Friction Force Research Articles

Interface friction between neighbor diamondene nanoribbons: A molecular dynamics study

Due to its unique carbon-carbon bond topology, diamondene exhibits different frictional properties compared to pristine graphene. This study evaluates the friction properties of diamondene ribbon (DR) for potential applications in the design of dynamic nanodevices. For a DR sample on a DR substrate at a specific temperature, it has a maximum static friction force (MSFF) that is about 38 times greater than that of a graphene counterpart with the same size. The rate of MSFF to the contact surface demonstrates the shear strength of a material. As an intrinsic property, the shear strength between DRs measures approximately 3.58 MPa at 10 K, which is much greater than that between graphene ribbons. When the pulling force on the DR sample exceeds MSFF, the sample undergoes a period of acceleration before reaching a stable sliding velocity. The viscous damping coefficient between DRs increases with increasing pulling force on the DR sample while decreasing with increasing temperature. The dynamic friction force behaves in a temperature-dependent manner due to the unstable bond topology of DRs at high temperatures. These studies address previous research lack regarding friction between carbon materials.

A Systematic Review of Effects on ACL Injury of Soccer Shoe Outsoles, Soccer Playing Field Surfaces, and Outsole–Surface Interface

Soccer is a sport with a high incidence of injuries. The most common injury occurs when the anterior cruciate ligament of the knee has undergone a sprain, strain, or partial or total rupture. Besides fitness factors (e.g., proprioception, balance and strength capabilities), a principal cause of ACL injuries is sport shoes and playing surfaces. Especially with the emergence of artificial surfaces (rubbers, turfs, concrete, asphalt, red turf), the ACL injuries dramatically increase. The cost of ACL injuries is high both in terms of career termination and in social and economic costs. Thus, it is necessary to understand the impact of sport shoes and playing surfaces on the ACL and how it can be mitigated. The present literature review followed the PRISMA methodology to identify the major biomechanical factors influencing the behavior of surfaces and shoes in relation to the ACL damage. Fifty-eight papers were identified. After reviewing the mechanism of injuries, we identified several distinct factors: type of outsole and mechanical arrangement of the outsoles; shear forces; characteristics of artificial turf surfaces; effect of weather on artificial surface aging and change in mechanical characteristics; outsole/ground interface; and the frictional, tractional and rotational forces in the pathogenesis of ACL injuries in soccer.

Transportation of Objects on an Inclined Plane Oscillating in the Longitudinal Direction Applying Dynamic Dry Friction Manipulations

A transportation system requires an asymmetry to achieve objects’ motion on an oscillating surface. Transportation methods based on vibrational techniques usually employ different types of asymmetries, such as temporal (time) asymmetry, kinematic asymmetry, wave asymmetry or power asymmetry. However, transporting an object on an inclined angle requires a relatively high net frictional force over each period of vibrational cycles due to the gravitational potential energy exerted on the object. This paper investigates the transportation of an object upward on an inclined plane that harmonically oscillates in its longitudinal direction. The novelty of this research is attributed to the upward motion of the object on the inclined plane, which is achieved by creating an additional asymmetry of the system through dry friction dynamic manipulations. For this reason, periodic dynamic dry friction manipulations have been employed to create the asymmetry of frictional conditions, resulting in a net frictional force that outweighs the gravitational force. A mathematical model has been developed using the Lagrange method, which describes the moving object’s motion. Moreover, the theoretical findings and results confirmed that the object’s velocity and direction can be controlled by dynamic dry friction manipulations. To demonstrate the technical feasibility of the proposed method, an experimental investigation was carried out where the results demonstrated that the control parameters significantly influence the characteristics of the directional motion of the moving object. This transportation method is beneficial for various modern industries engaged in transportation and manipulation tasks with objects spanning a broad range of sizes, including those operating at small scales for applications in lab-on-a-chip technology, micro-assembly lines, micro-feeder systems and other delicate component manipulation systems. The presented research advances the classical theories of vibrational transportation on inclined surfaces.

Analysis and evaluation of the synergistic effect of ceramic materials and surface texture on anti-abrasive particle wear under rolling conditions

Damage to mechanical components caused by contaminant ingress is a common failure. In response to this issue, this study introduces a synergistic abrasion reduction method based on the combined application of ceramic materials and surface texturing. Using cylindrical thrust roller bearings as an illustration, circular textures were applied to the raceways, and a small number of steel rollers were substituted with ceramic ones. Moreover, alumina was introduced into the lubricant as a contaminant. The frictional and dynamic performance of the "ceramic-textured surface" combination under lubricant contamination conditions was explored and compared with corresponding single abrasion reduction techniques. The synergistic abrasion reduction mechanism of the "ceramic-textured surface" combination was also examined. The findings reveal that under lubricant contamination conditions, the synergistic abrasion reduction method surpasses individual abrasion reduction methods and demonstrates a certain degree of complementarity. Compared with traditional all-steel bearings, textured bearings with four ceramic rollers have reduced the average frictional force by approximately 56.82 %, and the mass loss of the shaft washer and seat washer has been reduced by approximately 81.01 % and 80.86 %, respectively. Rolling elements treated with the synergistic abrasion reduction method exhibit enhanced resistance to abrasive particle wear. This improvement is attributed to the collaborative effects of various mechanisms, including crushing and refinement, capture and storage, grinding and finishing, as well as self-healing and smoothing.

Investigation of thermal effects in bulk oxide chemical mechanical polishing

Bulk oxide polishing occupies a substantial portion of time to achieve surface planarization in semiconductor manufacturing. Recently, thermal management has emerged as a critical issue in the polishing process. Fundamental research on thermal effects in oxide film polishing is essential for optimizing both the thermal management system and the polishing process itself. Experiments indicate that friction force, significantly influenced by wafer and retainer ring pressures as well as slurry species, plays a major role in determining polishing temperature, more so than slurry flow rate. An important finding is the temperature-dependent behavior of slurry particles, which generally reduce in size and concentrate more at higher temperatures, with aggregation starting at around 80 °C. High-temperature slurry deteriorated pad properties but enhance oxide film surface hydrolyzation. During a 60-s polishing process, the slurry temperature exhibited the maximum removal rate at 60 °C for fumed silica polishing, while for calcined ceria, the highest removal rate was observed at 20 °C. Pad B at ambient temperature, having similar hardness to Pad A at 60 °C, reduced the oxide film removal rate by 31.82 % for fumed silica and 40.94 % for calcined ceria. This indicates that pad hardness has a more pronounced effect on polishing with calcined ceria slurry.

Ultrahigh frequency primordial gravitational waves beyond the kHz: The case of cosmic strings

We investigate gravitational-wave backgrounds (GWBs) of primordial origin that would manifest only at ultrahigh frequencies, from kilohertz to 100 gigahertz, and leave no signal at LIGO, the Einstein Telescope, the Cosmic Explorer, LISA, or pulsar-timing arrays. We focus on GWBs produced by cosmic strings and make predictions for the GW spectra scanning over high-energy scale (beyond 1010 GeV) particle physics parameters. Signals from local string networks can easily be as large as the big bang nucleosynthesis/cosmic microwave background bounds, with a characteristic strain as high as 10−26 in the 10 kHz band, offering prospects to probe grand unification physics in the 1014–1017 GeV energy range. In comparison, GWB from axionic strings is suppressed (with maximal characteristic strain ∼10−31) due to the early matter era induced by the associated heavy axions. We estimate the needed reach of hypothetical futuristic GW detectors to probe such GWB and, therefore, the corresponding high-energy physics processes. Beyond the information of the symmetry-breaking scale, the high-frequency spectrum encodes the microscopic structure of the strings through the position of the UV cutoffs associated with cusps and kinks, as well as potential information about friction forces on the string. The IR slope, on the other hand, reflects the physics responsible for the decay of the string network. We discuss possible strategies for reconstructing the scalar potential, particularly the scalar self-coupling, from the measurement of the UV cutoff of the GW spectrum. Published by the American Physical Society 2024

Influence of friction between wood and support elements in the design of timber structures for roofing

Throughout history, wood has played a crucial role in all phases of building construction. Despite existing prejudices in Brazil regarding its use in structural systems, primarily due to the lack of dissemination of technical information, wood is gradually gaining more space in the market as a viable and environmentally sustainable alternative. With exceptional mechanical properties, wood is compatible with other widely used construction materials in the Brazilian structural market, such as concrete and steel. In this context, this research aims to analyze the influence of considering the friction coefficient caused by the sliding of the support with free horizontal displacements in isostatic trusses, investigating its impact on the design of the components that make up the truss. Such sliding generates a lateral friction force that promotes a restraining effect on the structure, potentially relieving stresses on the lower chord members. For this purpose, the Finite Element Method (FEM) is used as an analytical tool, supported by the iTruss verification software to validate the obtained results. By considering the frictional force generated on the support links of the analyzed trusses, the numerical results revealed changes in the design of structural profiles for all existing wood strength classes (D20, D30, D40, D50, and D60) in situations of friction between wood and wood, and between wood and concrete. A reduction in the volume of wooden pieces was observed, ranging from 5.88% to 8.54%, suggesting that the inclusion of the friction coefficient during structural calculations can result in savings, not only from a financial standpoint but also promoting environmental benefits by encouraging a more responsible use of wood in civil construction.

A computational framework for drop time assessment of a control element assembly under fuel assembly deformations with fluid-structure interaction and frictional contact

This paper presents a computational framework for drop time assessment of a control element assembly (CEA) under fuel assembly (FA) deformations. The proposed framework consists of three key components: 1) finite element modeling of CEA, 2) fluid-structure interaction to compute drag force, and 3) modeling of frictional contact between CEA and FA. Specially, to accommodate the large motion of CEA, beam elements based on absolute nodal coordinate formulation (ANCF) are adopted. The continuity equation is utilized to calculate the drag force, considering flow changes in the cross-sectional area during the CEA drop. Lastly, beam-inside-beam frictional contact model is employed to capture practical contact conditions between CEA and FA. The proposed framework is validated through experiments under two scenarios: free falls of CEA within FA, encompassing undeformed and deformed scenarios. The experimental validation of the framework demonstrated that the drop time of CEA can be accurately predicted under the complex coupling effects of fluid and frictional contact. The drop times of the S-shaped deformation case is longer than those of the C-shaped deformation case, affirming the time delay due to frictional force. The validation confirms the potential applicability to access the safety and reliability of nuclear power plants under extreme conditions.

Active nuclear positioning and actomyosin contractility maintain leader cell integrity during gonadogenesis

Proper distribution of organelles can play an important role in a moving cell's performance. During C.elegans gonad morphogenesis, the nucleus of the leading distal tip cell (DTC) is always found at the front, yet the significance of this localization is unknown. Here, we identified the molecular mechanism that keeps the nucleus at the front, despite a frictional force that pushes it backward. The Klarsicht/ANC-1/Syne homology (KASH) domain protein UNC-83 links the nucleus to the motor protein kinesin-1 that moves along a polarized acentrosomal microtubule network. Interestingly, disrupting nuclear positioning on its own did not affect gonad morphogenesis. However, reducing actomyosin contractility on top of nuclear mispositioning led to a dramatic phenotype: DTC splitting and gonad bifurcation. Long-term live imaging of the double knockdown revealed that, while the gonad attempted to perform a planned U-turn, the DTC was stretched due to the lagging nucleus until it fragmented into a nucleated cell and an enucleated cytoplast, each leading an independent gonadal arm. Remarkably, the enucleated cytoplast had polarity and invaded, but it could only temporarily support germ cell proliferation. Based on a qualitative biophysical model, we conclude that the leader cell employs two complementary mechanical approaches to preserve its integrity and ensure proper organ morphogenesis while navigating through a complex 3D environment: active nuclear positioning by microtubule motors and actomyosin-driven cortical contractility.

Quantitative derivation of a two-phase porous media system from the one-velocity Baer–Nunziato and Kapila systems

We derive a novel two-phase flow system in porous media as a relaxation limit of compressible multi-fluid systems. Considering a one-velocity Baer–Nunziato system with friction forces, we first justify its pressure-relaxation limit toward a Kapila model in a uniform manner with respect to the time-relaxation parameter associated with the friction forces. Then, we show that the diffusely rescaled solutions of the damped Kapila system converge to the solutions of the new two-phase porous media system as the time-relaxation parameter tends to zero. In addition, we also prove the convergence of the Baer–Nunziato system to the same two-phase porous media system as both relaxation parameters tend to zero. For each relaxation limit, we exhibit sharp rates of convergence in a critical regularity setting. Our proof is based on an elaborate low-frequency and high-frequency analysis via the Littlewood–Paley decomposition and includes three main ingredients: a refined spectral analysis of the linearized problem to determine the frequency threshold explicitly in terms of the time-relaxation parameter, the introduction of an effective flux in the low-frequency region to overcome the loss of parameters due to the overdamping phenomenon, and renormalized energy estimates in the high-frequency region to cancel higher-order nonlinear terms. To justify the convergence rates, we discover several auxiliary unknowns allowing us to recover crucial O(ε) bounds.

Seismic mitigation analysis of three-dimensional base-isolated nuclear structures with soil-dependent isolation system under extreme earthquakes

The Fukushima nuclear accident in March 2011 has raised more stringent requirements for the ability of nuclear power plants (NPPs) to withstand extreme disasters such as extreme earthquakes. To address this challenge, this study proposed a new hybrid multi-dimensional passive control system that combines three-dimensional base isolation and geotechnical seismic isolation. In this system, high-damper rubber bearings were employed to isolate horizontal seismic motions, whereas disc springs, accounting for frictional forces, were used to mitigate vertical seismic motions. Additionally, a geotechnical seismic isolation system arranged under the base mat was leveraged to further reduce the seismic response of the superstructure. Taking a large-scale reactor building in complex layered sites as an example, the effectiveness of the hybrid multi-dimensional isolation system was studied using a wave motion method. The research results indicate that when subjected to extreme earthquakes, hybrid multi-dimensional isolation exhibits superior isolation performance compared with three-dimensional base isolation, which can significantly reduce the three-dimensional dynamic response of nuclear structures without increasing the displacement of the isolation bearings. The proposed hybrid multi-dimensional isolation system offers an effective solution to the challenges faced by three-dimensional isolation systems, thereby enhancing the seismic resistance of nuclear structures against extreme earthquakes.

An atomic-scale insight into mechanical enhancement and frictional properties of amorphous/graphene multilayers

This study utilizes molecular dynamics simulation to explore the mechanical and friction properties of CuTa/Graphene A/GR multilayers during nanoscratching. By investigating the influence of amorphous layer thickness, substrate temperature, and scratching speed valuable insights into scratching behaviors are gained. Reducing the amorphous layer thickness enhances the normal force and contact pressure, effectively strengthening the A/GR multilayer, while decreasing the frictional force owing to the lubricating properties of graphene, resulting in a notable reduction in friction coefficient. Analysis of the deformation mechanism reveals that the graphene layer impedes shear band propagation, especially noticeable at thinner amorphous layer thicknesses. Additionally, the A/GR multilayer exhibits outstanding wear resistance at high temperature and speed, as indicated by a slightly increased wear atomic ratio.

Effect of Protein (Bovine Serum Albumin) Content on the Frictional Behaviour of Soft Contact Lenses Using a Dynamic Oscillating Tribometer

Proteins can adsorb on the surface of materials, such as soft contact lenses (SCLs), and can affect the hydrophobicity, roughness, and surface properties of the contact lenses (CLs), which, in turn, can influence the friction between the lenses and the ocular surface. Excessive friction between contact lenses and the ocular surface can lead to discomfort for the wearer and may cause irritation or inflammation of the cornea, better known as corneal ulcers (keratitis). Bovine Serum Albumin (BSA) is often used as a standard protein in biocompatibility testing of materials, including contact lenses. One standard commercial contact lens was tested under lubricated conditions to access the coefficient of friction (CoF). The contact was lubricated with a tear-like fluid (TLF) solution containing six different concentrations of BSA. In all cases, good linearity of the results of the friction force was verified, suggesting that the first friction law can be applied to determine the value of the coefficient of friction. It was found that friction increases with the increase in protein concentration.

Micro-Grinding Parameter Control of Hard and Brittle Materials Based on Kinematic Analysis of Material Removal

This article explores the intricacies of micro-grinding parameter control for hard and brittle materials, with a specific focus on Zirconia ceramics (ZrO2) and Optical Glass (BK7). Given the increasing demand and application of these materials in various high-precision industries, this study aims to provide a comprehensive kinematic analysis of material removal during the micro-grinding process. According to the grinding parameters selected to be analyzed in this study, the ac-max values are between (9.55 nm ~ 67.58 nm). Theoretical modeling of the grinding force considering the brittle and ductile removal phase, frictional effects, the possibility of grit to cut materials, and grinding conditions is very important in order to control and optimize the surface grinding process. This research introduces novel models for predicting and optimizing micro-grinding forces effectively. The primary objective is to establish a micro-grinding force model that facilitates the easy manipulation of micro-grinding parameters, thereby optimizing the machining process for these challenging materials. Through experimental investigations conducted on Zirconia ceramics, the paper evaluates a mathematical model of the grinding force, highlighting its significance in predicting and controlling the forces involved in micro-grinding. The suggested model underwent thorough testing to assess its validity, revealing an accuracy with average variances of 6.616% for the normal force and 5.752% for the tangential force. Additionally, the study delves into the coefficient of friction within the grinding process, suggesting a novel frictional force model. This model is assessed through a series of experiments on Optical Glass BK7, aiming to accurately characterize the frictional forces at play during grinding. The empirical results obtained from both sets of experiments—on Zirconia ceramics and Optical Glass BK7—substantiate the efficacy of the proposed models. These findings confirm the models’ capability to accurately describe the force dynamics in the micro-grinding of hard and brittle materials. The research not only contributes to the theoretical understanding of micro-grinding processes but also offers practical insights for enhancing the efficiency and effectiveness of machining operations involving hard and brittle materials.

Digital model of hydraulic drive for solar tracker rotary control

An important area in the field of solar energy is considered, focusing on the use of a hydraulic drive in high-power solar trackers. In the context of the relevance of environmental problems and the commitment to energy efficiency, the role of solar trackers in increasing the productivity of solar power plants is investigated. An analysis of current trends in the field of hydraulic drive is presented, highlighting the prospects for its application. The analysis of the directions of improvement of the drives of the solar tracker is carried out. The hydraulic drive of the tracker is considered as an object of regulation. Disturbing loads of various types acting in the process of changing the position of the tracker are determined. The main load acting on the tracker drive is positional, caused by the gas–dynamic effect of the wind flow impinging on the tracker plane or the ambiguity of the behavior of the snow and ice cover. It is determined that the inertial load, when turning a high-power tracker, has a significant effect on the friction forces in the attachment points of the hinge support mechanisms. Options for the implementation of new circuit solutions for the tracker hydraulic drive are considered. Using information from sensors of movement of the rods of hydraulic motors of the tracker position drive, the sun position sensor, the control electronic module positions the solar tracker platform by supplying control signals to the electric hydraulic distributors of the drive. The hydromechanical regulators of the pump adjust the characteristics of the system to a random change in external loads on the tracker. A mathematical model of the hydraulic drive of the basic circuit tracker has been developed. The digital model of the tracker drive is designed to optimize the operation of the hydraulic drive, taking into account various factors such as inertia, viscous damping, hydraulic losses, system nonlinearities, thermal losses, elasticity of elements and the impact of external factors. The results obtained emphasize the efficiency and accuracy of the control system, making the hydraulic drive an important element in the development of clean and efficient energy.

Investigation of Residual Stress Distribution and Fatigue of 7050-T7451 Alloy Hole Components with Laser Shock and Ultrasonic Extrusion

Small-hole structures, such as the millions of fastener holes found on aircraft, are typical stress-concentration structures prone to fatigue failure. To further improve the strengthening process of this small-hole structure, we make up for the limitations of laser shock processing (LSP) of small holes by combining it with the ultrasonic extrusion strengthening (UES) process to form a new strengthening method—laser shock and ultrasonic extrusion strengthening (LUE). The influence of the LUE process sequence and process parameters on residual stress distribution was studied through FEM, and the gain of fatigue life of specimens after LUE strengthening was also explored through tests. The results show that when using LUE technology, the friction force decreases with the increase in amplitude and decreases by 3.2% when the amplitude is maximum. The LUE process eliminates the thickness effect generated by LSP, which can achieve good stress distribution of small-hole components under smaller laser shock peak pressure, and reduces equipment power. LUE can significantly improve the fatigue life of small-hole components, and the maximum fatigue life gain can be up to 310.66%.

An Experiment on the Dwell Time Effect of Rubber Seal O-Rings: Friction Force in Intermittent Reciprocating Motion

The adhesive force between two contact surfaces often leads to an increase in the friction force of the rubber seal O-ring after a certain dwell time, forming dwell time effects and affecting the reliability of sealing. The dwell time effect may result in substantial instability with respect to the frictional behavior of rubber O-rings, which needs to be carefully taken into account in the design of rubber seals. Therefore, in this paper, the dwell time effect of the friction force was studied experimentally for intermittent reciprocating rubber seal O-rings coupled with stainless steel 316L and a sealing air medium. The friction force of three kinds of rubber materials, including fluorine rubber (FPM), silicone rubber (SI), and nitrile rubber (NBR), was measured under different dwell times, compression ratios, and seal pressure. The results showed that there was a rolling frictional force, and the second peak value of the frictional force caused by the O-ring’s rolling under shear action and after the maximum static frictional force was observed at the starting stage of reciprocating motion. For FPM O-rings, the rolling friction force was much greater than the maximum static frictional force at about four times the value of the compression ratio at 9% and seal pressure at 0; moreover, the force was much greater at greater compression ratios. The dwell time effect was significant in the friction forces of rubber O-rings. The friction force increases with an increase in dwell time. The increase in maximum static friction force exceeded 50% after 5 dwell days. The increase in seal pressure led to the disappearance of the rolling friction feature and the rapid increase in friction during the starting stage. Under gas seal pressure conditions, the dwell time effect still led to a significant increase in friction force. The obtained results might provide guidance for the material selection of sealing designs.

Flow of Hybrid Dust Micropolar Nanofluids Along the Symmetric Riga Surface with Heat Generation and Application of Cattaneo-Christov Theory

This study investigates the mechanical characteristics of a hybrid nanofluid containing dust and micropolar particles, flowing under mixed convection past a symmetric Riga surface using the Cattaneo-Christov (C-C) heat flux theory with consideration for heat generation effects. The analysis focuses on dust micropolar flow within a porous medium with a combination of hybrid nanoparticles CNTs - F with blood. The mathematical model describing this system involves a set of partial differential equations (PDEs), which are transformed into dimensionless ordinary differential equations (ODEs) and eventually into a form that can be solved using the MATLAB program. Graphical representations are employed to examine and discuss the impact of various flow parameters on the velocity and temperature profiles of the dust micropolar hybrid nanofluid. Several key findings emerge from this investigation. It is anticipated that an increase in the interaction between fluid particle parameters will result in a decrease in the temperature of the fluid phase and an increase in the temperature of the dust phase. Moreover, the study reveals that the Nusselt number is influenced by the mixed convection effects. Additionally, larger values of the heat generation parameter lead to higher temperatures in both the fluid phase and the dust phase. Conclusion: In summary, this study comprehensively investigates the dynamics of nanofluid flows over a Riga surface, considering parameters like , Pr, and βv. The findings highlight their significant impact on temperature distribution, fluid flow patterns, and friction forces. The results offer insights crucial for optimizing engineering systems like cooling technologies and heat exchangers. This research advances our understanding of nanofluid dynamics and provides valuable guidance for future studies and practical applications.

Progress in Theoretical Modelling of Macroscopic and Microscopic Dynamics of Bolted Joints in Complex Equipment

Bolt connection structure is a common form of connecting large and complex equipment. Its object contact surfaces under normal and tangential loads will appear in the form of slip and adhesion, which affects the service life of mechanical equipment. Bolted connection structures cause changes in stiffness and damping, which have great impacts on the dynamic characteristics. Experimental studies and numerical simulations have difficulty predicting the overall performance of bolts in a timely manner, hence cannot ensure the reliability and safety of complex equipment. In order to improve the overall performance of complex equipment, it is necessary to study the contact theory model of bolt connection structures. Based on the relationship between friction force and velocity in the classical friction model, the mathematical expressions of restoring force and tangential displacement in the kinetic theory model are deduced to predict the stiffness degradation of the bolted structure and to characterise the kinetic properties and laws of the bolted structure. From the perspective of theoretical calculation, it makes up for the situation in which it is difficult to measure the performance of bolts due to the existence of spanning scale and provides theoretical support for the reliability of connecting complex equipment. This paper summarises and analyses the contact theory model of bolt connection structures, ranging from macroscopic to microscopic; describes the static friction model, kinetic friction model, statistical summation contact model, fractal contact model; and analyses the influencing factors of the microscopic contact mechanism. The advantages and disadvantages of the kinetic theoretical models are described, the manifestation of friction and the relationship between tangential force–displacement are discussed, and the key research directions of the kinetic theoretical models of bolted structures in the future are elucidated.

Hybrid Finite-Element Material-Point Method for Reinforced Slopes

This paper proposes a modified Hybrid Finite-Element Material-Point Method (HFEMPM) for analyzing reinforced slopes. The method discretizes the soil using material points, and employs bar elements in the finite-element method to represent geosynthetics that can only withstand tensile loads. The interaction between geosynthetics and soil is naturally captured using the same background grid by HFEMPM. To capture their frictional contact more precisely, a specific procedure to evaluate the maximum frictional force of the bar exerted by the soil is proposed in this paper, which makes the modified HFEMPM more applicable in modelling reinforced soil. The μ(I) rheology from granular mechanics is introduced for stress updating of soil. The method is applied to simulate the experimental collapse of rod piles and centrifuge tests of reinforced slopes. Incorporating the μ(I) rheology for stress updating into the HFEMPM not only enables including the influence of particle size and initial soil strength on the stability of slopes, but also describing the effect of strain rate strengthening during the collapse process. Based on calculated results of stability with various reinforcement lengths and number of layers, a reference chart designed to summarize the optimal reinforcement scheme is provided as a guide in reinforced-soil engineering.