Computational Particle Mechanics最新文献

In this paper, the influence of soil spatial variability on the large deformation bearing capacity of rigid footing is presented. The random generalized interpolation material point (RGIMP) method, in which the large deformation GIMP method is combined with random field theory in a Monte Carlo simulation framework, was developed. The continuous penetration of a rigid footing in a spatially variable Tresca soil is modeled using the RGIMP approach. The results show that the average value of the bearing capacity factor of the spatially variable soil is often smaller than that of the homogeneous soil because the failure of the soil always occurs along the weak path. The average value of the bearing capacity factor decreases with increasing coefficient of variation (COV) and increases with increasing horizontal scale of fluctuation (SOF). Compared with the value of the horizontal SOF, the COV has a greater influence on the bearing capacity factor. The findings of this study are helpful for obtaining a better understanding of the bearing capacity of heterogeneous foundations.

Investigating and analyzing circulating tumor cells (CTCs) have shown to be an invaluable tool for early cancer detection and diagnosis. Microfluidic devices, which are inexpensive and simple to use, have recently gained a lot of attention for the enumeration and separation of CTCs. In this research, a novel sheathless double-loop spiral-based lab-on-a-chip is proposed dependent upon the functionality of inertial focusing for separating multiple CTCs such as MCF-7 (breast cancer CTCs) and A549 (lung cancer CTCs) distinctly from the normal cells like WBCs (white blood cells) and RBCs (red blood cells). The chip is designed and examined in numerical simulation using COMSOL Multiphysics 5.4 tool at various average flow velocities and Reynolds numbers (Re). In this study, the separation purities and recoveries of (sim ) 100% is gained by the chip at the Re values ranges from 71.75 ({text{to}}) 76.87 (flowrate of 87.8(-)94.1 ml/h), which indicates the high capability of separating multiple CTCs distinctly with high throughput.

This study explores the mechanical properties of particle- and unidirectional fiber-reinforced composite materials using the discrete element method (DEM) with an identical calibration technique. Determining micromechanical properties within DEM modeling is a time-consuming challenge typically requiring a distinct calibration approach for each specific model. In this research, we employ identical micromechanical properties for the generated discrete domain to simulate both types of composites. The findings in this paper suggest that an identical calibration procedure could potentially be effective for modeling composites, regardless of their varied reinforcement shapes. Given the computational costs associated with DEM modeling, this research presents a potential advancement in streamlining the DEM calibration process. The linear parallel-bond model served as the contact model in DEM simulations, offering realistic estimates for materials resembling cemented structures. Additionally, group logic was employed in DEM modeling to construct the reinforcement and matrix phases of the composites. Results were validated through FEM simulations and theoretical predictions, demonstrating a satisfactory level of agreement. Furthermore, this paper provides a comprehensive depiction of micro-crack initiation and propagation, along with various fracture modes, including matrix and fiber cracking, as well as matrix/fiber debonding, for both composite types.

Rubble stones are commonly found in many civil engineering components, such as foundations, walls. In general, rubble stone masonry walls are composed of irregular-shaped stone units and mortar. They are usually subjected to vertical and horizontal loads simultaneously and exhibit high degree of nonlinearity and discontinuity in service conditions. The combined finite-discrete element method (FDEM) was employed to investigate the mechanical behaviour of rubble stone masonry walls in this study. In order to overcome the disadvantages in both macro- and simplified micro-modelling, a detailed micro-modelling approach was utilised, i.e. stone, mortar and stone-mortar interface were considered explicitly, providing close approximation to physical structures. Stone units and mortar were discretised into linear triangular elements with finite element formulation incorporated in, and therefore, accurate estimate on structural deformation and contact forces can be obtained. Damage of rubble stone masonry was evaluated through cohesive fracture models. Numerical examples were validated, and further parametric discussions were performed. Influence of stone unit pattern, ratio of stone and strength of mortar on the failure behaviour of rubble stone masonry walls was revealed. A very good agreement between FDEM results and experimental data was observed. It was found that the higher the ratio of stone, the better the bearing capacity, and uniform-shaped stone units with regular distribution were recommended. In addition, use of mortar with both tensile and shear strengths higher than 0.2 MPa was suggested.

This paper presents a comprehensive study on the numerical and experimental simulation of smooth blasting in limestone. The calibration of the numerical model was initiated through Brazilian and uniaxial compression tests on limestone samples. Compressive strength and Brazilian tensile strength of limestone were 70 MPa and 8 MPa. This enabled the determination of essential micro-parameters. Subsequently, smooth blasting scenarios were simulated under two distinct conditions: with and without confinement. Under confinement conditions, models with dimensions of 600 mm * 900 mm were constructed. The blasting hole was strategically positioned at varying distances from the free boundary, accompanied by a row of parallel holes positioned behind it. A confining pressure of 10 MPa was applied. Appropriate values for normal and shear damping, as well as the allocation of a viscous boundary, were established. Normal and shear damping values were equal to 0.4 and 0.3, respectively. Throughout different stages of blasting, critical parameters such as crack growth patterns, particle velocity, and induced loads near the blasting hole were meticulously recorded. Measuring circles were strategically placed in proximity to both the blasting hole and free boundary to capture induced forces. Parallel to the numerical simulations, an unconfined experimental test was conducted on limestone samples with similar dimensions. However, it was observed that the reflected tensile stress wave at the surface of the empty hole exacerbated damage to the rock mass between the blast hole and the empty holes. The presence of multiple empty holes significantly influenced the extension of the blasting-induced main fracture. Various factors, including the distance between the explosion source and the empty holes, played a pivotal role in the reflection tensile failure on the surface with no holes. Furthermore, it was found that increasing the separation between the empty holes and the blasting hole led to a reduction in kinetic energy and high friction energy. Conversely, widening the blasting holes amplified both peak friction energy and kinetic energy. Elevating the confining pressure resulted in a decrease in both peak friction energy and kinetic energy, while simultaneously increasing the strain energy. Additionally, extending the distance between the blasting hole and the free border led to a reduction in flying rock. Confining the area had a dual benefit of reducing induced force and mitigating the quantity of flying rock. The results from the experimental test and numerical simulation exhibited a consistent trend.

A modified version of a nonlinear viscoelastic damping model is presented to better represent overall spherical particle response using the discrete element method (DEM) to simulate gravity-driven mixing of binary particles into a confined box. Nonlinear springs are used in the normal and tangential directions to simulate the contact forces, and an additional nonlinear annular spring is employed at the contact points to account for rolling friction. A viscous damping term related to the relative motion between contacting particles is applied to represent energy dissipation, and an alternative condition for checking the end of a collision is applied. The new model is shown to successfully recover the tangential force behavior in stick and sliding regions without having to introduce more complicated behavior. Results are in excellent agreement with existing benchmark tests, and the model is applied to evaluating several different mixing schemes using fixed geometric particle flow disruptors with sometimes surprising results.

This paper presents a computational study on the flow field, particle trajectory and deposition in a rectangular channel which includes multi-vibrating elastic ribbons mounted on different places of the channel. The diameter of particles varies between 10 μm and 40 μm. Two different places of a vibrating ribbon and four different places of multi-vibrating ribbons are considered. To compare, a fixed ribbon is also considered. Fluid flow equations are solved numerically based on the finite element method. The trajectory of particles was obtained by solving the equation of particle motion that included the inertial, viscous drag and gravity forces. The fluid–structure interaction was considered using an arbitrary Lagrangian–Eulerian method. Detailed analysis of the fluid velocity field and fluid–structure interaction is carried out to investigate the effect of vibrating ribbons on particle deposition. The results were compared with the available experimental and numerical data, and the accuracy of approach was evaluated. Results show that behind the vibrating ribbon, multiple vortices of different sizes are formed, which causes changes in the velocity gradient and flow fluctuations of the upstream and increases the percentage of particle deposition in that area compared to a fixed ribbon. For one ribbon cases, an increase in deposition efficiency is observed when the vibrating ribbon is mounted on the upper wall, and for multi-vibrating ribbon cases, this increase is also observed, but the percentage of deposition is lower than single-ribbon cases. In addition, increasing the diameter of particles and decreasing the Young’s modulus increase the deposition percentage of particles.

This study used an advanced modelling approach capable of capturing the complex behaviour of asphalt concrete to model the modified wheel tracking test using a recent advanced experimental test set-up in accordance with ASTM D8292-20. The modelling approach uses the discrete element method (DEM) to naturally produce the heterogeneous internal structure and governs the behaviour of asphalt concrete at the grain level by an interparticle contact model. The contact model used is capable of characterising the rate and time dependency, viscoelastic-damage, and plastic-damage behaviour of asphalt concrete utilising the coupling of an elastoplastic-damage law with a viscoelastic-damage law. Unlike the conventional wheel tracking tests run in a fixed boundary condition (fully confined), the modified wheel tracking test considers the effect of boundary conditions on the rutting behaviour of asphalt mixes. Through comparisons and verifications with laboratory data of the rutting test at different boundary conditions (fully confined and unconfined), the modelling approach shows its capability of capturing the rutting behaviour of asphalt concrete in the modified wheel tracking test. Micromechanics analysis shows that the third (tertiary) stage of rutting behaviour is due to the weakening of the internal structure of the asphalt samples with contact bond breaks over time, which is found in the unconfined test. Meanwhile, the tertiary stage hardly occurs in the fully confined test once densification leads to contact of the aggregate–aggregate skeleton, forming a rigid structure to resist the load with lateral support from the fixed boundary condition. Finally, a parametric study was also conducted to provide further insight into the current testing set-up, including the effect of the sample size and boundary condition on the rutting behaviour of asphalt concrete.

Proper diagnosis and successful cancer therapy monitoring depend on the early identification of circulating tumour cells (CTCs) in a patient's blood. One of the most promising techniques is the dielectrophoresis (DEP) to separate CTCs from the blood cells. In this paper, to separate distinct multiple CTCs like A549 (lung cancer) CTCs and MDA-MB-231 (breast cancer) CTCs from the normal cells like white blood cell (WBCs) variants and red blood cell (RBCs), a lab-on-a-chip (LOC) device is designed using the positive and negative DEP technique. Two different electrode geometrical shapes, various voltages on electrodes and flow velocity ratios between sample and buffer inlets have been investigated in terms of separation performance in COMSOL Multiphysics 5.4 simulation. The segregation results dependent on finite element method showed that the LOC with trapezoid microcut electrode geometry achieved nearly 100% separation purity and efficiency at 200 kHz driving frequency, 21.6 Vp-p (peak to peak) electrode voltage and 1:2 velocity ratio between sample and buffer inlets.

We anticipate that a design this thorough and methodical will be appropriate to produce DEP-based relevant cell separation biochips.