New Methodology for Steady-State Friction Measurements of Granular Materials Under Pressure

2016 ◽  
pp. 105-113
Author(s):  
M. Bek ◽  
J. Gonzalez-Gutierrez ◽  
I. Emri
Keyword(s):  
Steady State ◽  
Granular Materials ◽  
Friction Measurements

Molecular Dynamics Study of Cohesionless Granular Materials: Size Segregation by Shaking

1993 ◽  
Vol 07 (09n10) ◽  
pp. 1865-1872 ◽  
Author(s):  
Toshiya OHTSUKI ◽  
Yoshikazu TAKEMOTO ◽  
Tatsuo HATA ◽  
Shigeki KAWAI ◽  
Akihisa HAYASHI
Keyword(s):  
Molecular Dynamics ◽  
Steady State ◽  
Specific Gravity ◽  
Pressure Gradient ◽  
Granular Materials ◽  
Buoyancy Force ◽  
Temporal Evolution ◽  
Particle Radius ◽  
Size Segregation ◽  
Increasing Function

The Molecular Dynamics technique is used to investigate size segregation by shaking in cohesionless granular materials. Temporal evolution of the height h of the tagged particle with different size and mass is measured for various values of the particle radius and specific gravity. It becomes evident that h approaches the steady state value h∞ independent of initial positions. There exists a threshold of the specific gravity of the particle. Below the threshold, h∞ is an increasing function of the particle size, whereas above it, h∞ decreases with increasing the particle radius. The relaxation time τ towards the steady state is calculated and its dependence on the particle radius and specific gravity is clarified. The pressure gradient of pure systems is also measured and turned out to be almost constant. This suggests that the buoyancy force due to the pressure gradient is not responsible to h∞.

Novel Friction Test Structures for Microelectromechanical Systems

2006 ◽  
Author(s):  
Luke J. Currano ◽  
Miao Yu ◽  
Balakumar Balachandran
Keyword(s):  
Steady State ◽  
Friction Coefficient ◽  
Smooth Surface ◽  
Microelectromechanical Systems ◽  
Rough Surfaces ◽  
Sliding Contact ◽  
Silicon Surfaces ◽  
Mems Devices ◽  
Friction Test ◽  
Friction Measurements

Novel friction test structures that are suitable for determining the friction coefficient of vertical surfaces in microelectromechanical systems (MEMS) devices are fabricated and used to carry out friction measurements on smooth and rough deep reactive ion etched (DRIE) silicon surfaces. The results obtained for rough surfaces show that the friction coefficient decreases as the sliding contact is put through the first eight to ten cycles, before it reaches a steady-state value that closely matches the friction coefficient of the smooth surface.

Dynamics of Granular Compaction

1997 ◽  
Vol 07 (05) ◽  
pp. 1159-1165 ◽  
Author(s):  
Hisao Hayakawa ◽  
Daniel C. Hong
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Granular Materials ◽  
Hard Sphere ◽  
Dimensionless Parameter ◽  
Preliminary Investigation ◽  
State Density ◽  
Dynamic Evolution ◽  
Initial State ◽  
Granular Compaction

We investigate the way the disordered granular materials organize themselves in a vibrating bed, the intensity of which is given by the dimensionless parameter Γ. Based on the recognition that an assembly of mono-disperse and cohesionless granular materials is a collection of spinless hard sphere Fermions, we first demonstrate that the time averaged steady state density profile for weak excitation with Γ ≈ 1 is given by the Fermi distribution. This is consistent with the observed experimental data and the results of Molecular dynamics. We then present a dynamic model to study the dynamics of granular compaction, namely the dynamic evolution of the initial state ultimately relaxing toward this steady state. Our preliminary investigation reveals that the relaxation is exponential, which is not inconsistent with the available experimental data for low Γ.

Force Propagation of Flow of Granular Materials through an Orifice in Start up Stage

2012 ◽  
Vol 249-250 ◽  
pp. 807-811
Author(s):  
Hai Ping Zhu ◽  
Bo Shi Xia ◽  
Ai Bing Yu
Keyword(s):  
Steady State ◽  
Discrete Element Method ◽  
Granular Materials ◽  
Early Stage ◽  
Discrete Element ◽  
Granular Bed ◽  
Flat Bottom ◽  
Start Up ◽  
Force Propagation ◽  
Element Method

In this paper, early stage of granular materials flowing through the orifice of a cuboid hopper with flat bottom is investigated based on the results generated by using the discrete element method. The results show that in the start up stage of the flow, a switch curve is formed between static and flowing particles, and a force arch on which the forces are very small is generated below the switch curve. Both curves propagate into the granular bed with the discharge of particles, and reach the top of the bed when a steady state is achieved.

scholarly journals Steady state rheology of homogeneous and inhomogeneous cohesive granular materials

2019 ◽  
Vol 22 (1) ◽  
Author(s):  
Hao Shi ◽  
Sudeshna Roy ◽  
Thomas Weinhart ◽  
Vanessa Magnanimo ◽  
Stefan Luding
Keyword(s):  
Steady State ◽  
Granular Materials ◽  
Volume Fraction ◽  
Bond Number ◽  
Contact Friction ◽  
Volume Fractions ◽  
Wide Range ◽  
Homogeneous Stress ◽  
Shear Box ◽  
Opposing Effects

AbstractThis paper aims to understand the effect of different particle/contact properties like friction, softness and cohesion on the compression/dilation of sheared granular materials. We focus on the local volume fraction in steady state of various non-cohesive, dry cohesive and moderate to strong wet cohesive, frictionless-to-frictional soft granular materials. The results from (1) an inhomogeneous, slowly sheared split-bottom ring shear cell and (2) a homogeneous, stress-controlled simple shear box with periodic boundaries are compared. The steady state volume fractions agree between the two geometries for a wide range of particle properties. While increasing inter-particle friction systematically leads to decreasing volume fractions, the inter-particle cohesion causes two opposing effects. With increasing strength of cohesion, we report an enhancement of the effect of contact friction i.e. even smaller volume fraction. However, for soft granular materials, strong cohesion causes an increase in volume fraction due to significant attractive forces causing larger deformations, not visible for stiff particles. This behaviour is condensed into a particle friction—Bond number phase diagram, which can be used to predict non-monotonic relative sample dilation/compression.

Origins of granular memory in model sandpiles

1999 ◽  
Vol 02 (04) ◽  
pp. 339-348 ◽  
Author(s):  
G. C. Barker ◽  
Anita Mehta
Keyword(s):  
Steady State ◽  
Granular Materials ◽  
Lattice Model ◽  
Degrees Of Freedom ◽  
Statistical Properties ◽  
Intermittent Flow ◽  
Surface Dynamics ◽  
Coupled Dynamics ◽  
Grain Orientations

We describe a lattice model for intermittent flow in granular materials. This model includes degrees of freedom, related to lattice grain orientations, that are additional to those associated with the coupled dynamics of columns of lattice grains. We have explored the development of granular structures in model piles and shown that the surface dynamics of lattice grains is strongly linked to relaxations of granular structures in the pile. The coupling is shown to lead to two distinct avalanche morphologies in model piles that have been disturbed from their steady state. The change of behaviour is explained in terms of the statistical properties of surface instabilities.

The wear of metal-on-metal total hip prostheses measured in a hip simulator

2001 ◽  
Vol 215 (6) ◽  
pp. 523-530 ◽  
Author(s):  
S C Scholes ◽  
S M Green ◽  
A Unsworth
Keyword(s):  
Steady State ◽  
Wear Test ◽  
Wear Testing ◽  
Radial Clearance ◽  
Hip Prostheses ◽  
Wear Rates ◽  
Joint Friction ◽  
Metal On Metal ◽  
Before And After ◽  
Friction Measurements

New generation metal-on-metal prostheses have been introduced to try and overcome the problem of osteolysis often attributed to the wear particles of the polyethylene component of conventional metal-on-ultra-high molecular weight polyethylene (UHMWPE) joints. The wear rates of four metal-on-metal joints (two different clearances) were assessed along with that of a conventional metal-on-UHMWPE joint. Friction measurements of the metal-on-metal joints were taken before and after the wear test and compared. Two distinct wear phases were discernible for all the metal-on-metal joints: an initial wear phase up to 0.5 × 106 cycles and then a lower steady state wear phase. The steady state wear rate of the 22 μUm radial clearance metal-on-metal joint was lower than that for the 40 μUm radial clearance joint, although this difference was not found to be significant ( p > 0.15). The wear rates for all the joints tested were consistent with other simulator studies. The friction factors produced by each joint were found to decrease significantly after wear testing ( p < 0.05).

scholarly journals From solid to granular gases: the steady state for granular materials

2013 ◽  
Vol 37 (17) ◽  
pp. 2937-2951 ◽  
Author(s):  
D. Vescovi ◽  
C. di Prisco ◽  
D. Berzi
Keyword(s):  
Steady State ◽  
Granular Materials ◽  
Granular Gases

scholarly journals Strength of Granular Materials in Transient and Steady State Rapid Shear

2015 ◽  
Vol 103 ◽  
pp. 237-245 ◽  
Author(s):  
Ryan C. Hurley ◽  
José E. Andrade
Keyword(s):  
Steady State ◽  
Granular Materials ◽  
Transient And Steady State
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