. In this paper we study, in the context of a model for anti-plane shearing of a granular material, the effect of a small variation in material properties (e.g. in yield strength) within the sample. Using matched asymptotic expansions, we find that (i) the deformation is extremely non-uniform in a short time period immediately preceding the formation of shear-bands; and (ii) generically, a shear-band forms at a single location in the sample.

Shear band characteristics in high strain rate naval applications

2019 ◽  
Author(s):  
Michael J. P. Conway ◽  
James D. Hogan
Keyword(s):  
High Speed ◽  
Dynamic Compression ◽  
Shear Banding ◽  
Shear Bands ◽  
Critical Time ◽  
Strain Rates ◽  
Static Case ◽  
Dynamic Experiments ◽  
Naval Steels ◽  
Strain Responses

Abstract This paper explores the dynamic behavior of HSLA 65 naval steels, specifically focusing on the initiation and growth of shear bands in quasi-static and dynamic compression experiments and how these bands affect stress-strain responses. The results indicate that the yield strength for this HSLA 65 increases from 541 ± 8 MPa for quasi-static (10-3 s-1) to 1081 ± 48 MPa for dynamic rates 1853 ± 31 s-1, and the hardening exponent increases from 0.376 ± 0.028 for quasi-static to 0.396 ± 0.006 for dynamic rates. Yield behavior was found to be associated with the onset of shear banding for both strain-rates, confirmed through visualization of the specimen surface using high-speed and ultra-high-speed cameras. For the quasi-static case, shear banding and yielding was observed to occur at 2.5% strain, and were observed to grow at speeds of upwards of 38 mm/s. For the dynamic experiments, the shear banding begins at approximately 1.18 ± 0.06% strain and these can grow upwards of 2122 ± 213 m/s during post-yield softening. Altogether, these measurements are some of the first of their kind in the open literature, and provide guidance on the critical time and length scales in shear banding. This information can be used in the future to design more failure-resistant steels, which has broader applications in construction, defense, and natural resource industries.

Stress Driven Shear Bands and the Effect of Confinement on Their StructuresA Rheological, Flow Visualization, and Rheo-SALS Study

Langmuir ◽  
2005 ◽  
Vol 21 (20) ◽  
pp. 9051-9057 ◽  
Author(s):  
Vishweshwara Herle ◽  
Peter Fischer ◽  
Erich J. Windhab
Keyword(s):  
Flow Visualization ◽  
Shear Bands

Fast and efficient MPM solver for strain localization problems

2020 ◽  
Author(s):  
Antoine Guerin ◽  
Emmanuel Wyser ◽  
Yury Podladchikov ◽  
Michel Jaboyedoff
Keyword(s):  
Strain Localization ◽  
Strain Softening ◽  
Yield Criterion ◽  
Pure Shear ◽  
Shear Banding ◽  
Shear Bands ◽  
Material Point Method ◽  
Material Point ◽  
Point Method ◽  
Mapping Algorithm

<p><span><span>Strain localization problems, i.e., shearbandings, have received a lot of interest, especially when strain softening is disregarded from the elasto-plastic consistution relationship. Indeed, reproducing correctly oriented shear bands without softening allows to overcome the mesh-depenency problem. Our work focuses on a Material Point Method (MPM) implementation of strain localization to i) study the behavior of shear bands in order to ii) assess the capabilities of this quite recent numerical method. </span></span></p><p><span><span>To study strain localization and shear banding, we developped an efficient numercial Material Point Method (MPM) solver in Matlab, based on the Update Stress Last (USL) scheme enriched with the Generalized Interpolation Material Point (GIMP) variant, which fixes a major flaw of any MPM solver: the cell-crossing error due to discontinuous gradient of the basis functions. This home-made solver allows us to study strain localizations in either a fixed or continuously deforming continuum. The algorithm solves explicitly momentum equations in an updated lagrangian manner similarly to an explicit FEM solver. We therefore investigate the compression of an elasto-plastic domain under pure shear condition, thus reproducing the geometrical settings and pure shear conditions used in Duretz et al. (2018). Strain softening is disregarded since we do not want any mesh dependence within the solver. A Mohr-Coulomb yield criterion was selected and plasticity was computed by a return mapping algorithm, i.e., we did not use consistent tangent operator. Localization is triggered by a weaker circular inculsion in the center of the domain.. </span></span></p><p><span><span>Preliminary results demonstrates the suitability of the MPM solver to reproduce the correct shearbanding behavior under compression, for both static and dynamic meshes. The higher the resolution, the more accurate are the shear bands. Naturally, this implies future implementations of the solver in a GPU-accelerated environment to increase the numerical resolution. </span></span></p>

On the Stability of Taylor - Couette Flow With Axial Flow

2012 ◽  
Author(s):  
Emna Berrich ◽  
Fethi Aloui ◽  
Jack Legrand
Keyword(s):  
Flow Direction ◽  
Axial Flow ◽  
Diffusion Method ◽  
Diffusion Limit ◽  
Taylor Flow ◽  
Concentric Cylinders ◽  
Reflected Light ◽  
Helical Vortices ◽  
Taylor Couette ◽  
The Stability

An experimental investigation of Taylor-Couette flows with axial flow is presented. Two techniques are used: Visualization using the Kalliroscope and Electro-diffusion method using electrochemical probes. The fluid is confined between concentric cylinders. It is constituted by an electrochemical solution seeding with 2% of a rheoscopic liquid AQ-1000 (Kalliroscope Corp., U.S.A.). The rheoscopic liquid contains small particles reflecting light in dependence on their orientation imposed by the flow direction. The reflected light intensity of Kalliroscope flakes allows a qualitative study of the flow. While the polarography technique allows the measurement of diffusion limit current intensities delivered by the electrochemical probes. The frequency responses of the probe to the flow allow the determination of the instantaneous and local mass transfer and the instantaneous wall shear rate. Two protocols were adopted to study the effect of an axial flow superposed to Couette-Taylor flows and the history flow effect. The first one consists to impose an azimuthal flow to the inner cylinder. When the regime was established, we superposed the axial flow. This protocol was named “the direct protocol”. While the second protocol consists to impose firstly the axial flow on the gap of the system then the azimuthal flow. We named it “the inverse protocol”. We demonstrated that the Couette-Taylor flow with axial flow is strongly dependent on the flow history (the protocol). For the same Taylor number and axial Reynolds number, the resulting flow is completely different. An axial flow superposed to Couette-Taylor flow can delay the instabilities apparition; generate the displacement of the Taylor vortices in the same direction as the axial flow or in the opposite direction; and modify the instability character of the flow by developing helical vortices or wavy helical vortices.

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