Search Results (38)

To simulate the fracture behavior of members during structural collapse, this paper proposes a member fracture simulation algorithm that integrates the plastic hinge model with a ductile fracture damage model within the member discrete element method (MDEM) framework. The coupling is achieved by computing stresses at the four most unfavorable edge points of the contact section and using the minimum fracture strain as the section-level failure criterion. The algorithm is validated against a cantilever beam fracture example, yielding results in good agreement with reference data under two yield stress conditions. The fracture algorithm is then embedded as a self-contained module into an adaptively coupled DEM/FEM algorithm and applied to simulate the shaking table collapse test of a single-layer spherical reticulated shell. The simulation predicts structural collapse at a peak ground acceleration (PGA) of 2268 gal—consistent with the experimental value—with 126 members fractured at collapse onset, and reproduces the observed fracture sequence in which first-ring diagonal members near the supports fail progressively from the bottom upward. The proposed framework provides a computationally robust and practically deployable tool for collapse analysis of large-span reticulated structures, with direct implications for progressive-collapse prevention in seismic design and post-event structural forensic investigation of collapse mechanisms. Full article

In fluid analysis of stent models with a braided structure, conventional modeling using Finite Element Method (FEM) boundaries requires extremely fine fluid mesh resolution. The objective of this study is to propose a grid size design strategy for FEM–Discrete Element Method (DEM) coupled analysis. In the proposed method, the fluid is modeled using FEM, while the stent is modeled using a continuous arrangement of DEM particles. The volume-force-based coupling method eliminates the need for node sharing between the FEM and DEM, thereby reducing the modeling workload. In this study, we derived grid sizes based on flow analysis around a single strand and verified the flow analysis around a 3D braided stent model. The results showed that the proposed method reduced the number of fluid grids by approximately 44% compared to conventional methods. In this case, the maximum errors in velocity and pressure were 0.0064 m/s and 17.07 Pa, respectively, and high correlations of 0.9 or higher were obtained for both distributions. Furthermore, the maximum relative error in the drag coefficient was 4.332%. This study provides guidelines for a fluid grid size design method that enables the reduction in computational cost and modeling burden in fluid flow analysis around stents. Full article

China is rich in magnetite mineral resources, but they are generally characterized by low grade, fine dissemination size, and a high content of harmful impurities. Wet low-intensity magnetic separation (WLIMS) is an important method for processing fine-grained magnetite. However, during the separation process, fine magnetite particles are prone to magnetic agglomeration, which makes it difficult for conventional WLIMS separators to achieve high-selectivity separation. To address this issue, a novel WLIMS separator based on a rotating magnetic system was developed in this investigation, and its separation characteristics were systematically investigated through a combined approach comprising CFD–DEM–FEM multiphysics coupling simulations and experimental validation. Simulation results indicate that the rotating magnetic system significantly reduces the chain length and the structural stability of magnetic agglomerates just as magnetite particles enter the magnetic field region. Furthermore, under the rotating action of the magnetic system, the magnetic chains only enclose a portion of the intergrowth minerals, while gangue minerals remain unattached, which positively contributes to improved separation selectivity. Both laboratory-scale experimental results and industrial production data indicate that, compared to the conventional WLIMS separator, the rotating magnetic system WLIMS separator achieves significantly superior separation performance. For a magnetite ore with a grade of 57.68%, the rotating magnetic system WLIMS separator achieved an optimal concentrate grade of 65.43% (with a recovery of 94.78%), whereas the conventional WLIMS separator attained only 60.32% at a similar recovery rate. This investigation provides an important basis for the large-scale industrial application of rotating magnetic system WLIMS separators and the efficient development and utilization of fine-grained magnetite resources. Full article

To overcome the welding-induced residual tensile stress of Q235B welded joints, a sequential thermal-mechanical welding and DEM-FEM dynamic shot peening coupled model is established. The Goldak double-ellipsoidal heat source model is adopted to simulate welding temperature evolution, and the discrete element method fully considers random shot ejection and shot–shot collision energy attenuation, which addresses the simplification defect of traditional single-shot finite element models. The effects of shot diameter d, incident angle θ, initial shot velocity v and mass flow rate r_m on the residual compressive stress layer are systematically analyzed. Results reveal that larger shot diameter and initial shot velocity deepen the residual compressive stress layer. Meanwhile, the maximum residual compressive stress first increases and then decreases with the increase in r_m and θ. The optimal parameter combination is determined as d = 1 mm, θ = 60°, v = 60 m/s, r_m = 9 kg/min. Under these parameters, the maximum residual compressive stresses reach −306 MPa (σ_x) and −310 MPa (σ_z), with the depths of the residual compressive stress layer being up to 0.78 mm for σ_x and up to 0.66 mm for σ_z, respectively. Different from previous simplified simulations, this study quantifies the collision energy attenuation caused by shot trajectory overlap. This proposed model can provide guidance for post-weld surface strengthening of low-carbon steel engineering structures. Full article

To mitigate the spatial variation in shot velocities induced by nozzle geometry during shot peening of an arced surface (a peening configuration that uses an arc-shaped emission surface to replicate the actual nozzle-induced scattering effect, as distinct from the peening of a curved workpiece surface), this study introduces an approach for assessing surface roughness and residual stress through an average energy density function that integrates both the particle scattering angle and energy distribution characteristics. The study introduces a novel approach by incorporating an equivalent emission arc surface into finite element simulations. This innovative model effectively captures the scattering phenomenon observed in real shot peening processes and identifies this factor as a critical optimization parameter within energy field theory. A discrete element method–finite element method (DEM–FEM) coupled model has been established to simulate the shot peening process across various scattering angles. Systematic investigations reveal the significant impact of the scattering angle on the integrity of AISI 9310 steel, particularly in terms of residual stress and surface roughness profiles. The simulation outcomes demonstrate that the maximum residual compressive stress exhibits a non-linear trend: initially decreasing before increasing as the scattering angle is elevated, with the average energy density attaining its peak at a scattering angle of approximately 8°. Compared to conventional planar shot peening, the arc shot peening technique induces more pronounced surface strengthening effects in critical areas. These insights offer valuable theoretical guidance for optimizing the shot peening of an arced surface parameters, thereby enhancing surface integrity and potential fatigue performance. Full article

The gravitational field represents the fundamental stress field in geotechnical engineering. Its influence on soil mechanical behavior is manifested not only through variations in stress magnitude but also through stress gradient effects. However, existing soil mechanics frameworks and classical continuum-based numerical methods cannot characterize the intrinsic mechanical response of granular media under stress gradient conditions. Based on a previously established higher-order continuum theory incorporating stress gradient effects, this study develops a multiscale coupled Finite Element Method–Discrete Element Method (FEM–DEM) numerical framework. The method is implemented using Esys-escript in conjunction with the open-source discrete element platform Yade. By embedding representative volume elements (RVEs) at the finite element level and introducing gravity-induced stress gradients within the RVE using the discrete element method, stress gradient transfer and multiscale coupling are achieved. The proposed method is validated through numerical simulations of triaxial compression and trapdoor tests. The results demonstrate that the method can capture the microscale mechanisms associated with stress gradient effects and effectively resolve the constitutive solution difficulty encountered in the previously proposed generalized continuum framework incorporating stress gradients. The developed framework provides a new numerical tool for investigating the mechanical behavior of granular media under stress gradient conditions, with potential applications in geotechnical problems governed by gravitational fields, including deep underground engineering and extraterrestrial environments with non-conventional gravity. Full article

Soft robotics has become a dynamic field that emphasizes adaptability and safe interaction with complex environments. These structures utilize deformable materials and continuum mechanics to adapt their shape, absorb shocks, and perform tasks in unstructured environments. However, the design and optimization of these systems is challenging, primarily due to the nonlinear and discontinuous behavior of granular materials. In this paper, we address the role of simulation frames as an important tool for understanding, designing, and extending the functionality of software robotic devices utilizing granular jamming. The analysis suggests that DEM is essential for capturing particle-level mechanisms, while FEM is more effective for system-level optimization but tends to smooth out the transition of jamming. Hybrid FEM–DEM approaches provide the highest physical accuracy, albeit at an increased computational cost. Overall, the findings emphasize that the choice of framework must be application-oriented and that multiphysics coupling represents the future development. The review gives an up-do-date review of the simulation tools and approaches for granular-jamming-based systems with a specific focus on continuum arms with a granular-jamming-based central backbone. Such methods can be used for the optimization the back-bone geometry and its filling material (shape, porosity, granule size) with possible use in the real-time control of such arms. Full article

Hopper scales are critical dynamic metering equipment in industrial production, yet their metrological performance is often compromised by wear on weighing units over long-term service. This study proposes a wear state assessment method based on the evolution of vibration features. Focusing on the rocker-column weighing unit, we analyzed the mechanism by which geometric changes in the spherical indenter—caused by fretting wear—alter the system’s constraint state. A global-to-local coupled Discrete Element Method and Finite Element Method (DEM–FEM) model was constructed to account for material-structure interactions, alongside a dynamic simulation model considering wear evolution. The simulation accuracy was validated through a dedicated experimental platform. The results indicate that as spherical wear intensifies, the low-frequency swaying of the indenter is suppressed, causing the system’s vibration mode to transition from a flexible, swaying-dominated state to a high-frequency, rigid-impact-dominated state. In the frequency domain, this manifests as energy migration, characterized by attenuation of the low-frequency main peak and an elevation of the high-frequency broadband noise floor. Crucially, as a key innovation for wear diagnosis, this study reveals the directional sensitivity of statistical indicators. While the Root Mean Square (RMS) exhibits a non-monotonic V-shaped trend, the Kurtosis and Margin factors of the tangential vibration demonstrate superior monotonic sensitivity. Under severe wear conditions, these two indicators increase by 14 and 11 times, respectively. These findings provide highly effective diagnostic criteria and hold significant engineering application value for the predictive maintenance of industrial dynamic weighing systems. Full article

This study introduces a mesoscale modeling methodology for polyurethane-solidified ballast beds (PSBBs) that eliminates reliance on X-ray computed tomography (XCT) and addresses constraints in specimen size, capital cost, and post-processing complexity. The approach couples the Discrete Element Method (DEM) with the Finite Element Method (FEM). A high-fidelity discrete-element geometry is reconstructed from three-dimensional laser scans of ballast particles. The virtual-ray casting algorithm is then employed to identify the spatial distribution of ballast and polyurethane and map this information onto the finite-element mesh, enabling heterogeneous material reconstruction at the mesoscale. The accuracy of the model and mesh convergence are validated through comparisons with laboratory uniaxial compression tests, determining the optimal mesh size to be 0.4 times the minimum particle size (0.4 D_min). Based on this, a parametric study on the effect of sleeper width on ballast bed mechanical responses is conducted, revealing that when the sleeper width is no less than 0.73 times the ballast bed width (0.73 W_b) an optimal balance between stress diffusion and displacement control is achieved. This method demonstrates excellent cross-material applicability and can be extended to mesoscale modeling and performance evaluation of other multiphase particle–binder composite systems. Full article

Overburden layers, composed of unconsolidated sediments, are widely distributed in construction, transportation, and water conservancy projects, but their inherent defects (e.g., developed pores, low strength) easily induce engineering disasters. Grouting is a core reinforcement technology, yet traditional design relying on empirical formulas and on-site trials suffers from high costs and low prediction accuracy. Numerical simulation has become a key bridge connecting grouting theory and practice. This study systematically reviews the numerical simulation of overburden grouting based on 82 core articles screened via the PRISMA framework. First, the theoretical system is clarified: core governing equations for seepage, stress, grout diffusion, and chemical fields, as well as their coupling mechanisms (e.g., HM coupling via effective stress principle), are sorted out, and the advantages/disadvantages of different equations are quantified. The material parameter characterization focuses on grout rheological models (Newtonian, power-law, Bingham) and overburden heterogeneity modeling. Second, numerical methods and engineering applications are analyzed: discrete (DEM) and continuous (FEM/FDM) methods, as well as their coupling modes, are compared; the simulation advantages (visualization of diffusion mechanisms, parameter controllability, low-cost risk prediction) are verified by typical cases. Third, current challenges and trends are identified: bottlenecks include the poor adaptability of models in heterogeneous strata, unbalanced accuracy–efficiency, insufficient rheological models for complex grouts, and theoretical limitations of multi-field coupling. Future directions involve AI-driven parameter optimization, cross-scale simulation, HPC-enhanced computing efficiency, and targeted models for environmentally friendly grouts. The study concludes that overburden grouting simulation has formed a complete “theory–parameter–method–application” system, evolving from a “theoretical tool” to the “core of engineering decision-making”. The core contradiction lies in the conflict between refinement requirements and technical limitations, and breakthroughs rely on the interdisciplinary integration of AI, multi-scale simulation, and HPC. This review provides a clear technical context for researchers and practical reference for engineering technicians. Full article

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