scholarly journals Flows of cohesive granular media

2021 ◽  
Vol 249 ◽  
pp. 01001
Author(s):  
Sandip Mandal ◽  
Adrien Gans ◽  
Maxime Nicolas ◽  
Olivier Pouliquen
Keyword(s):  
Granular Media ◽  
Flow Behavior ◽  
Constitutive Relations ◽  
Shear Banding ◽  
Plane Shear ◽  
Simple Method ◽  
Plastic Properties ◽  
Shear Cell ◽  
Numerical Studies ◽  
Long Time

Cohesive granular media have broad applications in industries. However, our understanding of their flow behavior is still limited compared to dry granular media, although rich knowledge about their static and plastic properties has been gained. In this paper, we provide some insights into the flow behavior of cohesive granular media from our recent numerical studies using an inclined plane and a plane shear cell. We evidence that the cohesive nature of flows is significantly affected by material properties of the particles like stiffness and inelasticity in addition to the inter-particle adhesion and introduce the concept of “effective” adhesion, which incorporates the effects of these three variables. We propose constitutive relations involving dimensionless inertial number and “effective” cohesion number, based on the “effective” adhesion to describe the rheology. We also show that increasing adhesion increases the hysteresis in granular media, evidencing the existence of a prominent shear weakening branch in the friction coefficient versus inertial number rheological curve. Moreover, we reveal that this increasing hysteresis gives rise to the increasing occurrence of shear banding instability, pointing to the increasing possibility of jamming in cohesive granular media. Finally, we present a promising experimental approach to investigate the flow behavior of cohesive granular materials, based on a simple method of preparing a long time stable medium with a controlled adhesion between particles.

scholarly journals Rheology of Cohesive Granular Media: Shear Banding, Hysteresis, and Nonlocal Effects

2021 ◽  
Vol 11 (2) ◽  
Author(s):  
Sandip Mandal ◽  
Maxime Nicolas ◽  
Olivier Pouliquen
Keyword(s):  
Granular Media ◽  
Shear Banding ◽  
Nonlocal Effects

THE COMPOSITION DEVELOPMENT AND TECHNOLOGICAL RESEARCH OF THE ANTI-SCAR ECTOIN GEL

2021 ◽  
pp. 216-221
Author(s):  
Mayorova A.V. ◽  
Sysuev B.B. ◽  
Sysueva Y.V.
Keyword(s):  
Colloidal Stability ◽  
Protective Action ◽  
Topical Therapy ◽  
Hydrophobic Effect ◽  
Drying Characteristics ◽  
Plastic Properties ◽  
Technological Research ◽  
Technological Characteristics ◽  
Long Time ◽  
External Characteristics

The development of new means for topical therapy and prevention of scar formation of moisturizing and protective action based on ectoin can be promising. The optimal form is hydrogels, because of their adhesive and plastic properties, easily distribution and remaining for a long time on the skin. The purpose of this study was the development of the composition and technological research of the gel with ectoin for the prevention of skin scars. To select the optimal gel-forming agents’ technological studies (external characteristics, drying characteristics and film quality on the skin and on model surfaces, skin moisture, pH, the active substance release, thermal and colloidal stability, rheological properties) of model samples based on gel-forming agents, used in protective and anti-scar creams carried out. The composition of polymers xanthan and sodium carboxymethyl cellulose selected, which has improved adhesion and moisturizing properties, to reduce the frequency of application and provide a prolonged effect. The optimal concentration of dimethicone to enhance the protective effect and enhance the hydrophobic effect selected. The technological characteristics of model samples of ectoin gel investigated: description, pH, thermal and colloidal stability, viscosity, microbiological purity. The results indicate that the gel has the necessary technological characteristics that determine its quality. Thus, as a result of technological research, the composition of the anti-scar ectoin gel was developed.

scholarly journals The influence of pavement degradation caused by cyclic loading on its failure mechanisms

2016 ◽  
Vol 11 (3) ◽  
pp. 179-187 ◽  
Author(s):  
Marcin Gajewski ◽  
Stanisław Jemioło
Keyword(s):  
Yield Condition ◽  
Limit Load ◽  
Flow Rule ◽  
Smooth Approximation ◽  
Simple Method ◽  
Plastic Properties ◽  
The Road ◽  
Plastic Materials ◽  
Number Of Cycles ◽  
Elastic Plastic Materials

In this paper, a simple method is proposed to estimate capacity of multilayered road structure including the degradation of the elastic and plastic properties of the constituent materials. In the study boundary value problem modeling interaction of wheels with road surface layer in the frame of large deformation theory for elastic-plastic materials was formulated. Plastic properties of the material were described by the flow rule un-associated with yield condition. The Coulomb-Mohr yield condition was assumed and the potential for plasticity is its smooth approximation. In addition, in constitutive modeling the dependence of the Young’s modulus and cohesion of the material from the number of cycles is taken into account. This paper presents qualitative findings in relation to mechanical behavior of the road structure, i.e., for example, the development of plastic zones with increasing load for un-degraded and degraded materials. In addition, a parametric study of the influence of the degradation ratio of the elasticity and plasticity properties for road structure failure mechanism (limit load value) was made.

Long-time evolution and regions of existence of parametrically excited nonlinear cross-waves in a tank

1989 ◽  
Vol 209 ◽  
pp. 249-263 ◽  
Author(s):  
Lev Shemer ◽  
Eliezer Kit
Keyword(s):  
Boundary Condition ◽  
Parametric Excitation ◽  
Wave Breaking ◽  
Model Equation ◽  
Numerical Study ◽  
Parametrically Excited ◽  
Numerical Studies ◽  
Scaling Procedure ◽  
Long Time ◽  
Cross Waves

Results of an experimental and numerical study of parametrically excited nonlinear cross-waves in the vicinity of the cut-off frequency, are reported. Experiments are performed at three cross-wave modes and in the whole range of existence of cross-waves. Numerical studies are based on the solution of the nonlinear Schrödinger equation with a boundary condition at the wavemaker which corresponds to parametric excitation. The validity of the scaling procedure adopted in the model is verified experimentally. Dissipation is incorporated in the model equation and in the wavemaker boundary condition. The influence of the wave breaking on the range of existence of cross-waves is discussed and the relation between the maximum possible steepness of cross-waves and the limits of their existence is obtained.

Explicit Finite Element Simulation of Granular Flow in an Annular Shear Cell

2009 ◽  
Author(s):  
M. A. Kabir ◽  
C. F. Higgs ◽  
M. R. Lovell ◽  
V. Jasti ◽  
M. C. Marinack
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Granular Flow ◽  
High Speed ◽  
Flow Behavior ◽  
Shear Cell ◽  
Explicit Finite Element Method ◽  
Explicit Finite Element ◽  
Annular Shear Cell ◽  
Element Method

Explicit finite element method modeling of granular flow behavior in an annular shear cell has been studied and presented in this paper. The explicit finite element method (FEM) simulations of granular flow in an annular shear cell with around 1633 particles were performed, where the inner wheel rotated at a very high speed and the outer disk remained stationary. The material properties of the particles and the outer wheel were defined as elastic steel whereas the inner wheel was elastic aluminum. In this investigation, the explicit FEM model mimicked granular flow in an experimental set up where the inner wheel was rotated at a speed of 240 rpm. The FEM results for shearing motion and solid fraction were compared with experimental results from a granular shear cell.

Response of Honeycombs Subjected to In-Plane Shear

2016 ◽  
Vol 83 (6) ◽  
Author(s):  
Youming Chen ◽  
Raj Das ◽  
Mark Battley
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Young’S Modulus ◽  
Cell Walls ◽  
Young's Modulus ◽  
Constitutive Relations ◽  
Length Ratio ◽  
Plane Shear ◽  
Base Materials ◽  
Vertical Cell

Study on the response of honeycombs subjected to in-plane shear helps establish the constitutive relations for honeycombs and shed light on the mechanics of cellular materials. The present study explores the nonlinear elastic response of honeycombs under in-plane shear by analyzing the large deflection of cell walls in a unit cell. Governing equations are established which relate the macroscopic response of honeycombs to the deflection of cell walls. Solving these equations, the behavior of regular honeycombs under in-plane shear along horizontal (X) and vertical (Y) directions was investigated. It is found that the response of regular honeycombs under in-plane shear depends on the nondimensional shear stress which is a parameter combining the thickness-to-length ratio of cell walls, the Young's modulus of base materials, and macroscopic shear stress. Lateral shrinking is a distinctive characteristic for honeycombs under in-plane shear, which should be taken into account when establishing constitutive relations and performing simple shear experiments. Expressions for predicting the shear strength of honeycombs are formulated in this paper. It is noted that the normalized shear strength of regular honeycombs depends on two ratios: the thickness-to-length ratio of cell walls and the ratio of Young's modulus to yield strength of base materials, and the former has a dominant effect. By comparing honeycombs with cell walls of uniform thickness against honeycombs with vertical cell walls of double thickness, it is found that doubling the thickness of vertical cell walls of honeycombs increases their shear strength along horizontal (X) direction nearly twice, but does not improve the shear strength that much along the vertical (Y) direction.

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