Search Results (33)

For polar ships, navigation in ice-covered regions can lead to high risk to structural safety. To study the structural risk induced by ice loads, a risk assessment framework is proposed based on a probabilistic analysis. The fatigue failure probability is derived with the first-order second-moment (FOSM) method. Typical ice load cases are extracted as a joint probability distribution of ice thickness and ship speed, based on shipboard measurements. Equivalent fatigue stresses for each case are calculated using a coupled discrete element method (DEM) and finite element method (FEM), and fatigue failure probabilities are obtained via linear cumulative damage theory. The ultimate strength failure probability is derived from the reliability theory. The probabilistic distribution of load-carrying capacity for the bow structure, determined by the moment estimation method, is used as the structural resistance, while the ice load distribution identified from shipboard monitoring is treated as the external load. Considering both the likelihood and consequence of failure, a risk matrix is constructed to assess structural failure risk. Inspection and maintenance intervals are then proposed according to the assessed risk levels. This approach offers a quantitative basis for structural risk management, supporting safe navigation and efficient maintenance planning for polar ships. Full article

The shell liner is a core component of Semi-Autogenous Grinding (SAG) mills, suffering severe wear from ore impact and friction, and its shape directly affects grinding efficiency and maintenance costs. In this study, the Finnie wear model in EDEM2022 software was improved to predict the wear morphology evolution of shell liners. A Python-based coupled simulation of the Discrete Element Method (DEM, EDEM) and Finite Element Method (FEM, ABAQUS) was established to analyze liner wear mechanisms, stress states, and mill service performance (wear resistance, grinding efficiency, and stress distribution). The simulated wear profile showed high consistency with laser three-dimensional scanning (LTDS) results, confirming the improved Finnie-DEM model’s effectiveness in reproducing liner wear evolution. Shearing in crushing/grinding zones was the main wear cause, with additional contributions from relative sliding among ore, grinding balls, and liners in grinding/discharge zones. DEM-FEM coupling revealed two circumferential instantaneous wear extremes (Max^a > Max^b) and two lifter wear rate peaks (M^a > M^b). In the grinding zone, liner stress distribution matched wear distribution, with maximum instantaneous stress at characteristic points A and B—stress at A reflects liner impact degree, while stress at B indicates mill ore-crushing capacity. Optimizing flat liner shape adjusted wear rate peaks (M^a, M^b), improving overall liner wear. This optimization significantly affected stresses at A/B and ore normal collision but had little impact on mill energy efficiency. Full article

The dynamic fracture of rocks under impact loads has many engineering applications such as rock blasting. This study reviews the recent achievements of investigating rock dynamic fracturing and its application in rock blasting using computational mechanics methods and highlights the prospects of modelling them with a hybrid finite-discrete element method (HFDEM) originally developed by the authors. The review first summarizes the peculiarities of rock dynamic fracturing compared with static fracturing, which are that the physical-mechanical properties of rocks, including stress wave propagation, strength, fracture toughness, energy partition and cracking mechanism, depend on loading rate. Then the modelling of these peculiarities and their applications in rock blasting using fast developing computational mechanics methods are reviewed with a focus on the advantages and disadvantages of prevalent finite element method (FEM) as representative continuum method, discrete element method (DEM) as representative discontinuum method and combined finite-discrete element (FDEM) as representative hybrid method, which highlights FDEM is the most promising method for modelling rock dynamic fracture and blasting application as well as points out the research gaps in the field of modelling the dynamic fracture of rocks under impact loads. After that, the progress of shortening some of these gaps by developing and applying HFDEM, i.e., the authors’ version of FDEM, for modelling rock dynamic fracture and applications in rock blasting are reviewed, which include the features of modelling the effects of loading rate; stress wave propagation, reflection and absorbing as well as stress wave-induced fracture; explosive-rock interaction including detonation-induced gas expansion and flow through fracturing rock; coupled multiaxial static and dynamic loads; heterogeneous rock and rock mass with pre-existing discrete fracture network; and dynamic fracturing-induced fragment size distribution. Finally, the future directions of modelling the dynamic fracture of rocks under impact loads are highlighted and a systematic numerical approach is proposed for modelling rock blasting. Full article

High-gradient magnetic separation (HGMS) is a conventional and effective method for processing weak magnetic materials. A multi-field dynamic coupling simulation method integrating the Finite Element Method (FEM), Computational Fluid Dynamics (CFD), and the Discrete Element Method (DEM) was employed to investigate the separation behavior in HGMS. The dynamic deposition process of magnetic particles under the interactions of magnetic fields, fluid flow fields, and particle–particle forces was simulated using a two-way fluid–solid coupling algorithm based on the FEM-CFD-DEM coupling approach. Experimental results demonstrated that the particle deposition profiles predicted by the double-wire medium model were in good agreement with the measured data. The research findings indicated that the separation process could be divided into three distinct stages—the adsorption stage, the closure stage, and the clogging stage—each characterized by unique dynamic behaviors and pressure-drop evolution patterns. Additionally, the effects of key parameters such as the feeding velocity and medium filling ratio on the separation process were analyzed, providing theoretical foundations and technical support for the optimization of HGMS processes and the enhancement of separation efficiency. Full article

In this paper, a discrete element method (DEM) coupled with a finite element method (FEM) was used to elucidate the impact of packing structures and size ratios on the cold die compaction behavior of pure copper powders. HCP structure, SC structure, and three random packing structures with different particle size ratios (1:2, 1:3, and 1:4) were generated by the DEM, and then simulated by the FEM to analyze the average relative density, von Mises stress, and force chain structures of the compact. The results show that for HCP and SC structures with a regular stacking structure, the average relative densities of the compact were higher than those of random packing structures, which were 0.9823, 0.9693, 0.9456, 0.9502, and 0.9507, respectively. Compared with their initial packing density, it could be improved by up to 21.13%. For the bigger particle in HCP and SC structures, the stress concentration was located between the adjacent layers, while in the small particles, it was located between contacted particles. During the initial compaction phase, smaller particles tend to occupy the voids between larger particles. As the pressure increases, larger particles deform plastically in a notable way to create a stabilizing force chain. This action reduces the axial stress gradient and improves radial symmetry. The transition from a contact-dominated to a body-stress-dominated state is further demonstrated by stress distribution maps and contact force vector analysis, highlighting the interaction between particle rearrangement and plasticity. Full article

In this paper, the analysis method which coupled discrete element method (DEM) and finite element method (FEM) is used to simulate the double compaction of random packing of Cu and Al composite powders with multiple particle sizes. Cu and Al composite powders with varying particle size ratios from 1:2 to 1:5 were generated by DEM and then imported to MSC. Marc software (MSC.MARC2015 version) to construct FEM analysis. The effects of metal ratios, compaction pressure and size ratios on the relative density and von Mises stress of the compact were studied. The results show that the average relative density of the compact increases with the Al content, and the stress decreases. The stress in the Cu particle is particularly higher than that in the Al particle, mainly because the contact normal force of the Cu particle is nearly parallel at each contact surface. Therefore, the phenomenon of stress concentration is easier to occur within copper particles. When Al content is 30wt.%, the particle size difference enhances densification efficiency by up to 12.3%, as evidenced by an initial relative density increase from 0.7915 to 0.8047, primarily due to smaller Cu particles effectively filling interparticle voids. When the compaction pressure is fixed, the average relative density of the compact with the particle size ratio 1:5 is higher than the others, and the contact forces inside the particles significantly decrease. Full article

A numerical experimental method combining the discrete element method (DEM) and the finite element method (FEM) is proposed to analyze water channel flow in heterogeneous porous media such as landfill layers. In this study, non-spherical particles —thin plates and rods—are introduced into DEM-FEM coupling for the first time, which allows for the virtual reconstruction of complex pore structures beyond the capability of traditional experimental approaches, such as soil tanks or X-ray CT. Fluid flow simulations performed on three types of virtual porous media showed that only the case with non-spherical particles generated water channels. Tortuosity analysis was used to quantify the complexity of the flow paths and showed median values of 1.258 and 1.218 for homogeneous and particle size-distributed cases, respectively. In contrast, the case simulating waste media had a significantly lower median tortuosity of 1.051, with a skewed distribution toward shorter paths, indicating dominant water channels. This shift in tortuosity, coupled with higher variance, serves as quantitative evidence of water channel formation. The results demonstrate that tortuosity analysis complements streamline visualization and provides a reliable means to detect and compare water channel flow behavior. The proposed DEM-FEM framework enables both qualitative and quantitative understanding of flow dynamics in large-scale, highly heterogeneous porous systems and is expected to support further research and practical design in landfill and drainage engineering. Full article

Magnetic separation is an important method in the processing process, and its essence is the targeted dispersion of the mineral processing slurry pulp in the magnetic field space. The slurry is a complex multiphase fluid system with continuous phase carrying a large number of discrete phase particles, in which the magnetic particles agglomerate, migrate, and disperse under the dominance of magnetic force. In this process, there is nonlinear and unstable dynamic coupling between the continuous phase (liquid) and the discrete phase (solid particles) and between the discrete phases. In this paper, a dynamic cyclic multi-dipole magnetic moment algorithm with a higher calculation accuracy is innovatively proposed to calculate the magnetic interaction force between particles. Moreover, the P-E magnetization model suitable for a two-dimensional uniform magnetic field is further improved and optimized to make it applicable to a three-dimensional gradient magnetic field. Finally, based on the coupling of the Finite Element Method (FEM), Computational Fluid Dynamics (CFD), and Discrete Element Method (DEM), a dynamic coupling model capable of accurately simulating the magnetic separation process is developed. This model can be used to study the separation behavior of particles under a multiphase flow and multi-force field and to explore the motion behavior of magnetic particles. Full article

To address the significant cutting resistance and fracture susceptibility of rotary blades, an innovative blade design was conceived to minimize resistance and enhance fracture resistance. By analyzing the interaction between the blade, soil, and root systems, an optimized design for the blade structure’s breakage resistance was developed. The theory of eccentric circular side cutting edges was applied to redesign the curve of the side cutting edge, and kinematic analysis was conducted to determine the optimal edge angle (26.57°). A flexible body model of corn residues was established, and cutting resistance measurements indicated a 15.1% reduction in cutting resistance. The breakage resistance of the rotary blade was validated using a discrete element method–finite element method (DEM–FEM) coupling approach. The results demonstrated the following: neck stress (−16.85%), specific strength efficiency (+9.72%), specific stiffness efficiency (+9.78%), fatigue life (+39.08%), and ultimate fracture stress (+20.16%), thereby meeting the design objectives. The comparison between field trial results and simulation data showed an error rate (<5%), confirming the simulation test’s feasibility. These findings provide theoretical references for reducing cutting resistance and enhancing breakage resistance in rotary blades. Full article

The article describes the peculiarities of strength and stability evaluation for deep geotechnical structures located in salt rock masses at great depths. A number of numerical studies are presented for the deep mining excavations of various cross-sections. The numerical simulations are conducted using a specific coupled algorithm of the finite element method (FEM) and distinct element method (DEM), which allows not only the prediction of dangerous zones in the undermined rock mass but also to simulation of the block fracture of the rock mass directly. Potential critical zones in the rock mass are established using an original complex limit state criterion for rock masses and FEM simulation results. Mentioned original criterion is a specific multicriterial method, which considers potential tensile, compressive and shear failure as well as crack propagation. To define the block-structure formulation in the rock mass it is proposed to use the Lade criterion in the complex limit state zones. Furthermore, block-structured rock mass behavior is simulated using DEM to predict its block-like fracture. The results of numerical studies clearly show that the mechanical behavior of potash salt rock masses significantly differ at moderate and great mining depths. Namely, the volume of the limit state zones nonlinearly increases with the increase in the mining depths up to double the size of the excavation cross-section. However, the exact amount of potentially failed rock mass has to be established using the direct DEM simulation in the limit state zones. Full article

Wear can occur in flat die pelletizers, often reducing service life. This study explores the issue of die hole wear in the pelletizing process of a standard Total Mixed Ration (TMR) feed. The selected TMR formulation comprises varying proportions of corn, alfalfa hay, and quinoa. A coupled DEM-FEM analysis was used to examine stress–strain conditions in various die hole regions at different material ratios, predict the fatigue life of flat die materials in the pelletizing process, and validate the accuracy of investigating flat die wear through friction wear tests. It was found that the entrance of the die hole experiences the most severe conditions in terms of equivalent stress and elastic strain. The fatigue life is shortest at the entrance, with a maximum equivalent stress of 42.8 MPa, a maximum equivalent elastic strain of 2.5 × 10⁻³, and a minimum fatigue life stress cycle of 5.0 × 10⁵. In contrast, the equivalent stress and equivalent elastic strain at the middle and upper parts of the die hole are minimal, with an equivalent stress of 4.8 MPa and a minimum equivalent elastic strain of 2.8 × 10⁻⁴. Material wear tests revealed that the most severe wear on the flat die specimen occurred when the ratio of corn, alfalfa hay, and quinoa straw was 7:2:1, consistent with the findings from the DEM-FEM coupling method. The pelleting process, arising from the contact between the material and metal, encompasses adhesive wear, abrasive wear, and fatigue wear. Full article

Sudden leakage during tunnel construction poses a great threat to the safety of the tunnel. There are relatively few studies on the mechanism of structural collapse induced by tunnel leakage, so it is difficult to propose effective control measures. To solve this problem, a coupled fluid–solid strata analysis model and a nonlinear FEM tunnel model were established based on model test results to analyze the mechanism of tunnel collapse. The following conclusions were drawn: (1) A DEM-based coupled fluid–solid model combined with a nonlinear FEM tunnel model can effectively simulate the physical process of tunnel collapse. (2) The mechanism of tunnel leakage-induced strata response is the continuous destabilization and reappearance of the soil arching effect, which restricts the erosion of the soil and results in macroscopic soil caves, and finally leads to the impact load of the destabilized soil. (3) The process of the tunnel structure collapse is as follows: firstly, a large deformation of the tunnel structure is caused by the redistribution of external loads generated by the earth arching effect; then, due to the multiple impact loads from the destabilization of the soil, plastic hinges are generated at the tunnel joints, and the tunnel collapses. Full article

The microscale mechanisms underlying the suction anchor–sandy soil interaction under slidable pulling actions of mooring lines remain poorly understood. This technical note addresses this knowledge gap by investigating the suction anchor–sandy soil interaction from micro to macro, with a particular emphasis on the effect of interface friction. The discrete element method (DEM) was utilized to simulate the sandy soil, while the finite element method (FEM) was employed to model the suction anchors. The peak pulling forces in numerical simulations were verified by centrifuge test results. The research findings highlight the significant influence of interface friction on the pulling force–displacement curves, as it affects the patterns of suction anchor–sandy soil interactions. Furthermore, clear relationships were established between the magnitude of interface friction, rotation angle, and pullout displacement of suction anchors. By examining the macro-to-micro behaviors of suction anchor–sandy soil interactions, this study concludes with a comprehensive understanding of failure patterns and their key characteristics under different interface friction conditions. The findings proved that the interface friction not only influences the anti-pullout capacity but also changes the failure patterns of suction anchor–soil interactions in marine engineering. Full article

Vibrating flip-flow screens are widely employed in the deep screening processes of coal washing, solid waste treatment, metallurgy, and other fields, playing a crucial role in enhancing product quality and production efficiency. The screen surface and material movement of vibrating flip-flow screens are highly complex, and there is currently insufficient understanding of their screening mechanism, limiting further optimization and application. In this paper, the Discrete Element Method (DEM), Finite Element Method (FEM), and Multi-Body Dynamics (MBD) were integrated to establish a numerical coupling model for vibrating flip-flow screens, considering material loads, screen surface deformation, and screen machine dynamics. The Response Surface Method was utilized to analyze the significant impact of relative amplitude, tension amount, amplitude of driving screen frame, vibration frequency, and screen surface inclination on screening efficiency and material velocity. The results indicate that the most significant factor influencing the screening of flip-flow screens is the screen surface inclination. Based on a BP neural network, a five-degree-of-freedom inclination surrogate model for flip-flow screens was established. The whale algorithm was employed for multi-objective optimization of the surrogate model, resulting in a screen surface inclination distribution that meets the requirements of different operating conditions. Full article

The micromechanical mechanism of pipe instability under lateral force actions on sloping sandy seabeds is unclear. This study investigated the effects of slope angle and instability direction (upslope or downslope) on pipe–soil interaction instability for freely laid and anti-rolling pipes using coupled discrete element method and finite element method (DEM–FEM) simulations. The numerical results were analyzed at both macro- and microscales and compared with the experimental results. The findings revealed that the ultimate drag force on anti-rolling pipes increased with slope angle and was significantly larger than that on freely laid pipes for both downslope and upslope instabilities. Additionally, the rotation-induced upward traction force was proved to be the essential reason for the smaller soil deformation around freely laid pipes. Moreover, the shape differences in the motion trajectories of pipes were successfully explained by variations in the soil supporting force distributions under different slope conditions. Additionally, synchronous movement between the pipe and adjacent particles was identified as the underlying mechanism for the reduced particle collision and shear wear on pipe surfaces under a high interface coefficient. Furthermore, an investigation of particle-scale behaviors revealed conclusive mechanistic patterns of pipe–soil interaction instability under different slope conditions. This study could be useful for the design of pipelines in marine pipeline engineering. Full article