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Flow patterns in quasi-static deformation of dry granular materials

Viswanathan, K and Mahato, A and Chandrasekar, S and Murthy, TG and Koziara, T (2015) Flow patterns in quasi-static deformation of dry granular materials. In: 3rd International Symposium on Geomechanics from Micro to Macro, SEP 01-03, 2014, Univ Cambridge, Cambridge, ENGLAND, pp. 147-152.

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Official URL: http://dx.doi.org/10.1201/b17395-25

Abstract

We present an experimental and numerical study of the flow fields in slow deformation of a granular ensemble, composed of hard spherical, monodisperse particles. The model system is that of indentation by a flat punch under approximately plane-strain conditions. In the experiments, the region around the punch is imaged in-situ using a high speed imaging system. Flow parameters such as spatial velocity and strain are characterized using a hybrid image analysis technique. The deformation field shows various interesting features that resemble the deformation fields in the indentation of both metals and fluids. The formation of a stagnant zone right under the punch is strikingly similar to the slipline field solution for plane-strain punch indentation in plastically deforming metals. Also, regions of highly rotational flow are observed in the vicinity of the punch, resembling vortices and recirculation zones past sharp corners in fluid flow. These features illustrate the complex microscopic mechanisms underlying the deformation of granular materials, which precludes precise analysis using simple continuum constitutive laws. To better understand the microscopic mechanisms, we present numerical simulations of punch indentation using the discrete particle non-smooth contact dynamics method. By modelling the particles as perfect rigid bodies with simple Coulomb friction, it is seen that the experimental flow patterns are reproduced semi-quantitatively. The full 3D displacement field confirms the existence of local regions of non-zero vorticity and the formation of a stagnation zone under the punch. This simple model problem perhaps illustrates the difficulty involved in formulating a micromechanical description of the deformation, based on the connectivity of the grain network.

Item Type: Conference Proceedings
Additional Information: Copy right for this article belongs to the CRC PRESS-TAYLOR & FRANCIS GROUP, 6000 BROKEN SOUND PARKWAY NW, STE 300, BOCA RATON, FL 33487-2742 USA
Department/Centre: Division of Mechanical Sciences > Civil Engineering
Depositing User: Id for Latest eprints
Date Deposited: 28 Oct 2016 06:46
Last Modified: 28 Oct 2016 06:46
URI: http://eprints.iisc.ac.in/id/eprint/54799

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