Adhesion contact

Landman U, Luedtke W D and Ringer E M 1992 Moiecuiar dynamics simuiations of adhesive contact formation and friction Fundamentals of Friction Macroscopic and Microscopic Processes (NATO ASI Series E220) eds i LSinger and FI M Pollock (Dordrecht Kiuwer) pp 463-508... 

The volume of wear fragments can be related for adhesive contacts to sliding distance x as follows ... 

A triangular shaped wheel cover with the center cut out to provide hub access was then applied to a wheel. The cover was constructed from a heat shrinkable poly- 10 olefin ftlm. Tape was attached to the apex points of the triangle. The tape liner was removed and the three adhesive sites were fastened to the spokes. As an identical complementary cover was then applied to the opposite face of the wheel in a mirror image fashion. The 1 adhesive contact points were positioned to encapsulate the spoke on either side within the adhesive contact point. Heat was then used to shrink the covers and achieve a wrinkle-free condition. This example demonstrates that design can play a part in providing a stylish wheel cover that is capable of individualizing the bicycle to meet a wide variety of consumer tastes. 

Adhesives. Contact adhesives are blends of mbber, phenoHc resin, and additives suppHed in solvent or aqueous dispersion form they are typically appHed to both surfaces to be joined (80). Evaporation of the solvent leaves an adhesive film that forms a strong, peel-resistant bond. Contact adhesives are used widely in the furniture and constmction industries and also in the automotive and footwear industries. The phenoHc resins promote adhesion and act as tackifiers, usually at a concentration of 20—40%. In solvent-based contact adhesives, neoprene is preferred, whereas nitrile is used in specialty appHcations. The type and grade of phenoHc resin selected control tack time, bond strength, and durabiHty. 

When the surfaces are in contact due to the action of the attractive interfacial forces, a finite tensile load is required to separate the bodies from adhesive contact. This tensile load is called the pull-off force (P ). According to the JKR theory, the pull-off force is related to the thermodynamic work of adhesion (W) and the radius of curvature (/ ). 

There are two different scales of deformation in any adhesive contact (1) the bulk scale of deformation which is characterized by the radius a of contact area over which the compressive forces are significant and (2) the zone of action of surface forces or the cohesive zone at the edge of the contact, characterized by the length d over which the tensile forces are dominant. When the contact boundary is moving with a speed u, the two scales of deformation translate into two time scales, one on the order of a/ v) and the other of the order of (d/v). 

Viscoelastic contact problems have drawn the attention of researchers for some time [2,3,104,105]. The mathematical peculiarity of these problems is their time-dependent boundaries. This has limited the ability to quantify the boundary value contact problems by the tools used in elasticity. The normal displacement (u) and pressure (p) fields in the contact region for non-adhesive contact of viscoelastic materials are obtained by a self-consistent solution to the governing singular integral equation given by [106] ... 

Fig. 18. Adhesive contact of elastic spheres. pH(r) and pa(r) are the Hertz pressure and adhesive tension distributions, (a) JKR model uses a Griffith crack with a stress singularity at the edge of contact (r = a) (b) Maugis model uses a Dugdale crack with a constant tension aa in a < r < c [1111.

Fig. 20. The JKR represenUilion of loading experimental and modified data for a viscoelastic adhesive contact. Each set of points corresponds to a compression step in which the load P and contact radius a decreases and increases with time, respectively. LHS refers to the term on the left hand side of Eq. 61. It represents the equivalent of r/ in elastic JKR plot after being weighed by the viscoelastic factor (38. ...

Some rubber base adhesives need vulcanization to produce adequate ultimate strength. The adhesion is mainly due to chemical interactions at the interface. Other rubber base adhesives (contact adhesives) do not necessarily need vulcanization but rather adequate formulation to produce adhesive joints, mainly with porous substrates. In this case, the mechanism of diffusion dominates their adhesion properties. Consequently, the properties of the elastomeric adhesives depend on both the variety of intrinsic properties in natural and synthetic elastomers, and the modifying additives which may be incorporated into the adhesive formulation (tackifiers, reinforcing resins, fillers, plasticizers, curing agents, etc.). 

Gingell, D., Owens, N. (1992). How do cells sense and respond to adhesive contacts Diffusion-trapping of laterally mobile membrane proteins at maturating adhesions may initiate signals leading to local cytoskeletal assembly response and lamella formation. J. Cell Sci. 101, 255-266. 

Wahl, K.J., Asif, S.A.S., Greenwood, J.A., and Johnson, K.L., Oscillating adhesive contacts between micron-scale tips and comphant pol3miers, J. Colloid Interface Sci., 296, 178, 2006. 

The colloid probe technique was first applied to the investigation of surfactant adsorption by Rutland and Senden [83]. They investigated the effect of a nonionic surfactant petakis(oxyethylene) dodecyl ether at various concentrations for a silica-silica system. In the absence of surfactant they observed a repulsive interaction at small separation, which inhibited adhesive contact. For a concentration of 2 X 10 M they found a normalized adhesive force of 19 mN/m, which is small compared to similar measurements with SEA and is probably caused by sufactant adsorption s disrupting the hydration force. The adhesive force decreased with time, suggesting that the hydrophobic attraction was being screened by further surfactant adsorption. Thus the authors concluded that adsorption occurs through... 

Hygienic Guide Series Cyclohexanone. Am Ind Hyg Assoc J 26-.630, 1965 Sanmartin O, de la Cuadra J Occupational contact dermatitis from cyclohexanone as a PVC adhesive. Contact Dermatitis 27 189-190, 1992... 

Contact adhesives Contact adhesives are usually applied to both surfaces, which are then pressed together. Liquid copolymers of butadiene and acrylonitrile with carboxyl end groups are used as contact adhesives in the automotive industry. 

Many aspects of the social behavior of cells are determined by the composition, arrangement, and interaction of cell-surface molecules. Therefore, changes in the composition and structure of plasma membranes appear to contribute to differences in such characteristics as cell adhesion, contact inhibition, and tumorogenicity of cells. Cell-surface glycoproteins, in particular, participate in a number of membrane-modulated phenomena, including responsiveness to hormones, agglutination by lectins, recognition by antibodies, or uptake of nutri-... 

Excessive load, reduced fluid viscosity, and low speed can cause a breakdown of the lubrication layer to the point of a metal-metal contact. Direct adhesive contact can lead to molecular interaction strong enough to tear material out of the surface. This process is also known as cold welding . Metal surfaces under ambient conditions are usually covered with oxide layers that prevent cold welding at moderate loads. 

Fig. 2 Schematic depiction of wrinkle formation of a hard film in adhesive contact with a softer elastomeric substrate. The wavelength X is mainly determined by film thickness h and elastic properties of film and substrate. The amplitude A can be controlled by the strain...

Fig. 2. Photographic image of the surface forces apparatus Mark IV and images of FECO fringes when the mica surfaces are close to contact (1), and when they are in adhesive contact (2). Figure adapted from http //www.rsphysse.anu.edu.au/SFA/, with permission. From the Australian National University, Tim Wetherell.

Fig. 6. Development and disappearance of a refractive index discontinuity in the FECO, revealing a transient vapour bridge during the jump apart from adhesive contact of the DODAB surfaces in water, shown frame by frame. Times are relative to t — 0, defined as the time when separation is started. Reprinted with permission from Ref. [89]. 2005, American Chemical Society.

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