Article
Physics, Multidisciplinary
Stefan Luding
Summary: Soft granular materials exhibit different responses to externally applied deformations at different strain rates and system sizes. At moderate strain rates, the material evolves smoothly, while at slow strain rates, it toggles between an elastic reversible state and plastic dynamic events, causing irreversible rearrangement of the microstructure.
FRONTIERS IN PHYSICS
(2023)
Article
Chemistry, Physical
Stefan Luding, Kianoosh Taghizadeh, Chao Cheng, Lou Kondic
Summary: This study examines the evolution of dense granular systems in three dimensions during slow compression and decompression. It finds that the transitions in the system involve both smooth and continuous reversible events, as well as fast and discontinuous irreversible events. The analysis using persistent homology reveals that kinetic energy is correlated with the strength of rearrangements, while global mechanical measures, such as pressure, are strongly correlated with the evolution of topological measures quantifying loops in the force network. Surprisingly, some transitions are detected by persistent homology even when particle motion or rearrangement is weak or not observed at all.
Article
Mechanics
Rossella Laudani, Martin Ostoja-Starzewski
Summary: The violation of the entropy inequality in macroscopic granular media undergoing collisional dynamics is found to be a result of the fluctuation theorem of nonequilibrium thermodynamics. Through molecular dynamics simulations, it is determined that the occurrence of negative entropy increments is influenced by the Eulerian velocity gradient and the Young modulus of the disks.
JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME
(2021)
Article
Mechanics
T. Barker, M. Rauter, E. S. F. Maguire, C. G. Johnson, J. M. N. T. Gray
Summary: In the last fifteen years, there has been a paradigm shift in the continuum modelling of granular materials, with the development of rheological models and theories for particle segregation. This paper presents a unified framework based on the partially regularized incompressible -rheology and gravity-driven segregation theory, which couples segregation with flow for handling evolving free surfaces. The numerical method is extensively tested and compared with discrete element method simulations, showing promising results in capturing complex segregation patterns.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Multidisciplinary Sciences
Xiaohui Cheng, Shize Xiao, Alex Sixie Cao, Meiying Hou
Summary: This study investigates transitional regimes in granular shear flows, proposing a unified model to describe transitions between different flow states based on triaxial shear flow tests. The importance of granular viscosity under low pressure is highlighted in the transition between quasi-static and moderate Isotach type flow states.
SCIENTIFIC REPORTS
(2021)
Article
Computer Science, Interdisciplinary Applications
Yizhao Gao, Qingshuo Hao, Peng Yu, Yuzhen Yu, He Lv
Summary: This study proposes a new constitutive model for granular soils, considering two types of volume variations and the state dependency of material density. The model includes compression and unloading curves considering grain crushing, and can accurately describe the stress-dilatancy relation under different experimental conditions.
COMPUTERS AND GEOTECHNICS
(2023)
Article
Mechanics
Cornelius O. Horgan
Summary: Anssari-Benam and Bucchi (2021) have proposed a new two-parameter constitutive model for isotropic incompressible hyperelastic generalized neo-Hookean materials that is superior to the well-known Gent model when fitting various experimental data for rubber. They also establish a simple direct relation between the new model and the classical Gent model, allowing for the application of existing research results on rubber-like materials to the new model.
INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS
(2021)
Article
Mechanics
Hang-Yu Zhu, Chong Pan, Huan Lian
Summary: This study investigates the dependence of multi-scale droplet settling behavior on characteristic parameters of two-phase turbulent flow through sophisticated conditional analysis. The results show that there is a negative correlation between local particle concentration and settling velocity in the moderate-concentration range, while a positive correlation exists in the high-concentration range. Such a process is consistent with the so-called multi-scale preferential sweeping effect.
Article
Computer Science, Interdisciplinary Applications
Yang Xiao, Fang Liang, Zhichao Zhang, Huanran Wu, Hanlong Liu
Summary: Particle shape has a significant effect on the shear strength and shear dilatancy properties of granular materials. This study presents a granular thermodynamic theory to investigate the effects of particle shape and distribution on the mechanical properties and behavior of granular materials. The theory model outcomes closely resemble experimental results, effectively capturing the impact of particle shape on the mechanical properties and shear dilation of granular materials.
COMPUTERS AND GEOTECHNICS
(2023)
Article
Environmental Sciences
Wenxiang Xu, Kaixing Zhang, Yufeng Zhang, Jinyang Jiang
Summary: In this study, the influence of the geometrical and topological configurations of particles on the pore tortuosity and permeability of granular-porous media is investigated. A relaxation iteration scheme and a direction-guided rapidly exploring random tree algorithm are developed to study the effects of particle shape, fineness, and size distribution on the random packing fraction of particles. By comparing with experimental, theoretical, and numerical results, the proposed methods accurately predict the tortuosity and permeability. Furthermore, the impact of particle packing fraction, shape, fineness, and size distribution on the pore tortuosity and permeability is evaluated. The results have important implications for various scientific disciplines, including the properties of rocks, sandstones, and soils, as well as the design of ultra-high performance concrete.
WATER RESOURCES RESEARCH
(2022)
Article
Engineering, Geological
Alessandro Tengattini, Giang D. Nguyen, Gioacchino Viggiani, Itai Einav
Summary: This paper presents an experimental and analytical/numerical study of the mechanics of cemented granular materials. The study combines in situ X-ray tomography and finite element simulations to gain insight into the multiscale processes that drive the mechanical response of these materials. The paper explores the effects of boundary conditions on grain-scale processes and material properties, and validates a micromechanically inspired constitutive model at different scales.
Article
Engineering, Multidisciplinary
Fuzhen Chen, Tengda Shi, Hong Yan, Hongfu Qiang
Summary: A new constitutive model was designed in this study to consider the cohesion in dense granular media. The model includes a linear elastic-plastic constitutive relationship for the solid-like phase and a viscoplastic constitutive model for the liquid-like phase. Smoothed particle hydrodynamics method was used to discretely solve the new model, and its effectiveness was verified through various cases.
ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS
(2022)
Article
Mechanics
T. Barker, C. Zhu, J. Sun
Summary: Vertical chutes and pipes play a crucial role in industrial processes involving powders and grains. Through simulations and idealizations, the study reveals linear scaling laws and a novel rheology model for vertical flow, providing insights into the behavior of different flow regimes. The research highlights a linear relation between chute width and shear zone size, contrasting with previous findings and suggesting minimal finite-size effects for the inertial flows studied.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Physics, Multidisciplinary
Hugo Perrin, Matthieu Wyart, Bloen Metzger, Yoel Forterre
Summary: The study found that thin frictionless granular layers lack hysteresis in avalanche angle, but stability increases as the layer gets thinner. Steady rheological laws obtained for different layer thicknesses can be collapsed into a unique master curve, supporting the idea that nonlocal effects are a consequence of typical finite-size effects associated with the presence of a critical point.
PHYSICAL REVIEW LETTERS
(2021)
Article
Polymer Science
Wei Wang, Yang Liu, Zongwu Xie
Summary: This article proposes an improved hyperelastic constitutive model based on the Yeoh model to enhance its prediction performance for multiaxial deformation of hyperelastic polymeric materials. The modified model includes an additional correction term, derived from residual strain energy, to accurately predict equibiaxial deformation. The proposed parameter identification method ensures accurate parameter estimation for the modified model. Experimental validation shows that the modified model has significantly improved predictive ability and wider applicability compared to existing models.
Article
Materials Science, Multidisciplinary
K. Giannis, C. Schilde, J. H. Finke, A. Kwade, M. A. Celigueta, K. Taghizadeh, S. Luding
Summary: This study introduces a stress-based non-binary contact model by generalizing a classical force-displacement contact law, which enables more accurate simulation of multiple contacts on a single particle and captures stronger nonlinearity at higher stresses. The proposed multi-contact model can be easily integrated into any DEM implementation and remains relatively fast compared to more complex methods.
Article
Mechanics
S. Roy, S. Luding, W. K. den Otter, A. R. Thornton, T. Weinhart
Summary: The study focuses on liquid migration in shear bands of granular media, showing the significance of drift and diffusion mechanisms in influencing liquid concentration distribution. The analytical continuum model is validated by comparing with discrete particle method simulations.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Chemical
Mohamad Yousef Shaheen, Anthony R. Thornton, Stefan Luding, Thomas Weinhart
Summary: This study investigates the factors influencing powder layer quality in laser powder bed fusion (LPBF), including the effects of materials and process parameters on spreading, as well as the impact of factors such as particle shape and surface roughness on layer quality. The research reveals that different factors have a significant influence on powder layer quality, and there is a trade-off between material and process parameters.
Article
Multidisciplinary Sciences
Kianoosh Taghizadeh, Holger Steeb, Stefan Luding, Vanessa Magnanimo
Summary: The study investigates the wave propagation and elastic properties of waves in dense granular packings made of soft and stiff particles, emphasizing the effects of applied stress and rubber content on the mixtures. It highlights the transition in frequency domain from glass- to rubber-dominated regimes and the influence of rubber particles on energy dissipation. Mixtures with rubber content below 30% exhibit enhanced damping properties.
PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2021)
Editorial Material
Materials Science, Multidisciplinary
Diego Berzi, Dalila Vescovi, Shunying Ji, Xikui Li, Stefan Luding
Article
Engineering, Chemical
J. E. Alvarez, H. Snijder, T. Vaneker, H. Cheng, A. R. Thornton, S. Luding, T. Weinhart
Summary: This study presents a novel discrete element method framework for modeling the visco-elastic sintering kinetics in polymer powders. The framework considers three distinct sintering mechanisms and is implemented in an open-source software package. Experimental data analysis confirms the accuracy of the sintering time estimation compared to a widely-used model. This research provides an efficient and reliable approach for studying strength evolution in powder-bed fusion processes.
Article
Chemistry, Physical
Stefan Luding, Kianoosh Taghizadeh, Chao Cheng, Lou Kondic
Summary: This study examines the evolution of dense granular systems in three dimensions during slow compression and decompression. It finds that the transitions in the system involve both smooth and continuous reversible events, as well as fast and discontinuous irreversible events. The analysis using persistent homology reveals that kinetic energy is correlated with the strength of rearrangements, while global mechanical measures, such as pressure, are strongly correlated with the evolution of topological measures quantifying loops in the force network. Surprisingly, some transitions are detected by persistent homology even when particle motion or rearrangement is weak or not observed at all.
Article
Geography, Physical
Kenton R. Fisher, Ryan C. Ewing, Orencio Duran Vinent
Summary: This study assesses the long-term and seasonal geomorphological changes at Padre Island, Texas using aerial and satellite images, as well as LiDAR data. The findings suggest that increased rates of relative sea level rise and decreased sediment influx are the primary drivers of the observed changes in the island's geomorphology. The study highlights the importance of monitoring these changes for informed decision making in sensitive coastal landscapes.
EARTH SURFACE PROCESSES AND LANDFORMS
(2023)
Article
Engineering, Multidisciplinary
Hongyang Cheng, Anthony R. Thornton, Stefan Luding, Andrew L. Hazel, Thomas Weinhart
Summary: The finite element method (FEM) is commonly used for modeling continuum media, while the discrete element method (DEM) is used for discrete systems. This paper introduces the coupling between discrete and continuum methods by mapping discrete particle data onto smooth fields. The authors found that using this coarse-graining approach leads to more accurate results, reduced energy generation, and less numerical dissipation.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Article
Chemistry, Physical
Thejas Hulikal Chakrapani, Hanieh Bazyar, Rob G. H. Lammertink, Stefan Luding, Wouter K. den Otter
Summary: Darcy's law describes the flow of Newtonian fluids through porous media, while Brinkman extended it by adding a viscous stress term. The validity and value of Brinkman's term have been debated since its introduction.
Article
Physics, Multidisciplinary
H. Cheng, F. A. R. Anselmucci, X. Fan, Y. Zeng, S. Luding, V. Magnanimo
Summary: Vegetated soil, as a storage of carbon and widely used construction material, plays a crucial role in tackling climate change. Understanding the interaction between soil deformation, root growth, and water/solute uptake is urgently needed due to the expected impacts of climate change. This paper provides an overview of the latest knowledge in root-zone mechanics and bio-hydrology, identifies knowledge gaps, and proposes an integrated approach to study soil-water-root interaction.
Article
Mechanics
Thomas Pahtz, Orencio Duran
Summary: We use a numerical model to simulate non-suspended sediment transport across a wide range of particle-fluid density ratios. Based on simulations and experiments, we derive simple scaling laws for aeolian transport and find that the cessation threshold is controlled by only one dimensionless parameter. Only one existing model is somewhat consistent with the data, but it fails to capture the grain size dependence of the transport rate, indicating a lack of understanding in this area.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Multidisciplinary Sciences
K. Taghizadeh, M. Ruf, S. Luding, H. Steeb
Summary: This research focuses on performing ultrasound propagation measurements and micro-X-ray computed tomography imaging on prestressed granular packings prepared with biphasic mixtures of monodisperse glass and rubber particles at different compositions/fractions. The study reveals that the effective macroscopic stiffness of the granular packings transits nonlinearly and nonmonotonically toward the soft limit as the fraction of soft particles increases. The contact network of dense packings plays a key role in understanding this phenomenon.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Article
Engineering, Mechanical
Hongyang Cheng, Stefan Luding, Thomas Weinhart
Summary: The interaction between granular materials and deformable structures is important in various industries. A surface coupling method combining discrete and continuum methods is commonly used for numerical modeling. This study investigates the time evolution of linear momenta and energies in particle-continuum systems using a recently developed coarse graining method, and shows that it leads to more accurate predictions and reduces excess energies generated by the coupling method, particularly in dynamic particle-structure interactions.
ACTA MECHANICA SINICA
(2023)
Article
Physics, Fluids & Plasmas
Juan C. Petit, Nishant Kumar, Stefan Luding, Matthias Sperl
Summary: This study presents three-dimensional simulations of bidisperse granular packings using the discrete element method. The results show the existence of two jamming transitions, with the first one predominantly involving large particles and the second one involving small-large interactions. The effective transition densities are reduced when only nonrattlers are considered. The size ratio and concentration of small particles affect the behavior of the bulk modulus during the transitions. The findings provide insights for tuning or switching the bulk modulus and other properties of granular packings.
