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The contact behavior of a stepseal affects its reliability and remaining life. In this study, experimental and numerical analyses were performed to investigate the contact behavior of a typical stepseal. Its dimensions and material properties were also tested. The Mooney–Rivlin hyperelastic model was used to fit the stress–strain data of the rubber. A static contact pressure of 105.1 MPa was obtained using the Fujifilm pressure measurement film. A finite element model of a stepseal with reasonable element sizes was established. A comparison between the experimental results and finite element (FE) predictions shows that the finite element method underpredicts the maximum static contact pressure and contact length. For the maximum contact pressure, the test results were approximately 30.4% higher than those of the FE predictions. [ABSTRACT FROM AUTHOR]

• A coupled electromagnetic-mechanical model is built to calculate the coupling behaviors of superconducting coils. • Mechanical deformation impacts the motion of magnetic flux and changes the critical current of superconductors. • The roles of contact conditions in the superconducting coils are derived theoretically. • A mechanical homogenization model is proposed to simplify the model containing hundreds of contact pairs. Rare-earth based barium copper oxide (REBCO) superconducting coated conductors are promising candidates for the design of high field magnets. In a high magnetic field, these conductors have to withstand huge Lorentz force, which would threaten the safety of superconducting devices. Recently, researchers have found that the electromagnetic-mechanical coupling has a significant impact on the overall response of the magnet system. It has been demonstrated that mechanical deformation can lead to the movement of magnetic flux in superconductors and changes in the critical current of superconductors. To take into account the electromagnetic-mechanical coupling effects, REBCO coated conductors are modeled as deformable conductors based on continuum mechanics of electromagnetic solids. Then, a fully coupled electromagnetic-mechanical model is developed in this paper, which is verified with the experimental results. Furthermore, during the electromagnetic-mechanical coupling simulation, contact separation occurs in REBCO pancake coils. To characterize the global mechanical performance of the REBCO pancake coils (containing hundreds of contact conditions), the concept of flexural rigidity in elastic shell theory is employed. Then, a mechanical homogeneous model is proposed to simplify the model containing hundreds of contact pairs and enable the effective simulation of large-scale HTS systems. This framework can provide theoretical support to the mechanical research of high field magnets. [ABSTRACT FROM AUTHOR]

With the increasing requirements of agricultural machinery, the study of the contact relationship between the tire–soil interface and the improvement of traction efficiency has gradually become a main concern. In this study, the pattern on the agricultural tire was simplified into single-pitch pattern blocks. The pattern blocks were made of rubber material that was highly resistant to abrasion and bending. The experiment was carried out by pressing the three types of patterned block construction into the soil and the pure sliding under the soil. The simulation used the Coupled Eulerian–Lagrangian Method (CEL) to verify the experimental results. We found that the herringbone pattern block was subjected to the highest stress for the same depth of downward pressure. The horizontal force generated by the pure sliding was also the highest. The results showed that the numerically simulated and experimentally measured data exhibited similar trends and average values. In addition, the increase in the contact area between the tire and the soil reduced the compaction and sinking of the soil. The herringbone pattern structure not only had a large contact area but also produced the most significant shear force on the soil. Thus, it may generate greater traction in actual operations. [ABSTRACT FROM AUTHOR]

Adaptability to unstructured objects and the avoidance of target damage are critical challenges for flexible grippers in fruit-picking robots. Most existing flexible grippers have many problems in terms of control complexity, stability and cost. This paper proposes a flexible finger design method that considers contact behavior. The new approach incorporates topological design of contact targets and introduces contact stress constraints to directly obtain a flexible finger structure with low contact stress and good adaptability. The study explores the effects of design parameters, including virtual spring stiffness, volume fraction, design domain size, and discretization, on the outcomes of the flexible finger topology optimization. Two flexible finger structures were selected for comparative analysis. The experimental results verified the effectiveness of the design method and the maximum contact stress was reduced by about 70%. An adaptive two-finger gripper was developed. This design allows the gripper to achieve damage-free grasping without additional sensors and control systems. The adaptive and contact performances of the grippers with different driving modes were analyzed. Practical grasping tests were also performed, including evaluation of adaptive performance, stability, and maximum grasping weight. The results indicate that gripper 2 with flexible finger 2 excelled in contact stress and adaptive wrapping, making it well-suited for grasping unstructured and fragile objects. This paper provides valuable insights for the design and application of flexible grippers for picking robots, offering a promising solution to enhance adaptability while minimizing target damage. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article presents the latest progress in research on tire–pavement contact behavior. Firstly, the tire–pavement contact characteristics and their influencing factors are summarized. Then, the measurement methods and theoretical research on tire–pavement contact behavior are reviewed, and the advantages and shortcomings of different methods are compared and analyzed. Finally, analysis in the field of pavement engineering is summarized based on contact behavior. This article suggests a few key research directions: Tire–pavement contact behavior is influenced by multiple factors; therefore, multi-physical field-coupling analyses need to be carried out. Tire–pavement contact tests are mostly static and non-standardized, and it is a future trend to develop high-precision, low-cost, and standardized instruments that can measure dynamic contact. Theoretical research models rarely involve environmental factors; a contact model of the tire, pavement, and environment needs to be constructed that can truly describe the contact process. There is a relationship between contact characteristics and pavement performance; pavement performance evaluation indexes need to be established based on tire–pavement contact characteristics in the future. [ABSTRACT FROM AUTHOR]

Copyright of Tribologie und Schmierungstechnik is the property of Narr Francke Attempto Verlag GmbH & Co.KG and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Adaptability to unstructured objects and the avoidance of target damage are critical challenges for flexible grippers in fruit-picking robots. Most existing flexible grippers have many problems in terms of control complexity, stability and cost. This paper proposes a flexible finger design method that considers contact behavior. The new approach incorporates topological design of contact targets and introduces contact stress constraints to directly obtain a flexible finger structure with low contact stress and good adaptability. The study explores the effects of design parameters, including virtual spring stiffness, volume fraction, design domain size, and discretization, on the outcomes of the flexible finger topology optimization. Two flexible finger structures were selected for comparative analysis. The experimental results verified the effectiveness of the design method and the maximum contact stress was reduced by about 70%. An adaptive two-finger gripper was developed. This design allows the gripper to achieve damage-free grasping without additional sensors and control systems. The adaptive and contact performances of the grippers with different driving modes were analyzed. Practical grasping tests were also performed, including evaluation of adaptive performance, stability, and maximum grasping weight. The results indicate that gripper 2 with flexible finger 2 excelled in contact stress and adaptive wrapping, making it well-suited for grasping unstructured and fragile objects. This paper provides valuable insights for the design and application of flexible grippers for picking robots, offering a promising solution to enhance adaptability while minimizing target damage.

Slip behavior of planar discontinuities in rock masses is the basis of rock slope failure and fault movement. Local failure at different locations of the slip interface occurs before global slip failure, and a precursor signal [acoustic rock joint behavior (elastic stiffness, transmitted wave amplitude, etc.)] is generated. Therefore, detecting the precursor signal before shear stress reaches its peak can be used to predict the instability of rock slopes and fault slip in the macroscopic range. The composition of rocks, distribution of stress, roughness of joints and fault interfaces, and non-uniform distribution of the actual contact area are the primary factors that control the friction strength and slip behavior of joints. The combined influence of these factors enhances the complexity of monitoring local precursor signals. The distribution of rock joint stiffness has previously been obtained based on the elastic wave measurement method to determine the parameter characterization of rock joint contact behavior. Here, the evolution law of joint stiffness during uniaxial compression and shear was studied through laboratory tests and used to analyze the local contact state of rock joints and faults through the change of joint stiffness. A continuous and nondestructive monitoring method is proposed. [ABSTRACT FROM AUTHOR]

The dynamic contact behavior between multi-component droplets and the surface of iron ore dust was taken as the research object, analysis of the maximum spreading coefficient, maximum acting diameter, maximum acting area, and maximum bouncing height of solid-liquid contact, from a microscopic perspective, using high-speed photography and image analysis and processing technology. The experimental results indicate that (1) with the particle size of dust particles decreases, the solid-liquid contact behavior sequentially manifests as spread immediately after broken, retraction, negative bounce, primary bounce, and secondary bounce. (2) When the surface tension of the droplets decreases from 55.5 to 34.8 mN/m, the maximum spreading diameter of the droplet has increased by 30% to 40%, the maximum bounce heights (coefficients) decreased by 100%, 57.14%, and 53.57%, respectively, the maximum spreading coefficient of the droplet exhibits no obvious pattern. (3) With decreasing droplet surface tension, the unidirectional acting diameter and the maximum acting area increase when the dust surface size is over 100 μm. When the surface particle size is less than 100 μm, there is no significant change in the unidirectional acting diameter and maximum acting area despite decreasing surface tension. Thus, droplet diffusion is mainly influenced by particle size. These findings contribute to enhancing the theory of water mist dust removal and improving dust removal efficiency. [ABSTRACT FROM AUTHOR]

Partial wear is one of the fatal abnormal wears, which may pose a threat to the cutterhead or even the driving system. Considering the randomness of partial wear, the real-time detection and early warning of partial-wear states are very important, but it requires a deep understanding of the mechanism and characteristics of the interaction between the partial-worn cutter and rock. In this study, rock-cutting experiments are conducted on a cutter under partial wear via multifunctional cutter test machine. The key dynamic parameters of the partial-worn cutter (e.g., loading history during rock cutting) are analyzed. The influence of partial wear on cutter-rock contact behavior is examined with a particle flow discrete element model. The results show that after partial wear, the contact area of the cutter can be divided into two parts: an arc region and a linear region. Reduction in the projected area of the arc region decreases the normal force of the cutter. The appearance of the linear region and changes in the friction type between the cutter and rock from rolling to sliding increase the tangential force. The partial-worn cutter still has rock-breaking ability, but the linear contact region prolongs the working time of the cutter and generates more rock powder, ultimately increasing its rock-cutting specific energy. The results of this work reveal changes in rock-cutting characteristics of partial-worn cutters, providing workable theoretical support for the detection and early warning of partial wear in cutters. [ABSTRACT FROM AUTHOR]

During the start-up process, air foil thrust bearings (AFTBs) come into contact and are prone to localized overheating and even failure. Frequent starts and stops are the major sources of wear. In this study, a transient mixed lubrication model considering the air rarefaction effect is established. In the model, asperity contact between the top foil of the air foil thrust bearing (AFTB) and the rotor surface is considered using a deterministic approach, and the deformation of the foil structure is considered using the elastic-aerodynamic coupling. The influences of bearing compliance, external load, acceleration time and contact stiffness on the tribological properties during the start-up process are investigated. The results show that the lift-off speed increases with the increase of the bearing compliance and of the external load. Specifically, the lift-off speed of AFTBs increases from 1950 rpm to 5325 rpm when the bearing compliance increases linearly from 0.2 to 1.0. When the external load increases from 10 N to 80 N, the lift-off speed is increased by approximately 30 times, from 450 rpm to 13,575 rpm. Furthermore, a decrease in the acceleration time of the rotor generates a decrease in the lift-off time and an increase in the contact stiffness of the bearing leads to a decrease in the lift-off speed of the bearing. By exploring the effects of the bearing parameters and working conditions on the tribological performance of AFTBs during start-up, the results presented in this study can provide theoretical support for improving start-up performance and designing high-reliability and long-life AFTBs. [ABSTRACT FROM AUTHOR]

Friction between the fabric and tool surface is one of the most significant phenomena in manufacturing and application, and it mainly relates to the decisive contact behavior and the influence of tension and relative velocity. This article first investigates the contact behavior between the fabric and roller surface with a visualization method; then explores the influence of the tension and the relative velocity on the friction behavior of fabric/roller; and, finally, proposes a compound friction model considering the effects of tension and velocity and coupling the contact behavior of warp and weft for the friction behavior of glass-fiber woven fabric/roller. The results of a visualization investigation of the contact behavior reveal that the friction between the fabric and the roller is essentially the comprehensive result of the friction between the warp or weft at many fabric interlacing points and the roller. When the tension increases from 29.4 N to 196 N, the static and dynamic friction coefficients of the three fabric samples increased by 39.94%, 40.14%, 32.2%, 88.47%, 42.53%, and 38.17%, respectively. The effect of the velocity is affected by the fabric structure and tension conditions. According to our statistical results, the proposed model was found to agree well with the experimental results from capstan tests. [ABSTRACT FROM AUTHOR]

In water-based boundary lubrication regime, the contact gaps (or boundary lubricated film thickness) and surface pressure distribution must be determined to really understand the boundary lubricated contact mechanism. However, the accurate determination of these parameters is limited. In this study, a mechanical model based on boundary lubricated contact involving surface force effects is developed. The surface force distribution characteristics, normal force vs. central film thickness curve, and macroscale water-based boundary lubricated contact are investigated numerically. The results show that hydration directly affects surface force interaction. The accurate boundary lubricated film thickness and surface pressure distribution can be obtained using this model in point contact. Furthermore, the mechanism of macroscale water- based liquid boundary lubricated contact is investigated, in which a water-based boundary lubricated film is formed under appropriate operating conditions based on surface force effects during running-in. This study can reveal the water-base boundary lubricated contact behavior and the carrying capacity of the surface force effect, and provides important design guidance for the surface force effect to achieve liquid superlubricity in water-based boundary lubricated contacts. [ABSTRACT FROM AUTHOR]

This study investigated the frictional contact behavior of the plain cotton fabric with the metal through linear friction experiments and real contact analysis. It established a theoretical calculation model of the contact area based on the characteristics of contact behavior. The results indicate that the contact between the cotton fabric and the metal is a multi-point contact, with the contact occurring on the fabric knuckles. The contact behavior is mainly influenced by the normal load, fabric knuckle size, and the number of fabric knuckles. The theoretical calculation model of the contact area considers the multi-scale structural characteristics of cotton fabrics and validates the applicability of the friction adhesion theory to cotton fabrics. The effects of normal load and velocity on the tribological characteristics of cotton fabrics are explained based on the number of contact points. [ABSTRACT FROM AUTHOR]

Joining by forming operations presents powerful and complex joining techniques. Clinching is a well-known joining process for use in sheet metalworking. Currently, clinched joints are focusing on mechanically enhanced connections. Additionally, the demand for integrating electrical requirements to transmit electrical currents will be increased in the future. This integration is particularly important, for instance, in the e-mobility sector. It enables connecting battery cells with electrical joints of aluminum and copper. Systematic use of the process-specific advantages of this joining method opens up the possibility to find and create electrically optimized connections. The optimization for the transmission of electrical currents will be demonstrated for clinched joints by adapting the tool geometry and the clinched joint design. Based on a comparison of the electrical joint resistance, the limit use temperature is defined for the joining materials used based on the microstructural condition and the aging condition due to artificial aging. As a result of the investigations carried out, reliable current transmission at a constant conductor temperature of up to 120 °C can be achieved for clinched copper–copper joints. In the case of pure aluminum joints and mixed joints of aluminum and copper, long-term stable current transmission can be ensured up to a conductor temperature of 100 °C. [ABSTRACT FROM AUTHOR]

Background: The number of studies on internet-based guided self-help has rapidly increased during the last 2 decades. Guided self-help comprises 2 components: a self-help program that patients work through and usually weekly guidance from therapists who support patients using the self-management program. Little is known about participants' behavior patterns while interacting with therapists and their use of self-help programs in relation to intervention outcomes., Objective: This exploratory study aimed to investigate whether the number of messages sent to the therapist (ie, contact behavior) is an indicator of the outcome, that is, a reduction in depressive symptoms. Furthermore, we investigated whether adherence was associated with outcome. Most importantly, we investigated whether different combinations of adherence and contact behavior were associated with outcome., Methods: Drawing on a completer sample (n=113) from a randomized full factorial trial, participants were categorized into 4 groups. The groups were based on median splits of 2 variables, that is, the number of messages sent to therapists (low: groups 1 and 2; high: groups 3 and 4) and adherence (low: groups 1 and 3; high: groups 2 and 4). The 4 groups were compared in terms of change in depressive symptoms (measured with the Patient Health Questionnaire-9) from pre- to posttreatment and pretreatment to follow-up, respectively., Results: On average, participants sent 4.5 (SD 3.7) messages to their therapist and completed 18.2 (SD 5.2) pages of the program in 6.39 (SD 5.39) hours. Overall, analyses revealed no main effect for participants' messages (H1=0.18, P=.67) but a significant main effect for adherence on changes in depressive symptoms from pre- to posttreatment (H1=5.10, P=.02). The combined consideration of adherence and messages sent to the therapist revealed group differences from pre- to posttreatment (H3=8.26, P=.04). Group 3 showed a significantly smaller improvement in symptoms compared with group 4 (Z=-2.84, P=.002). Furthermore, there were group differences from pretreatment to follow-up (H3=8.90, P=.03). Again, group 3 showed a significantly smaller improvement in symptoms compared with group 4 (Z=-2.62, P=.004) and group 2 (Z=-2.47, P=.007). All other group comparisons did not yield significant differences., Conclusions: This exploratory study suggests that participants characterized by low adherence and frequent messaging do not improve their symptoms as much as other participants. These participants might require more personalized support beyond the scope of guided internet interventions. The paper underscores the importance of considering individual differences in contact behavior when tailoring interventions. The results should be interpreted with caution and further investigated in future studies., (© Oliver Thomas Bur, Thomas Berger. Originally published in JMIR Formative Research (https://formative.jmir.org).)

Triboelectric nanogenerator (TENG) is a micro/nano electromechanical power system that converts mechanical energy into electricity based on contact electrification and electrostatic induction. At present, research on improving TENG performance mainly focus on material optimization and texture fabrication. This paper proposes a simple material optimization method based on regulating the ratio of elastomer base to curing agent (base/agent ratio) of Polydimethylsiloxane (PDMS) to improve the performance of TENG with rectangular groove textures, and the influence of texture sizes on TENG output is explored. By analyzing the contact behavior, dielectric, and mechanical property, the influence mechanism of PDMS base/agent ratios and texture sizes on TENG performance is revealed. Results show that PDMS base/agent ratios affect TENG output mainly through material dielectric properties, while texture sizes mainly by contact behaviors. As the base/agent ratio decreases, although the real contact area and displacement of PDMS exhibit slight reductions, the relative permittivity of PDMS increases, and thus the surface charge density and performance of TENG increases. As the boss width increases or the groove width decreases, the displacement of PDMS declines, which would lead to the slight drop of the surface charge density, but the real contact area increases, which still results in improved TENG output. [ABSTRACT FROM AUTHOR]

Abstract Triboelectric nanogenerator (TENG) is a micro/nano electromechanical power system that converts mechanical energy into electricity based on contact electrification and electrostatic induction. At present, research on improving TENG performance mainly focus on material optimization and texture fabrication. This paper proposes a simple material optimization method based on regulating the ratio of elastomer base to curing agent (base/agent ratio) of Polydimethylsiloxane (PDMS) to improve the performance of TENG with rectangular groove textures, and the influence of texture sizes on TENG output is explored. By analyzing the contact behavior, dielectric, and mechanical property, the influence mechanism of PDMS base/agent ratios and texture sizes on TENG performance is revealed. Results show that PDMS base/agent ratios affect TENG output mainly through material dielectric properties, while texture sizes mainly by contact behaviors. As the base/agent ratio decreases, although the real contact area and displacement of PDMS exhibit slight reductions, the relative permittivity of PDMS increases, and thus the surface charge density and performance of TENG increases. As the boss width increases or the groove width decreases, the displacement of PDMS declines, which would lead to the slight drop of the surface charge density, but the real contact area increases, which still results in improved TENG output.

This article in the journal Gruppe. Interaktion. Organization (GIO) deals with the application of the theory of functional psycho-dynamic positions by Raoul Schindler on problem-solving groups. Until now, there has been no empirical research substantiating this model and the emergence of the group positions. To do so, the relationship between the functional group positions and members' contact behavior was examined with a sociometrical approach. A study with 138 participants from 22 groups was conducted. The results clearly confirm the model and show typical contact behavior patterns for each group position. Finally, types of informal group structures were compared in regards to group performance and practical applications for agile teams and shared leadership. [ABSTRACT FROM AUTHOR]

Cutting tools with round edge can enhance the performance of machining difficult-to-machine materials, while the complex contact mechanism related to micro cutting edge limits the deeper understanding of cutting mechanics. Material separation, which is associate to plough mechanism with formation of dead metal zone (DMZ), also requires the analysis of contact behavior. This study develops a contact model along the round edge together with the illustration of DMZ, with three contact feature points defined to explain the contact situation between workpiece and cutting edge. Among these feature points, two separation points related to DMZ classify the sliding and sticking region considering the dual-zone approach. The stagnation point is the zero shear stress point where a sudden change in shear stress direction happens. Besides, the parabolic stress model obtained from finite element simulations is established to define the normal contact distribution along the round edge. In this basis, the tool-based cutting forces are predicted with proposed contact model and two contact force components are classified for different contact regions. The proposed contact feature points and contact stress are validated through illustration with finite element simulations. Besides, orthogonal cutting tests ensure the practicality and accuracy of the proposed contact model and predicted cutting forces. [ABSTRACT FROM AUTHOR]

During the start-up process, air foil thrust bearings (AFTBs) come into contact and are prone to localized overheating and even failure. Frequent starts and stops are the major sources of wear. In this study, a transient mixed lubrication model considering the air rarefaction effect is established. In the model, asperity contact between the top foil of the air foil thrust bearing (AFTB) and the rotor surface is considered using a deterministic approach, and the deformation of the foil structure is considered using the elastic-aerodynamic coupling. The influences of bearing compliance, external load, acceleration time and contact stiffness on the tribological properties during the start-up process are investigated. The results show that the lift-off speed increases with the increase of the bearing compliance and of the external load. Specifically, the lift-off speed of AFTBs increases from 1950 rpm to 5325 rpm when the bearing compliance increases linearly from 0.2 to 1.0. When the external load increases from 10 N to 80 N, the lift-off speed is increased by approximately 30 times, from 450 rpm to 13,575 rpm. Furthermore, a decrease in the acceleration time of the rotor generates a decrease in the lift-off time and an increase in the contact stiffness of the bearing leads to a decrease in the lift-off speed of the bearing. By exploring the effects of the bearing parameters and working conditions on the tribological performance of AFTBs during start-up, the results presented in this study can provide theoretical support for improving start-up performance and designing high-reliability and long-life AFTBs.

Energy consumption is caused by the rolling resistance of tires as a vehicle moves forward, which contributes to resource consumption and the greenhouse effect. The objective of this paper is to investigate the variation of tire-pavement rolling energy consumption under different operating condition factors. For this purpose, a rolling finite element dynamic model was developed based on real tire and road contact. The correlation between the effective radius and free angle is determined during the free rolling process. The variations of different working conditions on rolling energy consumption under tire-road coupling were analyzed according to both tire and pavement factors, and the influence factors were analyzed by grey correlation analysis. The results show that the factors affecting the significance of rolling energy consumption in descending order are tire load, tire pressure, coefficient of friction, pavement stiffness, and rolling speed. Specifically, energy consumption can be increased by increasing the tire load or friction coefficient, the cumulative increase of rolling energy consumption reaches 68.3% and 14.51%, respectively. Energy consumption can be decreased by increasing the tire pressure or pavement stiffness, the cumulative decrease in energy consumption is 20.45% and 5%, respectively. In addition, the rolling energy consumption increases and then decreases within an increasing speed range(10–80 km/h). The speed trend inflection point is 20 km/h. The research results can provide a technical reference for the development of a low-energy consumption design scheme for tire-pavement systems. To better serve the construction needs of green low-carbon and sustainable road transportation. • Tire-pavement FE rolling model was built using ABAQUS with good reliability. • The rolling energy consumption linearly increases with tire load and friction coefficient. • Tire load has the highest impact on dissipation energy, followed by tire pressure, friction coefficient, rolling speed, and pavement stiffness. • The tire and pavement influence factors were analyzed by grey relational analysis. [ABSTRACT FROM AUTHOR]

Revealing the electro-mechanical contact characteristics between rough surfaces at extreme temperatures is critical to accurately assessing the service performance of equipment in aerospace, energy and other fields. In this paper, a theoretical model of electro-mechanical contact behavior at extreme temperatures is developed based on the consideration of the effect of temperature on material property parameters and interfacial morphologies. It reveals the mechanism of temperature variation on the contact behavior of rough surfaces. The results show large temperature changes affect the contact resistance and the real contact area, because of the in significantly different contact behavior between high temperature and low temperature. This study helps us to gain a deeper understanding of the effects of extreme temperatures on the contact behavior and provides a reference for the design of interfacial conductivity in engineering structures. [ABSTRACT FROM AUTHOR]

Joining by forming operations presents powerful and complex joining techniques. Clinching is a well-known joining process for use in sheet metalworking. Currently, clinched joints are focusing on mechanically enhanced connections. Additionally, the demand for integrating electrical requirements to transmit electrical currents will be increased in the future. This integration is particularly important, for instance, in the e-mobility sector. It enables connecting battery cells with electrical joints of aluminum and copper. Systematic use of the process-specific advantages of this joining method opens up the possibility to find and create electrically optimized connections. The optimization for the transmission of electrical currents will be demonstrated for clinched joints by adapting the tool geometry and the clinched joint design. Based on a comparison of the electrical joint resistance, the limit use temperature is defined for the joining materials used based on the microstructural condition and the aging condition due to artificial aging. As a result of the investigations carried out, reliable current transmission at a constant conductor temperature of up to 120 °C can be achieved for clinched copper–copper joints. In the case of pure aluminum joints and mixed joints of aluminum and copper, long-term stable current transmission can be ensured up to a conductor temperature of 100 °C.

Predator–prey interactions present heightened opportunities for pathogen spillover, as predators are at risk of exposure to infectious agents harbored by prey. Epizootics with high morbidity and mortality have been recorded following prey-to-predator spillover events, which have had significant conservation implications for sensitive species. Using felids as a detailed case study, we have documented both virulent and clinically silent infections in apex predators following transfer of microbes from prey. We draw on these examples and others to examine the mechanisms that determine frequency and outcome of predator exposure to prey-based pathogens. We propose that predator–prey dynamics should be more thoroughly considered in empirical research and disease dynamic modeling approaches in order to reveal answers to outstanding questions relating to pathogen bioaccumulation. Advances in pathogen detection technologies have allowed more thorough characterization of infections in free-ranging wildlife. In well-studied predators like Puma concolor , multiple occurrences of spillover following consumption of reservoir hosts as prey have been observed. Outcomes of predator exposures to infectious agents harbored by prey vary, but rarely result in widespread disease. Models of disease transmission have largely considered predator behavior in the context of effects in the prey species, versus consequences to the predator. However, certain prey-transmitted infections can result in high mortality rates, sometimes with significant negative impacts on conservation of vulnerable/threatened species. [ABSTRACT FROM AUTHOR]

The dynamic contact behavior of worn bearings with elastoplastic functionally graded coating is studied, and the interacting effect between worn band and functionally graded surface is analyzed. The surface deformation and roughness are included in the film thickness. The mixed elastohydrodynamic lubrication combined with point contact model is introduced to analyze the oil pressure in the contact zone. By using the Fourier transform method and Papkovich–Neuber potential function, the displacements and stress fields in the elastoplastic functionally graded coating are obtained. The second-order central difference method is used to solve the Reynolds equation. It is found that the repeated surface interaction can result in the sharp increase in pressure in bearings, and the oil pressure increases with increasing graded index. The entrainment of oil in the inlet and outlet zones becomes more evident if a large graded index is selected. [ABSTRACT FROM AUTHOR]

Background: The four components that make up the current dual-mobility artificial hip joint design are the femoral head, the inner liner, the outer liner as a metal cover to prevent wear, and the acetabular cup. The acetabular cup and the outer liner were constructed of 316L stainless steel. At the same time, the inner liner was made of ultra-high-molecular-weight polyethylene (UHMWPE). As this new dual-mobility artificial hip joint has not been researched extensively, more tribological research is needed to predict wear. The thickness of the inner liner is a significant component to consider when calculating the contact pressure., Aim: To make use of finite element analysis to gain a better understanding of the contact behavior in various inner liner thicknesses on a new model of a dual-mobility artificial hip joint, with the ultimate objective of determining the inner liner thickness that was most suitable for this particular type of dual-mobility artificial hip joint., Methods: In this study, the size of the femoral head was compared between two diameters (28 mm and 36 mm) and eight inner liner thicknesses ranging from 5 mm to 12 mm. Using the finite element method, the contact parameters, including the maximum contact pressure and contact area, have been evaluated in light of the Hertzian contact theory. The simulation was performed statically with dissipated energy and asymmetric behavior. The types of interaction were surface-to-surface contact and normal contact behavior., Results: The maximum contact pressures in the inner liner (UHMWPE) at a head diameter of 28 mm and 36 mm are between 3.7-13.5 MPa and 2.7-10.4 MPa, respectively. The maximum von Mises of the inner liner, outer liner, and acetabular cup are 2.4-11.4 MPa, 15.7-44.3 MPa, and 3.7-12.6 MPa, respectively, for 28 mm head. Then the maximum von Mises stresses of the 36 mm head are 1.9-8.9 MPa for the inner liner, 9.9-32.8 MPa for the outer liner, and 2.6-9.9 MPa for the acetabular cup. A head with a diameter of 28 mm should have an inner liner with a thickness of 12 mm. Whereas the head diameter was 36 mm, an inner liner thickness of 8 mm was suitable., Conclusion: The contact pressures and von Mises stresses generated during this research can potentially be exploited in estimating the wear of dual-mobility artificial hip joints in general. Contact pressure and von Mises stress reduce with an increasing head diameter and inner liner's thickness. Present findings would become one of the references for orthopedic surgery for choosing suitable bearing geometric parameter of hip implant., Competing Interests: Conflict-of-interest statement: All authors have no conflicts of interest to disclose., (©The Author(s) 2024. Published by Baishideng Publishing Group Inc. All rights reserved.)

Functionally graded surface has been a domain of research interest due to its use in various technologically advanced applications. The work focuses on static and dynamic analysis of rough fractal surface with exponentially graded material properties. The rough fractal surface is modeled in ANSYS with the coordinate points generated using the two variable modified Weierstrass–Mandelbrot function. Material gradation is applied to the rough surface model in such a way that, for any value of the gradation or inhomogeneity parameter, material properties at the top of the rough surface always remain constant. Force–displacement behavior of the fractal surface in contact with a rigid flat surface is determined through finite element simulation. A parameter representing the nonlinearity of the system is extracted from the force–displacement plot. It is found that higher is the inhomogeneity parameter, higher is the nonlinearity of the system. Furthermore, for a certain change in inhomogeneity parameter, the change in nonlinearity is higher for rougher topography. The dynamic contact system is found to be softening in nature, and the softening nature increases with higher inhomogeneity parameter. The phase plot of the vibrating contact system becomes more asymmetric with respect to the velocity axis for higher value of inhomogeneity parameter. [ABSTRACT FROM AUTHOR]

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Interaction forces between a robotic cuff and the skin during assisted walking with a lower limb exoskeleton may cause skin injuries over time, such as blisters and ulcers. This study proposes a sensing cuff that can monitor the contact behavior between the exoskeleton and skin during assisted walking, and a functional test and assisted walking experiments were conducted to evaluate the performance of the proposed device. The functional test of the sensing cuff showed good performance of capturing the contact behavior for safety evaluation. The walking experiment involved subjects walking on a treadmill with a lower limb exoskeleton under different conditions (i.e., walking speed and clothing), and the sensing cuff attached to the exoskeleton measured the interaction forces and slip velocity. The magnitude of shear force in the movement direction peaked near the beginning and within 40 – 50% of the gait cycle. The contact safety of the lower limb exoskeleton during assisted walking was then evaluated based on the calculated shear stress. The designed sensing cuff could provide sufficient information regarding contact behavior and contact safety during assisted walking. [ABSTRACT FROM AUTHOR]

Conventional pneumatic tires exhibit disadvantages such as puncture，blowout at high speed，pressure maintenance，etc. Owing to these structural inevitable weaknesses，non-pneumatic tires have been developed and are investigated. A non - pneumatic mechanical elastic wheel（NPMEW）is introduced and investigated as a function of static radical stiffness characteristics and contact behavior. A bench test method is utilized to improve the riding comfort and the traction traffic ability of NPMEW based on tire characteristics test rig，and the static radical stiffness characteristics and the contact behavior of NPMEW are compared with that of an insert supporting run - flat tire （ISRFT）. The vertical force-deformation curves and deformed shapes and contact areas of the NPMEW and ISRFT are obtained using a set of vertical loads. The contact behavior is evaluated using extracted geometrical and mechanical feature parameters of the two tires. The results indicate that the NPMEW appears to exhibit considerably high radical stiffness，and the numerical value is dependent on the mechanical characteristic of the flexible tire body and hinge units. NPMEW demonstrates more uniform contact pressure than ISRFT within a certain loading range，and it can efficiently mitigate the problem of stress concentration in ISRFT shoulder under heavy load and enhance the wear resistance and ground grip performances. [ABSTRACT FROM AUTHOR]

Abstract Multilayer coatings are often reported in the papers on surface engineering and have been proved to be able to enhance the toughness, anti-wear and bonding strength, while an understanding of their mechanical behavior is essential to their optimal design and tribological application. In this paper, a two-dimensional contact model of a multilayered solid in line contact with a rigid cylinder is developed based on a semi-analytical method. The frequency response functions, which are essential to producing the influence coefficients of the displacements and stresses components in the contact model with a conversion method based on the fast Fourier transform, are obtained by solving a system of linear equations concerning the unknown constants in the elastic field general solution of layered materials with a numerical method. The present model is validated by comparisons of the contact pressure and von Mises stress between the solutions of the present model and those of the Hertz theory and the finite element contact model. The effect of the elasticity modulus changing mode as well as the layer number of the multilayered solid is further studied by utilizing the present model. Highlights • The model with strong robustness adapts to various layer number and thickness. • The effect of the elasticity modulus changing mode was numerically investigated. • The effect of the layer number was also numerically investigated. [ABSTRACT FROM AUTHOR]

Efficient strategies for controlling low-frequency stick-slip vibrations during high-speed train braking are crucial for safe operations. This study applies surface texturing with micro-grooved textures on friction blocks and conducts tests to validate their suppression effect on stick-slip vibrations. Vibration analysis indicates that micro-grooved textures effectively mitigate system vibration intensity, decreasing amplitude and stick time as texture area density increases within a certain range. Further analysis reveals that these textures improve the contact behavior at the disc-block interface, reducing eccentric wear angle and contact plateau size. Changes in contact characteristics result in variations in the vibration response, thereby suppressing stick-slip vibrations. The research establishes a solid theoretical foundation and offers practical recommendations for reducing stick-slip vibrations in high-speed train brake systems. [ABSTRACT FROM AUTHOR]

Short-time withstanding current is a key parameter of air circuit breakers. Due to the structure of multiple parallel contacts, the outer movable conductors tilt and slide seriously when withstanding the large short-circuit current. This paper is aimed to investigate the contact behavior of the tilted contact. A new designed experimental setup to measure the minimum repulsion current and the contact resistance of the tilted contact is developed. Contact force and tilt angle can also be measured and adjusted. Based on the measured results and the impression marks of the tilted contact, it is concluded that the repulsion force and the contact resistance are increased seriously when the contact is tilted. During the contact tilting process, the contact type is changed from the line contact to the point contact and the contact center is offset to the edge of the movable contact. In addition, with the help of contact bridge model, it is also found that the contact type transition plays a dominant role on the increase of the repulsion force and contact resistance. [ABSTRACT FROM PUBLISHER]

This study investigates the effects of interfacial wear characteristics on stick-slip vibration under different normal loads. The results reveal that the amplitude and frequency of stick-slip vibration are correlated with changes in the coefficient of friction (COF) and normal force, which are affected by the uneven wear on the friction block surface. Uneven wear causes eccentric wear angles and larger contact plateaus at the leading edge due to a non-uniform contact stress distribution. Specifically, uneven wear affects the difference in the static and kinetic COFs, contact stiffness, and eccentric wear angle of the friction system, thereby influencing the stick-slip vibration characteristics. Increasing the effective contact area can promote a uniform contact stress distribution, optimizing the vibration characteristics of the system. • The stick-slip vibration behavior is affected by the uneven wear of the surface. • Uneven wear results from non-uniform contact stress distribution. • Uneven wear changes the contact status and thus deteriorates vibration response. • Increasing effective contact area can optimize system vibration response. [ABSTRACT FROM AUTHOR]

This paper develops a new test method to investigate the factors that influence contact behavior between fully cracked concrete surfaces. This test considers 36 specimens of recycled aggregate concrete (RAC) and conventional concrete. The material variables were the aggregate type (natural coarse aggregate (NCA) and recycled coarse aggregate (RCA)), surface roughness, and curing time before splitting (7 d and 28 d). Experimental results indicated that by increasing the gap between cracked surfaces from 0 mm to 4 mm, the maximum shear load was reduced, by 16.9–79% for different cases. Curing time and aggregate type were strong factors that affected the crack propagation and the contact behavior. Furthermore, for conventional concrete, increasing the curing time of concrete increased the maximum shear load by 0.47 times to 2.86 times; for RAC with higher quality RCA in this test, the shear load decreased by 21.8–65% with the increasing of curing time. The surface roughness has a positive effect on shear load, especially when the surface roughness increases greatly in this study. Walraven’s model predicted stronger effect of interface roughness than shown by the results of these experiments, suggesting that these specimens had limited aggregate interlock. The results suggest that the Walraven model might be modified by an appropriate factor to better account for aggregate properties. [ABSTRACT FROM AUTHOR]