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This paper gives a short overview on our recent investigations towards a multiscale modeling and simulation framework for metal-CNT interfaces. We employ three simulation approaches with well defined interfaces. For the simulation at device level we make use of a recently developed wave-function based effective-mass Schrodinger-Poisson solver which employs a hetero-junction like contact model to capture the physics in the contact region where the CNT is embedded into metal. The required model parameters are adjusted to TB and DFT simulation results. A comparison with experimental data for a short channel device shows the applicability of the proposed approach.

Development of equations to compute the steady-state temperatures of the contact region between a bus-bar and substation equipment is presented. The computation relies on solving a system of (nonlinear) equations, and the iterative process consists of suitable modification of some coefficients of proportionality, which control the unknown heat transfers. The processing will finish when the computed boundary temperatures achieve the initial ones, previously obtained by other computations or measurements. The computation was verified, performing it first for a given arrangement and measuring the practical values. Also, a succession of investigating computations was performed. Results are insensitive to "complementary" (i.e., internal-external, unmediated-mediated, etc.) changes of these coefficients. The coefficients influence only the adjacent temperatures; for example, increase that of the central region adjacent to them, and decrease that of the lateral neighbor region. Other analysis showed that for the...

A technique of pendant drop melt extraction (PDME) is reported and certain results describing thin stainless steel fibers obtained by means of PDME were studied. Adhesion interaction between metal melt and disc-crystallizer was also considered. The adhesion work was established to be approximately 1–2 J/m2. It was shown that melt adhesion to the disc-crystallizer is determined both by physical interaction and chemical processes in contact region.

A scheme of boundary element method for moving contact of two-dimensional elastic bodies using conforming discretization is presented. Both the displacement and the traction boundary conditions are satisfied on the contacting region in the sense of discretization. An algorithm to deal with the moving of the contact boundary on a larger possible contact region is presented. The algorithm is generalized to rolling contact problem as well. Some numerical examples of moving and rolling contact of 2D elastic bodies with or without friction, including the bodies with a hole-type defect, are given to show the effectiveness and the accuracy of the presented schemes.

Previous theoretical predictions of the transition velocity of solid armatures based on the velocity skin-effect (VSE) usually assume that adequate rail/armature contact pressure exists at the rear armature surface. It has also been shown that the rear angle (/spl phi/) of a triangular armature contact region should be minimized but that for /spl phi/ 10 mm and for values of /spl phi/ from 12/spl deg/ to 90/spl deg/. It is shown that the absence of adequate contact pressure at the rear armature surface results in significant reductions in the transition velocity in reasonable agreement with experimental results reported previously. An armature concept to overcome these reductions in transition velocity is discussed in which the rear armature contact regions (with /spl phi/

The problem of a punch shaped like an elliptic paraboloid pressed into an elastic plate is studied under the assumption that the contact region is small. The action of the punch on the plate is modeled by point forces and moments. The method of joined asymptotic expansions is used to formulate the problem of one–sided contact for the internal asymptotic representation; the problem is solved with the use of the results obtained by L. A. Galin. The coordinates of the center of the elliptic contact region, its dimensions, and the angle of rotation are determined. The moments which ensure translational indentation of the punch are calculated and an equation that relates displacements of the punch to the force acting on it is given.

We show that, in a nanometric size stable electrodeposited Ni contact, it is possible to modify the magnetoresistance by applying current pulses and external magnetic fields whereby the same current path is used for detection and modification. We can pass from positive to negative magnetoresistance with values as large as 25% at room temperature, all in the same contact. We propose that the effect may be due to switching and moving domain walls in the contact region under the combination of current effects and external fields.

Fur die elastische Scheibe werden die vollen Integralgleichungen des Kontaktproblems aufgestellt. Mit Hilfe der Methode des Riemannschen Randwertproblems erhalt man die exakte Losung fur den Fall mit vollkommenem Haften und fur die Einteilung der Beruhrungsflache in ein Haftgebiet und ein Gleitgebiet. In Anlehnung an die Frommsche Theorie zur Abhangigkeit der Losung vom Belastungsverlauf werden einige wichtige Anwendungen fur gebremste Scheiben behandelt. The exact integral equations of the contact problem for the elastic disk are represented. The exact solutions in case of rigid adhesion and for the division of the contact region for one adhesion zone and one sliding zone are obtained by the method of the Riemannian boundary value problem. A number of important applications for the deterred disk are treated, based on Fromm's theory about the dependence of the solution on the load history.

The lattice parameters of the crystalline scheelite phases prepared by mechanochemical synthesis in M’O-MO3 systems were determined by x-ray diffraction. Analysis of x-ray intensities showed that all of the synthesized materials were deficient in the harder constituent. The M’/M atomic ratio was found to correlate well (r = 0.91) with the relative difference in Mohs’ hardness between the constituent oxides. The structural data obtained on the products of mechanochemical synthesis after ∼102 impacts agree with theoretical predictions for the first impact, according to which mass transfer is due to rolls forming in the contact region between colliding particles, and the product of mechanochemical synthesis is the result of relaxation in a layer of rolls and voids in the process of rapid quenching under negative pressure. Estimates show that, on account of the low temperature in the contact region, the rate of mass transfer by rolls is about 3 orders of magnitude faster than that of diffusive transfer, even though the latter is favored by the deformation intermixing and high vacancy concentration (2 to 3 orders of magnitude higher than that in melts). The termcold melting is in full measure applicable to the mechanochemical processes in question

We use mid-infrared (MIR) spectroscopy to investigate the contact region at the Nb/InAs superconductor/semiconductor interface. We observe a remnant of the intersubband (ISB) resonance in Nb-clad InAs quantum wells, both in samples where we have grown Nb directly on InAs in situ, and samples where we have etch exposed the InAs surface before depositing the Nb. The presence of this remnant ISB indicates partial confinement of the electrons to the InAs. The similar resonance widths in the MBE grown Nb/InAs sample and the samples with Nb on etched InAs suggest that coupling of electron states in the InAs to those in Nb, rather than etch-induced damage, produces most of the resonance broadening.

The finite element method (FEM) has been used widely in tire engineering. Most tire simulations with FEM are static analysis, because tire is one of most complex structures. Recently, transient analysis has been studied with explicit finite element analysis code. In this paper, at first, we describe characteristics of tire analysis by means of FEM, and implicit/explicit finite element codes for analysis. And then we conduct tire cornering simulation with implicit and explicit finite element analysis codes, where implicit finite element analysis (FEA) describes the steady state cornering simulation and explicit FEA describes transient cornering simulation. In the case of implicit FEA, finite element model of tire requires the fine mesh only in the contact region because of formulation by moving reference frame technique. On the other hand, for explicit FEA, fine mesh is required in the circumferential direction of tire. Predicted cornering forces of passenger car's tire using implicit/explicit FEM are compared with experimental results obtained from MTS Flat-Test Tire Test Systems. We can get a good correlation between predicted ones and experimental ones. CPU time for cornering simulation using implicit FEM is shorter than that of explicit FEM. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1566–1572, 2000

The theory of normal contact of rigid bodies with allowance for Coulomb friction is developed. The Boussinesq principle is generalized to contact problems with friction.

The following problem is considered: a punch, disk-shaped in plan, whose base is an almost circular elliptical paraboloid, is pressed onto the boundary of an elastic half-space. The friction between the bodies in contact is ignored; the punch edges are allowed to separate from the elastic base. It is assumed that the contact region, which is not known a priori, is almost circular. The solution of the problem is constructed by the method of matched asymptotic expansions. The asymptotic form of the boundary of the contact region is presented in explicit form.

Mechanical Properties of Chalk with Emphasis on Chalk-Fluid Interactions and Micro- mechanical Aspects — The paper addresses the problem of water weakening effects in chalk. Using miscible fluids, capillary forces can be eliminated. Experience with water and methanol has revealed that methanol saturated chalk is considerably stronger than water saturated chalk. A study of water-methanol mixtures has shown that the transition is a gradual one, only dependent on the composition of the fluid. The changes in mechanical properties can be accounted for by repulsive forces at the grain contacts. The strong interaction between the highly polar water molecules and the chalk surface may give rise to charged or polarized layers which will develop repulsive forces when two surfaces are in close contact, like in the grain contact region.

This work examines the impact of the interaction between low cycle and high cycle fatigue load spectra on the near-surface stress field associated with conditions of fretting fatigue in the context of a multiaxial fatigue life parameter. Particular focus is placed on analysis of the edge of contact region identified routinely as the site of fretting-induced fatigue damage. Effects of low-cycle fatigue (LCF)—high cycle fatigue (HCF) interaction on the extent of stick and slip are analysed in detail for contacts involving a common titanium engine alloy, Ti–6Al–4V. The effects that this LCF/HCF interaction have on the nucleation of fretting fatigue cracks are then analysed, leading to the subsequent establishment of a relationship between number of LCF cycles to failure and relative HCF frequency and amplitude.

Plane steady contact problems of a rigid insulated cylinder sliding over a thermoelastic layer is solved. The heat generation in the contact region is caused by friction forces. The problem is investigated by the method of integral equations. An exponential series approximation is used for the evaluation of the kernels of integral equations. Numerical results are presented in diagrams.

Recent studies show that pseudo-elastic TiNi alloy exhibits high resistance to wear, compared to many conventional wear-resistant materials. It is demonstrated that hardness is not crucial to the wear resistance of this alloy, since its hardness is lower than those of conventional wear-resistant materials. In order to understand the excellent wear behaviour of TiNi alloy and determine the factors responsible for wear resistance of the alloy, the performance of Ti–50.3 at.% Ni alloy during a dry sliding wear process was investigated and compared to a 2Cr13 steel. It was demonstrated that the TiNi alloy performed much better than the 2Cr13 steel, although the latter has a higher hardness. It is expected that the high wear resistance of TiNi alloy is attributable to its special mechanical behaviour, in particular its so-called pseudo-elasticity, caused by reversible martensitic transformation. Mechanical and thermal properties of Ti–50.3 at.% Ni alloy were studied and a FEM analysis was made to investigate the plastic strain in the contact region and to correlate the wear behaviour of TiNi alloy to its pseudo-elastic and thermal properties that are influenced by the martensitic transformation.

The total dose effects of 60 Co γ-radiation on the electrical properties of double-barrier Resonant Tunneling Diodes have been studied. The devices manifest enhanced radiation hardness and conserve their operating parameters up to doses of 2〈10 9 rad. It is shown that all changes in the current-voltage characteristics stem from the effect of ionizing radiation on the undoped lay- ers. The radiation-stimulated diffusion of the heteropair components in the contact region is shown to be important for the voltage drop distribution.

Flat-ended or wedge-shaped rigid punch problem is considered in this paper. The punch is with one end sliding and the other end with a sharp corner coming into a half-plane. The model of the punch is that the flat-end punch is inclined by an angle e or the wedge-shaped punch with e is pushed vertically. A crack is assumed to be initiated from the end with the corner, and Coulomb's frictional force exists on the contact region. The general solution of the problem is derived in an analytical way, and the relation among the vertical load on the punch, rotating angle of the punch, and the contact length is found. Stress intensity factors of the edge crack are calculated in different cases. The resultant moments at the origin of the coordinates are also calculated, which can be used to decide the position of the vertical force on the punch.

Part 1 of this paper\[1] reviewed the modeling approaches and correlations used to study the interface heat transfer phenomena of the roll-strip contact region in rolling processes. The thermal contact conductance approach was recommended for modeling the interface phenomena. To illustrate, the recommended approach and selected correlations are adopted in the present study for modeling of the roll-strip interface region. The specific values of the parameters used to correlate the corresponding thermal contact conductance for the typical cold and hot rolling of steels are first estimated. The influence of thermal contact resistance on the temperature distributions of the roll and strip is then studied. Comparing the present simulation results with previously published experimental and analytical results shows that the thermal contact conductance approach and numerical models used can reliably simulate the heat transfer behavior of the rolling process.

In this paper, a two-dimensional contact problem of two dissimilar anisotropic elastic bodies is studied. The shapes of the boundaries of these two elastic bodies have been assumed to be approximately straight, but the contact region is not necessary to be small and the contact surface can be nonsmooth. Base upon these assumptions, three different boundary conditions are considered and solved. They are: the contact in the presence of friction, the contact in the absence of friction, and the contact in complete adhesion. By applying the Stroh’s formalism for anisotropic elasticity and the method of analytical continuation for complex function manipulation, general solutions satisfying these different boundary conditions are obtained in analytical forms. When one of the elastic bodies is rigid and the boundary shape of the other elastic body is considered to be fiat, the reduced solutions can be proved to be identical to those presented in the literature for the problems of rigid punches indenting into (or sliding along) the anisotropic elastic halfplane. For the purpose of illustration, examples are also given when the shapes of the boundaries of the elastic bodies are approximated by the parabolic curves.

Transparency of the tribological process by sensory and audio-visual process recording. By multi-media recording of the friction event the elementary contact processes get transparent so that damage causes can be recognized. For this additional to the usual tribological readings audio-visual information were time synchronously gathered. By use of thin integrated sensors temperature or pressure is measured continuously with high local resolution during the friction process inside the contact region. The damage mechanisms are analysed systematically and make influence measures possible to coating optimization to exclude an early failure of a tribological system.

A solution is obtained for a contact problem concerning the tension of a rectangular elastic plate with a circular hole into which a rigid stationary pin has been inserted. There is a small gap between the hole and the pin, which is of circular cross section. Friction acts in the contact region in accordance with the Coulomb law. The finite-element method and the Boussinesq principle are used to determine the load that realizes a specified contact region. Two variants of boundary conditions on the contour of the hole are examined.

The authors present the results of eigenstructure analyses of the dy namics of several manipulator and environment configurations and discuss the implications for successful force controller design. The manipulator configurations considered include single rigid link, sin gle flexible link, two rigid links, and two flexible links. In all cases, the tip of the manipulator is in contact with a deformable environ ment. Particular emphasis is placed on the interaction between the structural stiffness of the manipulator link and the stiffnesses of the contacting regions of the manipulator tip and the environ ment. It is shown that, for given link parameters, this interaction results in distinct changes in the modal structure of the manipula tor/environment system as the effective contact stiffness increases. In particular, the contact force response is dominated by a single mode for a given effective contact stiffness, whereas the control inputs excite all modes except those associated with the contact region vibration. The changes in the modal structure of the manip ulator/environment system predicted by the eigenstructure analysis are verified by experiment for the single flexible link configuration.

Summary Purpose . In this study the temporal texture differentia tion associated with the bone formation properties, around loaded oral implants after Platelet Rich Plasma (PRP) employment, was investigated in Panoramic Radi ographs. Materials and methods . Thirty eligible patients are ran domly assigned to two groups. The test group received PRP application around new implants, while in the con trol group no PRP treatment was made. The bone-to-im plant contact region was analyzed in a clinical sample of 60 Digitized Panoramic Radiographs, 30 corresponding to immediate implant loading (Class-I) and 30 after an 8 month follow-up period (Class-II). This region was sam pled by 1146 circular Regions-of-Interest (ROIs), result ing from a specifically designed segmentation scheme based on Markov-Random-Fields (MRF). From each ROI, 41 textural features were extracted, then reduced to a subset of 4 features due to redundancy and employed as input to Receiver-Operating-Characteristic (ROC) analy sis, to assess the textural differentiation between two classes. Results . The selected subset, achieved Area-UnderCurve (AUC) values ranging from 0.77-0.81 in the PRP group, indicating the significant temporal textural differ entiation has been made. In the control group, the AUC values ranged from 0.56-0.68 demonstrating lesser os seo integration activity. Conclusion . This study provides evidences that PRP ap plication may favor bone formation around loaded dental implants that could modify the dental treatment plan ning.

The focus of this work is on back contact improvement for sputtered CZTS thin film solar cells. Three methods have been investigated including a thin Ag coating, a thin ZnO coating on the Mo back contact and rapid thermal annealing of the back contact. All of these methods have been found to reduce defects such as voids as well as secondary phases at the back contact region and inhibit the formation of MoS2. Consequently all the mothods effectively enhances Voc, Jsc, FF and therefore efficiency significantly.

We introduce the vision-based tactile sensor, which can acquire multimodal tactile information including the contact force, slippage, shape, the contact region, and the location of an object. The sensor consists of a charge-coupled device (CCD) camera with red-green-blue channels, LED lights, a transparent acrylic plate, and a deformable touchpad. Since the touchpad is deformed by contact with the object, the analysis of the deformation yields tactile information, where we successfully use the image of the inside of the deformed touchpad captured by the CCD camera. The validation of the proposed method is confirmed through experimental results.

Spherical-tipped locators and clamps are often used for the restraint of workpieces within machining centres. For structurally rigid fixtures and workpieces, contact region deformation, slip, and lift-off are the predominant modes of workpiece displacement. Experimental evidence obtained thus far indicates that this displacement can be severe during clamping. In addition it can be a significant source of geometric error. However this error can be reduced significantly through tool path compensation. This paper describes two different techniques that can be used to determine workpiece displacement during clamping. The first applies eddy current displacement sensors to measure workpiece displacement online. The second applies an analytical model to predict workpiece displacement during clamp actuation. This paper also shows how workpiece displacement data can be used to compensate tool paths prior to machining. Lastly this paper describes an experimental study used to validate both techniques.

Implicit finite element analysis of sheet-forming operations depends on the ability to find a converged solution, which is frequently difficult because of changing contact and friction conditions at arbitrarily shaped interfaces. This sensitivity is aggravated when draw-in is significant, when the well angle is large, and when the contact region or character changes rapidly (during re-draw, for example). A new algorithm has been developed based on the mesh normal and using a consistent full set (N-CFS) of equations, including equilibrium and contact conditions in the non-linear set. The “N-CFS” algorithm exhibits remarkable stability and strong convergence. In fact, we have not found a well-posed problem, i.e. one which is physically stable within the discrete numerical framework, which exhibits numerical instability. The N-CFS algorithm is presented and several challenging example problems are solved, illustrating the robustness of the new method relative to standard implicit formulations. A series of smaller improvements for implicit methods are also outlined.

A direct optimization method for contact problems is shown that uses separate corrective force vectors for equilibrium and compatability. The geometric mediation across the contact region is accomplished by defining virtual nodes and elements. Integrations required on each contact surface are carried on a virtual mesh that reflects the mesh of the body for which forces are required. Examples demonstrate that the method is accurate and robust.

Three-dimensional stress-freezing photoelasticity is applied to analyse the stress in a variable-pitch lead screw at contact with two conical meshing elements. A PC-based image-processing system and the relevant digital techniques are used to collect the photoelastic data, and the cubic technique is used to evaluate the effective stress at the contact region. The model-making and computer aided data collection procedures are described. Contour plots of the effective stress at the contact regions are presented. It was found that the highest effective stress values on the two contact thread surfaces are approximately the same, although the exerting forces are quite different.

On the basis of the two-dimensional numerical solution of quasi-hydrodynamic equations for a semiconductor plasma the avalanche injection current filamentation is studied in GaAs n + -i-n + , n + -p-n + and n + -n-n + structures. It is demonstrated that a lengthy n + -contact region in these structures provides the spontaneous formation of multiple current filaments. Effect of structural parameters and dependence upon current are studied. Formation of multiple filaments is explained by a distinction between a small spatial parameter of instability (due to avalanche-injection modulation of the i-region conductivity) and a large spatial parameter of current damping (due to current spreading in the lengthy n + -contact region).

Previous theoretical predictions of the transition velocity of solid armatures based on the velocity skin-effect (VSE) usually assume a fixed geometry and that adequate rail/armature contact pressure exists. In this paper the effect of contact region geometry on the transition velocity is investigated and the optimum geometry derived. The critical geometrical parameters are considered to be the contact region angle /spl phi/ and rear radial depth. These parameters need to be as small as possible to maximise the transition velocity but large enough to maintain sufficient contact pressure to avoid the early initiation of a current wave which would reduce the transition velocity. Comparison of predicted and experimental results for 15 to 90 mm aluminium alloy armatures shows reasonable agreement. It is considered that the VSE is the dominant mechanism limiting the transition velocity of solid armatures provided their contact region geometry and structural design is such that adequate contact pressure is maintained.

International audience; Via a novel experiment, Liu et al. [Phys. Rev. B 85, 205418 (2012)] estimated the graphite binding energy, specifically the cleavage energy, an important physical property of bulk graphite. We reexamine the data analysis and note that within the standard Lennard-Jones model employed, there are difficulties in achieving internal consistency in the reproduction of the graphite elastic properties. By employing similar models which guarantee consistency with the elastic constant, we find a wide range of model dependent binding energy values from the same experimental data. We attribute some of the difficulties in the determination of the binding energy to: (i) limited theoretical understanding of the van der Waals dispersion of graphite cleavage, (ii) the mis-match between the strong bending stiffness of the graphite-SiO2 cantilever and the weak asymptotic inter-layer forces that are integrated over to produce the binding energy. We find, however, that the data do support determination of a maximum inter-layer force that is relatively model independent. We conclude that the peak force per unit area is 1.1 +/- 0.15 GPa for cleavage, and occurs at an inter-layer spacing of 0.377 +/- 0.013 nm.

Unexpectedly, under certain conditions, sessile drops from different but completely miscible liquids do not always coalesce instantaneously upon contact: the drop bodies remain separated in a temporary state of noncoalescence, connected through a thin liquid bridge. Here we investigate the transition between the states of instantaneous coalescence and temporary noncoalescence. Experiments reveal that it is barely influenced by viscosities and absolute surface tensions. The main system control parameters for the transition are the arithmetic means of the three-phase angles, $\overline{\Theta}_a$ and the surface tension differences $\Delta\gamma$ between both liquids. These relevant parameters can be combined into a single system parameter, a speciffic Marangoni number $\widetilde{M} = 3\Delta\gamma / (2\overline{\gamma}\overline{\Theta}_a^2)$. This $\widetilde{M}$ universally characterizes the coalescence respectively transition behavior as a function of both, the physicochemical liquid properties and the shape of the liquid body in the contact region. The transition occurs at a certain threshold value $\widetilde{M}_t$ and is sharp within the experimental resolution. The experimentally observed threshold value of $\widetilde{M}_t \approx 2$ agrees quantitatively with values obtained by simulations assuming authentic real space data. The simulations indicate that the absolute value of $\widetilde{M}_t$ very weakly depends on the molecular diffusivity., Comment: 9 pages, 6 figures

The coupled dynamic response of two cooperating robots handling two flexible payloads is treated using a new algorithm. In this algorithm, the dynamic equations describing the system are obtained using Lagrange's method for the rigid robot links and the finite element method for the flexible payloads. The contact between the flexible payloads is modelled using the penalty function method and a contact search algorithm is employed to identify the contact region.

Exploratory test results are presented for a series of mixtures of unexcited electrorheological (ER) fluids under elastohydrodynamic lubrication (ehl) conditions. These were obtained from direct observation of film formation in an optical interferometric apparatus. Results are presented as photographs of the fluid film and plots of film thickness versus speed for a range of ER fluid solid fractions. Adequate film formation is limited by the tendency of the solid particles to evade the contact region. At very low contact speeds particles enter the chl contact and generate a fluid film. At higher speeds the particulates do not become entrained in the contact; the film formation is then determined by the viscosity of the base fluid.

Spherical-tipped locators and clamps are often used for the restraint of workpieces during machining. For structurally rigid fixtures and workpieces, contact region deformation, slip, and lift-off are the predominant modes of workpiece displacement during clamp actuation and machining. This paper presents a general model for the quasi-static analysis of workpiece displacement. It also shows how meta functions can be applied to simplify the modeling of contact forces. Through the use of meta functions, the general model can be formulated and solved quickly. This paper concludes with a description of an experimental study used to validate this model.

The paper describes experiments on a metal ball rolled along parallel metal rails. An electrical force is developed on the ball in the direction of movement by passing current through it from one rail to the other. Contrary to the electromagnetic theory of the ball-bearing motor, the electrical force on a brass ball is of the same order as that on a steel ball. The results are discussed in terms of a torque exerted in the contact region.

This paper concerns the steady state roll contact between elastic cylinder and rigid plane with modified Coulomb's law of friction. A three-dimensional contact algorithm with the help of the finite element method is used for this problem. The stresses on the contact surface are displayed graphically. From the results we know that the friction will influence the distribution of pressure on the contact area and the contact region may be divided into multiphase stick-slip zones.

We use ab initio density-functional calculations to determine the interaction of a graphene monolayer with the Si(111) surface. We find that graphene forms strong bonds to the bare substrate and accommodates the 12% lattice mismatch by forming a wavy structure consisting of free-standing conductive ridges that are connected by ribbon-shaped regions of graphene, which bond covalently to the substrate. We perform quantum transport calculations for different geometries to study changes in the transport properties of graphene introduced by the wavy structure and bonding to the Si substrate. Our results suggest that wavy graphene combines high mobility along the ridges with efficient carrier injection into Si in the contact regions. DOI: 10.1103/PhysRevLett.110.176805

Delamination is the most harmful type of wear of hard coatings in practical use. It is generated even by a single action of indentation of a harder pin into the coating. Cracks of ring, radial and/or lateral types are generated around the contact region of the coating, and partial or general delamination of coating is induced depending on the contact conditions.

Experiments were performed to enable the development of a new theoretical model for the enhancement in CHF commonly observed with flow boiling on concave heaters as compared to straight heaters. High-speed video imaging and photomicrography were employed to capture the trigger mechanism for CHF for each type of heater. A wavy vapor layer was observed to engulf the heater surface in each case, permitting liquid access to the surface only in regions where depressions (troughs) in the liquid–vapor interface made contact with the surface. CHF in each case occurred when the pressure force exerted upon the wavy vapor–liquid interface in the contact regions could no longer overcome the momentum of the vapor produced in these regions. Shorter interfacial wavelengths with greater curvature were measured on the curved heater than on the straight heater, promoting a greater pressure force on the wavy interface and a corresponding increase in CHF for the curved heater. A theoretical CHF model is developed from these observations, based upon a new theory for hydrodynamic instability along a curved interface. CHF data are predicted with good accuracy for both heaters.

This study investigates the contact stresses in single-fastener mechanical joints in composite laminates with finite boundaries subjected to combined bearing-bypass and shear loading. The bearing stresses and the contact region are determined by imposing the appropriate mixed boundary conditions along the boundary of the hole. No-slip and slip zones of the contact region arising from the presence of friction are obtained as part of the analysis. A boundary collocation method, in conjunction with a complex variable formulation of the solution for anisotropic laminates, is utilized in the analysis.

The purpose of this study was to elucidate the interocclusal clearance between opposing upper and lower molars on the working side during lateral excursions. Three-dimensional scannings were made of both the shape of occlusal surfaces and jaw movements, and the data of the occlusal shape of the upper first molar was used to divide the tooth into 6 sections on the computer. The analytic parameters employed are the area of the region on the sections of the upper first molar, where the distance from its counterpart was equal to less than 0.3 mm (contact region) and 1.0mm (near contact region) in the intercuspal position and the four lateral positions. The aspect of changes of two regions was observed for the different sections.The results were as follows As the mesio-palatal section of the upper molar became separated from its counterpart more rapidly than any other section, the closing space, which opens in the mesio-palatal direction, was found between the opposing upper and lower molars on the working side during lateral movement. This is called the Squeezing Room and it is considered to be a place for crushing and compressing the food during mastication, and controls the flow of food on the occlusal surface.