A Molecular Dynamics approach has been used to compute the shear force resulting from the shearing of disks. Two‐dimensional mono‐disperse disks have been put in an horizontal and…
Abstract
A Molecular Dynamics approach has been used to compute the shear force resulting from the shearing of disks. Two‐dimensional mono‐disperse disks have been put in an horizontal and rectangular shearing cell with periodic boundary conditions on right and left hand sides. The shear is applied by pulling the cover of the cell either at a constant rate or by pulling a spring, linked to the cover, with a constant force. Depending on the rate of shearing and on the elasticity of the whole set‐up, we showed that the measured shear force signal is either irregular in time, regular in time but not in shape, or regular in shape.
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O. Pozo, B. Soulestin and N. Olivi‐Tran
We set up an original apparatus to measure the grain grain friction stress inside a granular medium composed of sodo‐silicate‐glass beads surrounded by a water vapor atmosphere.We…
Abstract
We set up an original apparatus to measure the grain grain friction stress inside a granular medium composed of sodo‐silicate‐glass beads surrounded by a water vapor atmosphere.We analyze here the influence of the physico chemistry of water on our glass beads and its consequences on our shear experiment. We found two scales in the analysis of the shear stress signal. On the microscopic scale of one bead, the experimental results show a dependence on the size of beads, on the shear rate and on humidity for the resulting stick slip signal. On the macroscopic scale of the whole assembly of beads, the behavior of the total amplitude of the shear stress depends on the size of the beads and is humidity dependent only for relative humidity larger than 80%. For high degrees of humidity, on the microscopic scale, water lubricates the surface of the beads leading to a decrease in the microscopic resistance to shear while on the macroscopic scale the resistance to shear is increased: the assembly of very humid grains behaves as a rheothickening fluid.
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This paper presents a unified framework to model the sintering process of fine powders. The framework is based on classical virtual power principle and its corresponding…
Abstract
This paper presents a unified framework to model the sintering process of fine powders. The framework is based on classical virtual power principle and its corresponding variational principle. Firstly, the classical models of solid state, viscous and liquid phase sintering are reproduced assuming single matter re‐distribution mechanism and using the virtual power principle as the starting point. Then we demonstrate how to obtain the governing equations for microstructural evolution using the variational principle. These provide a common thread through the existing sintering models. Finally a numerical solution scheme is briefly outlined for computer simulation of microstructural evolution using the variational principle as the starting point. The computer simulation can follow the entire sintering process from powder compact to fully dense solid and deal with fully couple multi‐physics processes involving all the possible underlying matter re‐distribution mechanisms. Several examples are provided to demonstrate the deep insights that can be gained into the sintering process by using the numerical tool.