In this contribution, cylindrical samples consisting of monodisperse soft
(rubber) and stiff (glass) particles are pre-stressed under uniaxial
compression. Acoustic P-waves at ultrasound frequencies are superimposed into
prepared samples with different soft-stiff volume fractions. Earlier
investigations showed the importance of particles networks, i.e. force chains,
in controlling the effective mechanical properties of particulate systems.
Measured P-wave modulus showed a significant decline while more soft particles
are added due to a change in microstructure. However, for small contents of
soft particles, it could be observed that the P-wave modulus is increasing. For
the understanding of such kinds of effects, detailed insight into the
microstructure of the system is required. To gain this information and link it
to the effective properties, we made use of high-resolution micro X-ray
Computed Tomography (micro-XRCT) imaging and combined it with the classical
stiffness characterization. Both performed in situ meaning inside the
laboratory-based XRCT scanner. With micro-XRCT imaging, the granular
microstructure can be visualized in 3d and characterized subsequently. By
post-processing of the data, the individual grains of the particulate systems
could be uniquely identified. Finally, the contact network of the packings
which connects the center of particles was established to demonstrate the
network transition from stiff- to soft-dominated regimes. This has allowed for
unprecedented observations and a renewed understanding of particulate systems.
It has been demonstrated that micro-XRCT scans of particles packings can be
analyzed and compared in 3d to gain extensive information on the scale of the
single particles. Here, the in situ setup and workflow from the start of
acquiring images in situ till the post-processing of the image data is
explained and demonstrated by selected results.Comment: 17 pages, 10 figures, submitted to Survey for Applied Mathematics and
Mechanics (GAMM Mitteilungen
