Shear flow of cohesive powders with contact crystallization: experiment, model and calibration

This work presents an experimental and numerical investigation of the shear flow of a cohesive, caking powder. Utilizing potassium chloride (KCl) as a model material, the bulk’s flow behavior with respect to storage time is measured with a Schulze ring shear tester. Our results suggest that KCl cakes on a characteristic timescale tc\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$t_\mathrm{c}$$\end{document}, which is independent of the normal load. Based on a detailed product characterization, a generalized elastoplastic contact model for discrete element simulations combined with an approach of successive calibration is proposed. Mircoscopic parameters, which are not measured directly, are used as effective ones to fit the flow behavior of an idealized ensemble of particles to the experimental findings. Within this process, we investigate the influence of these microscopic parameters on macroscopic quantities as well as the bulk’s structure. Successful calibration confirms that the rheology of complex bulk materials, such as KCl, can be predicted efficiently with simplified numerical simulations.