Discrete Element Method Research Articles

LBM-DEM modeling of particle-fluid interactions on active small solar bodies

Aeolian-like surface features observed on small Solar System bodies have piqued interest in their underlying formation mechanisms. Understanding the evolution of fluid-solid interactions is crucial for elucidating the nature of cometary activity. We established a resolved fluid-particle simulation approach and implemented it into our self-developed DEMBody and LBMCoupler codes to simulate the wind erosion process on comet 67P. We developed this novel framework by applying the lattice Boltzmann method-discrete element method (LBM-DEM) in a low-gravity and rarefied atmosphere environment. The inter-particle forces were modeled using the Hertz contact model, friction, and cohesion. The fluid field was calculated by solving the lattice Boltzmann equations, which use the distribution function as the variable. The fluid-particle forces were modeled using the partially saturated cells method, in which the force is calculated based on the populations of the fluid cells occupied by the solid phase. We conducted 2D and 3D validation simulations and a series of simulations of a regolith layer as a preliminary application to validate the framework. The validation results of the drag coefficient under 2D and 3D conditions are in good agreement with previous theoretical and numerical estimates. Additionally, the wind erosion process on the surface of comet 67P is reproduced using the presented approach. This preliminary application show that the threshold velocity to initiate grain motion on comet 67P is about $25$ $ m/s$, which is consistent with the observations that sediment transport driven by winds frequently occurs near the perihelion of comet 67P. The proposed LBM-DEM framework can be successively applied to simulate the fluid-solid interaction on small solar bodies that have extremely low-gravity and rarefied atmosphere environments. Future works based on this tool and focused on aeolian geologic landforms, such as sand dunes, can help us understand the dynamics of cometary activity.

FEM, DEM and FDEM applications on impact fracture of glass and laminated glass – A revie

Structural glass components are prevalently used in engineering. Due to the brittle nature, glass or laminated glass may fracture during an impact action, and the flying fragments may spread over a wide range, resulting in human injuries and asset losses. In this article, the authors aimed at providing a comprehensive review concerning the numerical applications on the impact fracture of glass and laminated glass. Relevant numerical applications employing the finite element method (FEM), discrete element method (DEM) and combined finite-discrete element method (FDEM) were reviewed, and features of the simulations were summarised. Insights into the accuracy, efficiency, ease of implementation and range of applicability were also provided. This review is meant for the rapid and beneficial understanding towards the impact fracture mechanism of glass and laminated glass.

An elastoplastic beam bond model for DEM simulation of deformable materials and breakage behaviors

AbstractIn modern chemical engineering production, numerous elastoplastic materials, often formed into agglomerates, frequently undergo plastic deformation and rupture. Understanding how these materials behave under different conditions is crucial for improving manufacturing processes and material design. In this work, an elastoplastic beam bond model for discrete element method (DEM) simulation was developed, in which a yield criterion is introduced into Timoshenko beam bond method. The model can simulate not just the initial elastic (stretchy) behavior of the materials but also their plastic (permanent) deformation behaviors. The model was applied to central collision of two agglomerates, agglomerate uniaxial compression, and agglomerate‐wall impact cases. It is shown that the updated model could predict the behavior of materials that undergo permanent changes under stress, compared to previous models that only considered elastic behaviors. This could enable more accurate simulations of particulate materials and aid in better process design.

Working performance of vertical spiral stirred mill based on discrete element method

The main structures and characteristic parameters that affect the working performance of vertical spiral stirred mill were analyzed and studied, and a method for selecting key working parameters was proposed. Based on the discrete element method, a simulation model of vertical spiral stirred mill was established, and the effects of spindle speed, agitator lead and grinding media size distribution on grinding performance were analyzed. A comprehensive grinding performance index was proposed, and orthogonal tests were conducted on each parameter to obtain the quantitative value of the grinding effect, and then the optimal working parameter combination under a specific weight coefficient was obtained, which provided a reference method for the optimal design of the mill.

Investigation of the Influence of Cutter Geometry on the Cutting Forces in Soft–Hard Composite Ground by Tunnel Boring Machine Cutters

Tunnel Boring Machines (TBMs) are integral to modern underground engineering construction, offering enhanced safety and efficiency. However, TBMs often face challenges in complex geological conditions, such as composite strata, resulting in reduced advancement speed and increased cutter wear. This study investigates the rock-breaking characteristics of TBM disc cutters in composite strata through numerical simulations using the Particle Flow Code (PFC) 5.0 software. Focusing on the Jinan Metro Line 6, the research analyzes cutter forces, rock crack propagation, and the impact of cutter edge shapes on rock-breaking efficiency. The discrete element method (DEM) is employed to simulate microscopic behaviors of rocks, providing insights into crack formation, expansion, and failure. This study’s findings reveal that cutter design and operational parameters can significantly influence cutter lifespan and efficiency. By modifying cutter spacing and penetration depth, enhancing rock-breaking efficiency, and grouting softer layers, TBMs can maintain effective excavation in composite strata. The study establishes a comprehensive understanding of the interplay between TBM cutters and complex geological conditions, offering actionable strategies to enhance TBM performance and mitigate cutter damage.

Numerical Studies of Influencing Factors on the Homogeneity of the Powder Mixture during the Powder Spreading Process of Powder Bed Fusion–Laser Beam/Metal

Recent studies have focused on the alloying of nitrogen (N) in high‐alloy stainless steels by powder bed fusion–laser beam/metal (PBF‐LB/M). However, N‐induced pore formation remains a challenge. To overcome this, a combined PBF‐LB/M and hot isostatic pressing (HIP) process is developed. AISI 304L stainless steel powder was mixed with silicon nitride (Si3N4) powder and processed by PBF‐LB/M, allowing partial retention of Si3N4. This helps to maintain sufficient N content while reducing pore formation. The microstructure is then homogenised by HIP. A major challenge of this process is to maintain the homogeneity of the deposited powder mixture on the powder bed to ensure a consistent N content in the final products. This study combines experimental and numerical methods to address this issue: scanning electron microscopy is used to characterize the microstructure and map the local N content, while various numerical studies based on the discrete element method are carried out to investigate the effects of layer thickness, substrate surface roughness, and powder properties on the intermediate product. The numerical approach effectively predicts the N content distribution and homogeneity on the powder bed. The models are validated with experimental data and optimal process conditions for PBF‐LB/M are identified.

The influence of sand content on dynamic behaviors of ballast bed from a multiscale perspective

In desert regions, sand intrusion into the ballast bed is unavoidable, leading to a reduction in the elasticity of the ballast bed and posing potential risks to the service safety. Previous studies have focused on the behaviors of sandy ballast beds in 2D planes using discrete element method (DEM), where sand content is typically calculated utilizing sand areas within the ballast voids, different from that using sand volumes or mass in 3D space. Therefore, the impacts of sand content on the multiscale responses of the ballast bed are not fully addressed. In this paper, 3D full-scale half-sleeper models with various sand contents are established via DEM. Multiscale responses of sandy ballast bed obtained by laboratory tests are utilized to verify the reliability of established models. Simulation results show that macroscopically, sand intrusion increases the stiffness and consequently reduces the elasticity of the ballast bed. Microscopically, sand contaminant restricts the translational acceleration of ballast particles, while simultaneously intensifying the angular acceleration. In terms of particle contact, the anisotropy of the directional distribution of contact force among ballast particles is weakened by sand contaminant. Therefore, the inter-particle contact force among ballast particles becomes more uniform, particularly beneath the rail. A normalized parameter is proposed to quantify the filling effect of sand contaminant, based on which the relationships between multiscale dynamic responses and sand content are linearized. The linearization results indicate that the sand intrusion has more significant impacts on the multiscale responses of the ballast bed under higher loading magnitude.

Discrete element model of low-velocity projectile penetration and impact crater on granular bed

The present study investigates the low-velocity impacts of a spherical projectile into a bed of spherical particles using Discrete Element Method (DEM) simulations and laboratory experiments. The findings reveal intricate forces and energy transformations, indicating the phenomena leading to projectile impact, penetration, cessation, and crater formation. The DEM result indicates that the penetration stopping time of the projectile is not influenced by impact velocity. Further, simulations show that projectile penetration depth correlates with 1/2.7 power of total impact height, while crater diameter and depth scale with 1/4.32 power of nondimensional impact energy. The shape of the resulting crater appears independent of impact velocity and the maximum diameter of the fluidized region varies with the 1/2.68 power of impact velocity. Experimental validation confirms the accuracy of predicted penetration depths and crater diameters, enhancing confidence in DEM simulations. These findings extend scaling laws and reveal the influence of larger particles on low-velocity impact dynamics, addressing unexplored aspects of granular cratering.

CFD-DEM study on the blocking conformation of pre-filled sand control screen by layering method

Preventing screen blockage due to sand poses a significant challenge. The article combines computational fluid dynamics (CFD) and discrete element method (DEM) to establish a fully coupled four-way interaction model. A sophisticated size particle injection model was established, taking into account the particle size distribution (PSD) characteristics of the formation. A layering method was used to study the sand control behavior of a high-performance pre-filled screen. The study also quantitatively investigated the impact of factors such as median sand size (D50), screen structure, and fluid velocity on both wellbore-screen annulus and internal screen plugging patterns. The findings reveal that the sand retention rate within the wellbore-screen annulus exceeds 93.8 %. The risk of pre-filled screen blockage is minimized when the ratio of gravel diameter to sand diameter falls within the range of 3.3–5. At a gravel filling rate of 97 %, fine sand predominantly moves radially, resulting in a low risk of blockage at the screen's entrance layer, thereby favoring oil and gas production. In cases with elevated fine sand content, it is advisable to maintain a production flow rate below 3 m/s to mitigate localized erosion damage caused by increased pressure resulting from screen blockage. This model holds significant importance in optimizing completion tools and production parameters.

Ground failure and soil erosion caused by bursting of buried water pipeline: experimental and numerical investigations

Pressurized water pipelines buried in an urban environment are prone to bursting failures, threatening public safety and traffic convenience. The limited studies in literature just focused on soil fluidization while few studies considered ground failure, shear strain, soil erosion and the influence of leakage locations during pipe bursts. In this study, extensive experimental tests along with a finite difference method – discrete element method (FDM-DEM) solid–fluid coupling analysis were conducted to investigate these issues. It was disclosed that the failure development during pipe bursts can be divided into three stages, i.e., seepage diffusion, erosion cavity expansion, and soil fluidization. By digital image correlation (DIC) analysis of the experimental results, a wedge-shaped displacement zone in ground was identified, with peak shear strain near its boundaries. Moreover, it was revealed that leakage locations affected the expansion origin of erosion cavity; as the burial depths increased, the ground heave range increased linearly; the maximum water outflow distance was closely related to the internal pressures of buried pipeline, which could be modeled by a square root formula based on turbulent jet theory. Mesoscopic analyses revealed that finer particles were more susceptible to erosion during pipe bursts because of the low possibility of forming strong connections with surrounding particles. The findings yielded from this study can enhance the understanding of pipe bursts and help professionals mitigate potential damage.

Modeling and chewing parameters calibration of Euryale ferox based on discrete element method.

Euryale ferox was chosen for this study to examine its mechanical properties during chewing. Experiments and the discrete element method were used to conduct the study. Initially, the intrinsic and contact parameters of E. ferox were established through physical tests. The maximum compressive force of breakage and chewing mechanical properties (hardness, springiness, and chewiness) were measured using a texture profile analyzer (TPA). A Hertz-Mindlin with bonding model of the E. ferox was constructed. Optimal values for significant factors, including the normal stiffness per unit area, shear stiffness per unit area, and bonding radius, were obtained through single-factor, Plackett-Burman, steepest ascent, and Box-Behnken response surface tests, with the maximum compressive force as the index. Under optimal parameter combination conditions, the relative error between the simulated and experimental values of the maximum compressive force was 0.79%, and the relative errors between the simulated and TPA test values of all indicators were less than 5.65%. This study provides a valuable reference for simulating the textural characteristics of agricultural products.

Impact of the Source Material Gradation on the Disaster Mechanism of Underground Debris Flows in Mines

In mines where the natural caving method is used, the frequent occurrence of underground debris flows and the complex mine environments make it difficult to prevent and control underground debris flows. The source is one of the critical conditions for the formation of debris flows, and studying the impact of source material gradation on underground debris-flow disasters can effectively help prevent and control these occurrences. This paper describes a multiscale study of underground debris flows using physical model experiments and the discrete-element method (PFC3D) to understand the impact of the source material gradation on the disaster mechanism of underground debris flows from macroscopic and microscopic perspectives. Macroscopically, an increase in content of medium and large particles in the gradation will enhance the instantaneous destructive force. Large particles can more easily cause disasters than medium and fine particles with the same content, but the disaster-causing ability is minimized when the contents of medium and large particles exceed 50% and 60%, respectively. With increasing fine particle content, the long-distance disaster-causing ability and duration is increased. On the microscopic level, the source-level pairs affect the initial flow mode, concentration area of the force chain, average velocity, average runout distance, and change in energy of the underground debris flow. Among them, the proportion of large particles in the gradation significantly affects the change in kinetic energy, change in dissipative energy, time to reach the peak kinetic energy, and time of coincidence of dissipative energy and gravitational potential energy. The process of underground debris flow can be divided into a “sudden stage”, a “continuous impact stage”, and a “convergence and accumulation stage”. This work reveals the close relationship between source material gradation and the disaster mechanism of underground debris flows and highlights the necessity of considering the source material gradation in the prevention and control of underground debris flows. It can provide an important basic theory for the study of environmental and urban sustainable development.

Modeling and failure mechanism study of unidirectional GFRP corrugated sandwich sheet piles based on discrete element method

In this paper, a DEM model of a unidirectional glass fiber reinforced polymer composite sandwich sheet pile (UGFRP-CSSP) is developed to elucidate the damage mechanisms under longitudinal bending and axial compression at the mesoscale, in order to bridge the gap between existing knowledge and its potential applications as sheet pile walls. A series of four-point bending and axial compression tests are performed on UGFRP-CSSP to validate the DEM model, which is calibrated through a sensitivity analysis of the mesoscopic parameters. The failure behavior, crack progress, and initial crack formation of the UGFRP-CSSP are investigated by correlating the results from physical experiments and numerical simulations. The research reveals that the DEM model accurately depicts the failure behavior under bending and compression of unidirectional (UD) composite elements, offering a mesoscopic perspective on the failure origins. It is identified that the tensile shear strength of the resin is the weak point leading to initial failure, as it is lower than that of the glass fibers. Longitudinal bending failure typically initiates at the skin-core interface and around the central axis of core, with cracks propagating longitudinally due to compression shear failure between fibers. Axial compression failure also occurs predominantly at the skin-core interface, with similar longitudinal cracking attributed to tensile shear failure at the acute angle fiber connections in the long span side. Finally, a new viewpoint was proposed that the fiber modulus may have a decisive impact on the failure behavior of UD composite materials.

Human Mastication Analysis-A DEM Based Numerical Approach.

Mastication is an essential and preliminary step of the digestion process involving fragmentation and mixing of food. Controlled muscle movement of jaws with teeth executes crushing, leading towards fragmentation of food particles. Understanding various parameters involved with the process is essential to solve any biomedical complication in the area of interest. However, exploring and analyzing such process flow through an experimental route is challenging and inefficient. Computational techniques such as discrete element numerical modeling can effectively address such problems. The current work employs the Discrete Element Method (DEM) as a numerical modeling technique to simulate the human mastication process. Tavares and Ab-T10 breakage models coupled with Gaudin Schumann and Incomplete Beta fragment distribution models have been implemented to analyze the fragmental distribution of food particles. The effect of particle shape (spherical, polyhedron, and faceted cylinder), size (aspect ratio), and orientation (vertical and horizontal) on breakage and fragment distribution is analyzed. To account for the elastic-plastic behavior and moisture content in food particles, modifications has been made in breakage models by incorporating numerical softening factor and adhesion force. The study demonstrates how numerical modeling techniques can be utilized to analyze the mastication process involving multiple process parameters.

Capturing the random mechanical behaviour of granular materials: a comprehensive stochastic discrete-element method study

This research pioneers a stochastic discrete-element method (DEM) by integrating the probability density evolution method (PDEM), offering a novel approach to connect particle-scale property uncertainties, specifically inter-particle friction coefficient (μ) and particle shear modulus (Gp), with macro-scale soil behaviour. Through 1100 DEM simulations, this study reveals that, for uniform particle size distribution, the uncertainty in μ substantially affects large-strain soil behaviour, with its effect being associated with packing density and soil state. The uncertainty effect of μ remains pronounced at the critical state, while the packing density effect diminishes. Stress distribution appears insensitive to uncertainty of μ, rather suggesting a predominant influence of particle size distributions. In contrast, the uncertainty effect of μ becomes negligible on small-strain behaviour, demonstrating a limited effect on small-strain stiffness. Uncertainty in Gp presents limited effects on large-strain behaviour, including stress ratios and dilatancy. At small strains, Gp shows a significant impact on stiffness, diverging from minimal influence identified for μ. This study presents a framework that integrates experimental techniques to study particle-scale uncertainty propagation, enhancing predictions of macro-scale soil behaviour. This approach could be beneficial for precise multi-scale simulations, incorporating particle-level uncertainties in engineering-scale models, thereby improving geotechnical practice predictability.

Design and Testing of Key Components for a Multi-Stage Crushing Device for High-Moisture Corn Ears Based on the Discrete Element Method

To improve the crushing efficiency and crushing pass rate of high-moisture corn ears (HMCEs), a multi-stage crushing scheme is proposed in this paper. A two-stage crushing device for HMCEs is designed, and the ear crushing process is analyzed. Firstly, a simulation model for HMCEs was established in EDEM software (2018), and the accuracy of the model was verified by the shear test. Subsequently, single-factor simulation experiments were conducted, with the crushing rate serving as the evaluation index. The optimal working parameter ranges for the HMCE device were identified as a primary crushing roller speed of 1200–1600 revolutions per minute (r/min), a secondary crushing roller clearance of 1.5–2.5 mm, and a secondary crushing roller speed of 2750–3750 r/min. A Box–Behnken experiment was conducted to establish a multiple regression equation. With the objective of maximizing the qualified crushing pass rate, the optimal combination of parameters was revealed: a primary crushing roller speed of 1500 r/min, a secondary crushing roller clearance of 2.5 mm, and a secondary crushing roller speed of 3280 r/min. The pass rate of corn cob crushing in the simulation test was 98.2%. The physical tests, using the optimized parameter combination, yielded a qualified crushing rate of 97.5%, which deviates by 0.7% from the simulation results, satisfying the requirement of a qualified crushing rate exceeding 95%. The experimental outcomes validate the rationality of the proposed crushing scheme and the accuracy of the model, providing a theoretical foundation for subsequent research endeavors.

Experimental evaluation of the effect of pullout velocity on the behavior of multi-plate anchors

The determination of the pullout capacity of anchors has been a key point of offshore and onshore applications, considering factors such as the shape, size, penetration velocities, and pull-out velocities of the anchors. Multi-plate expandable anchors can be considered as an alternative that exhibits higher capacity compared to single plate anchors. While previous studies have demonstrated the influence of penetration velocity, there is a lack of research investigating the pullout capacity of multi-plate expandable anchors. In the present study, experimental tests were conducted to investigate the effect of various pull-out velocities. Different soil relative densities and the distance between anchors were examined in the laboratory tests. The study also employed two analytical methods—constant control volume and movement control volume—to investigate the results of pull-out velocity. In addition, the Discrete Element Method (DEM) was used to analyze the effect of particle shape on the results. In the experimental tests, the findings suggest that increasing the pull-out velocity from 10 to 30 mm/min improved the pullout capacity of anchors and the optimal distance between plate anchors was determined to be 1B. The DEM findings showed that the sharp-cornered shape had good agreement with experimental results.

Experimental and numerical study on the force transmission in granular packings under the hypergravity

Granular materials are ubiquitous in our environment, and their mechanical behavior is determined by particle-scale properties. The contact forces under hypergravity, which are crucial to planetary geology, remain underexplored, while extensive research has focused on behavior under surface pressure. We measured the contact forces between granular particles using a novel matrix film sensor under both hypergravity and surface pressure conditions, which were achieved in centrifugal and servo-hydraulic tests. Additionally, computations using the discrete element method were conducted to investigate the different patterns of force transmission from a microscopic perspective. We found an intriguing invariance in the contact force distribution under increased surface pressure. However, hypergravity enhances the contact forces between unjammed fine particles, causing contact forces converge to the distribution observed under surface pressure. Finally, a power-law fitted correlation was proposed to estimate the difference in contact force distributions between conditions of hypergravity and equivalent surface pressure.

Heterogeneous temperature characteristics considering rainfall effect during construction of an integrally-poured rock-filled concrete arch dam

Integrally-poured arch dam with the material of rock-filled concrete (RFC) is a new and rapid construction technology for mass concrete structures. There is still limited literature regarding the heterogeneous temperature field of RFC, especially under special weather conditions. In this study, a novel mesoscale model of heterogeneous RFC was generated through a combination of the discrete element method (DEM), the finite element method (FEM), and the background grid mapping method (BGMM). Based on the monitoring experiments at the Longdongwan project, this study greatly enhances the simulation precision and details by incorporating a two-phase material of heterogeneous RFC model, i.e. the stochastic pre-laid rocks and layered SCC (self-compacting concrete), and refining the analysis time step to an hourly basis. The results show that: (1) An infinite heat convection coefficient on the exposed RFC surfaces was effective in simulating the rainfall effect, and the mesoscopic simulation results aligned well with the monitoring data. (2)The cold wave with rainfall can cause a notable drop of around 10 °C in the placement temperatures of both rocks and SCC, and lowered the temperature rise by about 5°C for the subsequent freshly poured RFC lift. (3) The hydration temperature rise was recorded the highest (13–14°C) in the areas near the dam abutment, due to challenges of placing rocks. These findings can provide insights and advice for similar construction scenarios.

Computed Tomography-Driven Analysis of Particle Breakage Using a Coupled FDM-DEM Approach

This study proposes a refined approach for simulating the mechanical behavior of soils under high stress by integrating the Finite Difference Method-Discrete Element Method (FDM-DEM) with in-situ experiment. This novel framework incorporates advanced technologies such as flexible membrane and X-ray computed tomography (CT) to enhance the predictive capabilities of the simulation with physical insight. The FDM-DEM model adeptly simulates irregular particle shapes, capturing their interactions and the dynamics of particle breakage. The use of flexible membrane within the model further enriches this approach by enabling the capture of deformation responses in granular materials during shearing. Moreover, the adoption of CT technology facilitates continuous optimization of the simulation process. Validation through in-situ experiments has confirmed the model's effectiveness. The ability of the model to predict areas of high stress concentration—and their correlation with observed particle breakage patterns—underscores the utility of the enhanced FDM-DEM framework as a robust predictive tool for understanding the behavior of granular materials under shearing.