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It is not currently possible to directly and noninvasively measure in vivo patellofemoral joint contact force during dynamic movement; therefore, indirect methods are required. Simple models may be inaccurate because patellofemoral contact forces vary for the same knee flexion angle, and the patellofemoral joint has substantial out-of-plane motion. More sophisticated models use 3-dimensional kinematics and kinetics coupled to a subject-specific anatomical model to predict contact forces; however, these models are time consuming and expensive. We applied a principal component analysis prediction and regression method to predict patellofemoral joint contact forces derived from a robust musculoskeletal model using exclusively optical motion capture kinematics (external approach), and with both patellofemoral and optical motion capture kinematics (internal approach). We tested this on a heterogeneous population of asymptomatic subjects (n = 8) during ground-level walking (n = 12). We developed equations that successfully capture subject-specific gait characteristics with the internal approach outperforming the external. These approaches were compared with a knee-flexion based model in literature (Brechter model). Both outperformed the Brechter model in interquartile range, limits of agreement, and the coefficient of determination. The equations generated by these approaches are less computationally demanding than a musculoskeletal model and may act as an effective tool in future rapid gait analysis and biofeedback applications. [ABSTRACT FROM AUTHOR]

To ensure that the discrete element model of the coal wall accurately reflects the actual cutting process of coal and rock during virtual prototype simulation of mining equipment, this study aims to expedite the development of intelligent mining machinery. Using coal samples from the 4602 working face of Yangcun Coal Mine, operated by Yanzhou Coal Mining Group, we conducted coal rock packing experiments and uniaxial compression tests to obtain the packing angle and compressive strength of the coal samples. Based on the experimental results, we designed Plackett–Burman experiments (PB experiments), steepest ascent experiments, and Box-Behnken experiments to study the influence of particle contact mechanics parameters and bonding mechanics parameters on the packing angle and compressive strength, using the packing angle and compressive strength as response variables. Our objective is to minimize the relative error between the simulated packing angle and the measured packing angle. We solved and optimized the parameter calibration model and conducted simulation calibration experiments based on the optimization results. A comparative analysis with the actual test results revealed that the maximum relative errors between the simulated and measured values for the packing angle and compressive strength were only 2.9% and 5.0%, respectively. Additionally, a discrete element model of a typical working face coal wall was established based on the parameters obtained from this calibration method. A bidirectional coupling model of the cutting process between the coal and rock was created using EDEM-RecurDyn to simulate the rigid-flexible coupling of the coal cutter. An experimental coal wall model was constructed based on similarity theory, and both simulation and physical experiments were conducted. The evaluation metrics for comparison were the time-domain and frequency-domain characteristics of the drum's vibration signals. The maximum relative error for the time-domain signal characteristics between the two experimental setups was only 4.19%, while the maximum relative error for the frequency-domain signal characteristics was 3.75%. This validates the feasibility of the proposed calibration method for the discrete element coal wall model and the accuracy of the calibration results. Furthermore, it demonstrates that the constructed discrete element coal wall accurately represents the actual coal and rock properties. The virtual simulation based on this model effectively replicates the interaction process between mining machinery and coal, providing a safe, efficient, and low-cost technological approach for performance analysis of mining equipment and intelligent control of supporting devices. [ABSTRACT FROM AUTHOR]

Current treatment strategy for managing Weber B ankle fractures is mainly governed by mortise congruency, malleolar alignment, deltoid ligament competence and fracture stability. While nonoperative treatment has yielded good functional outcomes in satisfactorily aligned stable injuries, a biomechanical rationale is not firmly established. Furthermore, current radiographic analysis is obscured by observer inaccuracy and beam rotation. This study aimed to utilize weightbearing CT and computational biomechanics to analyse 3D mortise displacement and contact mechanics in Weber-B ankle fractures and compare them with the uninjured contralateral side. 32 patients were included who sustained a Weber-B ankle fracture and underwent bilateral weightbearing CT imaging at injury. Segmentation into 3D models of bone was performed semi-automatically, and individualized cartilage layers were modeled based on a previously validated methodology. The 3D mortise congruency was evaluated by use of following parameters: alpha angle, fibular length, talocrural angle, medial gutter- and tibiofibular clear space- distance mapping. Contact mechanics were evaluated by the mean and maximum contact stress of the tibiotalar articulation. Statistical analysis revealed that there were no significant differences for all anatomical parameters. There was also no significant difference between the mean contact stress of the injured (2.10 ± 0.42 MPa) and uninjured side (2.10 ± 0.41 MPa), nor the maximum contact stress of the injured (7.67 ± 1.55 MPa) and uninjured (7.47 ± 1.67), respectively. Contact mechanics were unaffected in congruent Weber-B fractures. These findings support consideration of nonoperative management in such cases, given their presumably low risk for posttraumatic arthritic development in the long term. Level of Evidence: Level III; retrospective case-control study. [ABSTRACT FROM AUTHOR]

Contact problems involving deformable bodies are widespread in both industrial and everyday situations. They have a crucial impact on structural and mechanical systems, which has led to significant efforts in modeling and numerical simulations. These efforts aim to improve understanding and optimization in various engineering applications. This study examines the contact problem involving a functionally graded (FG) orthotropic layer resting on a rigid foundation, without considering frictional influences. A point load is applied to the layer through a rigid punch on its top surface. Additionally, the gravitational effects of the FG orthotropic layer are considered in the analyses. Material parameters and density of the FG orthotropic layer are presumed to exhibit exponential variations along the vertical axis. The resolution of the problem involves deriving stress and displacement expressions through the application of elasticity theory and integral transformation techniques. By imposing the pertinent boundary conditions onto these expressions, a singular integral equation is formulated, wherein the contact stress under the punch remains unknown. Employing the Gauss–Chebyshev integration method, this integral equation is subsequently numerically solved, particularly for a flat punch profile. The outcomes of this investigation encompass the determination of contact stresses under the punch, the critical separation load, and the critical separation point—marking the initial separation between the FG orthotropic layer and the rigid foundation. Additionally, the analysis yields dimensionless representations of normal stresses along the symmetry axis within the FG orthotropic layer, as well as shear stresses along a designated section proximate to the symmetry axis. Furthermore, it provides insights into the normal stresses along the x axis at the bottom surface of the FG orthotropic layer, contingent upon various parameters and distinct orthotropic material compositions. [ABSTRACT FROM AUTHOR]

The tire/road noise is one of the major problems facing the tire industry due to the nuisance felt by the vehicle's driver and passengers. Moreover, it is expected in the coming years that this sound nuisance will be one of the main sources of vehicle noise due to the transition from combustion engine driven vehicles to electric vehicles. Tire manufacturers have therefore refined the design of their tire structures to find technological solutions to reduce traffic noise. Tire/road noise is also generated by various mechanisms which depend on different parameters such as the properties of the tire, road texture and driving conditions. This noise is partly caused by the acoustic radiation induced by the tire vibrations due to contacts with the road. The simulation and analysis of the tire's vibrations remains a challenge for the tire industry. Indeed, the simulation of the full dynamic response of a rolling patterned tire requires not only taking onto account various nonlinearities but also the multi-scale nature of the generated dynamic response. Contrary to a straightforward strategy that consists in using a time integrator to predict the multi-scale dynamic response, the strategy proposed in this study is based on a two-step approach to separate the dynamics occurring at different scales. The mathematical formulation of the proposed method is detailed as are the different modeling choices to simulate tire rolling under imposed load. The sensitivity of the tire's vibrations response is analyzed under different rolling conditions and with respect to certain key tire tread pattern parameters. • An adapted two-step approach to simulate nonlinear vibrations by separating the dynamics occurring at different scales. • Mathematical formulation of the proposed method with different modeling choices to simulate tire rolling under imposed loads. • Application to patterned tires rolling on a smooth surface. • Examples of the tire's vibrations response under different rolling conditions and key tire tread pattern parameters. [ABSTRACT FROM AUTHOR]

Rupture discs, also known as bursting discs, are indispensable components in fluid-operated systems providing effective protection against hazardous over-pressure or partial vacuum. They belong to a special class of safety devices and are found in a variety of technical applications including pressure vessels, piping systems, reactors and boilers. In all application scenarios, rupture discs act as sacrificial parts that have to fail precisely at a predetermined differential pressure, opening a relief flow path for the working fluid. The membrane employed within rupture discs is usually made out of specific metal alloys or different material layers depending on the particular application. However, for many manufacturers of rupture discs, the production process is characterized by a lack of systematic procedures, relying instead on trial and error as well as empirical values. By means of thorough finite-element-based modeling and simulation of the bulge-forming process of rupture discs, including an elastic–plastic material law, large deformation, as well as contact mechanics, it is possible to accurately predict the resulting stress–strain behavior. All simulation results are rigorously validated through corresponding experiments conducted during the bulge-forming process. Therefore, this contribution provides a reliable basis for the parameter set-up during the manufacturing process of rupture discs. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive investigation into the impact of key parameters on contact adhesion layer properties using numerical simulations, addressing fundamental questions in contact mechanics. Aiming to explore interfacial penetration and contact pressure dynamics between a wavy punch and an adhesive-coated body, the study focuses on the influence of adhesive layer thickness, elasticity modulus, and punch geometry on mechanical behavior. The study includes the application of Green's function to address deficiencies in existing models, revealing how contact stiffness, influenced by the flexibility relationship between the coating and substrate, affects the size of the contact area. Finally, conclusions are drawn that adjusting coating factors can induce full contact conditions. Quantitative analysis shows a 2.23-fold increase in load-bearing capacity with a 2 mm increase in adhesive layer thickness, and a 23-fold increase with a toughness ratio rise from 0.1 to 5. These findings are recommended for optimizing adhesive layer properties, contributing to advancements in materials science and innovation. [ABSTRACT FROM AUTHOR]

As surface wear is one of the major failure mechanisms in many applications that include polymer gears, lifetime prediction of polymer gears often requires time-consuming and expensive experimental testing. This study introduces a contact mechanics model for the surface wear prediction of polymer gears. The developed model, which is based on an iterative numerical procedure, employs a boundary element method (BEM) in conjunction with Archard's wear equation to predict wear depth on contacting tooth surfaces. The wear coefficients, necessary for the model development, have been determined experimentally for Polyoxymethylene (POM) and Polyvinylidene fluoride (PVDF) polymer gear samples by employing an abrasive wear model by the VDI 2736 guidelines for polymer gear design. To fully describe the complex changes in contact topography as the gears wear, the prediction model employs Winkler's surface formulation used for the computation of the contact pressure distribution and Weber's model for the computation of wear-induced changes in stiffness components as well as the alterations in the load-sharing factors with corresponding effects on the normal load distribution. The developed contact mechanics model has been validated through experimental testing of steel/polymer engagements after an arbitrary number of load cycles. Based on the comparison of the simulated and experimental results, it can be concluded that the developed model can be used to predict the surface wear of polymer gears, therefore reducing the need to perform experimental testing. One of the major benefits of the developed model is the possibility of assessing and visualizing the numerous contact parameters that simultaneously affect the wear behavior, which can be used to determine the wear patterns of contacting tooth surfaces after a certain number of load cycles, i.e., different lifetime stages of polymer gears. [ABSTRACT FROM AUTHOR]

The current research on theoretical modeling of the surface roughness of brittle materials generally regards the tool as a rigid body. Incorporating tool factors into theoretical models of surface roughness is challenging because the influence of tool-workpiece coupling contact on surface roughness remains unclear. This paper investigates the tool-workpiece coupling contact mechanism using contact mechanics analysis: collision contact between the rake face and the material, adhesive contact between the cutting edge roundness and the material, and hertz contact between the flank face and the material. The tool-workpiece coupling contact causes the material to fracture and break, and the tool undergoes collision wear, adhesive wear, and abrasive wear. The formation of pits is attributed to the tool's cutting action on the workpiece, whereas the presence of hard convex peaks is a consequence of the workpiece's reverse cutting into the tool. A quantitative description of hard convex peaks and pits on machined surfaces was based on contact mechanics, fracture mechanics, and tribology. A novel theoretical model is developed for characterizing the surface roughness of brittle materials. Turning verification experiments were carried out using different tools, workpieces, and tool parameters. The predicted values and experimental measurements are similar and have the same trend, indicating that the model is accurate. This paper is the first to consider both the tool and the workpiece as the influencing objects of the surface roughness of brittle materials, and it innovatively incorporates tool wear and tool material properties into the parameters of the theoretical model of surface roughness. It offers a fresh perspective on predicting the theoretical surface roughness model for brittle materials. [ABSTRACT FROM AUTHOR]

Featured Application: Receding contacts appear in systems with conformal or almost conformal contacts e.g., bolted joints, guides, or cylindrical or spherical joints (including human hip joints). Receding contacts appear in many composite technical and biological systems at the points where tensile stresses would appear otherwise. Here, we consider the contact of a beam placed on an elastic foundation (or thin elastic layer) in the presence of adhesion. In contrast to non-adhesive receding contact, the contact area in adhesive receding contact does depend on the applied load. Decreasing the load from the state of initial contact opening leads to an increase in the contact area. At a certain critical load, the beam jumps into contact at once along its entire length. For long beams, the point of opening of the contact does not depend on the intensity of forces of adhesion, and the opening occurs in an unstable way. This can lead to acoustic effects like joint cracking. [ABSTRACT FROM AUTHOR]

Surface morphology plays a crucial role in friction between two contacting geomaterial surfaces, yet many questions remain unanswered regarding how detailed frictional responses deviate from analytical solutions for smooth surfaces due to the presence of roughness. In this study, we revisit the Cattaneo‐Mindlin problem for contacts between two fractally rough elastic or elasto‐plastic spheres generated based on ultra‐high degree (e.g., up to 2,000) spherical harmonics with the corresponding wavelength less than a thousandth of the mean grain diameter. Transverse contacts are simulated by finite element method, validated by the extended Cattaneo‐Mindlin solution to full slide regime for smooth sphere contacts. Extensive simulations are conducted to study contacts between two rough spheres with various surface geometries, micro friction coefficients, normal contact distances, relative roughness, fractal dimensions, and wavelength ranges. Out results indicate that: (a) the new analytical solution can approximately predict the macro contact response except for extremely high relative roughness and narrow wavelength range; (b) deviations induced by roughness from smooth sphere contacts can be neutralized by plasticity, high normal contact interference, and high micro friction coefficient; and (c) fractal dimension impacts frictional contacts less than relative roughness. The main cause of these phenomena can be credited to the underlying microscale contact information. Contact area and stress distributions and their evolutions provide concrete evidence of these observed behavior. This work provides a pathway for applying computational contact mechanics to many geophysical fields, such as the asperity model in earthquake science and the mechanics of granular materials. Plain Language Summary: Geophysical bodies, such as faults, rocks, and grains, exhibit surface roughness across length scales. Contacts between rough surfaces are usually simplified to a rough‐to‐flat contact scenario. To release these strong assumptions, for the first time, extensive finite element simulations are conducted for transverse contacts between two rough grains. Particularly, grain roughness is controlled by ultra‐high degree spherical harmonics, which enables depicting surfaces of diverse grains from silica sands up to asteroids. Our results highlight the importance of surface features in frictional contacts, and indicate that the effects of roughness can be alleviated by the plasticity, contact conditions, and high intrinsic friction coefficient. Furthermore, fractality, quantifying how much the surface fluctuates over length scales, impacts frictional contacts less than roughness amplitude. This study provides a pathway for applying computational contact mechanics to many geophysical applications involving frictional contacts, such as asperity models in earthquake science and mechanics of granular materials. Key Points: Transverse contacts are simulated between two fractal rough grains generated by ultra‐high degree spherical harmonics for the first timeCattaneo‐Mindlin solution is extended to the full slide regime, capable of predicting the critical partial‐to‐complete sliding transitionEffects of roughness can be generally neutralized by plasticity, high contact interference, and friction coefficient [ABSTRACT FROM AUTHOR]

Haemarthrosis is an inherent clinical feature of haemophilia, a disease characterised by an absence or reduction in clotting proteins. Patients with severe haemophilia experience joint bleeding leading to blood-induced ankle arthropathy (haemarthropathy). Altered biomechanics of the ankle have been reported in people with haemophilia; however, the consequence of this on joint health is little understood. The aim of this study was to assess the changes in joint contact due to haemophilia disease-specific gait features using patient-specific modelling, to better understand the link between biomechanics and joint outcomes. Four, image-based, finite element models of haemophilic ankles were simulated through consecutive events in the stance phase of gait, using both patient-specific and healthy control group (n = 36) biomechanical inputs. One healthy control FE model was simulated through the healthy control stance phase of the gait cycle for a point of comparison. The method developed allowed cartilage contact mechanics to be assessed throughout the loading phase of the gait cycle. This showed areas of increased contact pressure in the medial and lateral regions of the talar dome, which may be linked to collapse in these regions. This method may allow the relationship between structure and function in the tibiotalar joint to be better understood. [ABSTRACT FROM AUTHOR]

When cables use many wires packed in a hexagonal pattern wrapped by bands around the surface, effective stiffness plays an important role in structural integrity and safety. This paper studies cylindrical wires packed in a hexagonal lattice tightened up by wrapping bands. When a transverse load is applied, the stress transferred through the contacts between the wires can be represented by a center-center force network with the Hertz contact theory. When yielding is considered in the contact zone, an elastoplastic contact model is developed. The Singum model simulates the singular forces by the stress between continuum particles. The effective stress-strain relationship changes with the stress of the wrapping bands and exhibits isotropic behavior in the cross section. Therefore, the overall elastic behavior of the cable is transversely isotropic with a tailorable stiffness in the cross section by the wrapping force. This method is general for mechanical modeling of packed parallel wire cables, and its application to bridge cable testing and repair with development length prediction is underway. Practical Applications: This study introduces a novel approach, the Singum model, for analyzing the overall mechanical properties of packed wire cables, which are crucial for ensuring structural integrity and safety in various engineering applications. By investigating the effective transverse stiffness of packed wire cables through a combination of theoretical modeling, finite element analysis (FEM), and experimental tests, this research provides valuable insights into optimizing cable design and performance across diverse engineering applications such as cable domes, electric transmission lines, tramways, cable-stayed bridges, and suspension bridges. The findings highlight the significant impact of wrapping force on the effective stiffness of packed cylinders, offering engineers a means to tailor the stiffness of cable cross sections for specific requirements in these applications. This study provides a robust framework for advancing the understanding and optimization of packed wire cable systems in engineering practice with reasonable assumptions and simplifications, which can be tailored for specific materials or applications. [ABSTRACT FROM AUTHOR]

Research on White Etching Cracks (WEC) in multiple bearing applications has identified various drivers that cause them. Lubricants and electricity combined with contact mechanics have been proven to catalyze WEC significantly. However, none of these factors solely cause WEC on its own; instead, combinations of factors discretize whether WEC appears or not. Hence, the WEC phenomenon appears to be multidimensional, making WEC still unpredictable. The current paper is about a systematic study using a Deep Grove Ball Bearing test rig to investigate how lubricant chemicals, combined with electricity and variations in oil flow and pressure, lead to WEC formation. It becomes evident that even under critical conditions for WEC formation, increasing oil flow and decreasing contact pressure can prevent WEC. [ABSTRACT FROM AUTHOR]

Ultrasonic rolling extrusion process (UREP) is the newly arisen surface strengthening technology, which can effectively reduce the surface roughness of the workpiece and improve the residual compressive stress at the certain depth on the surface so that it has great adaptability to the enhancement of the surface properties of the bearing ring. Through theoretical analysis, finite element simulation, and experiment method, the surface mechanical properties and the surface roughness of UREP strengthening when applied to the material of the wind power bearing ring are studied. Firstly, the strengthening principle of UREP is illustrated. Secondly, according to the motion trajectory of the rolling ball during UREP, the kinematic model of UREP is established. The forming principle of the surface micromorphology during UREP is explored. Thirdly, based on the contact characteristics between the rolling ball and the surface of the workpiece, the contact mechanics model of UREP is established. Based on Hertz contact theory, elastoplastic mechanics theory, and contact mechanics theory, the mechanical properties of the contact area between the rolling ball and the surface of the workpiece during UREP are analyzed. Finally, the simulation and experiment of 42CrMo steel cylindrical workpiece during UREP are carried out, and the variation trends in the simulation values are found to be consistent with those observed in the experimental results. The results show that the residual compressive stress generated in the surface of 42CrMo cylindrical workpiece after UREP gradually increases with the increase of the layer depth and then decreases and transforms into the residual tensile stress. Moreover, the surface roughness first decreases and then increases with the rise of the amplitude and the static pressure. Similarly, it gradually improves when the feed rate and rotational speed rises. The established UREP simulation is useful for imitating the actual machining process of 42CrMo steel during UREP, which extends the effective way for UREP parameter optimization. [ABSTRACT FROM AUTHOR]

Solid-state Li-ion batteries, based on Ni-rich oxide cathodes and Li-metal anodes, can theoretically reach a high specific energy of 393 Wh kg−1 and hold promise for electrochemical storage. However, Li intercalation-induced dimensional changes can lead to crystal defect formation in these cathodes, and contact mechanics problems between cathode and solid electrolyte. Understanding the interplay between cathode microstructure, operating conditions, micromechanics of battery materials, and capacity decay remains a challenge. Here, we present a microstructure-sensitive chemo-mechanical model to study the impact of grain-level chemo-mechanics on the degradation of composite cathodes. We reveal that crystalline anisotropy, state-of-charge-dependent Li diffusion rates, and lattice dimension changes drive dislocation formation in cathodes and contact loss at the cathode/electrolyte interface. These dislocations induce large lattice strain and trigger oxygen loss and structural degradation preferentially near the surface area of cathode particles. Moreover, contact loss is caused by the micromechanics resulting from the crystalline anisotropy of cathodes and the mechanical properties of solid electrolytes, not just operating conditions. These findings highlight the significance of grain-level cathode microstructures in causing cracking, formation of crystal defects, and chemo-mechanical degradation of solid-state batteries. The performance of solid-state batteries is affected by stress responses of their complex microstructure to volume changes from Li+ intercalation. Here, authors present a chemo-mechanical model to study the impact of grain-level chemo-mechanics on the degradation of composite positive electrodes. [ABSTRACT FROM AUTHOR]

Predicting failure initiation in nonlinear composite materials, often referred to as metamaterials, is a fundamental challenge in nonlinear solid mechanics. Microstructural failure mechanisms encompass fracture, decohesion, cavitation, compression-induced contact and instabilities, affecting their unconventional static and dynamic performances. To fully take advantage of these materials, especially in extreme applications, it is imperative to predict their nonlinear behaviour using reliable, accurate and computationally efficient numerical methodologies. This study presents an innovative nonlinear homogenization-based theoretical framework for characterizing the failure behaviour of periodic reinforced hyperelastic composites induced by reinforcement/matrix decohesion and interaction between contact mechanisms and microscopic instabilities. Debonding and unilateral contact between different phases are incorporated by employing an enhanced cohesive/contact model, which features a special nonlinear interface constitutive law and an accurate contact formulation within the context of finite strain continuum mechanics. The theoretical formulation is demonstrated using periodically layered composites subjected to macroscopic compressive loading conditions along the lamination direction. Numerical results illustrate the ways in which debonding phenomena, in conjunction with fibre microbuckling, may influence the critical loads of the examined composite solid. The sensitivity of the results obtained through the proposed contact–cohesive model at finite strain with respect to its implementation is also explored. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'. [ABSTRACT FROM AUTHOR]

In order to obtain the contact resistance of relay contacts more accurately, a novel contact resistance model for the spherical–planar joint interface is constructed based on the three-dimensional fractal theory. In this model, three-dimensional fractal theory is adopted to generate a rough surface at microscopic scale. Then, using contact mechanics theory, the deformation mechanism of asperities on rough surfaces is explored. Combined with the distribution of asperities, a contact resistance model for the planar joint interface is established. Furthermore, by introducing the surface contact coefficient, cross-scale coupling between the macro-geometric configuration and micro-surface topography is achieved, and a contact resistance model for the spherical–planar joint interface is constructed. After that, experiments are conducted to verify the accuracy of the proposed model, and the maximum relative error of the proposed model is 8.44%. Ultimately, combining numerical simulation analysis, the patterns of variation in contact resistance influenced by factors such as macroscopic configuration and microscopic topography are discussed, thereby revealing the influence mechanism of the contact resistance for the spherical–planar joint interface. The proposed model provides a solid theoretical foundation for the optimization of relay contact structures and improvements in manufacturing processes, which is of great significance for ensuring the safe and stable operation of power systems and electronic equipment. [ABSTRACT FROM AUTHOR]

Modularity is essential for ensuring the efficient execution of system-of-systems (SoS) frameworks, demanding the managerial and operational independence of constituent systems. This study explores the feasibility of enforcing displacement compatibility between two interconnected, independent solid mechanics finite element models with a contact interface within an SoS. This work developed an approach that ensures operational independence by delaying displacement compatibility in one of the systems. The lagged system provides a trial displacement input to the leading system, which determines the displacement discrepancy between both systems. This error is used to calculate an equivalent pressure that enforces displacement compatibility between the models. The method was verified by modeling two specimens with a frictionless contact interface and comparing the results against a continuous model assuming a perfect bond between the specimens. Lastly, the method was implemented within an SoS for space habitats and proved effective in ensuring matching displacements at the contact surface between two interacting structural layers. The proposed approach preserves the modularity of coupled systems, avoiding complex iterative procedures and transferring mass and stiffness information between systems. Moreover, it allows the coupled models to be developed in independent coordinate systems, as they only pass scalar, coordinate-independent parameters through the input-output ports. [ABSTRACT FROM AUTHOR]

In contrast to indentation mechanics of homogeneous materials, insight into the deformation behavior of heterogeneous materials, such as those comprising inclusions and second-phase particles, is relatively limited, especially at length scales comparable to the inclusion size and depth, indentation depth, and indenter radius. Therefore, axisymmetric and plane-strain analyses of the effect of an elastic inclusion on the indentation mechanics of elastic-perfectly plastic half-spaces were performed with the finite element method. Numerical results of the mean contact pressure, equivalent plastic strain, and first principal stress obtained for a range of key geometrical parameters, such as indentation depth, indenter radius, inclusion depth, and inclusion diameter, yielded insight into the development of plasticity and tensile stresses that could lead to subsurface cracking and delamination at the inclusion-matrix interface. Simulations revealed the critical ranges of indentation depth, inclusion size, and inclusion depth yielding deformation and stress fields significantly different from those of homogeneous half-spaces. Specifically, the critical mean contact pressure for instigating plasticity below the contact interface, adjacent to the inclusion-matrix interface, and in the proximity of the contact edge in conjunction with the development of plastic zones and tensile stress bands in the subsurface were analyzed for a wide range of inclusion depth and indentation depth. The present analysis provides a computational framework for developing contact mechanics models for particle-reinforced half-space media. [ABSTRACT FROM AUTHOR]

We present a complete numerical analysis for a general discretization of a coupled flow–mechanics model in fractured porous media, considering single-phase flows and including frictionless contact at matrix–fracture interfaces, as well as nonlinear poromechanical coupling. Fractures are described as planar surfaces, yielding the so-called mixed- or hybrid-dimensional models. Small displacements and a linear elastic behavior are considered for the matrix. The model accounts for discontinuous fluid pressures at matrix–fracture interfaces in order to cover a wide range of normal fracture conductivities. The numerical analysis is carried out in the Gradient Discretization framework (see J. Droniou, R. Eymard, T. Gallouët, C. Guichard, and R. Herbin [ The gradient discretisation method , Springer, Cham, 2018]), encompassing a large family of conforming and nonconforming discretizations. The convergence result also yields, as a by-product, the existence of a weak solution to the continuous model. A numerical experiment in 2D is presented to support the obtained result, employing a Hybrid Finite Volume scheme for the flow and second-order finite elements (\mathbb {P}_2) for the mechanical displacement coupled with face-wise constant (\mathbb P_0) Lagrange multipliers on fractures, representing normal stresses, to discretize the contact conditions. [ABSTRACT FROM AUTHOR]

Archard’s wear law encounters challenges in accurately predicting wear damage and volumes, particularly in complex situations like asperity–asperity collisions. A modified model is proposed and validated, showcasing its ability to predict wear in adhesive contacts with better accuracy than the original Archard’s wear law. The model introduces an improved wear coefficient linked to deformation energy, creating a spatially varying relationship between wear volume and load and imparting a non-linear characteristic to the problem. The improved wear model is coupled with the Boundary Element Method (BEM), assuming that the interacting surfaces are semi-infinite and flat. The deformation energy is calculated from the normal contact pressure and displacements, which are the common outputs of BEM. By relying solely on these outputs, the model can efficiently predict the correct shape and volume of the adhesive wear particle, without resorting to large and often slow models. An important observation is that the wear coefficient is expected to increase based on the accumulated deformation energy along the direction of frictional force. This approach enhances the model’s capability to capture complex wear mechanisms, providing a more accurate representation of real-world scenarios. [ABSTRACT FROM AUTHOR]

The dynamics of thin-walled parts are highly affected by the clamping conditions. Clamping stiffness is a function of c lamping force and surface roughness profiles of the clamp and part. Since the surface profiles cannot be altered, estimating clamping stiffness as a function of the clamping force is essential to simulate vibrations of the machined thin-walled parts. This paper presents the modeling of clamping stiffness as a function of the applied clamping force and material properties. Surface profile parameters are estimated from the identified contact stiffnesses evaluated using the Finite Element (FE) model. The contact stiffnesses are either predicted directly from the proposed mechanics model of the part or estimated from the Fractal surface parameters. It is shown that an average clamping stiffness can be predicted from the Fractal surface parameters, or directly and more accurately from the static model of the clamped part. [ABSTRACT FROM AUTHOR]

To address the issue of header loss in millet combine harvesters, a double-chain millet harvester header was designed based on the principles of contact mechanics and tribology. Key component parameters of the header were determined, with the divider length and width measuring 0.56 m and 0.30 m, respectively. The divider angle was 40°, and the spiral angle was also 40°. A prototype was manufactured, and field performance tests were conducted. The results showed that the total header loss rate of the double-chain header was lower than that of the single-chain header under various combinations of header height and harvesting speed. The lowest total header loss rate, 3.12%, occurred when the header height was 0.2 m and the harvesting speed was 1.667 m/s, with a grain loss rate of 0.55% and a spike loss rate of 2.57%. This research provides a theoretical foundation for the development of low-loss, high-efficiency millet combine harvesters. [ABSTRACT FROM AUTHOR]

Atomic force microscopy was utilized to estimate the adhesion strengths to silicon nitride as well as the cellular elasticities of pathogenic Listeria monocytogenes EGDe cells cultured in media adjusted to five different pH conditions of growth (5, 6, 7, 8, and 9) under water with 0.0027 fixed ionic strength. Particularly, the role of adhesion on the bacterial elastic properties was investigated. The nonadhesive Hertz model of contact mechanics was used to extract Young's moduli of elasticity of bacterial cells from the approach force-indentation data. Additionally, the adhesive models of contact mechanics: Johnson–Kendall–Roberts (JKR) and Derjaguin–Muller–Toporov (DMT) were used to estimate Young's moduli of elasticity of bacterial cells from the retraction force-indentation data. Our results indicated that adhesion to silicon nitride was the highest for cells cultured at a pH of 7. Similarly, bacterial cells cultured at pH 7 were characterized by the highest Young's moduli of elasticities compared to the lower or higher pH conditions of growth. Young's moduli of elasticities estimated from the Hertz model were stiffer than those estimated using JKR or DMT models. As the adhesion between bacterial cells and indenters increased, the difference between the Hertz model and JKR or DMT models estimates of Young's moduli of elasticity increased as well. Contradicting the current norm of using the Hertz model to quantify bacterial elasticity in the literature, our results highlight the extreme importance of utilizing contact mechanics models with adhesion components in them such as the JKR and DMT models to estimate bacterial elasticity. [ABSTRACT FROM AUTHOR]

Short pitch corrugation has been a problem for railways worldwide over one century. In this paper, a parametric investigation of fastenings is conducted to understand the corrugation formation mechanism and gain insights into corrugation mitigation. A three-dimensional finite element vehicle–track dynamic interaction model is employed, which considers the coupling between the structural dynamics and the contact mechanics, while the damage mechanism is assumed to be differential wear. Various fastening models with different configurations, boundary conditions, and parameters of stiffness and damping are built up and analysed. These models may represent different service stages of fastenings in the field. Besides, the effect of train speeds on corrugation features is studied. The results indicate: (1) Fastening parameters and modelling play an important role in corrugation formation. (2) The fastening longitudinal constraint to the rail is the major factor that determines the corrugation formation. The fastening vertical and lateral constraints influence corrugation features in terms of spatial distribution and wavelength components. (3) The strengthening of fastening constraints in the longitudinal dimension helps to mitigate corrugation. Meanwhile, the inner fastening constraint in the lateral direction is necessary for corrugation alleviation. (4) The increase in fastening longitudinal stiffness and damping can reduce the vibration amplitudes of longitudinal compression modes and thus reduce the track corrugation propensity. The simulation in this work can well explain the field corrugation in terms of the occurrence possibility and major wavelength components. It can also explain the field data with respect to the small variation between the corrugation wavelength and train speed, which is caused by frequency selection and jump between rail longitudinal compression modes. [ABSTRACT FROM AUTHOR]

This investigation aimed to assess the impact of obesity on the load-transfer mechanism, longevity, and contact mechanics of cemented acetabular cups. Three obesity scenarios were considered: obese case-I (100–110 kg), obese case-II (120–130 kg), and obese case-III (140–150 kg). Utilising six finite element models, the effects of different bodyweights on load transfer, contact mechanics, and cup longevity during normal walking conditions were assessed. Muscle forces and hip joint reaction forces were adjusted and linearly calibrated based on obesity cases. Elevated stresses in cortical and cancellous bones, as well as the cement mantle, were observed in obese cases, suggesting a heightened risk of loosening and failure of the cemented fixation of the acetabular cup. Additionally, increased contact pressure and micromotion between articulating surfaces were noted in obese individuals, with a gradual escalation from obese case-I to obese case-III. These findings highlight the significant negative impact of obesity on the performance of cemented acetabular cups, emphasizing the importance of considering bodyweight variations in the design and assessment of orthopaedic implants for optimal functionality and durability. [Display omitted] [ABSTRACT FROM AUTHOR]

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This study presents a microscale framework for investigating the seismic stability of bridge-pier structures using the discrete element method (DEM), with a focus on rocking isolation mechanisms. The piers and the deck are modeled as rigid blocks that follow rigid body dynamics. The rigid block is modeled as a collection of glued particles with geometrical arrangement and physical properties that mimic an actual block. To facilitate numerical contact points between the base of the block and the flat base wall, smaller particle sizes were introduced at the base of the block. A Hertz contact model was employed to model the interaction between contacting entities for better estimation of the contact constitutive parameters. Validation was performed using well-documented experimental data featuring the free-rocking of a granite stone block as well as existing analytical techniques. DEM simulations were performed on single blocks as well as on a bridge deck-pier system subjected to dynamic and seismic loadings. The study shows the effectiveness of rocking isolation through a comparative analysis of acceleration and angular velocity under varying seismic intensities, with acceleration reduction up to 70% for piers and 60% for the deck in a high-intensity scenario, affirming the potential of rocking isolation as a viable seismic mitigation strategy. The study monitors the structural response, contact mechanics, and energy dissipation of the pier–deck system. The application of the DEM model advances the analysis of bridge pier and deck interactions under seismic loads, providing new insights into the detailed behavior of rocking bridge piers and their potential for seismic isolation. [ABSTRACT FROM AUTHOR]

The compression deformations of subsea connectors' sealing gasket dominate the sealing performance. Based on the previous study which has presented an analytical model for calculating compression deformations, a new analytical model that considers the deviations is proposed to predict compression deformations more exactly and effectively. The mathematical contact model of the metallic sealing structure is built on the basis of Hertz contact mechanics theory. Theoretical relationships between contact loads and contact pressure as well as contact width are established, and stress components equations under different loads are obtained. The compression displacements equation is presented by considering constitutive equations and geometric equations. Finite element method is adopted to verify predicted values in the new analytical model and the results show good agreement. This work will provide a theoretical method and guidance for designing structural parameters of the metallic lenticular gasket of the subsea connector in the subsea production system. [ABSTRACT FROM AUTHOR]

The tendency of relative motion via rolling between contacting objects exists in various aspects of industry and nature because, in many practical situations, forces and moments may be simultaneously induced at the contacting interfaces. Due to the presence of adhesion, which may be prominent on small scales, research on contacts with the tendency to roll, termed herein as rolling adhesion, is very limited. In the present work, a novel double-Hertz model is developed for adhesive contact between spherical objects subjected to the combined action of normal forces and moments. The results from the new model agree well with available numerical simulations and experimental results. It has been demonstrated that the contact behavior with the effect of rolling adhesion seemingly resembles that of conventional adhesive contact, but the applied moment may impact the pull-off force and may even induce novel contact instability if large enough. The resistance moment at the interface has also been obtained analytically, which is proportional to adhesion hysteresis and contact area. Given the applicability to the full range of the Tabor parameter and nonsingular stresses involved, these results might shed light on adhesive contacts with rolling adhesion and help to characterize them better than existent models. [ABSTRACT FROM AUTHOR]

Periacetabular osteotomy (PAO) is a common treatment for prearthritic hip dysplasia. The goal of this investigation was to determine if computationally assessed hip contact mechanics are associated with joint failure at minimum 10‐year follow‐up. One hundred patients with hip dysplasia (125 hips) completed patient‐reported outcomes an average of 13.8 years (range 10.0–18.0 years) after PAO. 63/125 hips were classified as having failed: 26 converted to total hip arthroplasty (THA) and 37 with significant disability indicated by modified Harris Hip Score (mHHS) ≤ 70. Differences in discrete element analysis‐computed contact mechanics were compared between (1) preserved and failed hips, (2) preserved hips and hips that failed by THA, and (3) preserved hips and hips that failed by mHHS ≤ 70. Failed hips had significantly higher preoperative contact stress and exposure metrics (p < 0.001–0.009) than preserved hips. Failed hips also had significantly higher postoperative peak contact stress (p = 0.018), higher mean contact stress (p < 0.001), and smaller contact area (p = 0.044). When assessed based on type of failure, hips that failed by THA had significantly higher postoperative contact stress and exposure metrics than preserved hips (p < 0.001–0.020). In hips that failed by mHHS ≤ 70, mean postoperative contact stress exposure was significantly higher compared to preserved hips (p = 0.043). Despite improved radiographic measures of dysplasia after PAO, pathologic joint contact mechanics can persist and predict treatment failure at minimum 10 years after surgery. Operative and nonoperative techniques specifically intended to reduce harmful contact mechanics in dysplastic hips may have the potential to further improve clinical outcomes after PAO. [ABSTRACT FROM AUTHOR]

In this study, we developed and parametrized a friction model for finite element (FE) cutting simulations of AISI4140 steel, combining experimental data and numerical simulations at various scales. Given the severe thermomechanical loads during cutting, parametrization of friction models based on analogous experiments has been proven difficult, such that the cutting process itself is often used for calibration. Instead, our model is based on the real area of contact between rough surfaces and the stress required to shear adhesive micro contacts. We utilized microtextured cutting tools and their negative imprint on chips to orient chip and tool surfaces, enabling the determination of a combined surface roughness. This effective roughness was then applied in contact mechanics calculations using a penetration hardness model informed by indentation hardness measurements. Consistent with Bowden and Tabor theory, we observed that the fractional contact area increased linearly with the applied normal load, and the effective roughness remained insensitive to cutting fluid application. Additionally, we calculated the required shear stress as a function of normal load using DFT-based molecular dynamics simulations for a tribofilm formed at the interface, with its composition inferred from ex-situ XPS depth profiling of the cutting tools. Our friction model demonstrated good agreement with experimental results in two-dimensional FE chip forming simulations of orthogonal cutting processes, evaluated by means of cutting force, passive force, and contact length prediction. This work presents a proof of concept for a physics-based approach to calibrate constitutive models in metal cutting, potentially advancing the use of multiscale and multiphysical simulations in machining. [ABSTRACT FROM AUTHOR]

New technologies in additive manufacturing have enabled the cost-effective production of gradient materials with desired multifunctional properties. In mechanical engineering, such functionally graded materials (FGMs) are often used within mechanical joints, as they ensure higher strength as well as wear resistance and prevent fretting fatigue. However, due to the variations in their composition and structure, theoretical predictions of their contact-mechanical behavior are significantly complicated. In this work, a general theory for solving tangential contacts between 3D power-law graded elastic solids of arbitrary geometry is presented. For multiple contacts, such as those occurring between two nominally flat but rough half-spaces, the well-known Ciavarella–Jäger theorem is established accompanied by a discussion of tangential coupling. Nevertheless, the focus of the work is on axisymmetric single contacts under arbitrary unidirectional tangential loading, for which closed-form analytical solutions are derived based on the Mossakovskii–Jäger procedure. In comparison to the results of common approximate methods, the solutions include the non-axisymmetric components of tangential displacements, which are indispensable for the accurate determination of the relative slip components and thus the surface density of frictional energy dissipation in the partial slip regime. Although a simplified approach is used for the calculation of the dissipated energy density, the results in the limiting case of homogeneous material are in excellent agreement with those from a full numerical computation. As an application example, the complete solutions for the tangential contact of parabolically shaped power-law graded elastic solids in the partial slip regime are derived and the influence of the material gradient as well as Poisson's ratio on the surface density of dissipated energy is investigated. [ABSTRACT FROM AUTHOR]

The occlusion of the teeth is affected due to the appearance of micro-cracks resulting from maximum stresses in the contact zones between the wire and the bracket under normal and tangential loading. The objective of this study is to evaluate the surface and volume constraints in the presence of bonding and partial sliding zones on the contact surface between wires and supports. Knowledge of these stress fields will make it possible to better limit the surfaces where most of the micro-cracks occur. Indeed, the evaluation of the stress will facilitate the modelling or application of established micro crack models on this subject, because the initiation of micro-cracks often appears on the contact surface or just below it. In this study, the two most common situations of contact between the wire and the bracket were studied; the first corresponds to the situation where the wire is positioned in the center of the support (classic friction), and the second corresponds to the situation where the inclined wire touches the ends of the supports (critical contact angle).The MATHCAD software was used to simulate the damage zones for normal loading in the two cases studied (classic friction, critical contact angle). We proposed a Hertzian loading for the first case and a linear loading for the second case. Also, the effect of the additional load during wire tightening applied by the orthodontist was studied. The charge concentration is located above the contact zone, of the order of 0.3P0 (pressure per unit of arbitrary normal length), according to Mathcad simulation results. The adhesion zone/micro-slip zone contact generates the largest tangential load, which is directed towards the side experiencing the most stress. We also observed that the stick area shifts towards the recessed side when the additional load is applied. Additionally, comparing the configurations, the critical contact angle resulted in a higher maximum shear stress. [ABSTRACT FROM AUTHOR]

Abstract In many insects the surface of the eye is nanostructured by arrays of protuberances termed ommatidial gratings which provide the cuticle with anti-reflective, anti-wetting and self-cleaning properties. The hypothesised anti-contamination role of the gratings against dust and pollen results from theoretical predictions on grating geometry and experiments on synthetic replicas of ommatidia surfaces but has not yet been proven in an animal. Whiteflies are biological test beds for anti-contamination surfaces because they deliberately distribute wax particles extruded from abdominal plates over their entire bodies. The numerous particles protect the animal against water evaporation and radiation, but may severely impair vision. Using scanning electron microscopy (SEM) and CryoSEM, we here show that the cornea of whiteflies exhibits ~ 220 nm wide mesh-like structures forming hexagonal gratings with thin ~ 40 nm connecting walls. Quantitative measurements of wax particles on the eye show that the nanostructures reduce particle contamination by more than ~ 96% compared to other areas of the cuticle. Altogether, our study is the first description of a predicted optimized grating geometry for anti-contamination in an arthropod. The findings serve as evidence of the high effectiveness of nanostructured surfaces for reducing contact area and thus adhesion forces between biological surfaces and contaminating particles.

This study presents a microscale framework for investigating the seismic stability of bridge-pier structures using the discrete element method (DEM), with a focus on rocking isolation mechanisms. The piers and the deck are modeled as rigid blocks that follow rigid body dynamics. The rigid block is modeled as a collection of glued particles with geometrical arrangement and physical properties that mimic an actual block. To facilitate numerical contact points between the base of the block and the flat base wall, smaller particle sizes were introduced at the base of the block. A Hertz contact model was employed to model the interaction between contacting entities for better estimation of the contact constitutive parameters. Validation was performed using well-documented experimental data featuring the free-rocking of a granite stone block as well as existing analytical techniques. DEM simulations were performed on single blocks as well as on a bridge deck-pier system subjected to dynamic and seismic loadings. The study shows the effectiveness of rocking isolation through a comparative analysis of acceleration and angular velocity under varying seismic intensities, with acceleration reduction up to 70% for piers and 60% for the deck in a high-intensity scenario, affirming the potential of rocking isolation as a viable seismic mitigation strategy. The study monitors the structural response, contact mechanics, and energy dissipation of the pier–deck system. The application of the DEM model advances the analysis of bridge pier and deck interactions under seismic loads, providing new insights into the detailed behavior of rocking bridge piers and their potential for seismic isolation.

This study introduces an advanced finite element model for the light weight deflectometer (LWD), which integrates contact mechanics with fully coupled models. By simulating LWD tests on granular soils at various saturation levels, the model accurately reflects the dependence of the LWD modulus on dry density, water content, and effective stress. This model addresses and overcomes the limitations of previous finite element models for this specific problem. Simultaneously, this research presents the first experimentally validated fully coupled contact impact model. Furthermore, the research provides a comparative assessment of elastoplastic and nonlinear elastic models and contrasts an enriched node-to-segment method (developed in this study) with the more precise mortar technique for contact mechanics. These comparisons reveal unique advantages and challenges for each method. Moreover, the study underscores the importance of careful application of the LWD modulus, emphasising the need for sophisticated tools to interpret soil behaviour accurately.

Abstract\nHIGHLIGHTSThe formation of a complex fracture network with sufficient proppant conductivity is crucial for the efficient development of deep shale gas. Due to cost considerations, quartz sand has commonly replaced ceramic proppant in the field. However, the significant crushing of quartz sand and its distribution as multiple particle sizes both before and after crushing, termed as particle size redistribution, raises concerns about its ability to meet the demands of the fracture network. Based on contact mechanics, we developed an evolutionary equation for fracture width that considers particle size redistribution. The particle crushing is described using a fragmentation replacement method, and changes in specific surface area before and after crushing are used to correct the permeability model of the fracture. By integrating models of fracture width and permeability evolution, we have established an analytical model for proppant conductivity that accounts for quartz sand crushing and its particle size redistribution. Numerical simulations further validate the predictive accuracy of our model. Sensitivity analyses investigate the impact of quartz sand degree of crushing, compressive strength, particle size, particle combination ratio, and closure pressure on fracture conductivity, demonstrating the reliability of quartz sand as a substitute for ceramic proppant in deep shale applications.Developed a new model for fracture conductivity considering the embedding and crushing of multiple particle sizes of quartz sand in a proppant monolayer.Demonstrated the reliability of replacing ceramic proppants with quartz sand in deep oilfield applications through model studies.Provided an alternative evaluation method for selecting and optimising sand addition during construction based on reservoir conditions. [ABSTRACT FROM AUTHOR]

Peeling of pressure‐sensitive adhesives from low modulus substrates such as human skin induces a significant out‐of‐plane deformation at the crack tip. In the context of medical adhesives, this deformation is related to the pain and injury caused to the skin and underlying tissue during removal. Here, a method is presented to measure the out‐of‐plane deformation of elastic substrates as a medical adhesive tape is removed from the surface, a necessary first step in the eventual quantification of pain. Elastic human skin analogs comprised of a simple bilayer with varied moduli across several orders of magnitude are fabricated. Next, a nonporous medical adhesive tape is peeled from these substrates and the deformation is quantified. A model derived from contact mechanics for a rectangular pressure is fit to the experimental data. By correcting for confinement effects and deformation within the adhesive, good agreement is found between the newly reported model in this study and the experimentally observed deformation. [ABSTRACT FROM AUTHOR]

The meniscus plays a crucial role in the proper functioning of the knee joint, and when it becomes damaged, partial removal or replacement is necessary to restore proper function. Understanding the stress and deformation of the meniscus during various movements is essential for developing effective materials for meniscus repair. However, accurately estimating the contact mechanics of the knee joint can be challenging due to its complex shape and the dynamic changes it undergoes during movement. To address this issue, the open-source software SCONE can be used to establish a kinematics model that monitors the different states of the knee joint during human motion and obtains relevant gait kinematics data. To evaluate the stress and deformation of the meniscus during normal human movement, values of different states in the movement gait can be selected for finite element analysis (FEA) of the knee joint. This analysis enables researchers to assess changes in the meniscus. To evaluate meniscus damage, it is necessary to obtain changes in its mechanical behavior during abnormal movements. This information can serve as a reference for designing and optimizing the mechanical performance of materials used in meniscus repair and replacement. [ABSTRACT FROM AUTHOR]

Switchable adhesion, a phenomenon characterized by the ability to transition between attachment and detachment states under external stimuli, has recently gained popularity in various advanced devices. The realization of the desired functionalities on such surfaces relies on intricate interfacial designs. A general understanding of the commonalities and distinctions among these designs can foster the development of refined switchable adhesion interfaces (SAIs). To address this, this review first examines adhesion interfaces by focusing on the fundamental interactions at the atomic/molecular level, adhesion models, and their correlation with the diverse forces/bonds that dominate the adhesion behaviors. The latest progress in SAIs based on various forces/bonds, including electrostatic force, van der Waals force, capillary force, chemical bond, and suction force, is then discussed with regard to their specific design strategies, such as structures, components, and triggers. Additionally, an extensive overview of the broad applications of SAIs in fields ranging from space to biomedicine is provided, along with an exploration of the prevailing challenges and potential opportunities. With the rapid progress that has been made in state‐of‐the‐art mechanisms and design strategies, SAIs are expected to undergo booming development in the foreseeable future. [ABSTRACT FROM AUTHOR]

Hydraulic stimulation is a critical process for increasing the permeability of fractured geothermal reservoirs. This technique relies on coupled hydromechanical processes induced through pressurized fluid injection into the rock formation. The injection of fluids causes poromechanical stress changes that can lead to fracture slip and shear dilation, as well as tensile fracture opening and propagation, so-called mixed-mechanism stimulation. The effective permeability of the rock is particularly enhanced when new fractures connect with pre-existing fractures. While hydraulic stimulation can significantly improve the productivity of fractured geothermal reservoirs, the process is also related to induced seismicity. Hence, understanding the coupled physics is central, for both reservoir engineering and seismic risk mitigation. This article presents a modelling approach for simulating the deformation, propagation and coalescence of fractures in porous media under the influence of anisotropic stress and fluid injection. It uses a coupled hydromechanical model for poroelastic, fractured media. Fractures are governed by contact mechanics and a fracture propagation model. For numerical solutions, we employ a two-level approach, combining a finite volume method for poroelasticity with a finite element method for fracture propagation. The study investigates the impact of injection rate, matrix permeability and stress anisotropy on stimulation outcomes. This article is part of the theme issue 'Induced seismicity in coupled subsurface systems'. [ABSTRACT FROM AUTHOR]

Purpose Methods Results Conclusion Level of Evidence To perform a systematic review and meta‐analysis of the existing literature on meniscal centralisation procedures, analysing its impact on meniscal extrusion, joint biomechanics and clinical and radiological outcome measures.The Cochrane Controlled Register of Trials, PubMed (MEDLINE) and Embase were used to perform a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses criteria. Biomechanical studies on healthy animal or human cadaveric knee joints that assessed meniscal extrusion or tibiofemoral contact mechanics (contact area and pressure) following centralization for meniscal pathologies were included. For clinical studies, those that prospectively or retrospectively assessed patient‐reported outcome measures (PROMs), postoperative knee motion, complications and radiological extrusion following centralization for meniscal pathologies were included.Fifteen studies were included in the analysis, comprising eight biomechanical, six clinical and one both. There were 92 knee specimens for biomechanical testing, of which 40 were human cadaveric and 52 porcine models. Biomechanical data revealed centralization to be commonly performed for posterior meniscal root tears and significantly reduced extrusion and contact pressure whilst improving contact area following a tear (p < 0.00001). Centralization restored extrusion to that of the native knee at all flexion angles described (0–90°, p = 0.25) and, compared to the torn state, brought tibiofemoral contact mechanics 3.2–5.0 times closer to the native state. Clinical data showed that 158 patients underwent centralization for extrusion. It improved postoperative Knee Injury and Osteoarthritis Outcome score (KOOS) (p = 0.006) and Lysholm scores (p < 0.00001) at 25.0 months, maintained extrusion reduction at 17.1 months (p < 0.00001) and preserved knee motion.Centralisation for various meniscal injuries associated with extrusion can reduce meniscal extrusion and improve joint biomechanics, along with clinical and radiological outcomes. Existing evidence is still scarce and exhibits a notable amount of methodological heterogeneity.Systematic review of Level IV evidence. [ABSTRACT FROM AUTHOR]

Contact mechanics analysis is crucial because such problems often arise in engineering practice. When examining contact mechanics, the material property of the contacting components is a crucially significant aspect. It is more complex to solve the contact mechanics of systems that are composed of materials that do not have a homogenous structure compared to materials that have homogeneous qualities throughout. While many studies on contact problems with homogeneous materials exist, those involving non-homogeneous materials are scarce in the literature. As material technology improves fast, there will be a greater need to solve such problems. In this respect, analytical and finite element method (FEM) solutions of the continuous and discontinuous contact problems of a functionally graded (FG) layer are carried out in this article. The FG layer in the problem rests on a rigid foundation and is pressed with a rigid punch. From the solutions, the contact length, contact stress, initial separation distance, and beginning and ending points of separation were determined, and the results were compared. It has been concluded that the FEM findings are consistent with the analytical results to a satisfactory degree. This study analyzes contact problem using different approaches and accounts for the influence of body force in a contact geometry that has yet to be reported. [ABSTRACT FROM AUTHOR]

This study offers a comparative study of the analytical and numerical methods for investigating a contact problem. The contact problem comprises a functionally graded layer supported by a half‐plane and loaded with a distributed load from the top surface. First, the analytical and numerical solutions to the problem are acquired by utilizing a theory of elasticity and finite element method, respectively. The problem is transformed into a system of integral equations in which the contact stress is an unknown function. The solution of the integral equation was achieved with Gauss–Jacobi integration formulation. The finite element model of the problem is created using ANSYS software, and the two‐dimensional analysis of the problem is performed. Results were obtained from the samples for different material properties and loading conditions. The distributed load width and non‐homogeneity parameters significantly impact on contact mechanics. The results indicate that the contact area and the contact stress obtained from finite element method (FEM) are close to the analytical results. As a result, acceptable error rates were obtained. Finally, this study provides evidence of a good agreement between the two methods. [ABSTRACT FROM AUTHOR]

A technique is proposed for reproducing particle size distributions in three‐dimensional simulations of the crushing and comminution of solid materials. The method is designed to produce realistic distributions over a wide range of loading conditions, especially for small fragments. In contrast to most existing methods, the new model does not explicitly treat the small‐scale process of fracture. Instead, it uses measured fragment distributions from laboratory tests as the basic material property that is incorporated into the algorithm, providing a data‐driven approach. The algorithm is implemented within a nonlocal peridynamic solver, which simulates the underlying continuum mechanics and contact interactions between fragments after they are formed. The technique is illustrated in reproducing fragmentation data from drop weight testing on sandstone samples. [ABSTRACT FROM AUTHOR]

Polymers are widely used in bearing applications. In the case of water-lubricated stern tube bearings, thermoplastic polyurethane (TPU)-based composites are used due to their excellent wear resistance, corrosion resistance, and tunable mechanical properties. Their tribological performance, however, depends on operating conditions. In this work, TPU was blended with carbon fiber, graphene platelet, and ultra-high molecular weight polyethylene (UHMWPE). Friction tests of TPU based-composites against copper countersurface were carried out in water to mimic the actual operating conditions of the bearing. Most of the resulting contacts were in the boundary lubrication regime, in which friction was attributed to both contact mechanics of asperities as well as water lubrication. Our results show that the viscoelasticity of TPU has a considerable impact on its tribological performance. Water lubrication at 50 °C promotes the softening of polymer surface material during sliding, resulting in higher fluctuation in the coefficient of friction and wear loss. This is attributed to the reduced thermomechanical properties. In addition, Schallamach waviness is observed on worn surface. The tribological properties of TPU are significantly improved by the inclusion of carbon fiber, graphene platelet, and UHMWPE. The formation of graphene transfer-layers and UHMWPE transfer film reduces friction and wear loss, while the inclusion of carbon fiber enhances wear resistance due to improved mechanical properties and load bearing capacity. [ABSTRACT FROM AUTHOR]

The dynamic effects involved in wheel-rail interactions can be increased by the traction force potentially causing rapid degradation of turnout rails. A precise stress/strain analysis is essential for wheel-rail frictional rolling contact and the related degradation. Therefore, an explicit finite element method is established considering dynamic effects related to the contact. Furthermore, the frictional rolling contact solutions and related degradation with different traction coefficient in turnout are investigated. The results indicate that the effect of asymmetric excitation caused by traction force and geometric irregularities will lead to yaw motion of wheelset. The width of running band on the switch rail is increased as the top surface width of the switch rail increases. In addition, the contact patch on the switch rail will gradually shift forward compared to that on the stock rail, leading to excessive shear stress and increase of microslip. Meanwhile, the adhesion-slip distribution, uneven wear and severe plastic deformation during transition are recognized. [ABSTRACT FROM AUTHOR]

The interfacial contact status of a joint determines the sealing performance of an aircraft hydraulic system, which is influenced by inevitable multiscale assembly errors and joint manufacturing deviations. To address these challenges, a novel geometric analysis model was heuristically created that incorporates assembly and manufacturing-related topographies to accurately estimate the initial relative assembly position of joint surfaces. A microscopic contact model was constructed using the reverse reconstruction approach based on measured surface characteristics. Combining the relative position, a multiscale finite element contact model was generated to investigate the impact of each scale topography on the contact state of the seal ring. The experimental data verified the simulated indentation findings, confirming the model's efficacy in estimating contact status and seal performance characteristics. It is found that the flare angle has a more obvious effect on the contact state of the sealing interface, and a 2° difference in angle under the same load can cause a 28.19% difference in contact area, which greatly affects the sealing performance. [ABSTRACT FROM AUTHOR]