Structural analysis and tracking of micron-sized glass particles during shear deformation: A study based on time-resolved tomographic data

Abstract

The interplay between structure and mechanical properties of fine and cohesive granular matter is of wide interest and far from being well understood. In order to study this relationship experimentally, it is desirable to record as much information on the particles and their motion behavior as possible during a shear experiment – ideally, the trajectory of every single particle. Observing the particle movements offers deep insights into changes in the mechanical behavior of the bulk (e.g., densification, loosening or formation of failure areas) and into the behavior of single particles. However, obtaining particle-level information on the dynamics of an entire shear-tester experiment remains a great challenge. In this paper we present an experiment and analysis methods which allow the extraction of the trajectories of almost all particles within a shear-tester. A fully functional micro shear-tester was developed and implemented into an X-ray microtomography device. With this combination we can visualize all particles within small bulk volumes of the order of a few μl under well-defined mechanical manipulation. The processing of time-resolved tomographic data makes it possible to localize and track particles despite large angle increments of up to 5° between tomographic measurements. We apply our methods to a torsional shear experiment with spherical micron-sized particles (∼30μm) and analyze the structural evolution of the sample. In addition, particle tracks provide detailed insights into the formation and evolution of the shear band.