Computational Particle Mechanics最新文献

The reduction in permeability of sediments due to blockages caused by suspended fine particles is a common concern for the extraction processes of oil, natural gas, or methane gas from methane hydrate. In this study, the permeability reduction caused by suspended fine particles was newly modelled. Solid–water two-phase flow in frame sand sediment was numerically simulated by a three-dimensional Lattice Boltzmann method. For frame sand, shapes of real sand grains were extracted by series expansion of spherical harmonics from CT-scan images and packed in a microscopic computational domain. For each fine particle, a motion equation is solved using the pressure integrated on its surface with considering its collision to the frame sand surfaces. The calculated relative permeability could not be modelled solely by the volume saturation of the fine particles, but also their specific surface area was required.

Particle finite element method (PFEM) can effectively simulate large deformation problems in geotechnical disasters such as landslides, debris flows, and dam breaks. In recent years, PFEM has attracted much attention at home and abroad. The research progress of PFEM for large deformation simulation in geotechnical engineering is reviewed. Firstly, the development history and basic idea of the PFEM are introduced. Then, the theoretical progress of the computational theory for PFEM in geotechnical engineering is presented. Finally, the application progress of the PFEM for large deformation simulation in geotechnical engineering is introduced, including collapse and landslide problems, structure–soil coupling large deformation problems, hydromechanical coupled problems, etc. Through the review of the research progress of PFEM for large deformation simulation in geotechnical engineering, the cognition of relevant researchers in this field is deepened, and the development of large deformation simulation theory and engineering application of PFEM for geotechnical engineering is promoted.

Image-based in situ coal/gangue identification has emerged as a pivotal tool for monitoring instantaneous gangue mixing ratios (IGMR) in fully mechanized top coal caving operations. However, intelligent coal caving control requires dynamic optimization based on the "top coal recovery rate–cumulative gangue mixing ratio (CGMR)" curve. This study establishes a predictive framework linking IGMR to CGMR through numerical simulations and machine learning. The authors proposed a particle swarm optimization–random forest (PSO–RF) hybrid model that outperforms conventional RF, achieving R² values of 0.937 (advancing direction) and 0.962 (layout direction). Feature importance analysis reveals scraper speed, coal caving position, and sequential/interval caving strategies as dominant factors influencing CGMR. Physical experiments validate the model's robustness, demonstrating a 56% reduction in prediction error compared to baseline methods.

To address the issues of soil compaction and elevated subsoiling resistance stemming from soil salinization, a dual-shovel subsoiling approach that adheres to the subsoiling principle was put forward. In constructing the discrete element model, three types of soil particle models were developed according to the actual morphology of saline-alkali soil. Quantitative analyses of the static angle of repose and frictional inclination angle of the soil were conducted. The static repose angle and frictional inclination angle of the soil were simulated and analyzed using EDEM software. The contact parameters were validated through real-world experiments to establish an accurate soil model. A bionic deep loosening model was constructed by referencing the largest toe of the armadillo’s forefoot, utilizing its outer contour coordinates to define the edge curve of the solid structure. In this study, a tillage model was established using the coupling method of Multibody Dynamics—Discrete Element Method (MBD-DEM). The deep loosening mechanism of the bionic deep loosening shovel on saline-alkali soil under various assembly parameters was investigated. Results indicate that the peak values of surface soil particle force and soil disturbance effects occur at spacings of 300 mm and 450 mm. Experimental results fluctuated in accordance with variations in shovel spacing. Considering the unique characteristics of farming in saline-alkali land, the disturbance rate of each soil layer relative to the range of soil disturbances was evaluated. When the shovel spacing was 450 mm, the soil disturbance range was 960.49 mm, with the disturbance of upper soil particles accounting for 59.77%. Among all tested spacings, the 400 mm shovel spacing demonstrated superior performance. This study provides fundamental data for assembling earth-touching components of agricultural machinery under Huang-Huai-Hai saline-alkali land working conditions and offers theoretical guidance for selecting optimal shovel spacing.

To determine the discrete element simulation parameters for the walnut kernel grading process, the stacking angle response of walnut kernels obtained from bench tests and simulation tests was used. The discrete element simulation parameters were calibrated using response surface optimization. The physical parameters required for the simulation test of the walnut kernel grading process were measured through bench testing. Discrete element simulation models of walnut kernels with varying degrees of completeness were established using 3D scanning technology and EDEM software. The walnut stacking angle was measured as 23.55° using the injection method, combined with MATLAB image processing for boundary fitting. The Plackett–Burman test, the steepest ascent test, and the Box–Behnken test were designed using Design–Expert software, with the stacking angle as the response value, to construct the regression model and optimize the parameters. The optimal combination of significant parameters is as follows: walnut kernel–walnut kernel rolling friction coefficient of 0.03, walnut kernel–walnut kernel static friction coefficient of 0.136, and walnut kernel–walnut kernel collision recovery coefficient of 0.26. The simulated and measured values of the natural angle of repose for walnut kernels under the optimal parameter combinations were compared. A two-sample t test (p > 0.05) confirmed that there was no significant difference between the two, verifying the reliability of the simulation parameters for walnut kernels. Using the Dalton plate-based loading device and the intermittent ladder loading device for walnut kernel discrete effect testing, the relative errors between the simulated and measured values of walnut kernel discrete rates for the two loading devices were 1.69 and 1.81%, respectively. These results indicate that the walnut kernel discrete meta-model and simulation parameters are reliable, providing a solid reference for the design and optimization of walnut kernel grading and sorting devices.

An advanced three-dimensional mathematical model for fluid dynamics, thermal transfer, solidification, and inclusion migration in continuous casting is formulated utilizing CFD-DEM methodologies. The arc-shaped arrangement of the cast billet and its vertical segments of designated height are employed to investigate the impact of the solid shell on fluid dynamics and the movement of inclusions. We obtain the inclusions, the floating rate, and the distribution of the slab. The results indicate that the fluid progresses toward the slab center along the solid shell after exiting the bottom recirculation zone. The floating rate of inclusions rises with a decrease in casting speed and an increase in the height of the vertical segment. Inclusions at 25 μm have a more uniform distribution compared to those at 50 and 100 μm.

Microencapsulated resin mineral composites (MRMC) are widely used in the infrastructure industry for their ability to intelligently detect and autonomously repair the microcracks, whereas the interactions between microcracks and components of self-healing composites have not been well understood. To reveal the damage behavior of MRMC, a mesoscopic fracture model of the self-healing composites was established based on the cohesive element, the variation rule of damage characteristics was analyzed at the mesoscopic level, and the effect mechanism of the microcracks was elucidated. The results show that the rupture behavior of the microcapsules is influenced by the relative positions of the components, and the mesoscopic damage of the self-healing composites is dominated by the tensile cracks. Increasing the microcapsule size can reduce the curvature of the microcrack path, reducing the rupture probability of microcapsules. The relationship between the mechanical properties of the materials and their repair potential is balanced when the volume fraction of microcapsules is at 5%. The effect mechanism of microcracks within the material is influenced by the geometrical characteristics of the aggregate and its spatial distribution pattern. The smaller the aggregate volume fraction and aggregate size is, the greater the randomness of the propagation path of microcrack is. These findings contribute to a better understanding of the intelligent repair behavior of MRMC, thereby providing technical support to improve the serviceability of the structural parts.

Polyvinyl chloride (PVC) foams are primarily used in many industries, such as construction, aerospace, marine, and automotive; thus, understanding their fracture behavior is vital. The paper presents a new study about the three-dimensional fracture behavior of PVC foams using the peridynamic method, where we pay more attention to the tearing fracture mechanics of these foams. We introduce an all-inclusive simulation framework incorporating peridynamic theory to estimate crack propagation in PVC foams. The fracture initiation, growth, and coalescence processes are efficiently captured using the proposed three-dimensional peridynamic model (3D-PDM). The effectiveness and validity of the proposed 3D-PDM are demonstrated through detailed comparisons with experimental data and measurements in predicting fracture patterns and failure loads. The results emphasize the capability of the peridynamic approach in capturing complex fracture phenomena in PVC foams. Therefore, the study provides an efficient tool for researchers and engineers to improve the design of foam-based structures, accordingly enhancing their safety and reliability. Our study not only provides a detailed investigation of the tearing mechanism in PVC foams under various loading and boundary conditions but also highlights the potential of the peridynamic model. The study reveals that bending on PVC foam increases in-plane tearing while decreasing through-the-thickness tearing. Further exploration of the proposed 3D-PDM applications in other polymeric and composite materials could be achieved, offering hope for its potential in fracture mechanics research.

Discrete element method (DEM) based on graphic processing unit (GPU) is widely utilized for studying the responses of geotechnical dense granular materials under periodic or traffic loading. However, limited computational efficiency of DEM hinders its further application. Conventionally, the criterion for updating particles’ potential contact list (i.e., Verlet list) is assessing whether the maximum particle displacement in global coordinate system exceeds the threshold. Although geotechnical dense particles exhibit considerable quasi-periodic displacement under periodic or traffic loading, the potential contact targets for most particles do not change during quite a few loading cycles. Therefore, there are numerous redundant updates of Verlet list induced by quasi-periodic displacement, restricting computational efficiency. In this study, we propose a novel criterion for Verlet list updating, in which the displacement of particles in local particle coordinate system is considered. Then, the proposed criterion is plugged in the MUSEN software. By simulating previous laboratory full-scale half-sleeper model tests, the accuracy and performance of the proposed criterion are testified based on GPU computing. The results show that compared to conventional criterion, the proposed criterion reduces the updates of Verlet list by 43–68% and improves the computational efficiency by 14–47%. This study indicates a potential way to improve computational efficiency of the GPU-based DEM for geotechnical dense granular materials under periodic loading.

The mechanical properties of castor stalk play an important role in the design of clamping, cutting, and harvesting devices, as well as in the comprehensive utilization of biological resources. The study measured the mechanical properties of the stalks and its contact parameters (stalk–stalk, stalk–steel) with experiment. The particle model with each layer of stalk tissue was established by the discrete element method (DEM). The contact and bonding parameters were calibrated through the stalk bending simulation. The accuracy of the model was verified by stalk cutting and compression simulation. Meanwhile, the fracturing process of stalks was analyzed. The mechanical behavior and motion laws among the particles in each layer of the stalk tissue during the compression process were analyzed. The results show that the model can reflect the mechanical properties of castor stalks. The equivalent stress of the pith part particles is greater than the CX (cortex and xylem part) particles in the compression process. The particle velocity on the upper side of the first layer in the pith is the largest, which is 8.01 (text{m }{text{s}}^{-1}). The particle velocity on the upper side of the CX is the smallest, which is 0.23 (text{m }{text{s}}^{-1}). The particle movement distance on the upper side of the CX is the largest, which is 9.68 mm. The particle movement distance on the lower side of the first layer in the pith is the smallest, which is 4.84 mm. These results are very important for studying the mechanical properties of castor stalk and the fracture mechanisms of stalk shear shearing and compressing.