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• 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]

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]

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]

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]

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]

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]

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]

The structural assessment of extant historical buildings constructed using ancient or traditional masonry is a critical research area for seismic retrofitting. In this study, the in-plane characteristics of the brick masonry of ancient mortars including mud, lime–mud, and lime–sand are investigated experimentally and numerically. For this purpose, several brick masonry prisms are constructed using these mortars. The brick and mortar properties are selected to match those of surviving heritage masonry buildings. Moreover, brick masonry prisms composed of cement and cement–lime (“bastard”) mortars are constructed for comparison. The in-plane responses of these masonry prisms are examined through compression, shear, and tension tests. Failure of brick masonry structure occurs frequently in mortar joints owing to its nonhomogeneous in-plane behavior. The experimental shear and tension responses of masonry joints are used to develop an appropriate contact behavior that can be used for modeling ancient masonry structure in Abaqus FEM software. The experimental tests on masonry prisms are modeled in the software, and the results of the analysis have exhibited reasonable accordance with those of the actual tests. [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]

The structural assessment of extant historical buildings constructed using ancient or traditional masonry is a critical research area for seismic retrofitting. In this study, the in-plane characteristics of the brick masonry of ancient mortars including mud, lime–mud, and lime–sand are investigated experimentally and numerically. For this purpose, several brick masonry prisms are constructed using these mortars. The brick and mortar properties are selected to match those of surviving heritage masonry buildings. Moreover, brick masonry prisms composed of cement and cement–lime (“bastard”) mortars are constructed for comparison. The in-plane responses of these masonry prisms are examined through compression, shear, and tension tests. Failure of brick masonry structure occurs frequently in mortar joints owing to its nonhomogeneous in-plane behavior. The experimental shear and tension responses of masonry joints are used to develop an appropriate contact behavior that can be used for modeling ancient masonry structure in Abaqus FEM software. The experimental tests on masonry prisms are modeled in the software, and the results of the analysis have exhibited reasonable accordance with those of the actual tests. [ABSTRACT FROM AUTHOR]

Two-dimensional contact problems including a Boussinesq model, a semi-infinite substrate punched by a rigid flat-ended indenter or a cylindrical one, are systematically investigated with a recently developed continuum theory, in which surface effect on mechanical properties of materials is considered based on the concept of surface energy density. The contact stress and displacement fields are analyzed. It is found that the surface energy density of the indented bulk substrate, as only one additional parameter, serves as an important factor to influence the contact properties in contrast to the classical contact models. All the results show that the semi-infinite substrate becomes hardened when the surface effect is considered. Scaling analysis further demonstrates that differences between the theoretical predictions with surface effect and the classical contact solutions without surface effect become significant only if the contact width is comparable with the ratio of the bulk surface energy density to the bulk shear modulus. Specially, in the two-dimensional cylindrical punch problem, the smaller the punch size or the external compressive load, the more serious the deviation of the nano-indentation hardness predicted by the theoretical model with surface effect and the classical contact one. The results should be helpful not only for precise measurement of nano-indentation hardness but also for accurate evaluation of service performance of nanomaterials and nano-devices. [ABSTRACT FROM AUTHOR]

The conventional pneumatic tires have disadvantages in terms of puncture, blowout at high speed, pressure maintenance, and so on. Due to these structural inevitable weaknesses, non-pneumatic tires have been developed and are being investigated. A new non-pneumatic elastic wheel was proposed and studied to solve these problems. As an important bearing member of the non-pneumatic elastic wheel, the force of hinge group is very complex and it has a significant effect on the performance of the wheel. However, in the complex off-road driving, the hinge group has to withstand complex random load and impact load, and inevitably there will be damage failure. In order to explore the performance change of the wheel after the failure of the important bearing parts, it is necessary to study the influence of the hinge group with local damage on the performance of the non-inflated elastic wheel. In this paper, an experimental study on basic characteristics of non-pneumatic elastic wheel with local hinge group fracture damage was conducted in order to enhance the reliability. Based on tire characteristic test-bed, the tests on basic characteristics of static radical stiffness and contact behavior as well as the modal test were conducted. The wheel with local damage, one hinge group of which was disassembled, was used to simulate hinge group fracture condition in this paper. The results show that the effect of the hinge group fracture damage on the wheel load characteristics is the decrease of the radial stiffness, and it is also related to the damage position on the non-pneumatic elastic wheel. The radial stiffness of non-damaged non-pneumatic elastic wheel is 593.06 N/mm, and the corresponding values of the non-pneumatic elastic wheel with fractured hinge group on horizontal position and vertical position are 443.2 and 385.4 N/mm, respectively. Compared with non-damaged non-pneumatic elastic wheel, the numerical value of radial stiffness is reduced by 25% and 35% respectively on horizontal position and vertical position when the fractured hinge group is installed. That is to say the consistency of radial stiffness and deformation uniformity get worse for the wheel with local damage, so the poor performance of riding comfort of non-pneumatic elastic wheel appears. The influence of the hinge group fracture damage on the grounding pressure distribution is the change of grounded imprinting length and grounded area. Under the same vertical load, these 2 indicators of the non-pneumatic elastic wheel with fractured hinge group increase compared with non-damaged non-pneumatic elastic wheel. When the vertical load is 7 262 N, the imprinting length of the non-pneumatic elastic wheel with fractured hinge group on horizontal position is 138 mm, and the numerical value of non-damaged non-pneumatic elastic wheel is 120 mm. The ground imprinting length of the damaged wheel is increased by 15% compared with that of the non-damaged non-pneumatic elastic wheel. The grounded imprinting width does not change, and the value remains at 285 mm. As a result, the total grounded area of the damaged wheel also increases. The area of the non-damaged non-pneumatic elastic wheel is 34 200 mm2, and the area of damaged wheel increases to 39 330 mm2. The contact length and area of the wheel with local damage are greater than corresponding values of the non-damaged non-pneumatic elastic wheel under the same load. The influence of the hinge group fracture damage on the wheel modal test is the change of the natural frequency, the damping coefficient and the modal shape. In addition to a few orders, the natural frequency of non-damaged non-pneumatic elastic wheel is greater than that of non-pneumatic elastic wheel with local damage hinge group, and the damping coefficient of the most of non-damaged non-pneumatic elastic wheel is less than that of non-pneumatic elastic wheel with local damage hinge group. The value of the amplitude of modes gets smaller for the non-pneumatic elastic wheel with local damage hinge group. [ABSTRACT FROM AUTHOR]

The present study establishes a solving model for analyzing the interwire wear evolution of a wire rope strand subjected to cyclic bending load, in which the frictional contact and sliding between the wires are considered simultaneously. A wear experiment between the wires is conducted to study the wear behavior of the wires. Meanwhile, the proposed model is verified experimentally. Then the interwire wear and its effect on the contact behavior of the strand are analyzed. The results show that the interwire wear only happens on the side further from the curvature center of the bended strand than its neutral layer, and no wear happens when the wires are apart from each other or the interwire slippage is zero. As the wear process goes on, the wear region extends only along the normal direction of the core-wire contact line, and the maximum wear depth occurs at the middle position between the neutral layer and the furthest location from the curvature center. The contact pressure is distributed uniformly along the normal direction of contact line, but a significant stress concentration and local deformation happen at the position furthest from the curvature center of the bended strand. [ABSTRACT FROM AUTHOR]

• Influence coefficients (ICs) for solving the inclusion problem of transversely isotropic half-space are given. • The influence of different inhomogeneities on contact behaviors is reported. • The effect of inhomogeneity anisotropic orientation on the stress field is shown. This paper presents a model for the contact involving inhomogeneities with a transversely isotropic matrix and a detailed investigation of the contact behavior of this type of material loaded by a rigid spherical indenter. The model is built on the core influence coefficients (ICs) for solving the inclusion problem of transversely isotropic half-space material and the numerical equivalent inclusion method (EIM). The frictionless contact responses of the transversely isotropic materials containing stiff or compliant, rigid or void, one-type or two-types, and single or double inhomogeneities are reported, and the effect of inhomogeneity anisotropy orientation on the stress field is also shown. The analysis results reveal that the von Mises stress produced by a set of adjacent cuboidal void and rigid inhomogeneity could be more than three times that in the corresponding homogeneous half space. In addition, the maximum value of the von Mises stress in the cross-section varies with the anisotropy orientation of inhomogeneities, and the symmetry of the disturbed stress field reflects the pattern of anisotropy of the inhomogeneous material, further proving the correctness of the proposed method in solving contact problems with various symmetries. [ABSTRACT FROM AUTHOR]

Many different types of elastomeric rings have been developed to suit various needs in industry. The X-ring was introduced as a result of the limitations of O-rings that twist, especially during dynamic application. A better understanding of the behavior and the stress distribution of the X-ring under a uniform squeeze rate and internal pressure is needed. We analyzed the contact stresses and internal stresses developed in an X-ring before and after forcing-out by using the photoelastic experimental hybrid method, ascertained the packing ability of an X-ring, and studied the failure criterion of an X-ring under uniform squeeze rate and internal pressure. Forcing-out in the X-ring occurred when the internal pressure was 3.92 MPa. After forcing-out, at an internal pressure of 5.88 MPa, the two lobes on the upper contact surface merged one contact side of the upper side immensely. Even after extrusion of the X-ring, the X-ring can be used to effectively contain the fluid. This is because the effects of extrusion on the X-ring affected the stress distribution of only two lobes close to the assembly gap and the two lobes are merge into one lobe. In addition, our experimental results show that the maximum shear failure criterion is suitable for the prediction of failure in X-ring seals. [ABSTRACT FROM AUTHOR]

Social network analysis (SNA) can be used to explore a population's social structure and how individuals contribute to social cohesion. Quantifying relationships between individuals in a network can vary depending on the data available or the relationship of interest. Studies of readily visible species can use direct interaction measures in SNA, while studies of cryptic species usually rely on the 'gambit of the group'; individuals observed in a group are considered associates. This study compared the association and pectoral fin contact (PFC) networks of Atlantic spotted dolphins around Bimini to test the 'gambit of the group' hypothesis. The association network had nearly three times as many edges than the PFC network. Still, the two networks were correlated; individuals with a relationship in one network had a comparable relationship in the other. Many network measures were also correlated across networks, suggesting association is an acceptable substitute for physical interaction in certain cases. The current study supports the 'gambit of the group', but also highlights the importance of considering what types of relationships are used in the analysis of the social system of the focal species. • Dolphin association network had ~3X as many connections as interaction network. • Association and interaction networks similarly correlated with dolphin age/sex. • 'Gambit of the group' hypothesis holds up well for study of single dolphin group. • Data collection methodology should be considered for cross-species comparisons. [ABSTRACT FROM AUTHOR]

Partial-length butt-welded joint is a typical weldment which is often used in vehicle parts such as car door and body. In order to clarify the influence of contact behavior on the final distortion and residual stress distribution in thin-plate butt-welded joints, a computational approach considering multiple nonlinearities was proposed based on ABAQUS code, and a series of three-dimensional thermal–elastic–plastic finite element models were developed to simulate welding distortion and residual stress in mild steel thin-plate butt-welded joints performed by partial-length welding. Meanwhile, the corresponding experiments were carried out to verify the calculation accuracy of the proposed computational approach. Moreover, the influence of initial gap size on welding distortion and residual stress was numerically and experimentally examined. Based on the simulated results, the formation mechanism of welding deformation in the thin-plate partial-length butt-welded joint was also discussed. • An advanced computational approach was developed to simulate residual stress and distortion for thin-plate joints. • The influence of contact behavior on welding distortion and residual stress of a butt-welded joint was clarified. • The formation mechanism of deflection in partial-length butt-welded joint was clarified. • The influence of initial gap size on welding distortion and residual stress was clarified. [ABSTRACT FROM AUTHOR]

• Rock cutting performance and contact behavior of partial-worn cutters are studied. • Cutting forces, rock fragments, cutter acceleration are analyzed. • Partial-worn cutters are able to break rock but energy consumption increases. • Above differences are attributed to motion modes and surface geometry changes. • This work provides theoretical support for monitor system of cutter partial-wear. The rock cutting performance and cutter-rock contact behavior of partial-worn cutters are investigated via scaled rock cutting experiments. The results reveal that the partial-wear of the cutter reduces the normal force, while the tangential force increases. Changes are also observed in the rock breaking mechanism. Although the rock breaking capacity of the partial-worn cutters is not significantly reduced, the increase of volume ratio of the rock powder results in a rise in specific energy, indicating that the energy utilization of the partial-worn cutters is relatively low. In addition, plastic deformation and abrasive wear are observed on the partial-worn cutter surface. The changes of motion modes and surface geometry play a key role in the above-mentioned phenomena. [ABSTRACT FROM AUTHOR]

A non-pneumatic tire appears to have advantages over the conventional pneumatic tire in terms of flat proof and maintenance free. A mechanical elastic wheel with a non-pneumatic elastic outer ring which functions as the air of the pneumatic tire was presented to reduce the risk of puncturing the conventional pneumatic tire and to enhance the grip performance. The mechanical elastic wheel structure was non-pneumatic integrated configuration which was flat proof and maintenance free of air-pressure. In this study, the static contact behavior of mechanical elastic wheel was investigated as a function of vertical loading and was compared with that of a pneumatic tire. The special suspended hub loaders of mechanical elastic wheel were employed to reduce the contact stiffness and increase contact area so that a stable friction was obtained. An analytical model for a non-pneumatic mechanical elastic wheel on rigid ground is presented. The model consists of a thin flexible annular outer ring and hinge units that connect the outer ring to a rigid hub. According to the wheel structure characteristic and bearing way, outer ring uniformly curved beam model was established based on a circular Timoshenko beam that takes into account deformations due to bending, shearing and circumferential extension, and discrete spoke which was accounted for only in tension was modeled based on continuous spoke model. In addition, the finite element model of mechanical elastic wheel was modeled by using the commercial finite element software ANSYS. To establish the finite element model, various nonlinear factors, such as the geometrical nonlinearity, material nonlinearity and contact nonlinearity, were all considered. In order to proved the validity of the analytical model and the finite element model, load characteristic test of the mechanical elastic wheel was conducted by tyre dynamic test-bed to obtain load-deflection curve. The results of analytical model and three-dimensional nonlinear finite element model were validated by the load characteristic test of mechanical elastic wheel. The trend of tested results were consistent with simulation results and analytical results. The prototype experiment confirmed the analytic model and the finite element model rationality. Finite element methods were used to analyze the contact pressure distribution and grip performance in static loading. Simulation results show that the radial stiffness of mechanical elastic wheel is greater than that of pneumatic tire, so that mechanical elastic wheel could maintain more better roundness and lesser rolling resistance than pneumatic tire. Through mechanic analysis, it shows that radial stiffness of mechanical elastic wheel is determined by stiffness of elastic outer ring, stiffness of hinges and the suspended hub loaders. Besides that, simulation results also show that the static contact pressure of mechanical elastic wheel on tire shoulder becomes protuberant with the increase of the vertical load, and the static contact pressure of mechanical elastic wheel is more evenly than that of traditional pneumatic tire. That is because the suspended hub loaders could reduce the stress concentration of tire shoulder and enhance tire wear resistance and grip performance by controlling outer ring deformation. The results can provide guidance for experiment research, structural optimization and improvements of vehicle dynamics. [ABSTRACT FROM AUTHOR]

• Effects of surface groove of disc cutter on rock fragmentation are studied. • Rock beneath the grooves is damaged due to interconnection of cracks generated by adjacent teeth. • So the amount of rock powder as well as the required energy are reduced. • Cutting forces and specific energy of the grooved cutter is reduced. Tunnel boring machines (TMBs) have a slow tunneling speed and low energy utilization rate in hard rock strata. A potential method to improve the cutting performance of cutters is the control of the contact state between the cutter and the rock using a specific geometric design of the contact surface. This paper discusses a design scheme of a TBM disc cutter with surface spiral grooves. Discrete element modeling, finite element modeling, and a scaled experiment are used to evaluate the rock cutting performance and contact behavior of the proposed cutter design. The results show that at the same penetration depth, the cutting force required by the spiral groove cutter is significantly lower than that of the traditional constant cross-section flat-top cutter. Moreover, the rock chip volume is slightly lower, and the rock cutting specific energy is lower. The reason is that the discontinuous contact area between the cutter and rock reduces the degree of rock fragmentation due to the presence of grooves, reducing the energy consumption for rock breaking. In addition, the grooves do not cause severe internal stress concentration inside the cutter, and the contact stress on the cutter's tooth surfaces is randomly distributed. This study confirms that the cutter shape is directly related to the cutter performance, indicating that a suitable cutter design improves the tunneling efficiency of a TBM. [ABSTRACT FROM AUTHOR]

Highlights: [•] A pair of novel approaches automatically identifies the worst load combination. [•] The approaches eliminate the need to explore analyses of all possible load cases. [•] Elastoplastic materials, contact conditions and/or nonlinear geometry are allowed. [•] Practical dependent pattern loads are incorporated using new linear constraints. [•] The proposed algorithm processes directly a 0–1 MPEC. [Copyright &y& Elsevier]

Highlights: [•] Synchronous diving behavior of pilot whales was revealed using animal-borne devices. [•] Constant vertical distance between whales was maintained by vertical speed adjustment. [•] One particular individual tended to be the initiator of the synchronous dives. [•] The animal-borne camera recorded body contact; the primary type was flipper-to-body. [•] Animal-borne devices are powerful tools for studying underwater social interactions. [Copyright &y& Elsevier]

Mother-calf interactions and the behaviors of mothers during separation from their calves were examined in four Commerson's dolphin ( Cephalorhynchus commersonii) mother-calf pairs. Four infants were observed: 56.8 h over 30 days from birth to 263 days of age, 36.9 h over 20 days from birth to 149 days of age, 10.4 h over 3 days from birth to 2 days of age, and 15.0 h over 3 days from birth to 2 days of age. All four pairs shared common characteristics in the rate and frequencies of mother-calf interactions and the behaviors of mothers during the first week of life. After the first week, individual differences in changes in the frequency of each behavior were observed. The three behaviors considered representative of maternal care (parallel swimming, synchronous breathing, and body-to-body contact) were frequently performed in the first week; thereafter, the frequencies declined. Separate behaviors of mothers were infrequent during the first week and increased with an increase in infants' age. Bumping by infants increased with time, suggesting an increase in soliciting by calves and conflict between mothers and calves. The frequency of flipper-to-body rubbing also changed but in a complex manner, probably because the calves needed to learn how to perform this behavior from their mothers and because initiator and recipient of this behavior can be changed quickly. [ABSTRACT FROM AUTHOR]

A controllable experimental method using a two-hemispherical-bead setup and a split Hopkinson pressure bar (SHPB) apparatus is implemented to study the dynamic elasto-plastic contact laws between ductile beads in contact. Beads made of four different met-als, either rate sensitive (stainless steel 302 and 440C) or rate insensitive (AI alloy 2017 and brass alloy 260), are used. The experimental elasto-plastic contact force-displacement curves are obtained under different loading rates. The effects of material rate sensitivity and bead pair size on the contact laws are studied, and the way that the rate sensitivity of the materials translates to rate sensitivity contact force-displacement relations is explored. The transmitted energy ratio, which is related to the macroscale concept of a coefficient of restitution, is also calculated and, for all materials, shows a decrease with increasing impact speed. In addition, the experimental contact force-displacement data, residual compressive displacement, and diameter of yield area are compared with predictions from several widely-used theoretical models to generalize these experimental results to arbitrary contact situations. [ABSTRACT FROM AUTHOR]

Rationale: The opioid system is involved in the regulation of several behavioral and physiological responses, controlling pain, reward, and addictive behaviors. Opioid administration, depending on drugs and doses, usually affects sociability reducing interactions between conspecifics, whereas some affiliative behaviors such as sexual activity, social grooming, and play behavior increase the endogenous opioid activity. Objectives: The possible interaction between endogenous opioids released during socio/sexual behavior and their analgesic effect on pain response is reviewed in the rodent literature. Results: Direct evidence for socially mediated opioid changes resulting in increase in nociceptive threshold derives from studies exploring the effects of defeat experiences, social isolation, maternal, sexual behavior, and social reunion among kin or familiar animals in laboratory rodents. Indirect evidence for endogenous activation of the opioid system, possibly affecting pain sensitivity, derives from studies investigating the relevance of natural social reward using the conditioned place preference protocols or analyzing ultrasonic vocalizations associated to positive affective contexts. Finally, genetic and epigenetic factors that affect the opioid system during development are reported to be involved in modulating the response to social stimuli as well as nociception. Conclusions: All studies highlight the relevance of affiliative contact behavior between conspecifics that is responsible for the activation of the endogenous mu-opioid system, inducing nociceptive threshold increase. [ABSTRACT FROM AUTHOR]

In this descriptive study, the potentially communicative functions of non-vocal behaviors produced by two species of dolphin, Atlantic spotted ( Stenella frontalis) and Indo-Pacific bottlenose ( Tursiops aduncus), were examined in the context of three focal events: depart (one or more dolphins depart company of others), join (two or more dolphins come together), and contact (dolphin makes contact with another using a part of its body). These particular events were chosen because they involve interactions between dolphins and so provide an opportunity to examine possible precursors or antecedents to specific social behaviors. Non-vocal behaviors occurring before and/or after these focal events were documented and analyzed in an attempt to determine if certain behaviors were consistently associated with the departure ( depart) or arrival ( join) of another dolphin, or with physical contact ( contact) between dolphins in each species. Touch behaviors were found to be significantly related to each of the three focal events so were examined in further detail. Overall, in comparing species, the Indo-Pacific bottlenose and Atlantic spotted dolphins in this descriptive study exhibited more similarities than differences in their use of touch behaviors in potentially communicative situations across five broad behavioral contexts. However, a difference in the use of touch behaviors produced before departing or after joining a conspecific was noted. Specifically, the spotted dolphins were more likely to use contact after joining than before departing, whereas the bottlenose dolphins were equally likely to use contact in both situations. [ABSTRACT FROM AUTHOR]

The problem of transverse low-velocity impact on a linearly in-plane prestressed sandwich panel has been considered in this article. The panel may be subjected to initial in-plane biaxial normal and shear stresses along the edges of the panel. Impact is assumed to occur normally over the top or the bottom face-sheets, at arbitrary location. The boundary conditions of the top and the bottom face-sheets are independent. The interaction between the impactor and the panel is modeled with the help of the system having three-degrees-of-freedom (TDOF) consisting of springs-masses-dashpot (SMD) or springs-masses (SM). The effects of initial biaxial stresses and transverse flexibility of the core are considered analytically. In order to determine all components of the displacements, stresses and strains in the face-sheets and the core, a numerical procedure based on improved higher-order sandwich plate theory (IHSAPT) and Galerkin's method, are employed. The deflections and the corresponding stresses in the panel with higher initial stresses are smaller than those with lower initial stresses. The effects of in-plane initial shear stresses on impact response are slightly greater than that of the other in-plane normal loading states. [ABSTRACT FROM AUTHOR]

The fundamentals of cohesive particulate solids' consolidation and flow properties using a reasonable combination of particle and continuum mechanics are explained. By means of the model "stiff particles with soft contacts," the combined influence of elastic, elastoplastic, and viscoplastic repulsion in particle contacts is derived. As a result, contact normal force displacement F[sub N](h[sub K]) and adhesion force models F[sub H] (F[sub N]) are presented that describe the instantaneous and time consolidation behavior at characteristic (averaged) particle contacts. The approach has been shown to be effective for the data evaluation of a very cohesive titania nanopowder (surface diameter d[sub S] = 200 nm, solid density ρ[sub s] = 3870 kg/m[sup 3]). [ABSTRACT FROM AUTHOR]

• The generation mechanism of contact between CRTS II slab track and bridge is discussed. • The method for investigating nonlinear contact behaviors between CRTS II slab track and bridge is proposed by considering a detained and nonlinear contact relationship between concrete base and deck. • The distributions and changes of gaps between CRTS II slab track and bridge subject to time-dependent bridge deformation are investigated. Concrete creep and concrete shrinkage are unavoidable in the operation of concrete bridges in high-speed railways, which lead to bridge deformation and then cause gaps between CRTS (China Railway Track System) II slab track and bridge. Aiming at the dynamic contact between CRTS II slab track and bridge due to time-dependent effect of bridge and its influence on train-track-bridge interaction, this work proposes a method for investigating this dynamic contact behavior after exploring its generation mechanism. Adopting the established model, the nonlinear contacts between CRTS II slab track and bridge are deeply analyzed from static and dynamic perspectives. Finally, the influence of the dynamic contact on the train-track-bridge interaction is also investigated. Results show that the proposed methodology is effective in studying the contact behaviors between CRTS II slab track and bridges subject to time-dependent effect of bridge. Gaps appear at beam-end locations, and sharp contact behaviors are aroused at the locations of gap-edges. The length of gap is greatly decreased by running train. Creep and shrinkage have great influence on the train vibrations, while have almost no effect on track-bridge vibrations. Interlayer forces of track are obviously affect by bridge deformation and running train. [ABSTRACT FROM AUTHOR]

• The geometry of the new design of CICC is formulated. • A simple theoretical model is proposed to study the contact behavior and tensile stiffness of the new design of CICC. • An efficient and stable full 3D numerical model has been developed for the identical contact and stiffness problems. Superconducting cable-in-conduct-conductors (CICC) are multi-stage structures with complex geometries. We study the contact behavior and tensile stiffness for a new design of CICC. The geometrical configurations of the new design of CICC is first formulated. Based on the superposition principle, a simple theoretical model is proposed to study the contact behavior of the new design of CICC. A wide range of numerical simulations have been performed by using finite element method. The contact force and tensile stiffness are analyzed by changing the winding laps of C u strand. Further, an extensive parametric study is conducted in which the effect of tensile stiffness on the contact properties are also considered. The results show the trend of the contact properties and tensile stiffnesses in the new design of CICC which can be used to optimize the superconducting CICC. This analytical and computational studies provide a guide for new design of CICC to improve the mechanical properties of CICC by controlling the winding patterns of each strand. [ABSTRACT FROM AUTHOR]

Waterproof membranes have higher initial strength, faster construction, and better waterproofing than conventional sheet membranes. In addition, their polymer constituents have much higher interfacial adhesion and tensile strength than those of conventional materials. However, despite their advantages, waterproof membranes are not widely used in civil construction. This study evaluates the material properties and interface parameters of a waterproof membrane by considering the results of laboratory experiments and numerical analysis. Since the contact behavior of a membrane at its interface with shotcrete is important for understanding the mechanism of the support it offers known as a shotcrete tunnel lining, modeling should adopt appropriate contact conditions. The numerical analysis identifies the suitability and contact conditions of the waterproof membrane in various conditions. [ABSTRACT FROM AUTHOR]

• An improved dynamical model is proposed for stick–slip actuators in bi-directional motion. • Contact behavior exists between the piezoelectric stack and its flexure-based preload mechanism. • Contact behavior can cause stepping inconsistency for stick–slip actuator. • Successful demonstration on simulations and experiments. The dynamics of piezoelectric stick–slip actuators is important for structural optimization and positioning control, yet challenging to model because of the potentially inconsistent stepping of these actuators in the forward and backward directions. This step inconsistency is found to be strongly associated with the inconsistent dynamic response of the piezoelectric feeding element arising from the contact behavior between the piezoelectric stack and its flexure-based preload mechanism. With this understanding, an improved dynamical model for the typical stick–slip actuator is established in which a non-smooth contact model is introduced. A prototype was built and tested, and with it the contact behavior was proved to cause the inconsistent responses of the piezoelectric feeding element, which in turn was verified to cause the inconsistent stepping characteristics of the stick–slip actuator. The simulated results obtained using the proposed model were in good agreement with the stepping curves of the slider in bi-directional motion under different working conditions. The proposed model provides a new perspective to explain and model the step inconsistency for stick–slip actuators in bi-directional motion, and has great potential in aiding the design and control of stick–slip actuators for bi-directional driving. [ABSTRACT FROM AUTHOR]

The behavior at an interface between carbon nanotubes (CNTs) and silver nanowire (AgNW) could hardly be observed experimentally on an atomic scale, and the interaction is difficult to accurately calculate due to nanometer size effects. In this work, the contact behavior is studied with the molecular dynamics (MD) simulation, which indicates that the CNTs and AgNW can move towards each other to form aligned structures with their interfaces in full contact. In these different composite systems, nanotubes may either keep their form of an inherent cylindrical structure or completely collapse into the nanoribbons that can tightly scroll on the AgNW periphery while wrapping it in a core-shell structure. Thus, the atomic configuration evolution that is affected by the van der Waals (vdW) interaction is closely analyzed to assist the understanding of interfacial contact behavior. [ABSTRACT FROM AUTHOR]

• A tolerance analysis method considering contact behavior for spur gears is proposed. • Both machining and assembly errors are considered based on skin model shapes. • Contact behavior is calculated using the boundary element method. • Notable effects of contact behavior on transmission performance are demonstrated. Tolerance analysis is an important approach for evaluating the accuracy and function of mechanical products. Research on tolerance analysis has mainly focused on the transfer and accumulation of geometric deviations during assembly, while the effects of contact behavior have not been considered in detail. Therefore, this paper presents a tolerance analysis approach to spur gears that takes into account the effects of contact behavior between mating tooth surfaces on transmission performance. Machining and assembly errors are represented based on the concept of skin model shapes. The contact behavior between mating tooth surfaces is calculated using the boundary element method (BEM) to perform tooth contact analysis (TCA). The proposed tolerance analysis approach is applied to a pair of spur gears as an example. The manner in which the transmission error, tooth contact pattern and contact pressure distribution are affected by machining and assembly errors is discussed. This research demonstrates the notable effects of contact behavior between mating tooth surfaces on transmission performance and provides a potential method for the tolerance analysis of other mechanisms. [ABSTRACT FROM AUTHOR]