Thermal cycling effects on the structure and physical properties of granular materials
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ORIGINAL PAPER
Thermal cycling effects on the structure and physical properties of granular materials Jibril B. Coulibaly1 · Manan Shah1 · Alessandro F. Rotta Loria1 Received: 2 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Over the past two decades, various investigations have shown that the application of thermal cycles of heating and cooling to granular materials causes permanent densification. However, prior to this study, significant associated effects of thermal cycles on the structural reorganization and physical properties of granular materials remained mostly unknown. To address these elusive aspects, this paper investigates the relationship between the microstructural changes induced by thermal cycling and their influence on the physical properties of granular materials using a multiphysical and multiscale computational approach. Microstructural changes are analyzed using coupled thermo-mechanical discrete element simulations and macroscopic physical properties are upscaled using homogenization. Multiple initial porosities and particle size distributions are investigated for a large number of thermal cycles of varying amplitude. Results demonstrate significant variations in the structure and properties of granular materials. Volumetric densification and fabric anisotropy increase monotonically with the amplitude and number of cycles. Coordination number exhibits a maximum for a critical temperature amplitude established theoretically to correspond to an optimal particle rearrangement. Mechanical stiffness and thermal conductivity increase in anisotropic fashion due to stress relaxation and fabric anisotropy and typically exhibit the most variation at the critical temperature amplitude. Intrinsic permeability to fluid flow decreases isotropically and monotonically with the amplitude and number of thermal cycles due to pore volume reduction. The critical temperature amplitude provides a limit to the thermal energy that can seemingly induce optimal and permanent structural reorganizations, as well as maximum variations of specific physical properties of granular materials. Keywords Thermal cycles · Granular materials · Microstructures · Physical properties · Homogenization
1 Introduction Granular materials are abundant and complex materials bearing primary importance in many scientific and engineering fields [1]. The processing-structure-properties relationship [2] allows unfolding key features of granular materials: the dependence of their physical properties on their structure, as well as the determination of their structure by the related processing. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10035-020-01054-6) contains supplementary material, which is available to authorized users. * Jibril B. Coulibaly [email protected] 1
Mechanics and Energy Laboratory, Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
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