Discrete Element Method Software Research Articles

Numerical study on microscopic behaviour of non-crushable cemented granular media subjected to direct shear test

ABSTRACT Granular media, though discontinuous and heterogeneous, exhibit discrete behaviour at the grain scale and continuum behaviour at the macroscopic level. Understanding the correlation between micro-macro-mechanical parameters is crucial. The Discrete Element Method (DEM) effectively bridges this micro-macro-mechanical gap. This study simulates the Direct Shear Test (DST) using DEM software PFC2D on synthetic cemented granular media (CGM) under varying normal loads and strain rates. It examines micromechanical features and correlates them with macroscopic observations, focusing on confinement pressure and strain-rate dependency. Significant volumetric dilation is observed during shearing at low normal loads, which diminishes at higher normal loads. Particle-scale shear mobilization is explored through shear band formation in the sample. Grain-scale contact force distribution is highly heterogeneous throughout the sample. A probability distribution study is carried out to explore the bond breakage effect on the global response, which confirms the bond breakage to be a pressure and strain-dependent phenomenon.

ESTUDIO COMPARATIVO DEL FACTOR DE EMPAQUETAMIENTO MEDIANTE SOFTWARES DE ELEMENTOS DISCRETOS

This paper performs a study of the Packing Fraction (PF) in different commercial DEM (Discrete Element Method) software. For this purpose, the influence of different geometrical and particle characteristic parameters on the PF by filling a cylindrical container are analyzed. The simulation software used are DigiDEM, DigiPac and StarCCM+. Simulations are performed to compare the simulation time and verification of results; the influence of increasing the particle diameter in the same container, the influence of increasing the particle diameter and the container in proportion, the influence of increasing the h/d ratio in cylindrical particles "pellets" and the influence of decreasing the h/d ratio in cylindrical particles "disks".

3D modelling of the hydraulic performance of open-graded asphalt using the DEM and CFD methods

In this study, we propose a modelling approach that combines computational fluid dynamics (CFD) and the discrete element method (DEM) to simulate the hydraulic performance of three-dimensional (3D) porous asphalt (PA) specimens. Initially, realistic aggregate appearances are captured through the image analysis technique. This information is then transferred to DEM software for the reconstruction of pore structure with distinct aggregate shapes following the real particle size distribution (PSD) as identified by local construction standards. The pore structure, reproduced via DEM, is used as input for CFD simulation to assess the hydraulic performance. To capture the dynamic of water motion simulation, the multiphase model, volume of fluid method (VOF), within CFD is applied to track and predict the interactions between different material phases, and the effect of porous structure to the hydraulic behaviour and performance. Results of numerical simulations indicate that PA samples with higher total porosity (air voids) have better pore connectivity and more effective porosity. For samples with the total porosity of 20%, the difference between the total porosity and the effective porosity was 14.8%; while a much lower difference of 8.3% was found for the higher porosity (25%) specimen. Compared with effective porosity, the reduction in active porosity reaches 58.8% in deeper layers for the sample at 20% total porosity, and only 32.2% for the sample at 25% total porosity. Overall, the results show that there is about a 4.57 times difference in hydraulic performance represented by mass flow rate among PA samples with 5% total porosity difference.

Breathing of a Silicon-Based Anode: Mechanical Discrete Approach Using DEM

Abstract Silicon is one of the most considered solutions to improve lithium-ion battery technology. Nevertheless, silicon shows a huge expansion, leading to a significant “breathing” of electrodes during cycling, i.e. a succession of swelling and shrinking. Irreversible volume changes are observed and conjectured to be related to microstructure changes. However, current publications addressing the modelling aspects mainly use analytical or continuous models. Thus, this study aims to apply discrete element method (DEM), a granular dynamics numerical tool, on a silicon-based anode in order to consider the complex internal microstructure and the associated micro-mechanics. In particular, a sample of anode was created using the DEM software LIGGGHTS and simplified linear breathing laws of particles were implemented. The global approach follows successive sensitivity analysis of granular/contact parameters to evaluate individually their capacity to reproduce more finely the observed breathing behaviour. So far, it is found that the breathing amplitude is mostly influenced by the silicon fraction and the breathing irreversibility by particles stickiness. The rigidity of particles also had a decreasing influence on swelling amplitude, but only for low values, far from practical ones, and the silicon content within the anode presented a linear influence on the swelling amplitude.

Calibration of Sliding Friction Coefficient in DEM between Different Particles by Experiment

Granular materials are widely prevalent in nature and industry, and the discrete element method (DEM) is the most effective method for the mechanical analysis of granular materials. Because of the difficulty inherent in friction coefficient determination, the friction behavior of granular geomaterials has always been a difficult problem in DEM. In order to study the variation rules of the sliding friction coefficients in DEM, an experiment designed to determine the sliding friction coefficient between particles with different shapes and different contact forms and an experiment designed to determine the sliding friction coefficient between particles and different boundaries were proposed, and the experimental results were fitted. In order to verify the reliability of the experiments, the fitting results were embedded into DEM software, and several packing experiments and simulation experiments were carried out and compared. The simulated results are detailed and discussed with reference to the experimental results as part of this paper. The results indicate that the simulation results are highly consistent with the experimental results, and the sliding friction coefficient obtained by the proposed experiment is in accordance with that determined theoretically. The sliding friction coefficient determined by fitting according to the experimental results can determine the sliding friction coefficient in DEM simulation and improve the accuracy of simulation results.

Mesoscale modeling of polypropylene fiber reinforced concrete under split tension using discrete element method

This study is proposed to determine the effectiveness of the discrete element method (DEM) in predicting the tensile properties of polypropylene fiber-reinforced concrete (PFRC). To calibrate and validate the proposed PFRC simulation model, splitting tensile tests were performed on limestone (granite)-polypropylene fiber reinforced mortar (PFRM) hybrid samples to investigate the effects of polypropylene fiber (PF) contents and aggregate types on the tensile properties of the interfacial transition zone (ITZ). The test improved the particle contact mode in the PFRC discrete element model. Based on DEM software (PFC3D), a multi-phase microscopic discrete element model was created, and the tensile properties of PFRC were predicted by simulating a splitting tensile test. The simulation results revealed that the proposed model could be more efficient in predicting the splitting tensile responses of PFRC. The improved flat joint-softening contact model is more accurate and stable for the bridging effect simulation of PF after concrete cracking.

Research on wheat flour‐making technology based on discrete elements

AbstractThe operating characteristics of a mill's rolling distance and roller speed during wheat‐milling were studied to provide a reference for optimizing the operating parameters of the mill. The high‐performance discrete element method software (EDEM) was used to establish a roller‐crushing system for wheat flour production. Numerical simulations of wheat flour production were performed using this system. It was found that increasing the roller distance of the flour mill machine could reduce the wear of the grinding rolls and the power of the grinding roll system, which reduced the crushing rate of wheat during the milling process. Increasing the grinding roll speed can reduce the wear of the grinding rolls but will increase the wheat‐crushing rate. At a constant fast roller speed, increasing the speed ratio increased the wheat‐crushing rate which reduced the power of the grinding roller system. During the grinding roll wear process, the obtuse and sharp angles gradually disappear. A comparison of the simulation and experimental results shows that the discrete element method can accurately predict the wear of the grinding roll.Practical ApplicationsThe milling machine is a key piece of equipment used for making wheat flour. The rolling distance, speed, and speed ratio of grinding rolls are important operating parameters during mill operation. Selecting specific parameters will directly affect the quality of wheat‐milling and the economic efficiency of the milling enterprise. This study adopted a discrete element method to study the effects of these parameters on wheat milling, providing a good reference for the technical personnel of milling enterprises.

Characterizing force-chain network in aggregate blend using discrete element method and complex network theory

The force chain network in aggregate blend indicates load transfer path and is the main carrier to resist external loads. The objective of this study is to analyze the force chain network characteristics of aggregate blend on the basis of complex network theory. The virtual aggregate blend models with three stone matrix asphalt (SMA) gradations and three dense asphalt concrete (AC) gradations were constructed using discrete element method (DEM). The force chain network topology structure of each aggregate blend was established according to the aggregate contact parameters extracted from DEM software and the introduced complex network theory. The characteristics of each force chain network were analyzed by the various network evaluation indicators. The results showed that there are two or more contacts between most particle pairs. The average coordination number and the average contact number of aggregate blend are not equal. The degree distribution of each gradation shows a good power-law distribution. The force chain network of aggregate blend is a scale-free network. Big particles have greater average strength and smaller average weight distribution difference compared with small particles. The reference lower limit has better clustering performance for SMA-16, and the reference upper limit has better clustering performance for AC-25. The average path length of SMA-16 is longer than that of AC-25, indicating that SMA-16 has better load transfer ability and skeleton properties.

Cost‐ and performance‐aware resource selection for parallel software on heterogeneous cloud

SummaryCloud providers offer flexible infrastructures and on‐demand services, including the capability to deploy low cost virtual resources of many different types. However, the diversity of cloud resources followed by the important trade‐off between cost and performance makes the resource selection a challenging task for users in the case of parallel communication‐intensive software. The paper presents cost‐ and performance‐aware resource selection for parallel discrete element method (DEM) software as a service (SaaS) on heterogeneous OpenStack cloud. The developed resource selection uses preliminary application‐specific benchmarks of size smaller than targeted problems and the performance prediction based on speedup of parallel computations to obtain Pareto optimal solutions and to select the best configuration of containers from user's perspective. Hybrid parallelization of DEM software is developed by using OpenCL for shared‐memory multi‐core architectures and MPI for internode communications on distributed‐memory computer clusters. Round up and proportional pricing schemes are examined and compared from a user's perspective. Lower cost of computations obtained by using the proportional pricing scheme is always preferable for users. However, the difference approaches 1.0% of the cost calculated by using proportional pricing scheme, when long lasting computations are performed. The prediction tends to underestimate the execution time of DEM SaaS, but its accuracy is sufficient to obtain the same Pareto optimal solutions by using measured and predicted execution times. Pareto front and linear scalarization propose to select configurations of containers capable of exploiting higher memory bandwidth, which is specific to memory bandwidth bound DEM computations.

Evolution of ice load prediction tools for hydrotechnical construction

The article provides an overview of the historical and contemporary developments in estimating ice loads on marine structures. It first underscores the significance of accurate ice load calculations for the safety and reliability of structures, and subsequently traces the evolution of ice load estimation techniques from past standards to current international standards and guidelines. The article then delves into the limitations of traditional methods for ice load estimation, which rely heavily on empirical data, before discussing the innovative and more precise discrete element method (DEM) for ice load estimation. The article outlines the benefits of using DEM over traditional methods and explores the diverse software options available for modelling ice loads on marine structures, including commercial and open-source alternatives. The article emphasizes the importance of staying up-to-date with the latest advancements in technology and techniques for ice load estimation, highlighting the crucial role that precise and reliable ice load estimation plays in ensuring the safety and dependability of marine structures in extreme environments. Overall, the article provides a comprehensive summary of the evolution of ice load estimation techniques for marine structures, from past norms to the contemporary use of DEM and advanced software packages. It underlines the necessity of continuous research to ensure that marine structures are constructed with the highest safety levels.

Earth Pressure of the Trapdoor Problem Using Three-Dimensional Discrete Element Method

Load transformation from the yielding part of the soil to the adjacent part is known as the soil arching effect, which plays an important role in the design of various geotechnical infrastructures. Terzaghi’s trapdoor test was an important milestone in the development of theories on soil arching. The research on earth pressure of the trapdoor problem is presented in this paper using the three-dimensional (3D) discrete element method (DEM). Five 3D trapdoor models with different heights are established by 3D DEM software PFC 3D. The variation of earth pressure on the trapdoor with the downward movement of the trapdoor, the distribution of vertical earth pressure along the horizontal direction, the distribution of vertical earth pressure along the vertical direction, the distribution of lateral earth pressure coefficient along the depth direction, the magnitude and direction of contact force chain are studied, respectively. Related research results show that the earth pressure on the trapdoor decreases rapidly after the downward movement of the trapdoor, and then reaches the minimum earth pressure. After that, the earth’s pressure will rise slightly, and whether this phenomenon occurs depends on the depth ratio. For the bottom soil, due to the stress transfer caused by the soil arching effect, the ratio of earth pressure in the loose area decreases, while the ratio of earth pressure in the stable area increases. With the trapdoor moving down, the vertical earth pressure along the depth in the stable zone is basically consistent with the initial state, which shows an approximate linear distribution. After the trapdoor moves down, the distribution of earth pressure along with the depth in the loose area changes, which is far less than the theoretical value of vertical earth pressure of its self-weight. Because of the compression of the soil on both sides, the lateral earth pressure coefficient of most areas on the central axis of the loose zone is close to the passive earth pressure coefficient Kp. The existence of a ‘soil arch’ can be observed intuitively from the distribution diagram of the contact force chain in the loose zone.

Discrete element analysis on the influence of drilling fluid pressure on core discing in pressure-preserved coring

In the process of coring in a high in-situ stress environment, the rock core is damaged due to stress release, and core discing is a prominent manifestation of this damage. Pressure-preserved coring has no direct effect on in-situ stress, and its influence on stress release is related to drilling fluid pressure. Yet fluid pressure in the coring process was not considered in most former numerical simulation studies on core discing. In this paper, the discrete element method software PFC3D is used to conduct a numerical simulation of the coring process. According to the two conditions without drilling fluid pressure and with it, and different horizontal in-situ stresses of 5-160 MPa, fracture and discing of the core with drilling are observed. In addition, the law of fracture and discing in the process of coring was studied, and the function of pressure-preserved coring to prevent fracture and discing is explored. Simulation results show nonlinear trends in distribution of discs both in time and in space.

Design and Parameter Optimization of a Soil Mulching Device for an Ultra-Wide Film Seeder Based on the Discrete Element Method

The soil mulching device plays an important role in the sowing stage of crops. Compared with the traditional narrow film planting mode, under the ultra-wide film planting mode adopted by crops in arid areas, the soil transportation distance inside the soil mulching device increases, resulting in the problem of uneven soil coverage thickness between sowing rows, which seriously affects the crop emergence rate. There are many methods available to solve the problems of ultra-wide film planting, such as theoretical analysis and discrete element method (DEM) simulation. In this paper, we design a covering device consisting primarily of the soil disc and the cylindrical sealer. By constructing and analyzing a mechanical model of the soil mulching device, the parameters related to the working performance are determined. In order to further optimize the parameters, the simulation model of the device and soil operation process is established by using DEM software. We design a single-factor simulation test. The structural parameters and operating parameters of the cylindrical sealer are divided into two experimental groups, and the soil transport volume (STV) and the coefficient of variation of the soil coating cover uniformity (G1) are used as response values. Based on the parameters of the single-factor test after narrowing the optimization range, the response surface test is designed. According to the experimental results, a quadratic regression model of STV and G1 is established, and the influence of the interaction of each parameter is analyzed. Finally, the optimal values of the structural parameters and operating parameters of the soil mulching device are determined. The actual field test was completed. The soil coverage thickness was between 1.42 cm and 1.50 cm, and G1 was 2.59%. The test results were very satisfactory. This shows that it is reliable to optimize the parameters of the soil mulching device by theoretical analysis and the DEM.

Prediction of Bucket Fill Factor of Loader Based on Three-Dimensional Information of Material Surface

The bucket fill factor is a core evaluation indicator for the optimization of the loader’s autonomous shoveling operation. Accurately predicting the bucket fill factor of the loader after different excavation trajectories is fundamental for optimizing the loader’s efficiency and energy cost. Therefore, this paper proposes a method for predicting the bucket fill factor of the loader based on the three-dimensional information of the material surface. Firstly, the co-simulation model of loader shoveling material is established based on the multi-body dynamics software RecurDyn and the discrete element method software (DEMS) EDEM, and the co-simulation is conducted under different excavation trajectories. Then, the three-dimensional material surface information before shovel excavation is obtained from DEMS, and the surface function of the material contour is fitted based on the corresponding shovel excavation trajectory information. Meanwhile, the volume of the material excavated by the loader is obtained by the numerical integration method, and it is divided by the rated bucket volume to obtain the estimated bucket fill factor. Finally, the actual volume of the material after the shovel excavation is divided by the rated bucket volume to obtain the accurate bucket fill factor. Based on this, the prediction model of the bucket fill factor is built. The experimental results show that the proposed method is feasible, with a maximum error of 4.3%, a root mean square error of 0.025 and an average absolute error of 0.021. The research work lays the foundation for predicting the bucket fill factor of construction machinery such as loaders and excavators under real working conditions, which is conducive to promoting the development of autonomous, unmanned, and intelligent construction machinery.

Design and Test of the Clearing and Covering of a Minimum-Tillage Planter for Corn Stubble

Conservation tillage technology can reduce wind erosion and soil erosion, improve soil fertility, avoid straw burning and relieve ecological pressure. It is an important measure to achieve sustainable agricultural development. In northeast China, there is a large amount of straw covering the ground after the corn machine harvest, which can easily lead to the blockage of the soil-touching parts during no-tillage seeding, affecting sowing quality and crop yield. In order to solve the above problems, the clearing and covering of a minimum-tillage planter for corn stubble was developed. The machine can complete multiple processes, such as seedbed preparation, seeding, fertilization, covering and suppression, straw covering, etc., in a single entity. This paper focuses on the design of the straw cleaning device and uses discrete element method software (EDEM 2018, Altair Engineering, Troy, MI, USA) to establish the straw cleaning device–straw–soil discrete element simulation model. The quadratic-regression orthogonal center-of-rotation combination test method is used to optimize the parameter combination of the machine, using the operating speed, the speed of the knife roller and the penetration depth of the knife as the test factors and using the rate of cleaning straw and the equivalent power consumption as the evaluation index. The results show that each factor has a significant influence on the performance evaluation indices, and the order of influence of each factor on the rate of cleaning straw is operation speed > penetration depth of knife > speed of knife roller, and the order of influence of each factor on the equivalent power consumption is penetration depth of knife > speed of knife roller > operation speed. The optimal combination of parameters is a 5.5–6.2 km/h operation speed, a 500 rpm speed of the knife roller, a 40 mm penetration depth of the knife, a straw-cleaning rate of more than 90% and an equivalent power consumption of less than 8 kW. This study provides technical and equipment support for the promotion of conservation tillage technology in Northeast China.

Analysis of the Regularity and Mechanism of Fault Activation Caused by Deep Continuous Mining of Shizishan Copper Mine, China

In order to study the law and mechanism of fault activation induced by deep continuous mining, this paper takes the fault activation caused by underground mining of Shizishan Copper Mine as the research object. On the basis of field investigation and theoretical analysis of fault activation, the law and mechanism of fault group activation induced by deep continuous mining in the Shizishan mining area are analyzed in detail based on the three-dimensional discrete element method software 3DEC. The results show that the fault effect of rock movement in the footwall of the main orebody in the mine area is obvious. The en echelon steep dipping fault group in the footwall of the goaf will move each fault block in the direction of the goaf and slip along the fault plane when the balance between mining and gravity is disrupted. The fault activation has a domino effect in time and space, and the mechanism of this effect is revealed. The research results have great significance for the deep mining area development, mining alignment arrangement, and disaster prevention and control caused by fault activation.

Lethe-DEM: an open-source parallel discrete element solver with load balancing

Approximately $${75}\%$$ of the raw material and $${50}\%$$ of the products in the chemical industry are granular materials. The discrete element method (DEM) provides detailed insights of phenomena at particle scale, and it is therefore often used for modeling granular materials. However, because DEM tracks the motion and contact of individual particles separately, its computational cost increases nonlinearly $$O(n_\mathrm{p}\log (n_\mathrm{p}))$$ – $$O(n_\mathrm{p}^2)$$ (depending on the algorithm) with the number of particles ( $$n_\mathrm{p}$$ ). In this article, we introduce a new open-source parallel DEM software with load balancing: Lethe-DEM. Lethe-DEM, a module of Lethe, consists of solvers for two-dimensional and three-dimensional DEM simulations. Load balancing allows Lethe-DEM to significantly increase the parallel efficiency by $$\approx {25}$$ – $${70}\%$$ depending on the granular simulation. We explain the fundamental modules of Lethe-DEM, its software architecture, and the governing equations. Furthermore, we verify Lethe-DEM with several tests including analytical solutions and comparison with other software. Comparisons with experiments in a flat-bottomed silo, wedge-shaped silo, and rotating drum validate Lethe-DEM. We investigate the strong and weak scaling of Lethe-DEM with $${1}\le n_\mathrm{c} \le {192}$$ and $${32}\le n_\mathrm{c} \le {320}$$ processes, respectively, with and without load balancing. The strong-scaling analysis is performed on the wedge-shaped silo and rotating drum simulations, while for the weak-scaling analysis, we use a dam-break simulation. The best scalability of Lethe-DEM is obtained in the range of $${5000}\le n_\mathrm{p}/n_\mathrm{c} \le {15{,}000}$$ . Finally, we demonstrate that large-scale simulations can be carried out with Lethe-DEM using the simulation of a three-dimensional cylindrical silo with $$n_\mathrm{p}={4.3}\times 10^6$$ on 320 cores.

Force-Chain-Based Analysis of Factors Influencing Pressure Arch Around Tunnel Under Earthquake

The force chain method is a powerful tool to analyze the pressure arch of a tunnel, which has important influence on the seismic stability of tunnel structures. The force distribution around the tunnel before and after an earthquake was observed with numerical simulation and shaking table test, and then some parameters related to the pressure arch around the tunnel were analyzed. The discrete element method software PFC was used to numerically simulate the variation of shape and height of pressure arch with tunnel depth before and after an earthquake. The effect of tunnel depth, span, section shape, lining stiffness, seismic spectrum, and seismic amplitude on the shape and height of pressure arch was numerically simulated. The numerical results show that the tunnel depth, span, section shape, and seismic amplitude have great effect on the pressure arch shape, while the lining stiffness and seismic spectrum has little effect on the pressure arch shape. In addition, the shaking table tests were conducted to observe the pressure arch shape before and after an earthquake, and the experimental results were applied to verify the numerical simulation results.

Damping considerations for rocking block dynamics using the discrete element method

AbstractIt is well established that unreinforced masonry (URM) buildings develop damage‐forming collapse mechanisms during high‐intensity earthquakes, with these mechanisms exhibiting large rocking displacements before collapsing. The Discrete Element Method (DEM) of analysis can realistically capture phenomena that involve large movements of elements, resulting in the technique being ideal for simulating the collapse of URM building elements. Consequently, extensive research using DEM to analyse the seismic response of URM buildings and building components has recently been published. However, the variety of reported damping approaches that have apparently led to DEM results that successfully replicate physical observations underscores the need for consistent guidance related to the assignment of damping factors. The Rayleigh damping distribution model implemented in the DEM software 3DEC was used to study the differences between mass proportional (MP) and stiffness proportional (SP) damping configurations. After reviewing phenomena that need to be damped and previous works where damping was implemented, the capabilities and drawbacks of the time‐efficient MP damping configuration were studied and the results compared to simulations with SP damping. When considering numerical simulations that incorporated MP damping and led to results that were seemingly well‐matched to experimental tests, it was found that the apparent robustness of decisions pertaining to the adopted input parameters was deceptive in most cases. Consequently, SP damping was recommended for all DEM rocking simulations, even though MP damping could be used with satisfactory accuracy in certain situations discussed herein. A pragmatic relationship between both damping strategies was proposed.

Calibration of parameters for discrete element simulation model for alfalfa with different moisture contents based on angle of repose test

During the simulation analysis of the discrete element method (DEM) for the alfalfa compression process, the input parameters in DEM software had a significant effect on simulation results. To obtain simulation parameters of the alfalfa with different moisture contents, a combination of angle of repose tests and simulation optimization design are presented in this paper. The repose angle of the alfalfa with moisture contents of 2.7%, 13.4%, 19.9%, 33.1%, and 74.5% was measured, and the results were 41.99˚, 38.30˚, 47.47˚, 56.31˚, and 63.09˚, respectively. Inclinometer tests, shear test, and restitution test were performed to evaluate the contact parameters. Taking contact parameters as the calibration object, the Plackett-Burman test was used to screen out which parameters had significant influence on the repose angle. The results of variance analysis showed the surface energy was the most significant parameter in the alfalfa repose angle test for each moisture content. Based on the Box-Behnken test, a second-order regression model of repose angle was obtained and the significance parameters were optimized and calibrated. The parameters calibrated in this paper can provide a reference for other simulations of alfalfa utilization.