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Author: search.filters.author.Kozlowski, RyanStart date: 2020

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    Universal features of the stick-slip dynamics of an intruder moving through a confined granular medium
    (2022-04-21) Pugnaloni, Luis; Carlevaro, Manuel; Kozlowski, Ryan; Zheng, Hu; Kondic, Lou; Socolar, Joshua E. S.
    Experiments and simulations of an intruder dragged by a spring through a two-dimensional annulus of granular material exhibit robust force fluctuations. At low packing fractions (φ < φ0), the intruder clears an open channel. Above φ0, stick-slip dynamics develop, with an average energy release that is independent of the particle-particle and particle-base friction coefficients but does depend on the width W of the annulus and the diameter D of the intruder. A simple model predicts the dependence of φ0 on W and D, allowing for a data collapse for the average energy release as a function of φ/φ0. These results pose challenges for theories of mechanical failure in amorphous materials.
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    Two approaches to quantification of force networks in particulate systems
    (2021-02-24) Basak, Rituparna; Carlevaro, Manuel; Kozlowski, Ryan; Cheng, Chao; Pugnaloni, Luis A.; Kramár, Miroslav; Zheng, Hu; Socolar, Joshua E. S.; Kondic, Lou
    The interactions between particles in particulate systems are organized in ‘force networks’, mesoscale features that bridge between the particle scale and the scale of the system as a whole. While such networks are known to be crucial in determining the system wide response, extracting their properties, particularly from experimental systems, is difficult due to the need to measure the interparticle forces. In this work, we show by analysis of the data extracted from simulations that such detailed information about interparticle forces may not be necessary, as long as the focus is on extracting the most dominant features of these networks. The main finding is that a reasonable understanding of the time evolution of force networks can be obtained from incomplete information such as total force on the particles. To compare the evolution of the networks based on the completely known particle interactions and the networks based on incomplete information (total force each grain) we use tools of algebraic topology. In particular we will compare simple measures defined on persistence diagrams that provide useful summaries of the force network features.