scholarly journals Shear strength and force transmission in granular media with rolling resistance

2008 ◽  
Vol 78 (2) ◽  
Author(s):  
Nicolas Estrada ◽  
Alfredo Taboada ◽  
Farhang Radjaï
Keyword(s):  
Shear Strength ◽  
Granular Media ◽  
Rolling Resistance ◽  
Force Transmission

Thermomechanical Stability of Interphases in Glass Reinforced Composites

1989 ◽  
Vol 170 ◽  
Author(s):  
A. T. Dibenedetto ◽  
Jaime A. Gomez ◽  
C. Schilling ◽  
F. Osterholtz ◽  
G. Haddad
Keyword(s):  
Thermal Stability ◽  
Shear Strength ◽  
Glass Fibers ◽  
Boiling Water ◽  
Reinforced Composites ◽  
Matrix Interface ◽  
Force Transmission ◽  
Silane Coating ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

AbstractThe thermomechanical stability of organosilane surface treatments for E-glass fibers used in fiber reinforced composites was evaluated. The effect of molecular structure of 40 to 80 namometer coatings on the force transmission across the fiber/matrix interface was measured as a function of temperature and exposure to water using a fiber fragmentation test. It was found that phenyl-substituted amino silanes exhibited better thermal stability, but were less resistant to boiling water, than the commierically available γ-amino propyl silanes. A bis-trimethoxy γ-amino propyl silane showed an increase in both the hydrolytic and thermal stability when compared to the commiercial product. A good balance of thermal and hydrolytic stability was also obtained with a methylaminopropyltrimethoxy silane coating.The strain energy released from the glass fibers upon decoupling from the poxy matrix or silane coating was found to be in the range of 145 to 186 g/m2 and varied no more than 20 percent over a temperature range of 25 to 75°C or when exposed to boiling water and then redried. It also varied very little with the silane coating used. In addition, the average shear stress attained at the fiber-matrix interface in an imbedded single fiber test at 25°C was as much as two times higher than the shear strength of the epoxy matrix and as much as five times higher at elevated temperature. These data lead one to the conclusion that the interphase failure in these composites is controlled by a plane strain fracture in the constrained region of the organic phase, near the fiber surface, rather than by the maximum shear strength in the interphase.

scholarly journals Experimental Study of the Composition and Structure of Granular Media in the Shear Bands Based on the HHC-Granular Model

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Guang-jin Wang ◽  
Xiang-yun Kong ◽  
Chun-he Yang
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Granular Media ◽  
Random Distribution ◽  
Shear Bands ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Coarse Grained ◽  
Composition And Structure ◽  
Coarse Grained Soil

The researchers cannot control the composition and structure of coarse grained soil in the indoor experiment because the granular particles of different size have the characteristics of random distribution and no sorting. Therefore, on the basis of the laboratory tests with the coarse grained soil, the HHC-Granular model, which could simulate the no sorting and random distribution of different size particles in the coarse-grained soil, was developed by use of cellular automata method. Meanwhile, the triaxial numerical simulation experiments of coarse grained soil were finished with the different composition and structure soil, and the variation of shear strength was discussed. The results showed that the internal friction angle was likely to reduce with the increasing of gravel contents in the coarse-grained soil, but the mean internal friction angle significantly increased with the increment of gravel contents. It indicated that the gravel contents of shear bands were the major factor affecting the shear strength.

Effects of Rolling Resistance on Shear Behavior and Anisotropy of Granular Matters

2013 ◽  
Vol 631-632 ◽  
pp. 198-204
Author(s):  
Yi Ming Liu ◽  
Hai Jun Mao ◽  
Chun He Yang
Keyword(s):  
Shear Strength ◽  
Discrete Element Method ◽  
Numerical Simulations ◽  
Rolling Resistance ◽  
Discrete Element ◽  
Shear Behavior ◽  
Contact Model ◽  
Biaxial Compression ◽  
Compression Tests ◽  
Dramatic Effect

Standard discrete element method does not take the effect of rolling resistance into account. To overcome this shortcoming, a contact model considering rolling resistance is developed and implemented into PFC2D. Using this contact model, a series of numerical biaxial compression tests are carried out. The results of these numerical simulations show that rolling resistance has remarkable effects on shear strength and shear dilatancy of granular matters, and these trends are agreed with previous studies, which proves that this model works well. Then the effect of rolling resistance on anisotropy of granular matters is studied in this paper. It can be seen that rolling resistance has dramatic effect on the anisotropy of granular matters. The anisotropy of granular matters increases with rolling resistance.

scholarly journals Comparison of the effects of rolling resistance and angularity in sheared granular media

2013 ◽  
Author(s):  
Nicolas Estrada ◽  
Emilien Azéma ◽  
Farhang Radjai ◽  
Alfredo Taboada
Keyword(s):  
Granular Media ◽  
Rolling Resistance

scholarly journals Rolling resistance of shallow granular deformation

2017 ◽  
Vol 473 (2207) ◽  
pp. 20170375
Author(s):  
Keaton J. Burns ◽  
Neil J. Balmforth ◽  
Ian J. Hewitt
Keyword(s):  
Theoretical Model ◽  
Granular Medium ◽  
Granular Media ◽  
Rolling Resistance ◽  
Optical Tracking ◽  
Leading Order ◽  
Air Drag ◽  
Glass Spheres ◽  
Acceleration Data ◽  
Model Predictions

Experiments are conducted to measure the resistance experienced by light cylinders rolling over flat beds of granular media. Sand and glass spheres are used for the beds. The trajectories of the rolling cylinders are determined through optical tracking, and velocity and acceleration data are inferred through fits to these trajectories. The rolling resistance is dominated by a velocity-independent component, but a velocity-dependent drag exceeding the expected strength of air drag is also observed. The results are compared to a theoretical model based on a cohesionless Mohr–Coulomb rheology for a granular medium in the presence of gravity. The model idealizes the flow pattern underneath the rolling cylinder as a plastically deforming zone in front of a rigidly rotating plug attached to the cylinder, as proposed previously for cylinders rolling on perfectly cohesive plastic media. The leading-order, rate-independent rolling resistance observed experimentally is well reproduced by the model predictions.

An Analysis of the Strength of Anisotropic Granular Assemblies via Discrete Methods

2014 ◽  
Vol 553 ◽  
pp. 525-530
Author(s):  
Sergio Andres Galindo-Torres ◽  
Dorival Pedroso ◽  
David Williams ◽  
Hans Mühlhaus
Keyword(s):  
Shear Strength ◽  
Granular Media ◽  
Three Dimensional ◽  
Spherical Particles ◽  
Triaxial Tests ◽  
True Triaxial ◽  
Polyhedral Particles ◽  
Granular Assemblies ◽  
Mean Pressure ◽  
Confining Pressures

This paper presents a study on the macroscopic strength characteristics of granular assemblies with three-dimensional complex-shaped particles. Different assemblies are considered, with both isotropic and anisotropic particle geometries. The study is conducted using the Discrete Element Method (DEM), with so-called sphero-polyhedral particles, and simulations of mechanical true triaxial tests for a range of Lode angles and confining pressures. The observed mathematical failure envelopes are investigated in the Haigh-Westergaard stress space, as well as on the deviatoric-mean pressure plane. It is verified that the DEM with non-spherical particles produces results that are qualitatively similar to experimental data and previous numerical results obtained with spherical elements. The simulations reproduce quite well the shear strength of assemblies of granular media, such as higher strength during compression than during extension. In contrast, by introducing anisotropy at the particle level, the shear strength parameters are greatly affected, and an isotropic failure criterion is no longer valid. It is observed that the strength of the anisotropic assembly depends on the direction of loading, as observed for real soils.

Shear strength and stress distribution in wet granular media

2009 ◽  
Author(s):  
Vincent Richefeu ◽  
Farhang Radjaï ◽  
Moulay Saïd El Youssoufi ◽  
Masami Nakagawa ◽  
Stefan Luding
Keyword(s):  
Shear Strength ◽  
Stress Distribution ◽  
Granular Media
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