Computational Particle Mechanics最新文献

Subway depots commonly incorporate ultra-small radius curves, particularly in entry and exit lines, where conventional sleepers exhibit limitations in maintaining track geometry. This can lead to track expansion, misalignment, and derailments. An enhanced sleeper with a raised platform was specifically designed for small radius curves in this paper. A field implementation was conducted on a section of the subway entry and exit line with a radius of R = 150 m. Single tie push tests (STPTs) were performed to evaluate the lateral resistance of the enhanced sleeper, type IIIa sleeper, and existing wooden sleepers. Additionally, a discrete element model of the “sleeper-ballast bed” system was developed to analyze the mechanical properties of the sleepers under STPTs and vertical loading conditions. Results showed that the lateral resistance of the existing wooden sleepers was only 4.04 kN, whereas the type IIIa sleepers demonstrated a lateral resistance of 21.96 kN. In contrast, the enhanced sleepers demonstrated a lateral resistance of 25.35 kN, representing a 15.4% increase compared to the type IIIa sleeper. The raised platform of the enhanced sleeper contributed 37.2% of the total lateral resistance value. Under vertical loading, the maximum vertical force on the enhanced sleepers was reduced by 10.3%, and the ballast stressdecreased by 8.1%. These findings indicate that the enhanced sleeper design not only improves track stability in ultra-small radius curves but also reduces maintenance needs and operational costs, offering a significant advancement in subway infrastructure.

Smoothed particle hydrodynamics (SPH) is a grid-free numerical method that relies on a Lagrangian description of the fluid. It has been used in a variety of multiphysics applications, including applications to free surface flow problems where surface tension plays a pivotal role. Accurate simulations of surface tension are crucial for a realistic description of multiphase flows and small-scale fluid systems, such as drops and bubbles. This article describes a novel approach based on a pair potential force within the SPH framework that simulates surface tension in a physically consistent manner. The Young–Laplace equation is used to calibrate the force term associated with the cohesive action so that there is a close correspondence between the calculated surface tension and the minimization of the surface area. The performance of the model has been assessed against a number of benchmark tests, including the spherization of cubic drops, the spreading of a drop impacting on a solid surface, and the drop oscillation in a gas environment. A comparison of experimentally obtained pendant drop images with the simulation results for distilled water, ethylene glycol and ethanol drops is also provided as a further validation test. The proposed approach has been shown to be accurate enough to simulate surface tension effects in liquid drops under a variety of dynamical conditions irrespective of the length scale, implying that it is particularly suitable for simulating microfluidic systems.

To investigate the mechanical and damage properties of rock specimens with different joint inclinations under seepage–stress coupling, a comparative numerical simulation test for different working conditions was developed using RFPA^2D-Flow code. The distinction between their mechanical properties was compared and analyzed. The damage properties of rocks with different joint inclinations under seepage–stress coupling were also investigated based on energy theory and regression analysis. A new pre-peak damage constitutive model was established. The results indicated that the peak strength declined and then enhanced with growing joint inclination, and the equivalent elastic modulus increased with growth of joint inclination, but they were both lower than intact rocks. As the joint inclination increases, the peak strain changes in a “W” shape. Based on the energy theory, the peak energy characteristics of rocks with different joint inclinations under seepage–stress coupling were investigated. The linear relationship between U and U^e and U^d before peak stress was obtained employing the regression method, which conforms to the linear energy storage law. Then, a damage constitutive model based on the linear energy storage law for jointed rocks under seepage–stress coupling condition was established, and the initial damage was considered. The stress–strain curves calculated according to the model are more consistent with the experimentally measured curves in the pre-peak stage, which verifies the validity of the model.

Grouting reinforcement technology is a method to reinforce fractured rock mass in rock engineering. Fillers will change the stress of the fracture, thus affecting the mechanical behavior and cracking behavior of the fractured rock mass. In this paper, uniaxial compression tests were conducted on red sandstone samples containing varying numbers of fractures, and the impact of fillers on the strength characteristics and damage progression in fractured red sandstone was investigated. A numerical simulation of the uniaxial loading process was conducted, examining the influence of fracture and filler presence on mesofailure mechanisms, focusing on mechanical properties, particle displacement and failure modes. The findings indicate that the filled specimens exhibit higher uniaxial compressive strength and elastic modulus compared to the unfilled ones. During the loading process, a phenomenon of stress concentration arises at the interfaces and tips of fractures, which subsequently triggers the formation of numerous microcracks. The emergence of fractures within the specimen leads to a substantial decrease in its crack initiation coefficient. When fractures are filled, the crack initiation coefficient significantly improves, requiring higher stress for failure. The damage evolution can be categorized into four stages: undamaged, initial damage, damage progression and ultimate failure.

Soft elasto-hydrodynamic lubrication (soft EHL), in which the structure is elastically deformed by the pressure of the fluid film, is ubiquitous in industrial machinery. In soft EHL, the structure has a relatively small Young’s modulus and is elastically deformed by the pressure of the fluid film acting on the structure. In this study, we developed a soft EHL model by coupling the moving particle simulation (MPS) method and the structure deformation equation. The proposed model is based on a particle method and has advantages in predicting complex oil geometries under soft EHL conditions. To validate the accuracy of the proposed model, a soft EHL phenomenon was simulated. As a result, the pressure and cylinder deformation obtained by the proposed model were in good agreement with the reference solutions based on the traditional Reynolds equation. In addition, the simulation efficiency of the proposed model was improved by introducing an extended multi-resolution particle technique.

This study introduces a rough interface construction method that considers the morphology of surrounding rock in mining stopes, applied to backfill-rock samples and numerical models. Using a smooth-joint model in the PFC3D numerical software, accurate contact conditions were achieved at the backfill-rock interface. This approach overcomes the limitations of simplified geometries in capturing the influence of rock morphology on shear behavior. Comparative analysis between experimental and simulation results showed that increasing cement content and normal stress enhances the shear strength of backfill-rock samples. Increased normal stress promoted microcrack propagation in concave regions of rough surfaces, strengthening failure resistance by improving backfill sliding resistance. Conversely, decreased cement content led to rapid microcrack development along mold edges, suggesting that lower cement content reduces shear resistance and influences failure characteristics. The PFC3D simulations successfully replicated stress responses and failure patterns observed in experiments, providing a robust framework for investigating the mechanical behavior and failure mechanisms of backfill-rock interactions. These insights provide a valuable basis for optimizing backfill-rock stability and improving underground mining safety and efficiency.

Screening experiments on friable materials have shown that significant crushing occurs in the rotary vibrating screen; however, many studies have not fully accounted for its impact on screening efficiency. This study investigates kaolin as a research subject to elucidate how material crushing influences screening efficiency. First, the bonded particle model within the discrete element method was employed to generate kaolin particle clusters, simulating their crushing behavior during the sieving process. The vibration frequency and amplitude were optimized through simulation experiments, revealing that a frequency of 13 Hz and an amplitude of 3 mm achieved the optimal balance between screening efficiency and material breakage. Comparative experiments demonstrated that incorporating ultrasonic vibration markedly enhanced screening efficiency. Vibration intensity was further analyzed to validate the accuracy of the selected parameter combination. Finally, physical experiments confirmed the accuracy of the simulation results, demonstrating that moderate crushing positively contributes to overall screening efficiency. This study elucidates the crushing mechanism of friable materials in rotary vibrating screens, providing a scientific basis for optimizing high-efficiency screening processes.

The absence of purely elastic properties in granular soil is attributed to the reversible sliding that occurs between particles during the loading–unloading cycle, leading to the dissipation of energy through friction. Instead of the strictly elastic domain, we opt for a quasi-elastic domain to examine elastic behavior within the confines of elastic theory. Within this quasi-elastic realm, the response deviates to some extent from the idealized pure elastic behavior posited by the elastic theory. As a result, the elastic constitutive relations applied to granular materials are no longer strictly accurate and may exhibit deviations. With the aim of exploring the deviation of the elasticity of granular materials from idealized pure elasticity, this paper proposes a quantitative approach to assess deviation of elasticity. Specific metrics are formulated to gauge the proximity to pure elasticity. Cyclic triaxial numerical simulation tests, utilizing the discrete element method and accounting for both spherical and non-spherical particles, are conducted to examine the progression of sliding friction energy dissipation and sliding contacts under shear stress within the quasi-elastic domain. The findings indicate that, both at the micro and macroscales, the evolution of quasi-elasticity can be consistently quantified. The threshold for intrinsic slip rate or energy dissipation rate, which corresponds to the termination of initial elasticity, can serve as a quantifiable measure for determining the effective applicability of elastic theory in soil mechanics.

A numerical method was developed to analyze liquid ring pumps on the basis of the MPS method, which is one of the representative particle methods. A liquid ring pump generates a vacuum by rotating an impeller and creating a liquid ring. The gas is compressed by the liquid ring and is discharged through outlets. The liquid behavior is simulated by the MPS method in two dimensions. The gas pressure, calculated by the equation of state, is used as a boundary condition for the liquid surface pressure. The turbulence effect is calculated by a turbulence model. The effects of inlet and outlet of gas and liquid were considered. The stability and accuracy of the developed method were validated with the experimental data under different suction pressures.

The rotary kiln has been widely used in the chemical pyrolysis industry for decades. This study focused on elucidating the impact of incorporating baffles on the motion of pesticide waste salt (WS) particles during pyrolysis in a rotary kiln. Through discrete element method software simulation, the effects of different baffle lengths (75 cm, 120 cm, and 150 cm) and baffle angles (0°, 15°, and 45°) were investigated to provide valuable insights into predicting the movement and heat transfer of WS. The simulation results indicated that the length of the baffle had a significant impact on the behavior of WS particles with longer baffles resulting in enhanced mean residence time and velocity of particles but the reduced temperature variations. These changes were accompanied by a cyclic pattern of initially rising and subsequently falling velocities. Conversely, the baffle setting angle exhibits an insignificant impact in most cases. Notably, the inclusion of baffles enhanced the elastic forces generated by particle collisions, as well as friction from rolling and relative sliding, which led to enhanced particle dispersion and rotation of WS particles. The findings confirmed that incorporating baffles positively affected both particle movement and heat transfer, thereby relieving the burden associated with subsequent management and disposal processes.