| 1. |
- Hall, Stephen, et al.
(författare)
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Experimental characterisation of (localised) deformation phenomena in granular geomaterials from sample down to inter- and intra-grain scales
- 2012
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Ingår i: Procedia Iutam. - : Elsevier BV. - 2210-9838. ; 4, s. 54-65
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Tidskriftsartikel (refereegranskat)abstract
- This paper outlines some recent advances in the full-field experimental characterisation of the mechanics of granular geomaterials (in particular, sands) using a range of methods that provide characterisation at different scales, from the sample-scale down to the inter- and intra-grain scale. The techniques used are “full-field” approaches involving in-situ x-ray micro-tomography, 3D-volumetric digital image analysis/correlation and grain ID-tracking, in-situ 3D x-ray diffraction and in-situ, spatially-resolved neutron diffraction. These methods provide new data on the mechanics of sand at different scales, including continuum measures of strain, porosity, and fabric plus discrete measures of particle kinematics and force transmission. The results of such measurements might be used to advance higher-order continuum theories, and provide the necessary input parameters, or to calibrate discrete grain-scale simulations of sand behaviour to explore loading paths that are inaccessible in the laboratory.
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| 2. |
- Sjödahl, Mikael, et al.
(författare)
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Digital volume correlation applied to compaction of granular materials
- 2012
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Ingår i: Procedia IUTAM. - : Elsevier BV. - 2210-9838. ; 4, s. 179-195
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Tidskriftsartikel (refereegranskat)abstract
- Compaction of powders and granular materials is an important process used to manufacture products including pharmaceuticals, ceramics, metals and explosives. In order to ensure mechanical integrity of the final product, an understanding of the compaction process, with particular reference to the homogeneity of the compacted bed, is required. In particular, it is necessary to have an improved understanding of the physics of the process, which can only be achieved through appropriate experimental measurements. X-ray tomography offers the opportunity to make full-field measurements of displacements in-situ: without removing the specimens from the die. This allows researchers to better understand the processes that take place at different stages in the compaction, and to more rigorously test numerical models.In this paper, we present data obtained using Digital Volume Correlation (DVC) to measure displacements in a compacted bed of sugar, with data obtained using X-ray microtomograpy. Instead of adding tracer particles, the natural, random, microstructure of the bed is used as the pattern for the volume correlation. The displacement data obtained are then used to calculate strain fields in the bed. A novel Finite Element (FE) based smoothing technique is applied to robustly smooth the data, allowing accurate and continuous strains to be calculated. These strains are compared to those calculated from the unsmoothed data. The paper presents details of both the DVC and FE smoothing routines
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