Compactness of bulk materials under conditions of combined vibration impact

Abstract

Bulk density and compactability of bulk materials play an important role in technological processes. Although compression by static loading can be reproduced and mathematically described, the effects of shocks and vibrations remain very poorly understood. The study of the rheological behavior of dispersed media under mechanical loading is of strategic importance for the optimization of industrial processes, where the porosity of the material critically depends on the systemic compaction state. Since standard methods for assessing compaction are predominantly qualitative in nature, ensuring the reproducibility of rheological characteristics in the aerated state as a basic level requires the implementation of precise mathematical models. Therefore, a study was conducted to study the effect of uniaxial loading and vibrations on the compression of bulk materials. The aim of the study is a comprehensive analysis of the effectiveness of the combined vibration effect on the compaction process of cohesive kaolin powder H1 special. Within the framework of the work, a logarithmic compaction model was used, which demonstrates a high quality of approximation for finely dispersed systems at peak static pressure, taking into account the Janssen characteristic length, lateral pressure coefficient and friction. It was established that the integration of dynamic loads significantly transforms the dimensionless compressibility coefficient: from the base level of 0.15 under static compression to 0.22 under axial vibrations
(50 Hz, ~2g) and 0.32 when adding a reversible torsional effect (45 Hz). Despite the fact that the additional dynamic pressure is insignificant compared to the static maximum, the main physical factor is the vibrational recompaction of the structure, which ensures an increase in bulk density due to the use of a combined compaction mode. The magnitude of the tangential acceleration allows you to effectively destroy cohesive arches, level the arching effect according to the Janssen model and eliminate radial density heterogeneity. The implementation of the developed design of the device for combined impact allows achieving almost doubling of bulk density and ensuring high homogeneity of the composite structure on an industrial scale.