Adhesion Theory Research Articles

Measurement of time-dependent adhesion between a polymer film and a flat indenter tip

We revisited an elasticity problem of flat indentation on an elastic film bonded to a rigid substrate and obtained the force–depth relation in a simple form. With the obtained force–depth relation, Kendall's elastic equilibrium theory of adhesion was extended to the adhesion between a flat tip and a compressible elastic film. Thus, the thermodynamic work of adhesion at the moment of debonding of a flat tip from an elastic film was expressed in terms of pull-off force, elastic constants and geometric parameters. It is worth noting that the obtained relation for elastic films is still valid for viscoelastic films if viscoelastic losses are limited to the process zone of debonding. This makes it possible to study the time-dependent adhesion of viscoelastic polymer films. Indentation experiments with a flat diamond tip were performed on SU-8 films, and the results verified that the extended form of Kendall's theory correctly compensates the effect of the finite thickness of the films on the work of adhesion. The indentation results also showed that the work of adhesion is strongly dependent on the unloading velocity of the tip, while indentation depth and dwell time have only minor effects on the work of adhesion.

A Model of Adhesion Excited Micro-vibrations

Understanding the mechanism of “rubbing” noise and low-amplitude friction exited vibration generation in steady sliding can be helped by models describing the contact interactions. In the current article, we consider a simple microscopic contact model for surfaces in sliding, which is based on the adhesion theory of friction. In the proposed model, we consider that the formation and shearing of a junction contributes to a small change in the real contact area. The model incorporates random size and random spacing between junctions. We investigate the dependence of the instantaneous real contact area on the average size and number of junctions. We find that from the viewpoint of vibration reduction, it is advantageous if the real contact area needed to support the given load is obtained as a sum of many small-sized micro-contacts, instead of few large-sized micro-contacts. The above result is in agreement with experimentally observed reduction of vibrations of a hard-disk slider after texturing.

Principle and Application of Pre-stressed Bumpy-ridge in Field of Heavy Mechanism

The technology ofpre-stressed bumpy-ridge is a joining method of subdivisions in the field of heavy mechanism.In nature, due to the creature's self-adaptive property,mechanical countercheck can be easily formed in two creatures,and then the joining is generated.In mechanical field,resistance against shearing will not increase unless the mechanical countercheck in two-dimension and the adhesion are formed under the full plastic deformation in the contact zone which is generated by high contact stress.Theory of pre-stressod bumpy-ridge is studied from the perspective of biology,elastic-plastic mechanics and adhesion theory,and the condi- tion of elastic-plastic contact and the formation of bumpy-ridge structure is analyzed by finite element method and experiment.By pre-stressed bumpy-ridge,the subdivisions are well joined into integer under pre-stress.In addition,the application of pre-stressed bumpy-ridge in the heavy mechanical field is introduced.

分子接着剤を用いる樹脂とシリコーンゴムの直接架橋接着

A new concept has been proposed for adhesion theory and technology, unifying various adhesion theories and simplifying adhesion technology. This purpose is achieved by using a molecular adhesive, 6-(3-triethoxysilylpropy-lamino)-1, 3, 5-triazine-2, 4-dithiol (TES), which contains two functional groups of dithiol triazinyl and alkoxysilyl groups in one molecule. Resins such as epoxy resin, polyamide, and polyester were pretreated by corona discharge to form OH groups on the surfaces. The OH groups react readily with TES by heating for 10min at 150°C to give TES containing resin surfaces. Silicone rubber adhered readily to the TES containing resin surfaces by hot-pressing for 10min at 160°C, with very high peel strength which is destroyed in rubber-phase. Peel strength decreased with surface roughness on resins, and the amount of TES decreased with the roughness.

Adhesion and Surface Issues in Cellulose and Nanocellulose

This paper provides a review of the scientific literature concerned with adhesion and surface properties of cellulose and nanocellulose. Cellulose is the most abundant chemical compound on earth and its natural affinity for self-adhesion has long been recognized. The ease of adhesion that occurs in cellulose has contributed to its use in paper and other fiber-based composite materials. Cellulose adhesion, which has received considerable attention over the past half century, occurs over a practical length scale ranging from the nanoscale to millimeters. Adhesion theories that have been examined in the bonding of cellulose fibers include: mechanical interlocking, adsorption or wetting theory, diffusion theory, and the theory of weak boundary layers. Cellulose fibers on the nanoscale are prepared in four different ways: (1) bacterial cellulose nanofibers, (2) cellulose nanofibers by electrospinning, (3) microfibrillated cellulose plant cell fibers and (4) nanorods or cellulose whiskers. Structure and properties of nanocellulose that are important include: morphology, crystalline structure, surface properties, chemical and physical properties, and properties in liquid suspension. Cellulosic nanofibers present a very high surface area which makes the adhesion properties the most important parameter to control for nanocomposite applications. In this paper, we will focus on discussion of the adhesion and surface characteristics of cellulose nanofibers that impact its properties and application in nanomaterials.

Effect of a complex of aliovalent cations on processes in an enamel melt-low-carbon steel system

The interrelationship of the corrosion activity of enamel melts containing a complex adhesion activator, their specific electric conductivity, and the strength of the adhesion of the corresponding coatings is investigated. The partial and integral effects of aliovalent oxides on the properties of prime vitreous enamels are determined. The principles of the electrochemical theory of adhesion of enamel coatings on steel, using a complex adhesion activator, are confirmed.

Modelling of vibrations excited by formation and shearing of adhesive micro-junctions during sliding

Understanding of the mechanism of “rubbing” noise and low amplitude friction exited vibration generation in steady sliding can be helped by models describing the contact interactions. In the current paper, we consider a simple microscopic contact model for surfaces in sliding, which is based on the adhesion theory of friction. In the proposed model, we consider that the formation and shearing of a junction contributes to a small change in the real contact area. The model incorporates random size and random spacing between junctions. We investigate the dependence of the instantaneous real contact area on the average size and number of junctions. We find that, from the viewpoint of vibration reduction, it is advantageous if the real contact area needed to support a given load is obtained as a sum of many small-sized micro-contacts, instead of few large-sized micro-contacts. The above result is in agreement with experimentally observed reduction of vibrations of a hard-disc slider after texturing.

Room Temperature Micro-Bonding of Fine Wires to Foils

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The effect of nominal specimen contact area on the wear coefficient of A6061 aluminium matrix composite reinforced with alumina particles

Earlier work with turning and pin-on-disc tests indicated that the wear coefficient values of tungsten carbide obtained could vary significantly due possibly to the different nominal contact areas used in the various testing processes [2–4]. This paper reports the results obtained from research work carried out earlier to determine the effect of nominal specimen contact area on the wear coefficient of A6061 aluminium matrix composite (MMC) containing 20% of alumina particles. The pin-on-disc testing method was used to conduct the wear tests with speeds of 200 and 275 m/min and loads of 74 and 98 N. Square pins with a length of 25 mm and with two different nominal contact areas of 6 × 6 mm 2 and 10 × 10 mm 2 were used. The discs were made of AISI-01 cold work tool steel with a hardness of about 62 HRC. Wear tests were carried out at distances from 250 to 12,000 m. It was found that the wear coefficient values obtained from the pins with a smaller nominal contact area were indeed lower by an average of about 12%, due to the availability of smaller asperity wear volumes. The results also agree with the adhesive wear theory. Hence one should exercise extreme care in the interpretation of wear coefficient data obtained from different testing methods, or from using different nominal specimen contact areas.

Adhesive contact to a coated elastic substrate

We show how the quasi-analytic method developed to solve linear elastic contacts to coated substrates (Perriot and Barthel 2004 J. Mater. Res. 19 600) may be extended to adhesive contacts. Substrate inhomogeneity lifts accidental degeneracies and highlights the general structure of the adhesive contact theory. We explain the variation of the contact variables due to substrate inhomogeneity. The relation to other approaches based on finite element analysis is discussed.

Cell/surface interactions and adhesion on Ti‐6Al‐4V: Effects of surface texture

This paper presents the results of an experimental study of the effects of surface texture on the interactions between human osteo-sarcoma (HOS) cells and Ti-6Al-4V. These include the Ti-6Al-4V with polished (smooth); Al(2)O(3) blasted (rough); and laser micro-grooved geometries with controlled spacings and depths. Immuno-fluorescence staining of adhesion proteins (actin and vinculin) was used to study the spreading and adhesion of HOS cells in 2 day culture experiments. Quantitative measures of adhesion were also obtained using an enzymatic detachment assay. The results are discussed within the context of existing theories of cell adhesion. The implications of the results are also examined for the design of textured surfaces in biomedical systems.

Friction analysis of microcosmic elastic-plastic contact for extrusion forming

In extrusion forming process, according to elastic-plastic contact between microcosmic rough surface of tool and workpiece, elastic-plastic contact model was founded and then real contact area, normal stress and normal deformation value were calculated in accordance with Hertz theory. Based on adhesive friction theory, the paper analyzes the formation mechanism of surface friction in extrusion process, and researches the relationship between friction coefficient and geometrical parameters of rough surface: tangential slope angle of asperity θ, the radius of asperity R 2 and the maximum height of asperity h. The interpretation of results shows that θ mostly affects friction coefficient, R 2 has little effect on friction coefficient and h has no effect on it. The results can guide the design of extrusion technology and the analysis of die life.

0926 金属の摩擦摩耗に及ぼす潤滑液溶存酸素の影響(S04-2 関節のバイオメカニズム(2),S04 関節のバイオメカニズム)

The relationship between the dissolved oxygen in lubricating liquid and the tribological characteristics of metal-on-metal artificial hip joints was investigated in this study. In a pin made from either a cobalt-chromium-molybdenum (Co-Cr-Mo) alloy or a carbon steel (S45C) sliding on the same material, a decrease in wear was often observed with the decrease in dissolved oxygen. This result cannot be explained by the traditional adhesion theory. Difference between the Co-Cr-Mo alloy and the carbon steel did not affect the wear reduction with decrease in oxygen concentration. Furthermore, the wear reduction with decrease in oxygen concentration could be observed in the distilled water.

In Memoriam: M. Eugene Merchant

In Memoriam: M. Eugene Merchant

Adhesion effects in material transfer in mechanical contacts

A series of molecular dynamics simulations of the contact and separation of a surface with an asperity (material A) and a flat substrate (material B) are performed, in which the A/B interfacial energies vary (leaving other properties unchanged). When the work of adhesion Γ is large, substantial plastic deformation occurs on separation, and some material is transferred to the opposing substrate. When Γ is small, separation of the materials occurs at a critical force, with no material transfer and no plastic deformation. A theory is developed, based upon a capillary equilibrium argument, that accurately predicts when material transfer from one surface to another will occur. When separation occurs without plastic deformation, the separation process can be described by Johnson, Kendal and Roberts (JKR) adhesive contact theory. The simulation results and theory clarify how interfacial adhesion can be manipulated to control surface roughening, material transfer and surface alloying in contacts.

Estimates of biomechanical forces in Magnaporthe grisea

The mechanical actions of the fungus Magnaporthe grisea raise many intriguing questions concerning the forces involved. These include: (1) the material properties of the appressorial wall; (2) the strength of the adhesive that keeps the appressorium anchored to the rice leaf surface; and (3) the forces involved in the penetration process whereby a peg is driven through the host cell wall. In this paper we give order of magnitude estimates for all three of these quantities. A simple Young-Laplace law type argument is used to show that the appressorial wall elastic modulus is of order 10–100 MPa; and an adaptation of standard adhesion theory indicates a lower bound on the strength of the appressorial adhesive to be of the order 500 J/m 2. Drawing on ideas from plasticity theory and ballistics, estimates of the penetration force raise interesting questions about experiments performed on the penetration of inert substrates by the fungus.

A new experimental procedure of evaluating the friction coefficient in elastic and plastic regions

The coefficient of friction is one of the parameters that show the amount of resistance to relative motion of two sliding objects. From the basic assumptions of the adhesive theory of friction, the value of the coefficient of friction will almost be equal to 0.2. In high vacuum conditions experimentally determined values of the coefficient of friction of six or more have been recorded, which clearly cannot be explained by simple model. It is this discrepancy between experiment and theory that led to the junction growth theory. In this research a new experimental investigation is described in which the coefficient of friction for steel–aluminum contact surface has been found. This test was conducted by using a testing machine on the basis of twist-compression test. The results showed that the coefficient of friction of steel–aluminum interface started at an initial value of 0.2 and increased almost to 0.8 in the elastic region and then decreased to the value of 0.6 in the plastic region.

Colloidal Aggregate Micromechanics in the Presence of Divalent Ions

Colloidal gels exhibit rheological properties, such as a yield stress and elasticity, which arise from the manner in which stress is transmitted through the microstructure. Insight into the mechanisms of stress transmission is critical in developing a full understanding of the mechanics of these materials. Paramount to this is a thorough knowledge of the interparticle interactions. In this work, we use optical trapping to study interactions between poly(methyl methacrylate) (PMMA) particles in adhesive contact by measuring the bending elasticity of directly assembled colloidal aggregates under various physicochemical conditions. The simplified geometry of the aggregate enables us determine the single-bond rigidity, which can then be related to the work of adhesion, W(SL), through the Johnson-Kendall-Roberts (JKR) theory of adhesion. We find that W(SL) is independent of ionic strength in flocculating monovalent salt solutions. However, more complex behavior is observed for divalent salts. Using zeta-potential measurements, we show that divalent cations adsorb to the particle surface. This results in the formation of ionic bridges between particles in adhesive contact. A model of the aggregate micromechanics that considers the divalent ion contribution to the surface energy provides a direct link between the interfacial properties of the particles, nanoscale contact interactions between particles, and the bulk gel modulus.

鋼構造露出柱脚におけるベースプレートと基礎モルタル間の摩擦抵抗

Shear friction between the base plate and base mortar contributes to the shear resistance of standard column bases. A value of 0.5 is adopted for the coefficient of shear friction in AIJ's design specifications, but the associated background data and theory is limited. Cyclic loading tests load and surface roughness as major parameters, twice as large as the coefficient expected for unchanged for slips that succeed the initial slip. A combined theory of adhesion and plowing, originally developed for friction between steels, is applied to interpret the friction behavior steel and mortar, indicating reasonable correlation with the corresponding test results.

High Speed Skating Rinks using Oriented Ice Crystals

Frictional anisotropy is observed with crystallographic planes and sliding orientations of ice. Availing this phenomenon, a high speed skating rink was made by use of a large-single crystal ice and its lowest frictional plane. Moreover, new rinks will be made using anisotropy in plastic deformation of ice. The lower friction of curling rinks and oriented snow grains at surface came in sight. These high speed rinks were derived from the basis adhesion theory, and self-inconsistency in frictional melting theory as classical frictional mechanism was revealed.