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

The classical adhesive contact models belong to isothermal adhesion theories, where the effect of temperature on adhesion was neglected. However, a number of experimental results indicated that the adhesion behaviors can be significantly affected by temperature. In this paper, the two-dimensional non-slipping anisothermal adhesion behaviors between two orthotropic elastic cylinders are investigated within the framework of the Johnson–Kendall–Roberts theory. The stated problem is reduced to the coupled singular integral equations by virtue of the Fourier integral transform, which are solved analytically with the analytical function theory. The closed-form solutions for the stress fields in the presence of thermoelastic effect are obtained. The stable equilibrium state of contact system is determined by virtue of the Griffith energy balance. The effect of temperature difference on adhesion behaviors between orthotropic solids is discussed. It is found that the difference between the oscillatory and non-oscillatory solutions increases with increasing the degree of anisotropy of orthotropic materials. The oscillatory solution cannot be well approximated by the non-oscillatory solution for the orthotropic materials with relatively high anisotropy. [ABSTRACT FROM AUTHOR]

This paper developed a finite element model based on the Derjaguin approximation and the Lennard–Jones potential to describe a single loading-remaining-unloading cycle of adhesive contact in elastoplastic and viscoelastic media. The effects of tangent modulus, the Prony coefficient, and the times on the adhesive contact behaviors were examined. Some complicated phenomena on rate-dependent adhesion in viscoelastic media and history-dependent adhesion in elastoplastic media were understood. The simulation results showed that both the pull-off force and final central gap were negatively correlated with tangent modulus while positively with the Prony coefficient; the pull-off force and the final central gap synchronously rose as the loading time or the remaining time increased; the effect of the remaining time on the pull-off force is stronger than the loading time. [ABSTRACT FROM AUTHOR]

Contact behaviors of medical devices, such as guidewires and catheters, are critical in endovascular surgeries. In this work, a new method to predict adhesive contact force between catheter and vascular artery is presented. Multi-asperity adhesion on the surface of vascular artery, deformation of asperity and deformation of vascular substrate are all considered. The single asperity behavior is described with Johnson-Kendall-Roberts (JKR) contact model. The multi-asperity behavior is based on Greenwood–Williamson (GW) asperity model. Vascular substrate is considered as elastic bulk substrate and its deformation is determined with Hertzian pressure from asperity on a circular region on the elastic half space. The model shows that the deformation of vascular substrate accounts for the majority of the total contact deformation and significantly affects the predicted contact force. The model is verified with published experimental data. The comparison shows that the model produces very accurate prediction of contact force between catheter and vascular artery when the contact force is compressive. Parametric analysis based on asperity topography is carried out. The analysis shows that the diameter of the circular region of the interface between asperity and vascular substrate has more significant effect on the estimation of contact force than the radius of asperity. Further validation of prediction accuracy of the model under experiment is needed. [ABSTRACT FROM AUTHOR]

This paper develops the adhesive contact theory for a one-dimensional hexagonal quasicrystal half-space punched by a spherical indenter on the basis of the classical adhesive contact models involving the Johnson–Kendall–Roberts (JKR) model, the Maugis–Dugdale (MD) model and the Derjaguin–Muller–Toporov (DMT) model. By using the superposition principle combined with the Griffith energy balance, all the significant physical quantities for adhesive contact, such as the energy release rate, indentation force, penetration depth, contact radius and pull-out force, are obtained for different models. The result for the DMT model is derived from the MD solution through a limiting procedure. A numerical calculation is carried out to verify the present analytical solutions, to compare different contact models, and to analyze the influence of the phason field on the results. It is indicated that the effect of the phason field on the result for the MD model is pronounced, especially for a small contact radius. However, the phason effect on the JKR and DMT results is not significant. The present solution can serve as a theoretical basis for nano-indentation and atomic force microscopy to measure the material properties of quasicrystals. [ABSTRACT FROM AUTHOR]

The bearing behavior of suction caissons supporting offshore wind turbines under two-way cyclic lateral loading and dead load in clay was investigated with consideration of soil strength degradation and adhesive interface friction between caisson walls and heterogeneous clay using the finite-element package ABAQUS. An ABAQUS built-in user subroutine was programmed to calculate the adhesive interface friction between clay and caisson walls. The results of parametric studies showed that the degradation of bearing capacity could be aggravated by the decrease of the aspect ratio. The offset between the rotation point of the soil inside the caisson and the central axis of the caisson increased with the increasing vertical load and number of cycles. The linearly increasing strength profile and adhesive interface led to the formation of an inverted spoon failure zone inside the caisson. The settlement-rotation curves in each cycle moved downwards with increasing number of cycles due to the soil strength degradation. [ABSTRACT FROM AUTHOR]

In the paper, we consider the tangential contact of single microasperities of the interacting surfaces the mechanical characteristics of which are close to the characteristics of typical rail steels. Using computer simulation by the method of discrete elements, we study the influence of the parameters of adhesive interaction of both external and internal surfaces on the regime of wear of asperities. It has been established that with increasing adhesion work, the wear regime changes from slipping (low wear) to grinding or brittle fracture of asperities (high wear), and this change is of threshold nature. An empirical sigmoid dependence of the location of the boundary between the two wear regimes (namely, the threshold value of the adhesive stress) on the value of the material hardening coefficient has been established. It is shown that the logistic nature of this dependence is due to the competition of two mechanisms of elastic strain energy dissipation, which determine the wear regime. These are plastic deformation and adhesion of the contacting surfaces. Special discussion is devoted to the influence of the scale factor on the threshold values of the mechanical characteristics of the material which provide the change of the wear regime. [ABSTRACT FROM AUTHOR]

The problem of multiple adhesive contact is considered for an elastic substrate modeled as a transversely isotropic elastic half-space. It is assumed that a large number of the Kendall-type microcontacts are formed between the substrate and circular rigid (i.e., nondeformable) and frictionless micropads, which are interconnected between themselves, thereby establishing a load sharing. The effect of microcontacts interaction is accounted for in the formulation of the detachment criterion for each individual microcontact. A number of different asymptotic models are presented for the case of dilute clusters of microcontacts with their accuracy tested against a special case of two-spot contact, for which an analytical solution is available. The pull-off force has been estimated and the effects of the array size and the microcontact spacing are studied. It is shown that the flexibility of the micropads fixation, which is similar to that observed in mushroom-shaped fibrils, significantly increases the pull-off force. The novelty of the presented approach is its ability to separate different effects in the multi-scale contact problem, which allows one to distinguish between different mathematical models developed for bioinspired fibrillar adhesives. [ABSTRACT FROM AUTHOR]

For compliant adhesive contact problems based on the Lennard-Jones potential, the non-convexity of the latter leads to jump-in and jump-off instabilities which can hardly be traced by using classical algorithms. In this work, we combine an adapted Asymptotic Numerical Method (ANM) and the multiscale Arlequin method to trace efficiently these instabilities. The ANM is used to trace the entire unstable solution path in a branch-by-branch manner. The Arlequin method is used to achieve a refined resolution in the vicinity of the contact surface and to reduce possible spurious numerical oscillations due to coarse surface discretizations. Numerical results, validated by comparison with available ones, reveal the accuracy, efficiency and robustness of the proposed global methodology. [ABSTRACT FROM AUTHOR]

The surface micro-interaction model of Lennard-Jones (LJ) is used for adhesive contact problems (ACP). To address theoretical and numerical pitfalls of this model, a sequence of partitions of contact models is adaptively constructed to both extend and approximate the LJ model. It is formed by a combination of the LJ model with a sequence of shifted-Signorini (or, alternatively, -Linearized-LJ) models, indexed by a shift parameter field. For each model of this sequence, a weak formulation of the associated local ACP is developed. To track critical localized adhesive areas, a two-step strategy is developed: firstly, a macroscopic frictionless (as first approach) linear-elastic contact problem is solved once to detect contact separation zones. Secondly, at each shift-adaptive iteration, a micro-macro ACP is re-formulated and solved within the multiscale Arlequin framework, with significant reduction of computational costs. Comparison of our results with available analytical and numerical solutions shows the effectiveness of our global strategy. [ABSTRACT FROM AUTHOR]

An analytical approach has been presented to analyze the asymmetric and axisymmetric interactions between an annular crack and a rigid disc inclusion embedded in a transversely isotropic full-space. With the aid of a method of potential functions, Hankel and Abel transforms, the solution of the problems is reduced to a system of Fredholm integral equations, which are solved by using a numerical method. In each case, the stiffness of the disc inclusion and the stress intensity factor at the tips of the annular crack for different degrees of material anisotropy and different ratios of the inner and outer radius of the crack are illustrated graphically. Several limiting cases such as penny-shaped crack and external crack along with some exact solutions are presented to demonstrate the efficiency of the method. [ABSTRACT FROM AUTHOR]

Recently proposed formulation of the boundary element method for adhesive contacts has been generalized for contacts of power-law graded materials with and without adhesion. Proceeding from the fundamental solution for single force acting on the surface of an elastic half space, first the influence matrix is obtained for a rectangular grid. The inverse problem for the calculation of required stress in the contact area from a known surface displacement is solved using the conjugate-gradient technique. For the transformation between the stresses and displacements, the Fast Fourier Transformation is used. For the adhesive contact of graded material, the detachment criterion based on the energy balance is proposed. The method is validated by comparison with known exact analytical solutions as well as by proving the independence of the mesh size and the grid orientation. [ABSTRACT FROM AUTHOR]

Adhesion has been demonstrated to play an important role in contact and friction between objects at small scales. While various models have been established for adhesive contact under normal forces, studies on the adhesive contact under tangential force have been far fewer, which if any, are mostly confined to the non-slipping situations. In the present work, a model has been proposed for adhesive contact with local sliding under tangential forces. Herein, the onset of local sliding in adhesive contact has been addressed by assuming the nucleation of dislocations. By analogy with the emission of dislocations at a crack tip, the critical tangential force for the onset of sliding has been determined, and its effect on the evolution of contact size has also been studied. Comparison with relevant experiments has verified the validity of the present model. [ABSTRACT FROM AUTHOR]

In this paper, the properties of carbon fibers before and after their gaseous oxidation are evaluated using the RAMAN spectroscopy and electron paramagnetic resonance. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) multiscale moving contact line model is combined with a soft matter cell model to study the universal dynamics of cell spreading over elastic substrates. We have studied both the early stage and the late stage cell spreading by taking into account the actin tension effect. In this work, the cell is modeled as an active nematic droplet, and the substrate is modeled as a St. Venant Kirchhoff elastic medium. A complete 3D simulation of cell spreading has been carried out. The simulation results show that the spreading area versus spreading time at different stages obeys specific power laws, which is in good agreement with experimental data and theoretical prediction reported in the literature. Moreover, the simulation results show that the substrate elasticity may affect force dipole distribution inside the cell. The advantage of this approach is that it combines the hydrodynamics of actin retrograde flow with moving contact line model so that it can naturally include actin tension effect resulting from actin polymerization and actomyosin contraction, and thus it might be capable of simulating complex cellular scale phenomenon, such as cell spreading or even crawling. [ABSTRACT FROM AUTHOR]

A new linear elastic and perfectly brittle interface model for mixed mode is presented and analysed. In this model, the interface is represented by a continuous distribution of springs which simulates the presence of a thin elastic layer. The constitutive law for the continuous distribution of normal and tangential initially-linear-elastic springs takes into account possible frictionless elastic contact between adherents once a portion of the interface is broken. A perfectly brittle failure criterion is employed for the springs, which enables the study of crack onset and propagation. This interface failure criterion takes into account the variation of the interface fracture toughness with the fracture mode mixity. A unified way to represent several phenomenological both energy and stress based failure criteria is introduced. A proof relating the energy release rate and tractions at an interface point (not necessarily a crack tip point) is introduced for this interface model by adapting Irwin's crack closure technique for the first time. The main advantages of the present interface model are its simplicity, robustness and computational efficiency, even in the presence of snap-back and snap-through instabilities, when the so-called sequentially linear (elastic) analysis is applied. This model is applied here in order to study crack onset and propagation at the fibre-matrix interface in a composite under tensile/compressive remote biaxial transverse loads. Firstly, this model is used to obtain analytical predictions about interface crack onset, while investigating a single fibre embedded in a matrix which is subjected to uniform remote transverse loads. Then, numerical results provided by a 2D boundary element analysis show that a fibre-matrix interface failure is initiated by the onset of a finite debond in the neighbourhood of the interface point where the failure criterion is first reached (under increasing proportional load); this debond further propagates along the interface in mixed mode or even, in some configurations, with the crack tip under compression. The analytical predictions of the debond onset position and associated critical load are used for several parametric studies of the influence of load biaxiality, fracture-mode sensitivity and brittleness number, and for checking the computational procedure implemented. [ABSTRACT FROM AUTHOR]

A quasi-static rate-independent model of delamination of linearly elastic bodies at small strains, sensitive to mode of delamination, using interfacial damage and interfacial plasticity as two internal parameters, is further developed with the aim to extract representations typically employed in engineering interface-models, i.e. fracture envelope and fracture energy dependence on the mode mixity, which are suitable for the model fitting to experimental data. Moreover, two concepts of solutions are implemented: globally stable energy-conserving solutions or stress-driven maximally-dissipative local solutions, arising by the fully implicit or by a semi-implicit time-stepping procedures, respectively, both yielding numerically stable and convergent time-discretizations. Spatial discretization is performed by the symmetric Galerkin boundary-element method (SGBEM). Alternating quadratic programming is implemented to cope with, respectively, global or local, energy-minimizations in the computation of the time-discretized solutions. Sample 2D numerical examples document applicability of the model as well as efficiency of the SGBEM numerical implementation and facilitate comparison of the two mentioned solution concepts. [ABSTRACT FROM AUTHOR]

A quasistatic rate-independent adhesive delamination problem of laminated plates with a finite thickness is considered. By letting the thickness of the plates go to zero, a rate-independent delamination model for a laminated Kirchhoff-Love plate is obtained as limit of these quasistatic processes. The same dimension reduction procedure is eventually applied to processes which are sensitive to delamination modes, namely opening vs. shearing is distinguished. [ABSTRACT FROM AUTHOR]

The problem of quasistatic and rate-independent evolution of elastic-plastic-brittle delamination at small strains is considered. Delamination processes for linear elastic bodies glued by an adhesive to each other or to a rigid outer surface are studied. The energy amounts dissipated in fracture Mode I (opening) and Mode II (shear) at an interface may be different. A concept of internal parameters is used here on the delaminating interfaces, involving a couple of scalar damage variable and a plastic tangential slip with kinematic-type hardening. The so-called energetic solution concept is employed. An inelastic process at an interface is devised in such a way that the dissipated energy depends only on the rates of internal parameters and therefore the model is associative. A fully implicit time discretization is combined with a spatial discretization of elastic bodies by the BEM to solve the delamination problem. The BEM is used in the solution of the respective boundary value problems, for each subdomain separately, to compute the corresponding total potential energy. Sample problems are analysed by a collocation BEM code to illustrate the capabilities of the numerical procedure developed. [ABSTRACT FROM AUTHOR]

Indentation testing has long been used to measure the mechanical properties of a wide range of materials from metals and ceramics to brain tissue and hydrogels. The purpose of this study was to build and validate a Nano-Tissue Indenter (NTI) capable of performing indentation testing on micro-scale structures within the liver's extracellular matrix. Two silicone-based tissue simulant materials were selected with elastic properties similar to hydrogels used for liver cell cultures. Samples of each material formulation, EcoFlex0030 (EF30) and EcoFlex0010 (EF10), were indented with NTI and also tested in unconfined compression to provide benchmark shear moduli. The resulting force and displacement measurements from NTI with resolutions of 300 nN and 700 nm respectively were analyzed using the Pietrement-Troyon model of adhesive contact. Using this method, NTI was able to distinguish a 10 kPa difference in shear modulus between EF30 and EF10 with comparable significance as unconfined compression ( p < 0.001). General agreement between the results of the two test methods is evidenced by the overlapping of the mean ± S.D. range for the NTI-indentation and benchmark unconfined compression shear moduli measured for both formulations. NTI was used successfully to perform nano-indentation tests on samples of compliant material undergoing adhesive contact, similar to the extracellular matrix of organs such as the liver. [ABSTRACT FROM AUTHOR]

In order to model the adhesive contact across different length scales, a multiscale approach is developed and used to study the adhesive contact behaviors between a rigid cylinder and an elastic face-centered cubic (FCC) substrate. The approach combines an atomistic treatment of the interfacial region with an elastic mechanics method description of the continuum region. The two regions are connected by a coupling region where nodes of the continuum region are refined to atoms of the atomistic region. Moreover, the elastic constants of FCC crystals are obtained directly from the Lennard-Jones potential to describe the elastic response characteristics of the continuum region, which ensures the consistency of material proprieties between atomistic and continuum regions. The multiscale approach is examined by comparing it with the pure MD simulation, and the results indicate that the multiscale modeling approach agrees well with the MD method in studying the adhesive contact behaviors. [ABSTRACT FROM AUTHOR]

This is a justification for standardizing the adhesive contact parameters of finished surfaces of end gauges and precision parts in connections with maximal adjoining surface areas. A criterion is proposed for evaluating the mutual positions of surfaces in the nanometer range by contact and contactless measurement techniques. Experimental data demonstrating the ineffectiveness of press fits of cylindrical pieces fabricated with nanometer tolerances are presented, along with data on the properties and features of tapered connections. [ABSTRACT FROM AUTHOR]

An adhesion map provides quantitative criteria for the appropriate selection of adhesion models applicable to a specific adhesive contact problem of fine particles in complex particulate flows. In this paper, three different general adhesion models are used to construct adhesion maps. The applicable regimes on the adhesion map for different approximate adhesion models are determined according to their underlying limitations. It is found that the choice of general model has limited influence on the structure of a constructed adhesion map. On the contrary, the regime of application for each approximate model is sensitive to the approximation level. A three-dimensional, more intuitive adhesion map based on physical parameters of particles is also built. Finally, recent applications of adhesion models in discrete element method (DEM) investigations of fine-particle flow dynamics are briefly discussed. [ABSTRACT FROM AUTHOR]

A study is reported of a cellular entity (liquid-filled microcapsule) adhered on a flat glass substrate in response to changes in osmotic pressure and temperature. High-resolution reflection interference contrast microscopy (HR-RICM) and phase-contrast microscopy were developed for probing the adhesion contact area, capsule-substrate separation profile and adhesion energy of the adhering microcapsule. The new technique increased the detection limit of the measured capsule wall-substrate separation in the cohesive zone from 1 to 4.5 microm and improved the spatial resolution of the heterogeneous contact zones. A theoretical model was applied to correlate quantitatively the adhesion energy to the area of the contact zone. The work demonstrated the possibility of ascertaining the quantitative interfacial adhesion energy of a liquid-filled microcapsule using the present technique and represents the first step in extending this novel approach to study more complicated systems, such as cell-substrate interactions, in the future. [ABSTRACT FROM AUTHOR]

Exemplified by adhesive contact of a rigid sphere with equiaxially stretched elastomeric substrates, the effect of finite pre-strain on adhesion behavior is studied based on the JKR model. The analysis indicates that the pre-strain reduces the contact area between the sphere and the substrate, but does not alter the adhesion strength. [ABSTRACT FROM AUTHOR]

We study experimentally and theoretically the equilibrium adhesive contact between a smooth glass lens and a rough rubber surface textured with spherical microasperities with controlled height and spatial distributions. Measurements of the real contact area A versus load P are performed under compression by imaging the light transmitted at the microcontacts. A(P) is found to be non-linear and to strongly depend on the standard deviation of the asperity height distribution. Experimental results are discussed in the light of a discrete version of Fuller and Tabor's (FT) original model (Proc R Soc A 345:327, 1975), which allows to take into account the elastic coupling arising from both microasperities interactions and curvature of the glass lens. Our experimental data on microcontact size distributions are well captured by our discrete extended model. We show that the elastic coupling arising from the lens curvature has a significant contribution to the A(P) relationship. Our discrete model also clearly shows that the adhesion-induced effect on A remains significant even for vanishingly small pull-off forces. Last, at the local asperity length scale, our measurements show that the pressure dependence of the microcontacts density can be simply described by the original FT model. [ABSTRACT FROM AUTHOR]

A simple model of cell-substrate adhesion, in response to osmosis change, is derived to describe quantitatively the interrelationships between osmotic inflation, contact area and angle, membrane stretching and adhesion strength. As the cell inflates, the contact area shrinks in dimension, until the cell is eventually lifted off the substrate. The theoretical prediction is consistent with other published data. [ABSTRACT FROM AUTHOR]