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As railway transportation advances towards higher speeds and increased axle loads, the fatigue damage between wheels and rails has become more severe, significantly limiting the service life and safety of trains. Therefore, developing upgrade wheel-rail materials with enhanced contact fatigue properties has been considered an effective approach to avoid damage. This study reports a newly developed heavy-haul wheel steel with a superior rolling contact fatigue performance and the fatigue damage of wheel was studied by a novel RCF tester with a vision system. The results indicate that the newly developed heavy-haul wheel steel (NW) consists of smaller pearlite layer spacing and reduced proeutectoid ferrite. The NW steel demonstrates outstanding fatigue resistance in both oil and dry conditions, with a fatigue life 2.7 times longer than CL65 wheel steel and superior performance compared to most typical wheel steels. With increasing in pearlite content and decreasing in pearlitic interlamellar spacing, the fatigue damage degree of wheels under oil or dry contact conditions decreases obviously, leading to a significant enhancement in fatigue life. Properly controlling the pearlite content and the interlamellar spacing can optimize the fatigue properties of wheel materials. The vision system observed that the average area and perimeter of the defects gradually increased on the sample surface. The shape of the defect became more rounded under oil contact conditions but showed the opposite result in dry contact. When subjected to cyclic loading, surface cracks propagated along various paths after initiation, eventually forming different morphologies of peeling. The results will not only help optimize wheel materials for heavy-haul railways, but also offer an effective means for analyzing damage evolution in wheel-rail contact. [ABSTRACT FROM AUTHOR]

The overtopping-inundation process of a tsunami results in the collisions of drifting objects on the coast, which damage structures, thereby increasing the risk of collapse. This study conducted laboratory experiments on the collision between a drifting container caused by the overtopping-inundation process of a solitary wave and a fixed port crane's leg. The movement trajectory and velocity of the container as well as the collision velocity by solitary wave inundation, were analyzed using motion analysis software. Overall, increasing solitary wave scale, collision velocity, and drifting object weight and decreased distance between the two objects tended to increase the collision force. However, different experiment results were also obtained due to pitching in objects that fully floated without bottom friction owing to the solitary wave bore. This resulted in line-to-surface collisions. Thus, surface-to-surface contact occurred under the incomplete floating condition owing to the difficulty because of interference with the bottom; however, the collision force decreased under complete floating conditions owing to line-to-surface contact. Therefore, the contact condition according to the floating behavior must be considered a parameter while predicting the collision forces of drifting objects. Thus, surface-to-surface contact occurred under the incomplete floating condition owing to the difficulty because of interference with the bottom; however, the collision force decreased under complete floating conditions owing to line-to-surface contact. Therefore, the contact condition according to the floating behavior must be considered a parameter while predicting the collision forces of drifting objects. [ABSTRACT FROM AUTHOR]

We consider a frictionless contact model whose constitutive law and contact condition are described by means of subdifferential inclusions. For this model, we deliver a variational formulation based on two bipotentials. Our formulation envisages the computation of a three-field unknown consisting of the displacement vector, the stress tensor and the normal stress on the contact zone, the contact being described by a generalized Winkler condition. Subsequently, we obtain existence and uniqueness results. Some properties of the solution are also discussed, focusing on the data dependence. [ABSTRACT FROM AUTHOR]

We characterize the passage from nonlinear to linearized Griffith-fracture theories under non-interpenetration constraints. In particular, sequences of deformations satisfying a Ciarlet-Nečas condition in S B V 2 and for which a convergence of the energies is ensured, are shown to admit asymptotic representations in G S B D 2 satisfying a suitable contact condition. With an explicit counterexample, we prove that this result fails if convergence of the energies does not hold. We further prove that each limiting displacement satisfying the contact condition can be approximated by an energy-convergent sequence of deformations fulfilling a Ciarlet-Nečas condition. The proof relies on a piecewise Korn-Poincaré inequality in G S B D 2 , on a careful blow-up analysis around jump points, as well as on a refined G S B D 2 -density result guaranteeing enhanced contact conditions for the approximants. [ABSTRACT FROM AUTHOR]

Serious wheel polygonal wear usually causes drastic wheel/rail interactions, which threats the running safety of railway vehicles. This paper presents an investigation into the effect of polygonal wear of heavy-haul locomotive wheels on the dynamic performance and wheel/rail interactions through extensive on-site tests and numerical simulations, in which a special attention is paid to locomotive vibrations and dynamic wheel/rail tangential forces. The measured results conducted on two objective locomotives were firstly compared, including the characteristics of wheel polygonal wear and locomotive vibrations in vertical, longitudinal and lateral directions. A 3D heavy-haul train-track coupled dynamic model was then formulated to investigate wheel/rail dynamic interaction induced by polygonal wear of locomotive wheels. A low adhesion zone (LAZ) and a PI-based anti-slip control algorithm were embedded into the dynamic model to analyse the effects of wheel polygonal wear on wheel/rail longitudinal and lateral interactions under normal and low adhesion conditions. The results show that the severe wheel polygonal wear affects not only the vertical but also the longitudinal performance of the wheel/rail system notably. The wheel high-order polygonal wear has a conspicuous effect on longitudinal, lateral and vertical vibrations of locomotive system components. [ABSTRACT FROM AUTHOR]

Rolling ceramic thermal insulation balls have advantages of low cost, large output and easy control of particle size, so it is likely to become the main raw material for 3D printing in the future, but there is little research on its thermal insulation. In this study, we used three kinds of rolling aluminum oxide balls as raw materials to obtain single-granularity-level and multi-granularity-level bulk materials. And the effects of temperature, particle size, and thermal fatigue times on the thermal conductivity of the samples were analyzed. Additionally, the experimental results were verified by FloEFD heat conduction simulation software using finite analysis method to analyze their heat conduction characteristics. With the increase of temperature from 400 °C to 1500 °C, the thermal conductivity of single-granularity-level and multi-granularity-level bulk materials increased linearly. The thermal conductivity of single-granularity-level bulk materials have no direct relationship with the particle size, and the thermal conductivity of multi-granularity-level materials with small particle size difference was a bit lower than that of materials with large particle size difference, and a bit higher than that of materials with single-granularity-level. The simulation results showed that the main reason for the above phenomenon was that the point contact between particles played a dominating role in the heat transfer process. When the contact area increased, the thermal conductivity increased obviously, and the thermal conductivity with the increasing of temperature decreased in a quadratic curve. The improved model considering the shrinkage could improve accuracy of simulation results. Heat flux at the surface contact area was 10.19 times higher than that of the point contact and 15.10 times higher than that of the solid-gas contact at 400 °C. Therefore, reducing the surface contact area and increasing the porosity could significantly reduce the thermal conductivity of the materials. [ABSTRACT FROM AUTHOR]

• The effect of stack and contact model on macro-properties is analyzed in pore scale. • Re K for flow state transition in single layer and staggered stacked mesh is found. • Neglecting inertia force cause 50 % error of permeability for Forchheimer flow. • Applicability of various thermal conduct models to local contact k eff is discussed. • Permeability predictive correlations and k eff theoretical model is proposed. Metallic woven mesh screens are representative porous media with periodic structures, which have great application prospects in emerging technology and industrial equipment. However, the effect of their pore structure on macroscopic properties is not clear, which limits their large-scale engineering application. In this paper, to investigate the influence mechanism of stacking patterns and wire contact conditions on flow and heat conduction from the pore scale, a representative elementary volume model of the square-shaped plain copper micromesh was reconstructed according to the geometric parameters obtained by the optical microscope and porosity test experiment. Furthermore, based on the understanding of microscopic mechanism, the theoretical calculation model for macroscopic characteristics was proposed. The results show that the flow characteristics in meshes are mainly affected by stacked patterns. When Re K is 0.08 and 0.28, the flow in single layer and staggered stacked woven meshes transitions from Darcy flow to Forchheimer flow. In Forchheimer flow regime, neglecting the inertia force causes a maximum 50 % error for permeability calculation. The permeability empirical correlations for Darcy and Forchheimer flow are proposed according to Kozeny-Carman and Kozeny-like model. The z -direction effective thermal conductivity of copper woven meshes is significantly affected by wire contact conditions, the maximum value is from 2.5 to 13.5 W/(m·K). The z -direction effective thermal conductivity of tangent and gap contact conditions can be described by the ZBS model, while the random model is suitable for that of overlapped contact conditions. The x -direction thermal conductivity is little affected by contact conditions, the maximum value is 50.3 W/(m·K), but the tortuosity effect of copper wires should be considered for calculation. The calculation model of anisotropic thermal conductivity for single-layer woven meshes is established according to Kirchhoff's law, which is also extended to the staggered stacked woven meshes by introducing a compactness factor. [ABSTRACT FROM AUTHOR]

Deformation of acetabular cups when press-fitted into an undersized cavity is inevitable due to the inhomogeneous stiffness of acetabular bone. Thinner cups or screw holes might increase the risk of high cup deformation. The aim of this study was to examine the influence of cup design and liner assembly on the deformation response during cup implantation. Acetabular cups with different designs were implanted into polyurethane foam models simulating the anatomical situation with nominal press-fits of 1mm and without nominal press-fits (line-to-line). Deformations were determined using a tactile coordinate measuring machine. A 3D laser scanner was used to determine the contact conditions at the cup-cavity interface. Polyethylene and ceramic liners were assembled to the implanted cups and the influence of the insertion on the deformation response evaluated. Fixation strength of the cups was determined by push-out testing. Cup deformation increased with smaller wall thickness (P < 0.037) and screw holes (P < 0.001). Insertion of ceramic liners reduced the deformation (P < 0.001), whereas polyethylene liners adapted to the deformation of the implanted cups (P > 0.999). Thin-walled cups exhibited a higher fixation strength for similar implantation forces (P = 0.011). Thin-walled cups achieved higher fixation strengths and might be more bone-preserving. However, in combination with screw holes and high press-fit levels, wall thickness should be considered carefully to avoid excessive cup deformations leading to potential complications during liner assembly. Line-to-line insertion of thin-walled cups should be accompanied with a rough surface coating to minimize the loss of fixation strength due to the low press-fit fixation. • Reduced cup wall thickness and screw holes increased cup deformation. • Thin-walled cups achieved higher fixation due to increased cup deformation. • Polyethylene liner adapted to the cup deformation after assembly. • Insertion of ceramic liner reduced the cup deformation. [ABSTRACT FROM AUTHOR]

Dynamic contact resistance measurement (DRM) is an effective technique to evaluate the contact condition in substations without dismantling circuit breakers. However, performing DRM tests with unsuitable test parameters will cause low repeatability of the test results, and even lead to the misdiagnosis of contact condition. Performing the DRM tests at high DC injected current can improve the repeatability. This paper studies the mechanism of the DC injected current on the repeatability of the DRM test results, and it also promotes a new determination method of the DC injected current amplitude. The impact of the DC injected current on DRM test results is reviewed. The mechanism of the DC injected current on DRM test results is investigated by analysing the chemical composition of the contact surface, the force exerted on the contacts, and the temperatures of a‐spots on the contacts' surface. Results indicate that not the Lorentz force, but the temperature of a‐spots is the primary influencing factor. The amplitude of the DC injected current can be determined by calculating the temperatures of the a‐spot on the contacts' surface. And this method can also be used for other SF6 circuit breakers. [ABSTRACT FROM AUTHOR]

This paper mainly focused on the establishment of the moisture diffusion models of two-component foods under different contact conditions in an impermeable package. Two-component foods were simulated by cookies (low water activity component) and agar gels (high water activity component). The different contact conditions were achieved by full contact, non-contact, and partly contact of the two components. Optimized moisture diffusion models that considered the air resistance of these contact conditions were deduced and established based on the Fick's second law and the solution of partial differential equations. Model verification was carried out by comparing the measured data and the predicted ones, results showed the models of all contact conditions had high accuracies, where the Af values were all closed to 1. [ABSTRACT FROM AUTHOR]

Abstract Background Reaming of the acetabular cavity and cup implantation directly influence the hip rotation center and contact area between implant and bone. Previous studies have reported on an altered rotation center after total hip arthroplasty, but have not studied the influence of reaming and cup implantation separately. Aim of this study was therefore to analyze the individual influence of acetabular reaming and subsequent cup implantation on the rotation center and how this influences the contact conditions at the bone-implant interface. Methods Acetabular press-fit cups were implanted into the left and right hips of three full cadavers (n = 6). CT scans were performed to calculate the change in hip rotation center after reaming and prior to liner insertion. 3D models of the cups were used to determine the polar gap, the contact conditions and the effective press-fit. Findings Reaming the acetabular cavity shifted the rotation center medially (median 5.8 mm, range 4.8–9.1), superiorly (5.3 mm, 3.0–7.0) and posteriorly (2.9 mm, 1.0–5.3). With cup implantation, the rotation center shifted back towards the native position, but no full restoration was observed. The degree of shift increased with the size of polar gap (r s = 0.829, P =.042), which inversely reduced the contact area (r s = 0.886, P =.019). Interpretation This study reveals that the dominant factor in hip rotation center restoration is the reaming process, while the cup implantation for a given nominal press-fit has only a small influence. Increasing the press-fit would improve the restoration but bares the danger of insufficient bone coverage and periprosthetic fractures due to the high forces needed. Highlights • Acetabular reaming is the dominant factor to restore the hip rotation center. • Acetabular reaming shifts the hip rotation center away from its native position. • No full restoration of the altered rotation center achieved with cup implantation. • Restoration of the hip rotation center is dependent on cup seating and press-fit. • Medialization during acetabular reaming tended to increase implant bone coverage. [ABSTRACT FROM AUTHOR]

Analytical solutions can quickly and simply evaluate stresses and displacements in tunnels and are widely adopted in the preliminary design phase of tunnels. Tunnels must be able to withstand static loading and seismic loading. This paper proposes new analytical solutions for the stresses and displacements of tunnels under static and seismic loading. The tunnel lining is treated as a thick-walled cylinder. Moreover, the contact stiffness coefficient k 0 and the stress release coefficient η 0 are introduced to consider the arbitrary contact conditions at the ground–lining interface and the amount of excavation unloading. The new analytical solutions are verified by comparison with finite element analysis results. The results demonstrate the accuracy and applicability of the proposed analytical solutions. In addition, parametric analyses are conducted to explore the effects of the stress release coefficient η 0 and stiffness coefficient k 0 at the ground–lining interface, as well as the incident angle α of shear waves. The analysis results indicate that the proposed analytical solutions offer satisfactory performance and can be applied as an effective tool for preliminary tunnel design. [ABSTRACT FROM AUTHOR]

A new analytical model for forming force prediction in the whole process of incremental sheet forming (ISF) is presented in this work. The modelling of contact region, thickness distribution and strain components are carried out as the basis for the prediction of vertical and horizontal forces. The effect of local contact behaviour and material deformation, as well as the behaviours of global bending, changes of deformation mode and contact condition are taken into account in the modelling of ISF force history. The force prediction model at both plane strain and biaxial tension condition areas is developed based on the differences in contact region and thickness distribution between these two different deformation states. Validated by ISF tests for a truncated cone and pyramid part with varying drawing angles, the prediction of force history captures well the fluctuation of different force components due to the change of deformation conditions and provides an insight into the material deformation mechanisms and the direct correlation to forming force characteristics of the whole ISF process. In a practical case, the model is successfully applied to the force prediction in ISF-based cranial plate manufacture. The model is also validated by a series of ISF tests with accurate force predictions of both the peak and stabilised forces. [Display omitted] • A new force prediction model with consideration of complicated deformation in ISF. • Forming force history of the whole ISF process. • Demonstration of a direct correlation between ISF forces and deformation states. • ISF force dependency on local contact, deformation, and global bending. • Comprehensive and accurate force prediction in ISF. [ABSTRACT FROM AUTHOR]

The stress distribution and failure process in the Brazilian test disk are numerically studied using the continuum-based discrete element method. The stress distribution in the immediate contact vicinity between disk and jaws with two types of contact conditions are compared, and the position of failure initiation is determined based on the generalised Griffith criteria. Moreover, the whole process of the Brazilian test is modelled for disks with various material properties under two contact conditions and the modelled Brazilian tensile strengths of the disks are obtained. Numerical simulations show that the distribution of stress components in the vicinity of the contact have remarkable differences between the two contact conditions, and the difference increase with the increasing of loading level and disk's elastic modulus. However, the stress distributions exhibit almost no difference on the disk's centre area. The disk's elastic modulus and the ratio of compressive strength to tensile strength are the main factors that influence the distribution of stresses in the vicinity of the contact, thereby affecting the failure initiation and tensile strength, especially under no-cushion contact conditions. The thin plastic cushion can alleviate the stress concentration in the vicinity of the contact between the disk and jaws, and cracks initiating from the vicinity of the contact can be avoided for almost all of the rock-like materials. However, the enlarging contact ranges will result in a larger deviation between the test results and the real tensile strength. An improved Brazilian test method considering two contact conditions of with and without cushions for rock and rock-like material is proposed. [ABSTRACT FROM AUTHOR]

This work investigates the static and dynamic tooth root strains in spur gear pairs using a finite element/contact mechanics approach. Extensive comparisons with experiments, including those from the literature and new ones, confirm that the finite element/contact mechanics formulation accurately predicts the tooth root strains. The model is then used to investigate the features of the tooth root strain curves as the gears rotate kinematically and the tooth contact conditions change. Tooth profile modifications are shown to strongly affect the shape of the strain curve. The effects of strain gage location on the shape of the static strain curves are investigated. At non-resonant speeds the dynamic tooth root strain curves have similar shapes as the static strain curves. At resonant speeds, however, the dynamic tooth root strain curves are drastically different because large amplitude vibration causes tooth contact loss. There are three types of contact loss nonlinearities: incomplete tooth contact, total contact loss, and tooth skipping, and each of these has a unique strain curve. Results show that different operating speeds with the same dynamic transmission error can have much different dynamic tooth strain. [ABSTRACT FROM AUTHOR]

An analytical solution can easily and quickly give the internal forces in tunnels due to seismic waves, by which, the relationship between the key parameters could also be clarified. These methods are widely used in preliminary seismic design of tunnels. This paper presents new analytical solutions for thrust and moment of circular composite-lined tunnels with arbitrary layer linings under obliquely incident SV waves and P waves. Wherein, the lining is regarded as a thick-wall cylinder. Moreover, the proposed analytical solutions can consider different contact conditions of the ground-tunnel and lining-lining interface. The new analytical solutions are verified by comparing with the dynamic finite element analysis results. The results show the accuracy and applicability of the proposed analytical solutions. Parametric analyses are performed to explore the effects of the flexibility coefficient δ , incident angle and steel lining on the seismic response of tunnels. [ABSTRACT FROM AUTHOR]

A three-dimensional finite element model used to simulate the bolted joint is created using ABAQUS package. The stress concentration factors at the roots of the thread are first studied with a preload of 38.4 kN. Under harmonic transverse shear displacement, not only the stress variations at ten specified points of the first thread but also contact conditions between the contacting surfaces are studied. By changing the preload value, relative displacement, the coefficient of friction between the two clamped plates successively and the loading frequency, their effects on the hysteresis loops of the transverse load versus the relative displacement of the joint are then analyzed. Finally the hysteresis loops are produced by the Masing model. It is found that due to the greatest stress concentration factor, fatigue failure will occur at the root of the first thread. With the increase of preload value, the amplitude of displacement and the coefficient of friction, frictional energy dissipation of the joint increases. Very good agreement is achieved between the hysteresis loops produced from the fourth-order Masing model and the detailed ABAQUS model and therefore the fourth-order Masing model can replace the time-consuming finite element model. [ABSTRACT FROM AUTHOR]

Abstracts: Steam generator is one of the major components in the nuclear power plant comprising pressure-retaining boundary. Typically, there are thousands of thin-walled tubes as well as several support plates in a steam generator. According to the operating experience of the steam generators, a lot of cracks have been found in the tubes. Therefore, an accurate integrity assessment of the tubes is crucial for maintaining safety as well as reliability of a nuclear power plant. The steam generator tubes are supported by several support plates, and deformations of the tubes are partially restrained depending on the crack location and the gap between the tube and the support plate. In the authors' previous study, it has been reported that burst pressures for circumferentially cracked tubes are significantly affected by the support plate and existing solutions differ from the actual burst pressure. However, this interaction effect for axially cracked tubes has not been fully investigated while those are frequently occurred during operation. In this paper, therefore, a number of elastic-perfectly plastic finite element analyses were performed considering the contact interaction between the tube and the support plate. The burst pressure is then evaluated in accordance with the lower bounding limit theorem and the support-induced interaction effects on the burst pressure were determined. [Copyright &y& Elsevier]

Abstract: The tribological conditions at the contact between the cutting tool and the chip are of great importance when analyzing the machining process. By knowing the contact conditions on the rake face of the cutting tool the wear on the clearance and rake face may be predicted in terms of size and type of wear. A certain value of the surface stresses is often thought of as leading to a higher wear rate of the cutting tool and thus a shorter tool life. In this article two different methods for experimentally measuring the contact condition on the clearance and rake face of the cutting tool are presented and illustrated with results obtained while turning AISI 4140. Results are also obtained in terms of how the surface roughness value of the cutting tool influences the contact condition. It was found that the tool surface topography may have a significant impact on the tribological performance during machining. [Copyright &y& Elsevier]

Decrease projected length of bolts due to bending deformation in timber joints compresses the steel washers onto timber member and increases lateral resistance of the joints. As this lateral strength increase primarily depend on bearing characteristics of timber beneath the steel washers, a finite element analysis was performed to predict their bearing-embedment behavior. A 3-D finite element model consisting of 8-node solid and contact pair elements was developed using ANSYS assuming an anisotropic plasticity model for timber and an elastic-perfectly plastic model for the washers. Material constants for both steel washer and timber member were obtained from previous test data. The results of the analysis were in good agreement with the experimental load-embedment curves as well as the analytical curves obtained in a previous study based on a rigid-body-spring-model. The same approach was also used to evaluate the effective bearing length (under uniform compression) of a 50 mm depth timber block partialy compressed. [ABSTRACT FROM AUTHOR]

Abstract: We solve a particular system of nonlinear ODEs defined on the two different components of the real line connected by the nonlinear contact condition We show that, for a prescribed power-law nonlinearity and using the solution , a self-similar solution to the porous medium equation in the two-component domain can be constructed. We provide the rigorous proof of a theorem in which the formula for the free boundary already presented in Filo and Pluschke (2009) is given. [Copyright &y& Elsevier]

Abstract: The onset of plastic yielding in a spherical shell loaded by a rigid flat is studied for stick and slip contact conditions using finite element analysis. The effect of various material properties on the critical normal load, critical interference and critical contact area at the onset of plastic yielding is investigated and the location where plastic yielding first occurs is determined. A comparison is made with results obtained previously for slip contact condition. Substantial differences are found at low to medium Poisson’s ratio values, while some similarities are found to occur for high Poisson’s ratio values. In particular, a spherical shell is more prone to yield under stick than under slip contact condition. [ABSTRACT FROM AUTHOR]

Abstract: We consider a system of two porous medium equations defined on two different components of the real line, which are connected by the nonlinear contact condition First we prove existence and uniqueness of a solution on a bounded domain. Furthermore, we are interested in the behaviour of the interface of the porous medium equation when it crosses the contact line S between the two components. To this end we solve the Cauchy problem on unbounded components, consider self-similar solutions for special and derive a formula for the shape of the interface in that case. [Copyright &y& Elsevier]

In this paper, the orbital forming simulation of an automotive hub bearing was studied to predict forming conditions and performances using the explicit finite element method. To set up an efficient solution technique for the orbital forming, axisymmetric finite element models and 3D solid element models were numerically solved and compared to each other. The time scaling and mass scaling techniques were introduced to reduce the excessive computational time caused by small element size in case of the explicit finite element method. It was found from the numerical results on the orbital forming that the axisymmetric element models showed the similar results to the 3D solid element models in forming loads whereas the deformations at the bearing inner race were quite different. Finally the strains at the bearing inner race and the forming forces of the peen were measured by test for the same product used in the numerical analysis, and were compared with the 3D solid element results. It was shown that the test results were in good agreements with the numerical ones. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the conditions under which a marine ice sheet may adopt a steady profile. The ice is treated as a linear viscous fluid caused to flow from a rigid base to and over water, treated as a denser but inviscid fluid. The solutions in the region around the point of flotation, or ‘transition’ zone, are calculated numerically. In-flow and out-flow conditions appropriate to ice sheet and ice shelf flow are applied at the ends of the transition zone and the rigid base is specified; the flow and steady free surfaces are determined as part of the solutions. The basal stress upstream, and the basal deflection downstream, of the flotation point are examined to determine which of these steady solutions satisfy ‘contact’ conditions that would prevent (i) the steady downstream basal deflection contacting the downstream base, and (ii) the upstream ice commencing to float in the event it was melted at the base. In the case that the upstream bed is allowed to slide, we find only one mass flux that satisfies the contact conditions. When no sliding is allowed at the bed, however, we find a range of mass fluxes satisfy the contact conditions. The effect of ‘backpressure’ on the solutions is investigated, and is found to have no affect on the qualitative behaviour of the junctions. To the extent that the numerical, linearly viscous treatment may be applied to the case of ice flowing out over the ocean, we conclude that when sliding is present, Weertman''s ‘instability’ hypothesis holds. [Copyright &y& Elsevier]

Abstract: Therapeutic vascular catheterization techniques are sometimes hampered by the frictional forces between the blood vessel and the catheter, when contact points of the vessel are changing and deforming during the movement of the catheter. The goal of the present study was to characterize frictional interactions between the blood vessel wall and the catheter using experimental and numerical analysis. First, the frictional force was measured with an experimental apparatus that uses a ball and flattened porcine aorta to simulate frictional forces between the catheter and the vessel. Second, catheter motion was characterized by two-dimensional numerical calculations based on the experimental results. Experimental analysis demonstrated that slip occurred and that friction coefficient between the vessel and the catheter and the deformation of the specimen were small when the contact between the ball and the aorta occurred at a small angle. The compliance of the specimen in the normal direction obtained by the experiment was by far larger than that calculated according to the Hertzian contact theory. Numerical analysis shows that this difference of the parameter of the vessel, which must be determined accurately in surgical simulator, could affect the trajectory of the catheter. [Copyright &y& Elsevier]

Abstract: This paper is a study on the development of a sensor for detecting the catheter''s contact conditions. The sensor is composed of a rubber layers, cupper plates and three strain gauges. The sensor is assumed to be mounted on the tip of a catheter, and it is hollowed for the work space of the catheter. The equations relating the sensor output with the contact conditions are formulated in the three gauges output. The obtained results show the good correspondence of the estimated contact information with the applied conditions. [Copyright &y& Elsevier]

Friction stir welding (FSW) experiments were conducted, using a work hardened aluminium alloy and a cast aluminium alloy followed by examination focusing on the upper weld zone. The examination has revealed the feature of the major forward flow due to the forward motion of the shoulder. A thin shear layer was identified between the tool shoulder and the workpiece with a distinctive shear flow direction. The thickness of the shear layer was alloy dependent. An embedded layer in the upper weld zone has also been identified. The flow phenomena leading to this will be discussed. A velocity profile in the shear layer, based on the apparent alignment of Si particles in the cast alloy after FSW, has suggested a dominant sliding contact condition. [ABSTRACT FROM AUTHOR]

Abstract: A combined experimental and theoretical investigation was conducted to examine the thermal conductivity of layers of wire mesh screen. Employing a carefully controlled sintering process, layers of sintered wire screen were examined experimentally. The experimental results indicate that the effective thermal conductivity in the z-direction (i.e., normal to the plane of the wire screen layers) for single layer, inline structures and staggered multilayer wire screens is approximately 4–25% and 6.4–35% times that of the solid metal thermal conductivity, respectively. In addition to the conductivity of the base material, the contact conditions between the individual wires, as well as between the individual layers were found to be the most important factors in the determination of the effective thermal conductivity. In parallel with the experimental investigation, an analytical model was developed and shown to accurately predict the effective thermal conductivity of these layers as a function of the contact conditions between the wires, between the individual layers, and between the solid heating surface and the first layer of screen. In addition to the contact conditions, this new model is strongly dependent on three geometric parameters: the mesh number, M, the wire diameter, d, and the compression factor, cf. Experimental data from this and other investigations were used to verify the accuracy of the model, which was shown to accurately predict the effective conductivity as a function of the above mentioned parameters. In addition, a comprehensive literature review was performed and analyzed in order to further substantiate the validity and accuracy of this new model. The resulting conclusions highlight the importance of the contact conditions between the wires in the individual layers, and between the layers and the solid surface. [Copyright &y& Elsevier]

Abstract: In isothermal upset forging of pure aluminum, the change in the contact condition and the lubricant behavior were evaluated by continuously measuring the ultrasonic reflection intensity from the contact interface between the tool (die) and workpiece. The relationships between ultrasonic reflection intensity, forging temperature, lubrication, forging pressure and workpiece surface during forging were examined. Depending on forging temperature, the conditions of the lubricant entrapment on the surface of the workpiece exhibited significant changes. The condition of lubricant pools and lubricant film was evaluated during warm and hot forging using the ultrasonic reflection intensity. The change in the contact condition and the lubricant behavior during warm and hot forging were measured with high sensitivity by the proposed ultrasonic measurement. The lubrication conditions can be optimized based on the in situ evaluation of the contact conditions. [Copyright &y& Elsevier]

Abstract: Background. Superficial conditions and integrity of collagen network play an important role on the lubrication performance of articular cartilage. In this work, a technique based on the evanescent waves is used for the evaluation of contact condition during friction tests. Methods. The frictional and superficial characteristics of the normal and degraded articular cartilages with high and low concentration of collagenase were evaluated. The optical apparatus was set in order to decrease the intensity of a light reflected at the interface between a prism and specimens when collagen fibers are found near the interface. Findings. For all conditions, an increase in the attenuation of reflectance as the friction coefficient increases was observed with reasonable correlation. For the specimens degraded with collagenase, low friction and reduced attenuation of reflectance were observed at the beginning of sliding followed by a gradual increase in both friction and attenuation of reflectance. In comparison to the degraded specimens, normal specimens presented high friction at beginning and low friction at the end of test. Interpretation. The superficial conditions and the presence of water at the articular surface play an important role in the lubrication of synovial joints. The ability to retain water for degraded specimens is impaired due to the loss of proteoglycan observed in the histological sections and hence, their low friction observed at the beginning of the test is not sustained for a long time. The use of evanescent waves demonstrated to be very useful in the analysis of the contact condition of articular cartilage. [Copyright &y& Elsevier]

The objective of the present paper is to investigate the effect of including the tool probe in the numerical modelling of three-dimensional heat flow in friction stir welding (FSW). The heat flow close to the probe/matrix interface is investigated. In the models presented, the heat is forced to flow around the 'probe hole'. In this manner, the material flow through the probe region, which often characterises other thermal models of FSW, is avoided. This necessitates controlling the convective heat flow by prescribing the velocity field in the narrow shear layer at the tool/matrix interface. As a consequence the sliding, sticking, or partial sliding/sticking condition can be modelled. Six cases are established, which are represented by three stages of refinement of the heat source model, combined with two different contact conditions, i.e. full sliding and full sticking. [ABSTRACT FROM AUTHOR]

This paper describes the effects on machine slide-guide contact conditions caused by thermal deformation. Since a slide guide has a large friction surface, the motion is greatly influenced by thermal distortion caused by heat generation in the ball nut and the bearing support, during machining processes. This study investigated the typical behavior of the friction coefficient in response to both the external load and the linear speed. This then led to investigating the thermal effects on the slide motion. The thermal deformation of the slide table was measured with respect to the running time and the linear motion and the frictional power were monitored and compared directly with the thermal distortion. [Copyright &y& Elsevier]

Analytical solutions based on the elastic foundation beam model for the bending response of circular tunnels under longitudinally propagating shear waves are studied considering the tangential contact conditions at the ground-tunnel interface. First, two kinds of new analytical solutions based on Timoshenko beams resting on Winkler or Pasternak foundations are developed considering different contact conditions at the ground-tunnel interface. The contact conditions are considered by introducing a spring-type flexibility coefficient in the force–displacement relationship. Then, the new analytical solutions, as well as the traditional solutions using Euler or Timoshenko beams on Winkler or Pasternak foundations, are compared with the dynamic numerical results. The new analytical solutions exhibit good agreement with the dynamic numerical results for different contact conditions. However, due to the neglect of the tangential interaction between the tunnel and surrounding ground, traditional solutions are only suitable for predicting the seismic response of tunnels in the full-slip condition. Finally, a parametric study is conducted to investigate the effects of the earthquake frequency, ground condition, lining thickness and contact condition. The proposed analytical solutions can be used to predict the seismic response of circular tunnels under longitudinally propagating shear waves in engineering design. [ABSTRACT FROM AUTHOR]

Fretting wear tests of Zircaloy-4 alloy against Inconel 718 alloy were conducted on a fretting wear rig. The contact state and fretting running characteristics of Zircaloy-4 alloy were investigated. The running condition fretting map of Zircaloy-4 alloy presents three regimes, namely, partial slip regime, mixed slip regime, and gross slip regime. Slight degradation was observed in the partial slip regime. In the mixed slip regime, adhesive wear of the stick zone and oxidation wear of the slip zone are the main damage mechanisms, and cracking was observed at the stick-slip boundary. Severe material detachment due to wear is predominant in the gross slip regime, and the main damage mechanisms are adhesion, plastic deformation, surface fatigue, frictional oxidation and abrasion. • The RCFM of Zircaloy-4 alloy presents three regimes: partial slip regime, mixed fretting regime, and gross slip regime. • The MRFM of Zircaloy-4 alloy presents three domains: slight degradation, adhesion and cracking, and severe wear. • The sliding state is closely related to the tangential force of the contact surface. • The MSR was the most critical for crack nucleation and propagation. • Wear accompanied by severe oxidation is the main damage mechanism in the GSR. [ABSTRACT FROM AUTHOR]

When a longitudinal wave passes through a contact interface, second harmonic components are generated due to contact acoustic nonlinearity (CAN). The magnitude of the generated second harmonic is related to the contact state of the interface, of which a model has been developed using linear and nonlinear interfacial stiffness. However, this model has not been sufficiently verified experimentally for the case where the interface has a rough surface. The present study verifies this model through experiments using rough interfaces. To do this, four sets of specimens with different interface roughness values (Ra = 0.179 to 4.524 μm) were tested; one set consists of two Al6061-T6 blocks facing each other. The second harmonic component of the transmitted signal was analyzed while pressing on both sides of the specimen set to change the contact state of the interface. The experimental results showed good agreement with the theoretical prediction on the rough interface. The magnitude of the second harmonic was maximized at a specific contact pressure. As the roughness of the contact surface increased, the second harmonic was maximized at a higher contact pressure. The location of this maximal point was consistent between experiments and theory. In this study, an FEM simulation was conducted in parallel and showed good agreement with the theoretical results. Thus, the developed FEM model allows parametric studies on various states of contact interfaces. [ABSTRACT FROM AUTHOR]

The mechanical analysis of multiple tunnels at great depth is an extremely common problem in practical engineering. Previous studies usually used the Schwarz alternating method to solve the multiple-tunnel problem with an iterative scheme, which resulted in low efficiency and precision. To this end, this paper presents a non-iterative analytical method to calculate the mechanical field of multiple lined tunnels. In this method, the analytic function is expanded by Laurent series on each tunnel boundary so that the stress and displacement fields in the whole multiply-connected domain can be expressed accurately. The conformal mappings of different tunnels are independent of each other, which makes it convenient to deal with multiple arbitrary-shaped boundaries. The basic equations for solving the mechanical fields are obtained according to the contact conditions and stress boundary conditions. In the solving process, the Fourier transform method is used to transform the boundary conditions into the frequency equations. Compared with the Schwarz alternating method, our method can directly obtain the high-quality result without any iteration. Finally, several examples are given to verify the accuracy and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

SUMMARY The authors thank the discussers R.Conti, L.De Sanctis and G.M.B.Viggiani for their interest to the paper entitled 'Influence of diaphragm wall installation on the numerical analysis of deep excavation' and for providing the opportunity to submit additional information to clarify some issues. The authors broadly agree with the comments which deal with three main aspects of the paper: presence of water and type of analysis, constitutive modelling and numerical strategies. The present reply addresses some additional issues that the discussers find not clear on the original paper submitted by the writers. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

• MD simulation for effect of surface roughness of nominally flat NW on friction. • Enhanced proximity of contacting atoms at asperities of rough NW due to adhesion. • High interfacial strength of rough NW due to increased potential energy barrier. • No significant difference in friction between rough and flat NWs. • Feasible underestimation of interfacial strength of nominally flat NW. At the nanoscale, the interfacial shear strength is often determined without considering the uncertainty in the contact condition. The contact between flat surfaces is particularly obscure because of their atomic-level irregularities. This study conducts molecular dynamics simulations to investigate the contact condition between nominally flat surfaces. Simulations using nanowires with flat and rough surfaces are conducted to assess the interfacial shear strength involved with the contact condition. The simulation result shows that the interfacial shear strength of the nanowire with a flat surface is 1.9 MPa. Although a rough nanowire has a much smaller real contact area than the flat nanowire, the rough nanowire exhibits similar frictional force and much greater shear strength (22.8 MPa) compared to the flat nanowire. The distance between the nanowire and the substrate is examined to reveal the mechanism, and the rough nanowire showed a shorter distance than the flat nanowire. The shorter distance is attributed to the concentrated normal force at the contact junction and causes a high frictional force per contact area because of its larger potential energy barrier. The interfacial shear strength can feasibly be underestimated for a nominally flat-facet nanowire. [ABSTRACT FROM AUTHOR]

The cohesive zone in the blast furnace is largely affected by the softening and melting behaviors of ferrous burden. The Visual High Temperature Method (VHTM) has been employed, in present work, to explore the softening and melting behavior of sinter, two different types of lump ores, and one acid pellet. All iron bearing materials are observed to swell before they shrink. This observation is more dominant in case of dense structured lump ore B. The shrinking temperature intervals are different from one another. This contributes to the gas permeability of ore layer in the cohesive zone because "ore window" is formed. In addition to this, the softening and melting behavior of mixed burdens (consist of sinter and other acid materials) have also been studied. Results display that the softening and melting behavior of all materials are improved. This observation is more dominant for lump ore A. It is attributed to high temperature interactions between sinter and acid iron bearing materials. The high temperature interactivity is largely influenced by the chemical compositions, pore structure, and contact condition. Experimental results of two groups of integrated burdens verify the importance of high temperature interaction for improving the softening and melting characteristics of iron bearing materials. Visual high temperature method is used to study the softening and melting behaviors of single and mixed materials. Results show that softening and melting behaviors are different, which contributes to the gas permeability of ore layer in the cohesive zone. High temperature interaction between sinter and acid materials helps to improve the softening and melting characteristics of burdens. [ABSTRACT FROM AUTHOR]

In diesel soot oxidation studies, both well-defined model soot and a reliable means to simulate realistic contact conditions with catalysts are crucial. This study is the first attempt in the field to establish a lab-scale continuous flame soot deposition method in simulating the “contact condition” of soot and a structured diesel particulate filter (DPF) catalyst. The properties of this flame soot were examined by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM) for structure analysis, Brunauer-Emmett-Teller (BET) for surface area analysis, and thermogravimetric analysis (TGA) for reactivity and kinetics analysis. For validation purposes, catalytic oxidation of Tiki® soot using the simulated contact condition was conducted to compare with the diesel particulates collected from a real diesel engine exhaust system. It was found that the flame soot is more uniform and controllable than similar samples of collected diesel particulates. The change in T50 due to the presence of the catalyst is very similar in both cases, implying that the flame deposit method is able to produce comparably realistic contact conditions to that resulting from the real exhaust system. Comparing against the expensive engine testing, this novel method allows researchers to quickly set up a procedure in the laboratory scale to reveal the catalytic soot oxidation properties in a comparable loose contact condition. [ABSTRACT FROM AUTHOR]