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discrete element modeling of 3D irregular concave particles: Transport properties of particle-reinforced composites considering particles and soft interphase effects

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2022年 394卷 1页

作者： Xu, Wenxiang Zhang, Bin Jia, Mingkun Wang, Wei Gong, Zheng Jiang, Jinyang Hohai Univ Inst Struct & Mat Mech Coll Mech & Mat Nanjing 211100 Peoples R China Southeast Univ Jiangsu Key Lab Construction Mat Nanjing 211189 Peoples R China

Particles of complex morphologies and their surrounding soft interphase are main constituents that play a significant role in the transport properties of particle-reinforced composites (PRCs). It has been a crucial but unresolved issue how to derive the volume fraction of soft interphase around three-dimensional (3D) irregular concave particles, as well as it remains to be virgin to explore the effective transport properties of three-phase PRCs composed of homogeneous matrix, 3D irregular concave particles of a relatively high packing density and their surrounding soft interphase. To this end, this work initially develops a discrete element modeling (DEM) of 3D irregular concave particles with monodispersity in size to generate random dense packing structures, where an innovative mathematical-controllable parameterized method is proposed to devise diverse irregular concave particle shapes. The proposed particle design method is not only universal and controllable to generate a given particle shape, but also can be directly linked with an experimental measurement using digital scanning. In addition, an efficient two-step numerical strategy is presented to check the inter-particle contact detection and collision. Then, the volume fraction of soft interphase around monodisperse concave particles is numerically derived for the first time by using the Monte Carlo random point sampling simulation. The Monte Carlo simulation has good accuracy to obtain the soft interphase volume fraction, which is confirmed by comparing with the theoretical formulae for spherical particle systems. Next, a dual-probability-Brownian motion (DP-BM) scheme along with the level set algorithm is extended to investigate the effective transport properties like thermal conductivity of three-phase PRCs. Comparison against the finite element method (FEM), the proposed DP-BM scheme is more user-friendly and efficient to estimate the effective transport properties of PRCs within an accuracy level. The

关键词： Particle-reinforced composites 3D concave particles Interphase Transport properties discrete element modeling

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discrete element modeling of a Subduction Zone with a Seafloor Irregularity and its Impact on the Seismic Cycle

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Acta Geologica Sinica(English Edition) 2022年第3期96卷 776-790页

作者： JIAO Liqing CHAN Chung-Han Luc SCHOLTÈS Aurélia HUBERT-FERRARI Frédéric-Victor DONZÉ Paul TAPPONNIER SinoProbe Center Chinese Academy of Geological SciencesBeijing 100037China Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China Earthquake-Disaster&Risk Evaluation and Management(E-DREaM)Center National Central UniversityTaoyuanChina Department of Earth Sciences National Central UniversityTaoyuanChina CNRS IRDOPGCLaboratoire Magma et VolcansUniversitéClermont AuvergneClermont-FerrandFrance Department de Geography Universitéde LiegeLiegeBelgium Institut des Sciences de la Terre UniversitéGrenoble AlpesGrenobleFrance National Institute of Natural Hazards MEMCBeijing 100085China

Seafloor irregularities influence rupture behavior along the subducting slab and in the overriding plate,thus affecting earthquake *** seafloor irregularities increase the likelihood of large earthquakes in a subduction zone remains contested,partially due to focus put either on fault development or on rupture ***,we simulate a subducting slab with a seafloor irregularity and the resulting deformation pattern of the overriding plate using the discrete element *** simulations illustrate the rupture along three major fault systems:megathrust,splay and backthrust *** results show different rupture dimensions of earthquake events varying from tens to ca.140 *** results suggest that the recurrence interval of megathrust events with rupture length of ca.100 km is ca.140 years,which is overall comparable to the paleoseismic records at the Mentawai area of the Sumatran *** further propose the coseismic slip amounts decrease and interseismic slip amounts increase from the surface downwards *** conclude that the presence of seafloor irregularities significantly affects rupture events along the slab as well as fault patterns in the overriding plate.

关键词： discrete element modeling subduction zone megathrust splay backthrust faults seamount Mentawai

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Prediction of casted muck pile profiles using discrete element modeling and the Monte Carlo approach

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SIMULATION MODELLING PRACTICE AND THEORY 2025年 140卷

作者： Lamont, R. Schafrik, S. Diddle, B. Silva, J. Calnan, J. Agioutantis, Z. Dyno Nobel SALT LAKE CITY UT USA Univ Kentucky Dept Min Engn Lexington KY 40506 USA Dyno Consult Salt Lake City UT USA

In applicable orebodies, well-designed cast blasting has proven to be a more efficient method of material transportation than traditional options. Cast blast design has historically been based upon the modification of previous field observations. More recently, numerical models have been developed to predict blasting effects such as vibration and sound, among many. The discrete element modeling method, which creates a large quantity of individual particles, has experienced successful application in modeling blasted rock movement. This work examined several potential improvements to the prediction of muck pile profiles and evaluated their effect based on measured results. Model element shapes, sizes, and distributions were found to have little effect on predictive ability. A stochastic approach was taken to simplify the effect of several pre-blast variables into only initial velocity, which proved to be a valid assumption. A modest central portion of the bench was found to represent the entire bench accurately. Several factors were found to have a high impact on final muck pile profiles, including friction, pit floor variation, and timing. The results illuminate the effects of several parameters crucial to increasing the ability of operators to optimize cast blasts.

关键词： Cast blasting discrete element modeling Monte Carlo approach Predictive modeling

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discrete element modeling and Experimental Investigation on the Effects of Soil Fabric and Gradation on the Behavior of Granular Soils

Discrete Element Modeling and Experimental Investigation on ...

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作者： Basson, Mandeep Singh University of California Davis

学位级别：Ph.D., Doctor of Philosophy

The inherent particulate nature of granular soils, such as sands and gravels, plays an important role in their engineering behavior. This dissertation aims to advance the fundamental understanding of the effect of fabric- and stress-induced anisotropy, and gradation on the micro- and macro-scale behavior of coarse-grained granular *** first portion of this dissertation addresses the direction-dependent characteristics exhibited by soils reflected in the anisotropy of their responses. Studies have shown that both the depositional processes and particle arrangements (i.e., fabric-induced anisotropy), and the stress state and history (i.e., stress-induced anisotropy) impact the anisotropic behaviors observed at the macroscopic level. Quantifying these anisotropies has been challenging, necessitating specialized geotechnical testing and imaging equipment. To overcome these challenges, a novel experimental testing setup is introduced, designed to measure shear wave velocities (VS) along different orientations and polarization planes using piezoelectric bender elements (BEs) to obtain angular distributions of VS. Subsequently, two investigations on shear wave propagation are presented, using the developed setup and discrete element Method (DEM) simulations, to explore the effects of fabric- and stress-induced anisotropy on the VS anisotropy. The experimental tests were performed on glass beads and angular natural sands, while the DEM simulations used spherical and rod-like clumped particles. These specimens were subjected to isotropic and one-dimensional (1D) compression. The results reveal that the angular distributions of VS and measurements obtained along different polarization planes (i.e. VS,HH, VS,HV, and VS,VH) can discern the effects of fabric and stress anisotropy. The observed trends indicate a relationship between the angular distributions of VS and of the alignment of particles and interparticle contact forces. A framework is presented based on the VS me

关键词： Coarse grained discrete element modeling Granular soils Shear waves Soil fabric

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discrete element modeling of distal deformation propagation in thrust wedge and implications for early deformation on northern Tibetan and Iranian Plateaus

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JOURNAL OF STRUCTURAL GEOLOGY 2024年 184卷

作者： Zhou, Chao He, Jiankun Su, Hao Wang, Weimin Wang, Xinguo Zhao, Youjia Jiang, Yong Chinese Acad Sci Inst Tibetan Plateau Res State Key Lab Tibetan Plateau Earth Syst Environm & Resources TPESER Beijing 100101 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China Univ Sci & Technol China Sch Earth & Space Sci Lab Seismol & Phys Earths Interior Hefei Peoples R China

Coulomb critical wedge theory predicts that thrust wedges would grow sequentially from the hinterland to the foreland, meaning that distal deformation occurs last. However, in the northern Tibetan and Iranian Plateaus, far away from the southern collision zones, widespread deformation occurs soon after collisions of Arabia and India with Eurasia. Additionally, despite the prevalence of weak lower crust and distal pre-existing faults or weak zones, their relationship to early distal deformation remains poorly understood. For this reason, we run systematic experiments of discrete element models involving basal decollement layer as well as distal pre-existing fault. Our model results reveal that (1) the presence of pre-existing faults is necessary for the occurrence of early distal deformation;(2) the early deformation of distal pre-existing fault is dependent on basal decollement strength and independent of model width;(3) strong basal decollement fails to activate the distal pre-existing faults, instead weak basal decollement can deform them at the early stage;(4) in the presence of weak basal decollement, a slower shortening rate not only facilitates greater shortening absorption by the distal pre-existing fault at the early stage but also results in a more pronounced deviation from sequentially-forward deformation propagation. These findings demonstrate that the preferential reactivation deformations of distal pre-existing faults are mechanically controlled by a weak basal decollement layer. Together with geological and geophysical observations, we suggest that the early deformations of northern Tibetan and Iranian Plateaus may be the result of the reactivation of pre-existing faults due to the existence of weak lower crust soon after collisions.

关键词： Thrust wedge discrete element modeling Weak lower crust Pre-existing faults Deformation propagation Northern Tibetan and Iranian Plateaus

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discrete element modeling of Delamination in Laboratory Scale Laminated Rock

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MINING METALLURGY & EXPLORATION 2021年第1期38卷 433-446页

作者： Shi, Qingwen Mishra, Brijes West Virginia Univ Dept Min Engn Morgantown WV 26505 USA

Laminated rock can delaminate and fail under certain stress states. Delamination-caused roof fall and cutter roof failure is a common failure mechanism in roadways in Pittsburgh coal seam due to the existence of laminated shale roof. Two-dimensional numerical models were developed at laboratory scale based on the bonded particle method in order to simulate the delamination with particle flow code. In these models, an assembly of bonded particles and parallel weak planes represents the laminated rock. This model calibrated the micro-parameters of the bonded particle material and weak planes with laboratory data. The mechanism of fracturing and delamination in a laminated specimen was investigated using unconfined and confined compression test and unsupported roof compression test. The numerical results show that, under a constant horizontal stress, delamination occurs when the stress is much lower than its compressive strength. The confined compressive test indicates that delamination is restrained by applying confining stress since delamination-caused failure does not occur during any stage of the confined compressive test. Unsupported roof compression tests showed propagation of cutter roof failure with initiation of cracks and delamination at the intersections of the roof and ribs. An outer failed zone and inner failed zone form separately. The separated zones connect and form an opening in the roof. The presented numerical results provide additional insight into process of delamination.

关键词： discrete element modeling Laminated rock Delamination mechanism Cutter roof failure

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discrete element modeling of a particle heater for energy storage systems

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POWDER TECHNOLOGY 2023年 414卷

作者： Schirck, Jason Ma, Zhiwen Morris, Aaron Purdue Univ Dept Mech Engn W Lafayette IN 47906 USA Natl Renewable Energy Lab Golden CO 80401 USA

A heater where particles fall under gravity and flow over a series of hot angled surfaces is simulated. The conductive, convective, and interphase heat transfer are simulated for all particles via discrete element modeling (DEM). The heater inclination angle, particle-particle and particle-wall friction coefficients, and thermal contact resistances are parametrically varied. Decreasing the inclination angle increases the residence time and overall heat transfer coefficient. Low values of the friction coefficients slow the particles and increase heating, but moderate to high values of friction dilute the flow and decrease the heat transfer. The contact resistance between particles is difficult to accurately characterize, so a wide range is studied. The contact resistance is altered by varying the particle roughness from 27.5 nm to 1 mu m, which reduces the overall heat transfer coefficient by 25%. A reduced order model is developed and validated to extrapolate the small-scale DEM results to a larger-scale system.

关键词： Heat transfer Particles discrete element modeling Thermal energy storage

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Evaluating the mechanical properties of anisotropic shale containing bedding and natural fractures with discrete element modeling

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International Journal of Coal Science & Technology 2022年第2期9卷 91-106页

作者： Yingjie Li Lihong Song Yuanjun Tang Jianping Zuo Dongjie Xue School of Mechanics and Civil Engineering China University of Mining and Technology(Beijing)Beijing 100083China

Natural fracture data from one of the Carboniferous shale masses in the eastern Qaidam Basin were used to establish a stochastic model of a discrete fracture network and to perform discrete element simulation research on the size efect and mechanical parameters of *** solutions of fctitious joints in transversely isotropic media were derived,which made it possible for the proposed numerical model to simulate the bedding and natural fractures in shale *** results indicate that there are two main factors infuencing the representative elementary volume(REV)size of a shale *** frst and most decisive factor is the presence of natural fractures in the block *** second is the anisotropy ratio:the greater the anisotropy is,the larger the *** bedding angle has little infuence on the REV size,whereas it has a certain infuence on the mechanical parameters of the rock *** the bedding angle approaches the average orientation of the natural fractures,the mechanical parameters of the shale blocks decrease *** REV representing the mechanical properties of the Carboniferous shale masses in the eastern Qaidam Basin were comprehensively identifed by considering the infuence of bedding and natural *** the numerical model size is larger than the REV,the fractured rock mass discontinuities can be transformed into equivalent continuities,which provides a method for simulating shale with natural fractures and bedding to analyze the stability of a borehole wall in shale.

关键词： Shale discrete fracture network Natural fracture Anisotropy discrete element modeling

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Research on discrete element modeling and numerical simulation of cutting rock behavior under impact load

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ENERGY SCIENCE & ENGINEERING 2022年第7期10卷 2420-2436页

作者： Zhang, Heng Ni, Hongjian Huang, Bin Liu, Shubin Wang, Yong Liang, Hongjun Guo, Xing China Univ Petr East China Sch Petr Engn Qingdao 266580 Peoples R China China Univ Petr East China Key Lab Minist Educ Unconvent Oil & Gas Dev Qingdao Peoples R China CNPC Tarim Oilfield Co Oil & Gas Engn Res Inst Korla Peoples R China Shanxi Yanchang Petr Grp Co Ltd Res Inst Xian Peoples R China

Combining well-drilling hammers with polycrystalline diamond compact bits to break rock under cutting load and impact load is an effective way to improve drilling efficiency. Although impact load can enhance the cutting efficiency of the cutter, excessive impact can also cause the cutter to be subjected to additional vibrations, which can decrease its working life. Knowledge of laws governing the changes in the cutting force of the cutter under impact load is essential for the design and selection of well-drilling hammers. Based on rock scratch tests and finite element rock cutting model, a discrete element modeling (DEM) rock cutting model was established to analyze the rock breaking and cutting force. Then, the material parameters of rock samples were determined, and the simulation parameters were corrected. Finally, a DEM rock cutting model under an impact load was established. The results showed that when there was an obvious difference between the average cutting force and mean peak cutting force, which corresponded to the rock-breaking transition from ductile to brittle, with introduction of the impact load leading to an earlier transition. The cutting force variance was proportional to the impact amplitude, and the increase in the cutting force variance became more obvious when the static load exceeded the critical transition weight. When the ratio of the impact amplitude to the static load was greater than 50%, the mean and variance of the cutting force increased rapidly. Under the same impact amplitude, the impact frequency had little effect on the average cutting force, but a higher frequency could significantly reduce the variance of the cutting force under a high static load (i.e., it could alleviate the fluctuation of the cutting force). These results provide a reference for the selection of well-drilling hammers and optimization of the impact load.

关键词： discrete element modeling impact drilling PDC bit rock cutting force well-drilling hammer

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discrete element modeling of hydrogel extrusion

Discrete element modeling of hydrogel extrusion

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作者： Rohit Boddu Rowan University

学位级别：硕士

Hydrogels are widely used in extrusion bioprinting as bioinks. Understanding how the hydrogel microstructure affects the bioprinting process aids researchers in predicting the behavior of biological components. Current experimental tools are unable to measure internal forces and microstructure variations during the bioprinting process. In this work, discrete element modeling was used to study the internal interactions and the elastic deformation of the molecular chains within hydrogel networks during the extrusion process. Two-dimensional models of hydrogel extrusions were created in Particle Flow Code (PFC; Itasca Co., Minneapolis, MN). For our model's calibration, hydrogel compression testing was used in which a cluster of particles is pushed in the vertical direction with a confined load similar to the uniaxial compression test. The parameter sensitivity study was performed using a set of parameters, e.g., coefficient of friction, restitution coefficient, and stiffness. Force distribution among the particles during the extrusion process was then predicted using the results of the study. Using this model, we analyzed the distribution of internal forces.

关键词： hydrogels bioprinting extrusion manufacturing discrete element modeling forces

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