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The relationship between an external stress applied to a bulk and its resulting porosity—i.e. its compaction behavior—is studied in this work, varying the median particle diameter by using different batches of carbonyl iron powder (CIP) as well as by mixing them. Firstly, compaction equations of other authors and an algebraic relation suggested by us are presented. Secondly, these descriptions are compared to data obtained by compacting CIP. Last, for powder mixtures, the role of the particles’ median and mean diameters is studied in experiments and DEM-simulations, respectively. We show that they take on the role of the relevant length scale appearing in the algebraic compaction law. [ABSTRACT FROM AUTHOR]

Steady state flow of powders is a crucial concept to investigate the powders’ strength and flow properties. This state is defined as a continuous deformation of the material without volume change while the stresses at the specimen’s boundaries remain constant. Recent investigations have shown that this state, especially for cohesive powders, is not always as constant as it should be by definition. This paper presents experimental and numerical work, both for cohesive and non-cohesive powders. The experimental part focuses on the use of different control strategies, leading to steady state flow of different quality. Differences between steady state flow for cohesive and non-cohesive powders are shown. [ABSTRACT FROM AUTHOR]

Steady-state flow of powders is defined as a continuous deformation of the material without volume change while the stresses at the specimen's boundaries remain constant. Recent investigations have shown that this state, especially for cohesive powders, is not always as steady as it should be by definition. In this article a recent extension of the true biaxial shear tester is introduced that allows a view of the shear motion of the brick-shaped powder specimen inside the tester. By applying a dark-colored powder pattern onto a light powder sample, the movement of the powder can be captured using a CCD camera. Development of shear bands and inhomogeneities of the sample can be visualized. Experiments with a cohesive powder with purely strain-controlled, volume-preserving shear cycles, as well as mixed stress-strain controlled experiments, are presented. The recorded images as well as stress-strain data from discrete elements simulations are compared to the experimental results. [ABSTRACT FROM AUTHOR]