A Novel Micro-shear Tester for Failure Analysis of Fine and Cohesive Granular Matter
We apply a novel micro-shear tester (μST) to investigate the shear flow behaviour of very small granular volumes (15 μl). We compare the results to standard ring shear devices which confirm that these small volumes are sufficient for granular flow analysis, and hence are helpful to identify the stable and unstable areas of very small granular quantities. Within the laboratory experiments we realised shear tests by using a torsional shear movement which was applied to a cohesive granular calcium carbonate. For the analysis of the shear behaviour the yield loci are used which were derived from the bulk shear and normal stresses. The comparison of the yield loci determined by μST and ring shear device shows only a minor deviation. A particle characterization of the calcium carbonate material according to the particle size distribution with a mean grain size of 5 μm using laser diffraction and determining cohesion forces on single particles with 34 nN using an atomic force microscope (AFM) is part of this study. Finally, we combine a X-ray computed tomography (XCT) with the μST to reveal changes in the microstructure and notice shear bands caused by the shearing process.
KeywordsFailure behaviour Granular flow Micro-shear tester X-ray computed tomography Atomic force microscopy Calcium carbonate
We wish to thank, Stefan Kreiter and Jürgen Tomas for very constructive reviews. We also would like to thank the DFG for financial support within SPP 1486.
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