Search Results (1,018)

Accurate discrete element method (DEM) modelling of mature peanut plants is essential for simulating peanut harvesting, pod detachment, and harvest-loss formation. However, existing peanut DEM models are usually simplified as isolated pods, rigid cylindrical particles, or partial stem–pod structures, which limits their ability to represent the flexible deformation of vines and pod stalks and the fracture behaviors at the pod–pod stalk junction. In this study, a DEM-based flexible plant model was developed for mature peanut plants. The geometric dimensions, contact parameters, and mechanical properties of peanut pods, pod stalks, and stems were measured through physical experiments. The Hertz–Mindlin model was used for non-bonded contacts, whereas the Hertz–Mindlin with Bonding model was adopted to represent the flexible connections among plant organs and the fracture behaviors of the pod–pod stalk junction. The main DEM parameters were calibrated using Plackett–Burman screening, steepest ascent experiments, and central composite design. The results showed that the tangential stiffness per unit area and tangential critical stress at the pod–pod stalk junction were the dominant factors affecting pod detachment force. The optimized parameter combination was a tangential stiffness per unit area of 4.738 × 10⁵ N/m³ and a tangential critical stress of 9.350 × 10⁵ Pa, corresponding to a simulated tensile force of 6.73 N. Model validation was performed by comparing peanut harvesting simulations with field trials. The relative error of pod loss rate between simulation and field measurement was less than 7.55%, and the t-test result indicated no significant difference between the two datasets (p > 0.05). These results demonstrate that the proposed flexible peanut plant model can effectively characterize pod–pod stalk separation and can provide a reliable DEM modelling basis for peanut harvesting process analysis and equipment optimization. Full article

To clarify the spreading law of river crab pellet feed in a centrifugal spreading mechanism and provide a physical basis for the path planning of automatic feeding boats, this study took 4.0 mm sinking extruded river crab feed as the research object. A systematic research method combining physical experiments and Discrete Element Method (DEM) simulation was established. Physical experiments were conducted to calibrate the intrinsic parameters (density, Poisson’s ratio, elastic modulus) and contact parameters (friction coefficients and restitution coefficients between feed and 304 stainless steel/ABS plastic, as well as between feed particles) of the pellet feed. On this basis, a DEM simulation model of a vibration blanking-dual disc centrifugal spreading mechanism was constructed using the multi-sphere aggregation method and the Hertz-Mindlin (no-slip) contact model. A Central Composite Design (CCD) response surface experiment was employed to investigate the spreading law, with boat speed (0.5–1.5 m/s) and spreading disc rotation speed (800–1000 rpm) as independent variables, and unilateral spreading width (W), track superposition uniformity (ω), and transverse coefficient of variation ($Cv$) as response indicators to characterize spreading range and particle distribution. The results showed that the spreading disc rotation speed had an extremely significant effect (p < 0.0001) on all three response indicators, while boat speed had no significant effect. The feed exhibited a characteristic double fan-shaped superposition distribution pattern. Through multi-objective optimization, the optimal operational parameters were determined as a boat speed of 1.0 m/s and a spreading disc rotation speed of 879 rpm, yielding a unilateral spreading width of 2.9 m, a track superposition uniformity of 88.31%, and a transverse coefficient of variation of 8.33%. This study establishes a quantitative method for analyzing feed spreading characteristics and clarifies the spreading range and particle distribution law, providing a reliable physical basis for full-coverage path planning of crab pond feeding boats. Full article

During horizontal drilling in coal-rock gas reservoirs, the particle size distribution (PSD) of drilled cuttings directly affects drilling efficiency, hole cleaning, and wellbore stability. However, the evolution of cuttings PSD and its controlling mechanisms during coal-rock fragmentation remain insufficiently understood. In this study, a drill bit–coal-rock interaction model was established using the discrete element method (DEM) and calibrated against uniaxial compression experiments. The effects of weight on bit (WOB), rotational speed, and depth of cut (DOC) on cuttings PSD were quantitatively investigated. The results show that the relative influence on the maximum cutting size followed the order of DOC > WOB > rotational speed, whereas the influence on the average cutting size followed the order of rotational speed > WOB > DOC. Increasing DOC from 0.5 mm to 1.5 mm increased the maximum cutting size from 11.6 mm to 29.4 mm. Increasing WOB promoted the generation of medium- and large-sized cuttings, thereby increasing hole-cleaning requirements. Meanwhile, increasing rotational speed from 40 rpm to 90 rpm reduced the average cutting size and shifted the dominant cutting fraction from 4–6 mm to 1–4 mm. DEM observations reveal that cutting PSD evolution is jointly controlled by primary brittle fracture and secondary particle breakage through a five-stage fragmentation process involving stress concentration, microcrack initiation, crack propagation and coalescence, fragment detachment, and secondary fragmentation. Field validation using 146 cutting samples demonstrated the applicability of the proposed optimization strategy. Under the investigated drilling conditions, a DOC of approximately 0.5 mm and a rotational speed of 70–90 rpm were found to effectively limit oversized cutting generation. These findings improve the mechanistic understanding of cutting PSD evolution and provide practical guidance for drilling parameter optimization and hole-cleaning management in coal-rock gas horizontal wells. Full article

To enhance the precision of Discrete Element Method (DEM) simulation parameters for the grading of mechanically harvested fresh tea leaves, this study systematically measured the intrinsic physical and basic contact parameters of the Yinghong No. 9 cultivar. Addressing the distinction between primary and secondary contact interfaces during roller screening, the extreme boundary validation method was first employed to determine simplified fixed values for the contact parameters of the secondary component. Based on the measured physical angle of repose of 36.3°, Plackett–Burman screening, steepest ascent, and Box–Behnken tests were conducted sequentially to construct and optimize a second-order regression model relating significant parameters to the angle of repose. The results indicated that the static friction coefficient between tea leaves (0.723), the rolling friction coefficient between tea leaves (0.031), and the static friction coefficient between tea leaves and the PVC roller (0.547) were the key parameters affecting the angle of repose. Verification tests demonstrated that the simulated static angle of repose was 36.9° against the measured 36.3°, yielding a relative error of 1.65%. The simulated dynamic angle of repose in the rotating drum was 39.8° compared to the physical 38.3°, representing a relative error of 3.92%, and the errors in screening efficiency on the grading bench were all less than 5%. These results indicate that the calibrated parameters accurately characterize the material properties of mechanically harvested tea leaves, providing a reliable theoretical foundation for the structural optimization of grading equipment. Full article

Dense granular materials under low confining stress and low shear velocity—conditions relevant to low-pressure powder handling, near-surface transport, and the upper layers of stored bulk solids—remain insufficiently characterized at the microstructural level. We perform three-dimensional discrete element method (DEM) simulations of annular shear of monodisperse glass spheres at σ = 1 kPa and v = 0.01 m/s, corresponding to an inertial number I ≈ 1.06 × 10⁻³ at the quasi-static limit of the dense flow regime. The steady-state friction coefficient stabilizes at μ_ss ≈ 0.78, consistent with the quasi-static limit of the μ(I) framework. The solid volume fraction decreases monotonically from φ ≈ 0.50 at the base to φ ≈ 0.35 near the top, while the tangential velocity decays exponentially with depth (decay length δ_s ≈ 10 mm). Particle trajectory tracking reveals a sharp kinematic transition near z ≈ 5–6 mm separating a quasi-rigid basal layer (z ≲ 5 mm) from an upper shear-active zone (z ≳ 6 mm). The contact force distribution follows an exponential decay P($f$/$⟨f⟩$) ∝ exp(−β·$f$/$⟨f⟩$) with β ≈ 0.45, with strong force chains selectively concentrated in the upper zone. Together, these four microstructural descriptors co-locate within a single transition band, providing quantitative benchmarks for material characterization and constitutive modelling at the lower boundary of dense flow. Full article

The goaf backfilling with the coal gangue is an effective strategy for mitigating the mining-induced surface subsidence and reducing the solid waste accumulation. However, the conventional backfilling methods often suffer from limited transport efficiency, poor material distribution, and high operational cost. The present paper proposes a novel technique using an inclined spiral propeller to propel the gangue particles into the goaf, aiming to improve both the backfill rate and spatial uniformity. A three-dimensional parametric model of the inclined screw conveyor is developed, and the discrete element method (DEM) is employed to simulate the dynamic transport and placement of the gangue particles. An L9 ($3^3$) orthogonal experimental design is implemented to systematically evaluate the effects of the rotational speed (240, 300, 360 r/min), inclination angle ($30°$, $45°$, $60°$), and screw pitch (180, 240, 300 mm) on the two critical performance indicators, namely, filling mass and spreading coverage area. The range analysis and matrix analysis are performed to determine the primary influencing factors and to identify the optimal parameter combination for the multi-objective performance. The results show that the inclination angle is the dominant factor for the filling mass, with a $60°$ angle yielding the highest throughput (38.60 kg). In contrast, the rotational speed is the dominant factor for the spreading coverage area, where an increase from 240 to 360 r/min nearly triples the covered area. The optimal compromise for the comprehensive backfilling performance is the rotational speed 360 r/min, inclination angle $60°$, and screw pitch 300 mm, which simultaneously achieves the high transport capacity (36.65 kg) and the largest spreading area (2.87 ${\mathrm{m}}^2$). The present study provides a theoretical and methodological foundation for the engineering design of efficient, low-cost goaf backfilling systems. Full article

Blast furnace (BF) ironmaking is a complex multiphase process involving gas–solid flow, heat transfer, chemical reactions, burden movement, and phase transformation under high-temperature conditions. Since many internal states of the blast furnace cannot be directly observed during operation, numerical simulation and mathematical modeling have become important tools for understanding furnace behavior and optimizing operational parameters. This paper reviews recent advances in blast furnace numerical simulation and internal state reconstruction methods. Existing approaches, including packed-bed flow models, cohesive zone reconstruction methods, burden distribution models, and temperature field prediction methods, are summarized and discussed. In addition, the evolution of blast furnace mathematical models from early one-dimensional steady-state formulations to modern three-dimensional multifluid and hybrid simulation approaches is reviewed. Recent developments in computational fluid dynamics (CFD), the discrete element method (DEM), digital twin, and data-driven modeling are also discussed. Compared with traditional simplified models, modern multidimensional and hybrid approaches show improved capability in describing asymmetric furnace inner states, multiphase transport behavior, and operational parameter effects under industrial conditions. However, challenges still remain in achieving computational efficiency, parameter calibration, multiphase coupling, and real-time industrial application. Future studies are expected to focus on the integration of mechanism-based simulation and intelligent data-driven methods to improve prediction accuracy, operational adaptability, and intelligent control capability in blast furnace ironmaking. Full article

Water damage under the coupled effects of traffic load and pore water pressure (PWP) is a primary cause of early failure in asphalt pavements. Although dense-graded pavements generally have low void ratios, excess PWP poses a severe threat to durability under extreme conditions. These conditions include heavy rainfall, water accumulation in wheel tracks, and upward capillary water rise. In this study, a mesoscopic model considering fluid–solid coupling effects was established using the Particle Flow Code in the 2 Dimensions (PFC2D) platform, which is based on the discrete element method (DEM). A parallel-bonded stress corrosion model was introduced to describe damage evolution. The results show that the maximum positive PWP increased monotonically with load, reaching a distinct peak value at a critical loading frequency under specific load amplitudes. At this critical frequency, the fatigue life was significantly shortened compared to lower-frequency conditions. The PWP response exhibited a clear phase lag relative to the applied load, with the lag angle increasing alongside frequency. Furthermore, the absolute value of the minimum PWP continued to increase with fatigue damage accumulation. This indicates that regions with a vacuum suction effect were continuously expanding, which is a key reason for asphalt film stripping from the aggregate surface. These findings provide a theoretical basis for understanding mesoscopic water damage mechanisms in asphalt pavements and offer a reference for durability design. Full article

Biomimetic design has been used to reduce the high operating resistance of agricultural soil-engaging components, thereby lowering energy consumption. However, most existing contour-based structural biomimetic designs rely on a single or a few biological samples, making the resulting designs susceptible to individual variation and randomness in sample selection. To address this issue, this study used the abdomen of antlion larvae as a biological prototype. Abdominal contours of 85 antlion larvae were extracted from the front, top, and side views, and elliptic Fourier descriptors (EFDs) were used for contour normalization, averaging, and reconstruction to obtain population mean contours. Seven biomimetic wedge specimens were designed based on the population mean contours, and vertical penetration and horizontal cutting tests were conducted in two different media. The results showed that in the vertical penetration tests, the B-FT specimen, which integrated contour features from the front and top views, exhibited the best drag-reduction performance. Its average penetration resistance decreased by 44.26% and 32.81% in quartz sand and loam soil, respectively. In the horizontal cutting tests, the B-FTS specimen, which integrated contour features from all three views, showed the lowest average cutting resistance, with reductions of 17.62% and 36.47%, respectively. The FTS contour features were further applied to the biomimetic design of a subsoiler tine and validated by discrete element method (DEM) simulation and soil bin tests. Compared with the standard subsoiler tine, the biomimetic subsoiler tine reduced draft force by 11.57% in the simulation and by 12.61% in the soil bin test. These results demonstrate the drag-reduction effectiveness of population mean contours and provide a statistically grounded geometric reference for the biomimetic low-resistance design of agricultural soil-engaging components. Full article

The discharge behavior of granular materials from double-orifice silos is strongly affected by the inter-orifice spacing, yet the mechanical role of the inter-orifice region remains unclear. In this study, discrete element method (DEM) simulations are combined with experiments to investigate the formation, stability, and collapse of an inter-orifice quasi-solid region and its impact on the discharge rate. The results show that increasing the inter-orifice spacing progressively weakens shear transmission between adjacent outlets, promoting the development of a low-velocity, load-bearing quasi-solid region. Based on μ(I) rheology and a nonlocal granular fluidity framework, the quasi-solid region is shown to be controlled by local shear activation rather than by geometric separation alone. Once the inter-orifice quasi-solid region is formed, this region restricts the spatial extension of shear bands near the outlets, leading to a reduction in the effective shear area and a corresponding decrease in the discharge rate. A critical inter-orifice spacing is identified, beyond which the two outlets discharge independently. These findings provide a mechanistic understanding of flow-rate regulation in multi-orifice silos, offering guidance for the design of granular discharge systems. Full article

Residual film recovery is a crucial approach to mitigating agricultural “white pollution” and ensuring sustainable land use. Currently, the development of residual film recovery machines relies primarily on theoretical analysis and field performance tests. The lack of support from computational simulation models often leads to suboptimal mechanical performance, severely restricting the design and optimization of recovery equipment. To address this, this study proposes a method for constructing and experimentally validating a discrete element model of plow-layer residual film using EDEM software. First, field tests were conducted to measure soil compaction and residual film distribution at various depths. The ultimate tensile force of the residual film was also evaluated to provide fundamental data for model development. Using the Hertz–Mindlin with bonding contact model in EDEM, the intrinsic parameters of the residual film were selected and optimized. Combined with a Box–Behnken experimental design, a quadratic regression model relating normal stiffness per unit area, critical normal stress, and bond radius to the ultimate tensile force of the film was constructed. The optimal parameter combination was determined as follows: normal stiffness = 1.11 × 10⁶ N·m⁻³, critical normal stress = 2.45 × 10⁶ Pa, and bond radius = 0.03 mm. Under these parameters, the theoretically predicted ultimate tensile force was 1.18 N, and the simulated value yielded a relative error of only 1.69%, validating the effectiveness of the single-film model. Furthermore, using the field-measured data, a coupled film–soil model was established via the “rainfall” method to conduct simulated penetration tests. Parameter calibration was executed using the multivariate Newton–Raphson iteration method. The optimal bonding parameters for soil particles were identified as follows: normal stiffness per unit area = 9.6 × 10⁵ N/m², shear stiffness per unit area = 9.6 × 10⁵ N/m², critical normal stress = 5.38 × 10⁵ Pa, critical shear stress = 5.38 × 10⁵ Pa, and bond radius = 4.3 mm. The average simulated penetration resistance was 59.61 N, showing a relative error of 5.91% compared to the field-measured value of 56.28 N. These results demonstrate that the developed coupled film–soil DEM can be effectively applied to simulate the lifting and throwing processes of plow-layer residual film recovery machines, thereby providing vital modeling support for the design and optimization of residual film recovery mechanisms. Full article

Road engineers still face a critical challenge in improving the crack resistance of cement-stabilized macadam (CSM) base courses. This study employs the discrete element method (DEM) with realistic aggregate morphologies from X-ray computed tomography to model normally bonded and weakly bonded CSM. The mesoscopic parameters of normally bonded models were calibrated against laboratory unconfined compressive strength (UCS) tests, and a weakening ratio of bond strength (Wr_bs) was introduced to define the weakly bonded model. The results show that UCS decreases monotonically with the reduction in Wr_bs and the increase in Rr_ca. The maximum strength reduction reaches 26.3% at the extreme condition of Rr_ca = 100% and Wr_bs = 50%. Despite this reduction, the UCS of weakly bonded specimens remains compliant with Chinese specifications for base course materials when designed with appropriate parameters. Notably, weakly bonded specimens exhibit a more dispersed crack distribution and a more gradual energy dissipation process. This mechanism is associated with a reduced tendency for macroscopic crack initiation and propagation, suggesting the potential of weakly bonded CSM to enhance crack resistance. This work provides a mesoscopic theoretical foundation for the engineering application and sustainable development of weakly bonded CSM in pavement base courses. Full article

Garlic, a significant global specialty economic crop, is currently facing severe challenges from labor shortages and escalating production costs. Achieving full-process mechanized production is the core approach to ensuring sustainable industrial development and enhancing international competitiveness. This paper systematically reviews the research progress and application status of mechanized equipment throughout the entire crop cycle of garlic production, including seeding, field management, harvesting, and post-harvest processing and sorting. The study reveals that garlic equipment is undergoing a profound transformation from traditional mechanization to “opto-electro-mechanical integration” and intelligence. In the seeding phase, breakthroughs have been made in pneumatic precision seed-metering and machine vision-based clove bud orientation technologies, significantly improving the quality of upright planting. In field management, precise variable-rate application and targeted weeding have been preliminary realized through plant protection Unmanned Aerial Vehicle (UAV) downwash airflow field simulation (CFD) and deep learning-based image segmentation. In the harvesting phase, relying on 3D Discrete Element Method (3D-DEM) soil-cutting simulation and adaptive profile root-trimming technology, the industry is accelerating the transition from inefficient segmented harvesting to low-damage combined harvesting. In the post-harvest phase, hyperspectral imaging (HSI) and multi-label convolutional neural networks (CNNs) have been utilized to achieve high-speed non-destructive detection of internal and external quality. However, industry still faces critical bottlenecks such as the insufficient integration of machinery and agronomy, poor robustness of intelligent perception algorithms in complex environments, and high damage rates of core soil-engaging components. Future research should focus on lightweight algorithm deployment, digital twin-driven virtual prototyping, and the construction of regional standardized machinery–agronomy systems, aiming to build an efficient and universal intelligent production closed-loop for garlic. Full article

Uneven energy distribution and suboptimal fragmentation in bench blasting of hard–soft interbedded rock masses are critical challenges in open-pit mining. In this study, a five-hole bench blasting numerical model is developed using the discrete element method (DEM) to systematically investigate the effects of hard ore layer position, dip angle, and thickness on blasting performance. Numerical results indicate that while hard–soft layering has limited influence on overall bench fragmentation, it strongly controls block size distribution. Hard ore layers located in the upper or lower parts of the bench tend to form concentrated zones of large blocks, whereas those in the middle part achieve more uniform fragmentation, reducing the oversized block rate by approximately 57% and 45% compared with upper and lower locations, respectively. The dip angle of hard ore layers exhibits a nonlinear effect on the oversized block rate, reaching a maximum at 20°, and layer thickness is positively correlated with large-block occurrence. Based on these findings, a refined blasting strategy for hard–soft interbedded rock masses is proposed. Numerical simulations demonstrate that introducing satellite holes and implementing staged charging reduce the oversized block rate by 13% and 36%, respectively. Field bench blasting trials further indicate that top air-deck charging is beneficial for improving fragmentation uniformity in heterogeneous rock masses. These results provide a scientific basis for optimizing bench blasting parameters under complex lithological conditions. Full article

Powdered organic fertilizer is crucial for sustainable agriculture, but its poor flowability and hygroscopic compaction and caking nature cause frequent blockages during mechanized strip application. While a single Johnson–Kendall–Roberts (JKR) discrete element method (DEM) model simulates powder flow well, it fails to reflect the mechanical breakage of hard caked lumps. Thus, this study established a comprehensive DEM model simultaneously simulating both powder and caked lumps. Based on coarse-graining theory, 0.147 mm particles were scaled to 2 mm spheres. Contact parameters (e.g., JKR surface energy) were calibrated using response surface methodology, yielding a repose angle simulation error of only 0.18%. The actual three-dimensional (3D) geometry of caked lumps was reconstructed via 3D scanning, and breakage mechanical parameters were accurately calibrated by combining uniaxial compression tests with a Bonding model (errors for ultimate load and displacement < 2%). Applying this model to an anti-blocking fertilizer discharge device, simulations and performance tests demonstrated an acceptable macroscopic representation of both powder flow and lump breakage. The optimized device achieved a strip application uniformity coefficient of variation of 3.87–6.40%. By simulating the complex coexistence of powder flow and lump breakage, this study provides a feasible parameter calibration method and numerical reference for optimizing anti-blocking discharge devices. Full article