scholarly journals Adhesion and friction in hard and soft contacts: theory and experiment

Friction ◽  
2021 ◽  
Author(s):  
Valentin L. Popov ◽  
Qiang Li ◽  
Iakov A. Lyashenko ◽  
Roman Pohrt
Keyword(s):  
Contact Area ◽  
Adhesive Contact ◽  
Contact Boundary ◽  
Boundary Line ◽  
Chemical Inhomogeneity ◽  
Low Velocity ◽  
Rubber Layer ◽  
Interface Waves ◽  
Rolling Contacts ◽  
Adhesive Contacts

AbstractThis paper is devoted to an analytical, numerical, and experimental analysis of adhesive contacts subjected to tangential motion. In particular, it addresses the phenomenon of instable, jerky movement of the boundary of the adhesive contact zone and its dependence on the surface roughness. We argue that the “adhesion instabilities” with instable movements of the contact boundary cause energy dissipation similarly to the elastic instabilities mechanism. This leads to different effective works of adhesion when the contact area expands and contracts. This effect is interpreted in terms of “friction” to the movement of the contact boundary. We consider two main contributions to friction: (a) boundary line contribution and (b) area contribution. In normal and rolling contacts, the only contribution is due to the boundary friction, while in sliding both contributions may be present. The boundary contribution prevails in very small, smooth, and hard contacts (as e.g., diamond-like-carbon (DLC) coatings), while the area contribution is prevailing in large soft contacts. Simulations suggest that the friction due to adhesion instabilities is governed by “Johnson parameter”. Experiments suggest that for soft bodies like rubber, the stresses in the contact area can be characterized by a constant critical value. Experiments were carried out using a setup allowing for observing the contact area with a camera placed under a soft transparent rubber layer. Soft contacts show a great variety of instabilities when sliding with low velocity — depending on the indentation depth and the shape of the contacting bodies. These instabilities can be classified as “microscopic” caused by the roughness or chemical inhomogeneity of the surfaces and “macroscopic” which appear also in smooth contacts. The latter may be related to interface waves which are observed in large contacts or at small indentation depths. Numerical simulations were performed using the Boundary Element Method (BEM).

scholarly journals Диссипация механической энергии в осциллирующем адгезионном контакте между жестким индентором и эластомером

2020 ◽  
Vol 46 (21) ◽  
pp. 44
Author(s):  
Я.А. Ляшенко ◽  
В.Л. Попов
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Direct Observation ◽  
Contact Area ◽  
Indentation Depth ◽  
Adhesive Contact ◽  
Critical Value ◽  
Chemical Inhomogeneity ◽  
Maximum Indentation Depth

A model of hysteresis in an adhesive contact under oscillating loading is proposed, based on the chemical inhomogeneity of the indenter surface. Results of numerical simulation are compared with experimental data obtained with a setup allowing direct observation of the dynamics of contact area. It is shown that the hysteresis almost disappears if the amplitude of the oscillating load is smaller than a critical value depending on the maximum indentation depth.

Edges of Regression and Limit Normal Point of Conjugate Surfaces1

1998 ◽  
Vol 122 (4) ◽  
pp. 419-425 ◽  
Author(s):  
Ningxin Chen
Keyword(s):  
Differential Geometry ◽  
Contact Boundary ◽  
Boundary Line ◽  
Tangent Point ◽  
Common Tangent ◽  
Numerical Examples ◽  
Envelope Surface ◽  
The Common ◽  
Conjugate Surfaces ◽  
Definition Of

The presented paper utilizes the basic theory of the envelope surface in differential geometry to investigate the undercutting line, the contact boundary line and the limit normal point of conjugate surfaces in gearing. It is proved that (1) the edges of regression of the envelope surfaces are the undercutting line and the contact boundary line in theory of gearing respectively, and (2) the limit normal point is the common tangent point of the two edges of regression of the conjugate surfaces. New equations for the undercutting line, the contact boundary line and the limit normal point of the conjugate surfaces are developed based on the definition of the edges of regression. Numerical examples are taken for illustration of the above-mentioned concepts and equations. [S1050-0472(00)00104-5]

scholarly journals Free and constrained inflation of a pre-stretched cylindrical membrane

2014 ◽  
Vol 470 (2169) ◽  
pp. 20140282 ◽  
Author(s):  
Amit Patil ◽  
Arne Nordmark ◽  
Anders Eriksson
Keyword(s):  
Time Integration ◽  
Adhesive Contact ◽  
Contact Boundary ◽  
Stress Distributions ◽  
Governing Equations ◽  
Soft Substrate ◽  
Softening Effect ◽  
Contact Conditions ◽  
Time Integration Method ◽  
Principal Stretches

This paper presents the free and constrained inflation of a pre-stretched hyperelastic cylindrical membrane and a subsequent constrained deflation. The membrane material is assumed as a homogeneous and isotropic Mooney–Rivlin solid. The constraining soft cylindrical substrate is assumed to be a distributed linear stiffness normal to the undeformed surface. Both frictionless and adhesive contact are modelled during the inflation as an interaction between the dry surfaces of the membrane and the substrate. An adhesive contact is modelled during deflation. The free and constrained inflation yields governing equations and boundary conditions, which are solved by a finite difference method in combination with a fictitious time integration method. Continuity in the principal stretches and stresses at the contact boundary is dependent on the contact conditions and inflation–deflation phase. The pre-stretch has a counterintuitive softening effect on free and constrained inflation. The variation of limit point pressures with pre-stretch and the occurrence of a cusp point is shown. Interesting trends are observed in the stretch and stress distributions after the interaction of the membrane with soft substrate, which underlines the effect of material parameters, pre-stretch and constraining properties.

Adhesive Contacts for Graded-Elastic Coatings Using Fourier Series Decomposition

2011 ◽  
Author(s):  
S. J. Chidlow ◽  
W. W. F. Chong ◽  
M. Teodorescu ◽  
N. D. Vaughan
Keyword(s):  
Fourier Series ◽  
Analytic Solution ◽  
Adhesive Contact ◽  
Solution Technique ◽  
Control Case ◽  
Principal Stresses ◽  
Pressure Distributions ◽  
Surface Deflection ◽  
Elastic Layers ◽  
Adhesive Contacts

We propose a semi-analytic solution technique to determine the subsurface stresses and local deflections resulting in an adhesive contact of graded elastic layers. Identical pressure distributions, typical for a Maugis parameter λ = 1, were applied to a range of graded elastic coatings. The principal stresses and surface deflection in both regions (graded elastic layer and substrate) are computed in terms of Fourier series. This control case has the advantage that the response of different coatings can be easily monitored and compared.

Adhesive Contact of Bodies Having an Elliptical Contact Area

2005 ◽  
Author(s):  
K. L. Johnson ◽  
J. A. Greenwood
Keyword(s):  
Closed Form ◽  
Contact Area ◽  
Adhesive Contact ◽  
Contact Radius ◽  
General Shape ◽  
Elliptical Contact ◽  
Jkr Theory ◽  
Two Bodies

The so-called JKR theory of adhesion between elastic spheres in contact (Johnson, Kendall & Roberts 1971, Sperling 1964) has been widely used in micro-tribology. In this paper the theory is extended to solids of general shape and curvature. It is assumed that the area of contact is elliptical which turns out to be approximately true, though the eccentricity is different from that for non-adhesive contact. Closed form expressions are found for the variation with load of contact radius and displacement, as a function of the ratio of principal relative curvatures of the two bodies in contact. The pull-off force is found to decrease with increasing eccentricity from its value of 3πΔγR/2 in the case of contact of spheres of radius R.

A General Three-Dimensional Numerical Technique for Determining the Contact Area of an Arbitrary Punch on an Elastic Half-Space

2016 ◽  
Vol 08 (01) ◽  
pp. 1650005 ◽  
Author(s):  
Jing Jin Shen ◽  
Feng Yu Xu ◽  
Guo Ping Jiang
Keyword(s):  
Numerical Method ◽  
Contact Area ◽  
Numerical Technique ◽  
Three Dimensional ◽  
Contact Problems ◽  
Linear Interpolation ◽  
Contact Boundary ◽  
Reciprocal Theorem ◽  
Normal Contact ◽  
Indentation Force

The paper presents a numerical method for determining the contact area in three-dimensional elastostatic normal contact without friction. The method makes use of the theorem developed by Barber, the contact area is that over which the total indentation force achieves its maximum value. By approximating the punch by linear interpolation, the analytical expression for the indentation force is derived by virtue of the reciprocal theorem. The physical meaning of the parameter which determines the contact boundary is discussed, and its feasible range corresponding to the contact area is found. Then, the numerical algorithm for determining the parameter is developed and applied to solve several normal contact problems. The results show that the proposed numerical method possesses a good property on accuracy and convergency.

scholarly journals A Shear Strength Model for a Subsidence Backfill Body Based on Adhesion Friction Theory

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Lei Liu ◽  
Shengyou Zhang ◽  
Weidong Liu ◽  
Wei Sun ◽  
Jinxin Li
Keyword(s):  
Shear Strength ◽  
Contact Area ◽  
Adhesive Contact ◽  
Calculation Model ◽  
Strength Calculation ◽  
Strength Analysis ◽  
Actual Contact ◽  
Actual Contact Area ◽  
Friction Theory

Proper determination of the shear strength of the backfill body used to fill the subsidence is the basis for subsidence restoration and the stability analysis of materials. This study developed a shear strength calculation model for the backfill body by introducing adhesive friction theory into the shear strength analysis. A direct shear test was performed in the laboratory to verify the proposed method. Test results suggested that the shear strength calculation method based on adhesive friction theory can calculate the variation in the actual contact area between grains in the tested samples undergoing shearing and estimate the peak shear strength. The actual contact area was divided into two components, namely, adhesive contact area Arm and contact area reduction caused by shear displacement, which exhibited a maximum at Armax. The shear strength values calculated by this method were smaller than laboratory values, and their differences increased with the rock proportion in the backfill body. The differences between the theoretical and experimental values of shear strength increased with the rock grain size. The results of theoretical calculation, combined with the results of laboratory experiments, can provide support for the proper determination of shear strength of the backfill body.

scholarly journals On a Simplified Model for Numerical Simulation of Wear During Dry Rolling Contacts

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
L. Chevalier ◽  
A. Eddhahak-Ouni ◽  
S. Cloupet
Keyword(s):  
Contact Area ◽  
Power Distribution ◽  
Contact Problems ◽  
Rolling Contact ◽  
Normal Loading ◽  
Fast Determination ◽  
Wear Process ◽  
Simplified Approach ◽  
Rolling Contacts

We deal with rolling contact between quasi-identical bodies. As normal and tangential problems are uncoupled in that case, the simplified approach to determine contact area and normal loading distribution for rolling contact problems is presented in Sec. 2. In Sec. 3, the solution of the tangential problem is used to update the rolling profiles and enables to follow the wear evolution versus time. The method used to solve the normal problem is called semi-Hertzian approach with diffusion. It allows fast determination of the contact area for non-Hertzian cases. The method is based on the geometrical indentation of bodies in contact: The contact area is found with correct dimensions but affected by some irregularities coming from the curvature’s discontinuity that may arise during a wear process. Diffusion between independent stripes smoothes the contact area and the pressure distribution. The tangential problem is also solved on each stripe of the contact area using an extension of the simplified approach developed by Kalker and called FASTSIM. At the end, this approach gives the dissipated power distribution in the contact during rolling and this power is related to wear by Archard’s law. This enables the profiles of the bodies to be updated and the evolution of the geometry to be followed.

scholarly journals Cortactin is necessary for E-cadherin–mediated contact formation and actin reorganization

2004 ◽  
Vol 164 (6) ◽  
pp. 899-910 ◽  
Author(s):  
Falak M. Helwani ◽  
Eva M. Kovacs ◽  
Andrew D. Paterson ◽  
Suzie Verma ◽  
Radiya G. Ali ◽  
...  
Keyword(s):  
Contact Zone ◽  
Adhesive Contact ◽  
Actin Dynamics ◽  
Contact Formation ◽  
Biochemical Interaction ◽  
Embryonic Life ◽  
Generating Capacity ◽  
Mediated Contact ◽  
Adhesive Contacts ◽  
Cell Cell

Classical cadherin adhesion molecules are key determinants of cell–cell recognition during development and in post-embryonic life. A decisive step in productive cadherin-based recognition is the conversion of nascent adhesions into stable zones of contact. It is increasingly clear that such contact zone extension entails active cooperation between cadherin adhesion and the force-generating capacity of the actin cytoskeleton. Cortactin has recently emerged as an important regulator of actin dynamics in several forms of cell motility. We now report that cortactin is recruited to cell–cell adhesive contacts in response to homophilic cadherin ligation. Notably, cortactin accumulates preferentially, with Arp2/3, at cell margins where adhesive contacts are being extended. Recruitment of cortactin is accompanied by a ligation-dependent biochemical interaction between cortactin and the cadherin adhesive complex. Inhibition of cortactin activity in cells blocked Arp2/3-dependent actin assembly at cadherin adhesive contacts, significantly reduced cadherin adhesive contact zone extension, and perturbed both cell morphology and junctional accumulation of cadherins in polarized epithelia. Together, our findings identify a necessary role for cortactin in the cadherin–actin cooperation that supports productive contact formation.

scholarly journals Boundary element method for nonadhesive and adhesive contacts of a coated elastic half-space

2019 ◽  
Vol 234 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Qiang Li ◽  
Roman Pohrt ◽  
Iakov A Lyashenko ◽  
Valentin L Popov
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Half Space ◽  
Adhesive Contact ◽  
Elastic Half Space ◽  
Fourier Space ◽  
Numerical Tests ◽  
New Formulation ◽  
Adhesive Contacts ◽  
Element Method

We present a new formulation of the boundary element method for simulating the nonadhesive and adhesive contact between an indenter of arbitrary shape and an elastic half-space coated with an elastic layer of different material. We use the Fast Fourier Transform-based formulation of boundary element method, while the fundamental solution is determined directly in the Fourier space. Numerical tests are validated by comparison with available asymptotic analytical solutions for axisymmetric flat and spherical indenter shapes.

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