Adhesion Theory Research Articles

Examining Pipe–Borehole Wall Contact and Pullback Loads for Horizontal Directional Drilling

Pipeline pullback load is a crucial basis for drill rig selection and pipeline strength design. This paper presents a new pullback load calculation model from the perspective of pipe–borehole wall contact. The pipe–borehole wall contact analysis includes the distribution of contact pressure and the relationship between the external load and compressive displacement. The friction force between the pipe and the borehole wall was calculated based on the pipe–borehole wall contact analysis and adhesion theory without depending on the empirical friction coefficient. The effects of the eccentricity were also considered when calculating the fluid drag force. Through case studies, we verified the applicability of the model and discussed the possible reasons for the errors between the theoretical and field-measured results. This study can provide a helpful tool for analyzing the pipe–borehole wall contact and pullback loads for horizontal directional drilling.

Study on the frictional contact behavior of plain cotton fabric with metal

This study investigated the frictional contact behavior of the plain cotton fabric with the metal through linear friction experiments and real contact analysis. It established a theoretical calculation model of the contact area based on the characteristics of contact behavior. The results indicate that the contact between the cotton fabric and the metal is a multi-point contact, with the contact occurring on the fabric knuckles. The contact behavior is mainly influenced by the normal load, fabric knuckle size, and the number of fabric knuckles. The theoretical calculation model of the contact area considers the multi-scale structural characteristics of cotton fabrics and validates the applicability of the friction adhesion theory to cotton fabrics. The effects of normal load and velocity on the tribological characteristics of cotton fabrics are explained based on the number of contact points.

From Tooth Adhesion to Bioadhesion: Development of Bioabsorbable Putty-like Artificial Bone with Adhesive to Bone Based on the New Material "Phosphorylated Pullulan".

Bioabsorbable materials have a wide range of applications, such as scaffolds for regenerative medicine and cell transplantation therapy and carriers for drug delivery systems. Therefore, although many researchers are conducting their research and development, few of them have been used in clinical practice. In addition, existing bioabsorbable materials cannot bind to the body's tissues. If bioabsorbable materials with an adhesive ability to biological tissues can be made, they can ensure the mixture remains fixed to the affected area when mixed with artificial bone or other materials. In addition, if the filling material in the bone defect is soft and uncured, resorption is rapid, which is advantageous for bone regeneration. In this paper, the development and process of a new bioabsorbable material "Phosphorylated pullulan" and its capability as a bone replacement material were demonstrated. Phosphorylated pullulan, which was developed based on the tooth adhesion theory, is the only bioabsorbable material able to adhere to bone and teeth. The phosphorylated pullulan and β-TCP mixture is a non-hardening putty. It is useful as a new resorbable bone replacement material with an adhesive ability for bone defects around implants.

Controlling the Friction Coefficient and Adhesive Properties of a Contact by Varying the Indenter Geometry

In the present paper, we describe a series of laboratory experiments on the friction between rigid indenters with different geometrical forms and an elastic sheet of elastomer as a function of the normal load. We show that the law of friction can be controlled by the shape of the surface profile. Since the formulation of the adhesive theory of friction by Bowden and Tabor, it is widely accepted and confirmed by experimental evidence that the friction force is roughly proportional to the real contact area. This means that producing surfaces with a desired dependence of the real contact area on the normal force will allow to “design the law of friction”. However, the real contact area in question is that during sliding and differs from that at the pure normal contact. Our experimental studies show that for indenters having a power law profile f(r) = cnrn with an index n < 1, the system exhibits a constant friction coefficient, which, however, is different for different values of n. This opens possibilities for creating surfaces with a predefined coefficient of friction.

Sliding frictional and adhesive coupling contact analysis of FGPM layered half-space under an insulating indenter

This paper proposes an analysis model for the sliding frictional and adhesive coupling contact problem in the plane strain state between the FGPM layered half-space and an insulating indenter. The electro-mechanical properties of FGPM layer vary exponentially along the thickness direction. By applying the Fourier integral transformation and superposition principle to the governing boundary value problem, the general solution for the sliding frictional and adhesive coupling contact problem can be derived by using the Maugis type of adhesion theory and extended Amonton’s law of friction. A Cauchy singular integral equation is further derived for present problem which is then numerically solved. The primary aim of this paper is to provide insight into the likely behavior for the effect of the gradient index, friction coefficient and adhesion parameters on the surface electro-mechanical response of FGPM layered half-space. For given values of parameters R, w, βh and μ, when value of σ0 decreases from infinity to zero there is a continuous transition from the JKR approximation to the DMT approximation. The research not only helps to further understand the frictional and adhesive damage mechanisms of MEMS devices composed of FGPM, but also provides reference basis for FGPM layer experimental analysis and intelligent structure design.

Effects of surface-attached durations, nutrients, and relative humidity on the resuspension of bacteria during human walking

Resuspension caused by human walking activities is an important source of indoor bioaerosols and has been associated with health effects such as allergies and asthma. However, it is unknown whether inhalation of resuspended bioaerosols is an important exposure pathway for airborne infection. Also, crucial factors influencing the resuspension of settled microbes have not been quantified. In this study, we experimentally investigated the resuspension of culturable bacteria from human-stepping on polyvinyl chloride (PVC) flooring under different conditions. We determined the bacterial resuspension emission factor (ER), a normalized resuspension parameter for the ratio of resuspended mass in the air to the mass of settled particles, for two common bacteria, Escherichia coli and Salmonella enterica. The investigation involved varying factors such as microbial surface-attached durations (0, 1, 2, and 3 days), the absence or presence of nutrients on flooring surfaces, and changes in relative humidity (RH) (35%, 65%, and 85%). The results showed that, in the absence of nutrients, the highest ER values for E. coli and S. enterica were 3.8 × 10−5 ± 5.2 × 10−6 and 5.3 × 10−5 ± 6.0 × 10−6, respectively, associated with surface-attached duration of 0 days. As the surface-attached duration increased from 0 to 3 days, ER values decreased by 92% and 84% for E. coli and S. enterica, respectively. In addition, we observed that ER values decreased with the increasing RH, which is consistent with particle adhesion theory. This research offers valuable insights into microbial resuspension during human walking activities and holds the potential for assisting in the assessment and estimation of risks related to human exposure to bioaerosols.

Frictional evolution process and stability properties of Longmaxi shale under fluid injection

The frictional stability of rocks is fundamental in controlling the instability and activation of faults. Given the strong correlation between seismic events in the Sichuan Basin of China and hydraulic fracturing for shale gas extraction, we conducted a series of velocity-stepping friction experiments with Longmaxi shale from the Changning shale gas extraction block under fluid injection. The experimental results indicate that the frictional process of Longmaxi shale can be divided into four distinct stages and the effective normal stress can demonstrate the influence of injection pressure. Additionally, the phenomenon of a decreasing friction coefficient μ with increasing effective normal stress can be explained by the frictional adhesion theory and a competitive mechanism between the deformation of asperities and microscopic dilatant slip. As the injection pressure increases, the friction state of Longmaxi shale transitions from velocity-strengthening to velocity-weakening, which is beneficial for potential seismic slip. After friction, the fracture surface experiences wear, and the surface morphology of the left and right parts exhibits a symmetrical distribution. With increasing effective normal stress, the morphological evolution of fractures becomes more prominent, which is related to the variation in the effective contact area. Based on the experimental results, we propose that the uneven distribution of fluid pressure on the Longmaxi shale fracture may also contribute to the transformation of frictional stability. When studying the frictional properties of rocks under fluid injection, it is also necessary to focus on the evolution of fluid pressure distribution on the fracture surface during the frictional process.

On the effect of the height distribution function in adhesion of non Gaussian random rough surfaces, and a simple analytical model (BAM)

Two apparently very different theories of adhesion of rough surfaces called BAM (bearing-area-model), and that of Persson–Tosatti lead to similar predictions concerning the stickiness of Gaussian surfaces: the role of roughness is mainly governed by the low wavevector content of the PSD. Here, we study the adhesion of non-Gaussian surfaces by means of a DMT-based simplified BEM (Boundary-Element-Method), and report a clear difference in the adhesion and stickiness of surfaces with different height distribution function. We then obtain analytical equations for a generalized BAM model. Results of the extended BAM theory compare reasonably well with numerical BEM-DMT predictions. We also notice that any theory based on the surface energy, would show instead insensitivity to height distribution.

A multi-scale roughness rock joint model considering laboratory-scale irregularities using wear theories

The shear strength of a rock fracture is influenced by surface irregularities, geometric parameters, loading conditions, and rock mechanical properties. A new shear model, derived from the energy balance equation, explicitly accounts for the contributions of shear-off component, related to the indentation of surface roughness, and the contributions of basic friction angle and asperity sliding, related to the inclined friction component, to the total shear strength. The progressive roughness degradation is considered in the model by incorporating adhesion and abrasion wear theories. Additionally, multi-scale surface roughness is integrated in the model, as various scaled asperities have different influences on shear behaviour. Due to the distinct influences of various scaled asperities on shear behaviour, their contributions during shear are also taken into account within the model utilising multi-scale roughness theory. Moreover, the model has been implemented into three-dimensional distinct element code (3DEC) using the built-in programming language FISH and verified with experimental data incorporating laboratory-scale rock fractures. The proposed model offers new insights into roughness degradation and yields good prediction performance, as demonstrated by an average error (σ‾ave) of 4.95 % ± 0.03 for the τ−us behaviour, a Normalised Objective Function (NOF) of 0.16 for the us−un behaviour.

Nanoscale profiling of the relationship between in-situ organic matter roughness, adhesion, and wettability under ScCO2 based on contact mechanics

Understanding the interface and wetting phenomenon between CO2 and shale in the reservoir environment plays a key role in realizing efficient shale gas development and long-term stable carbon sequestration in the formation. However, previous studies on the interaction between CO2 and reservoir rocks focused on macro-scale and batch experiments of inorganic minerals, and the mechanism at the nanoscale, especially the micro-wetting behavior of the organic interface, remains unclear and needs to be investigated urgently. In this paper, based on the atomic force microscopy (AFM) tapping mode and the AM-FM viscoelastic mapping mode, the in-situ organic matter (OM) morphology and the change of the relationship between the adhesion force and the interfacial wettability under carbon dioxide immersion are investigated, respectively, and the carbon dioxide wettability behavior at the organic interfaces is deeply revealed in the nanoscale. Among them, the contact angle is obtained by the adhesion work combined with the Johnson-Kendall-Roberts (JKR) adhesive contact theory. The results show that the surface roughness of the OM keeps increasing with the ScCO2 immersion time, while the surface adhesion keeps decreasing at the same time. Although the contact angle decreases continuously with immersion time, the OM is always hydrophobic, i.e., CO2 wetting. It can be seen that the surface roughness has a negative correlation with the contact angle, which keeps decreasing with decreasing adhesion. This indicates that ScCO2 immersion expands the gas adsorption sites and at the same time reduces the interfacial energy of the OM slightly, which is extremely beneficial for CO2 to enhance shale gas recovery and to implement long-term stable carbon geologic sequestration. Therefore, this study reveals the mechanism of the carbon sequestration process at the organic interface in depth within the nanoscale for the first time, which provides a new perspective to deeply understand the long-term adsorption and capture variation process of OM in deep reservoirs.

Interfacial adhesion between electrical contacts determined by surface quality

ABSTRACT Micro-Electromechanical-Relay (MER) has widely achieved application in the field of engineering thanks to the excellent features and ever-growing interest in microelectronic products. However, the adhesion phenomenon between gold-sputtered contact pairs in MER usually brings about operating failure of normally closed contacts limiting the reliability level of MER. In this paper, various contact combinations between electrical contact pairs are assembled to simulate real contact conditions, and associated failure type is built by taking advantage of mechanical adhesion theory to reveal failure mechanism about cold adhesion. It is found that the adhesion force is correlated closely with the surface roughness of contact pairs. The specific contact combination is a significant effective strategy to reduce the adhesion failure between electrical contacts.

Flexible hydrogels connecting adhesion and wetting.

Raindrops falling on window-panes spread upon contact, whereas hail can cause dents or scratches on the same glass window upon contact. While the former phenomenon resembles classical wetting, the latter is dictated by contact and adhesion theories. The classical Young-Dupre law applies to the wetting of pure liquids on rigid solids, whereas conventional contact mechanics theories account for rigid-on-soft or soft-on-rigid contacts with small deformations in the elastic limit. However, the crossover between adhesion and wetting is yet to be fully resolved. The key lies in the study of soft-on-soft interactions with material properties intermediate between liquids and solids. In this work, we translate adhesion to wetting by experimentally probing the static signature of hydrogels in contact with soft PDMS of varying elasticity of both the components. Consequently, we probe this transition across six orders of magnitude in terms of the characteristic elasto-adhesive parameter of the system. In doing so, we reveal previously unknown phenomenology and a theoretical model which smoothly bridges adhesion of glass spheres with total wetting of pure liquids on any given substrate.

Adhesion theory and model for air humidity impact on dust emission

It has been suggested that air humidity influences dust emission under very dry conditions and adhesion might be the responsible process which changes the binding between soil particles. The process of adhesion is so far poorly understood and difficult to quantify. Here, a critical examination of the relevant studies is provided, and an adhesion model is proposed. Both isothermal-kinematic and diffusion processes can limit the soil liquid–water and water–vapor exchange in soil, but for the particle size range concerned in aeolian studies, diffusion appears to be the limiting process. The model shows that soil moisture in the topsoil layers is positively correlated with air humidity, but with delays of several hours. The model performance is influenced by several parameters but is particularly sensitive to the equilibrium soil water–vapor content. This implies that soil microscopic properties can strongly influence adhesion. A new formulation of soil water retention function covering the entire soil moisture range is also proposed, which links soil water retention function and pore size distribution. Using a relationship between soil particle-size and pore-size distributions, an adhesion-affected grain size can be estimated, which defines the upper size limit of soil particles influenced by soil moisture. This study explains how air humidity influences soil moisture through adhesion and dust emission and why low air humidity promotes the emission of finer dust particles.

Lattice-based mesoscale simulations and mean-field theory of cell membrane adhesion.

Adhesion of cell membranes involves multi-scale phenomena, ranging from specific molecular binding at Angstrom scale all the way up to membrane deformations and phase separation at micrometer scale. Consequently, theory and simulations of cell membrane adhesion require multi-scale modeling and suitable approximations that capture the essential physics of these phenomena. Here, we present a mesoscale model for membrane adhesion which we have employed in a series of our recent studies. This model quantifies, in particular, how nanoscale lipid clusters physically affect and respond to the intercellular receptor-ligand binding that mediates membrane adhesion. The goal of this Chapter is to present all details and subtleties of the mean-field theory and Monte Carlo simulations of this mesoscale model, which can be used to further explore physical phenomena related to cell membrane adhesion.

Adhesion of Varnish Coatings as a Background for Analogue and Digital Printing Technologies

In analogue and digital printing technologies, from 3 up to 12 layers of lacquer products are applied. Technological parameters significantly influence the adhesion in the coating system. This article refers to the analysis of the influence of selected technological parameters, such as the number of layers, energy doses distributed by the radiators, and line speed, on the topography and adhesion of varnish coatings formed in the process of varnishing with rollers and UV-curing systems. The appropriately prepared surface can be used as a background layer for the analogue and digital printing technology. Manufacturers must adapt the production process to the particular varnish to obtain finished products with the best possible performance properties. The state of surface free energy and finally adhesion can be assessed by theoretically determining the possibility of an adhesive bonding between the product and the substrate, taking into account the assumptions of the adsorption theory of adhesion and measurement of the contact angle (Θ). An experimental confirmation of adhesion measurements included removing the coatings from the substrate via stamps glued to the coating.

A mechanically-derived contact model for adhesive elastic-perfectly plastic particles, Part I: Utilizing the method of dimensionality reduction

In this two part series (Zunker and Kamrin, 2024), we present a contact model able to capture the response of interacting adhesive elastic-perfectly plastic particles under a variety of loadings. In Part I, we focus on elastic through fully-plastic contact with and without adhesion. For these contact regimes the model is built upon the method of dimensionality reduction which allows the problem of a 3D axisymmetric contact to be mapped to a corresponding problem of a 1D rigid indenter penetrating a bed of independent Hookean springs. Plasticity is accounted for by continuously varying the 1D indenter profile subject to a constraint on the contact pressure. Unloading falls out naturally, and simply requires lifting the 1D indenter out of the springs and tracking the force. By accounting for the incompressible nature of this plastic deformation, the contact model is able to capture multi-neighbor dependent effects such as increased force and formation of new contacts. JKR type adhesion is recovered seamlessly within the method of dimensionality reduction by simply allowing the springs to ‘stick’ to the 1D indenter’s surface. Because of the mechanics-focused formulation of the contact model, only a few physical inputs describing the interacting particles are needed: particle radius, Young’s modulus, Poisson ratio, yield stress, and effective surface energy. The contact model is validated against finite element simulations and analytic theory—including Hertz’s contact law and the JKR theory of adhesion. These comparisons show that the proposed contact model is able to accurately capture plastic displacement, average contact pressure, contact area, and force as a function of displacement for contacts as well as particle volume within the elastic to fully-plastic regimes.

Investigation on the mechanism of air/condensate bubble flotation of emulsified oil droplet

Crude oil droplets in oilfield-produced water are highly emulsified, and the poor attachment between gas bubbles and oil droplets limits the effectiveness of oil-water separation during flotation processes. This paper proposes a new surface-functionalized bubble called a condensate bubble and evaluates its flotation performance based on surface properties and adhesion theory mechanism to address this issue. The surface chemical properties of the oil droplets were characterized using X-ray photoelectron spectroscopy (XPS), contact angle measurement, and zeta potential. Induction time and flotation tests were conducted to compare the attachment effects between air or condensate bubbles and emulsified oil droplets. The interaction forces were calculated using DLVO and extended DLVO theory. The experimental results showed that crude oil contains functional compounds containing oxygen that make it tough to float. However, the contact angle between the oil surface and condensate bubble was greater than 150°, demonstrating that the condensate liquid bubbles have better hydrophobicity than air bubbles. The micro-flotation experiments indicated that condensate bubbles have a strong collection capacity for emulsified oil droplets, which was confirmed by induction time tests. In 70 mM NaCl brine, the oil removal efficiency of condensate bubble flotation could reach 82%, which was a 30% improvement compared to air bubble flotation. However, DLVO theory failed to predict the flotation with a concentration higher than 10 mM NaCl. The extended DLVO theory accounted for hydrophobic interactions, which were observed due to similar solvent extraction and hydrophobicity of the condensate liquid film. As a result, the condensate bubble-oil droplet system exhibited stronger hydrophobic attraction, successfully confirming and illustrating the superiority of the condensate bubble in flotation.

Mucoadhesive Buccal Films

Pharmaceutical formulations are experiencing a significant transformation as novel drug delivery techniques become increasingly available and effective. While there are many different types of medical dosage forms, each has its own limitations, such as tablet choking and painful parenteral dosages. Buccal drug delivery, which involves administering medication to the oral cavity, offers a convenient and easy-to-administer alternative. The oral route of medication administration has numerous benefits, including avoiding liver metabolism, enhancing drug bioavailability, and improving the onset of action. By directly entering the systemic circulation, active pharmaceutical ingredients can produce their therapeutic effects. As the buccal mucosa has a high degree of permeability and blood supply, it is a highly accessible drug delivery system. There are six theories that explain mucosal adhesion: electronics, wettability, adsorption, degradation, diffusion, and mechanics. Various in vitro and in vivo approaches have been used to study buccal drug delivery systems. This paper discusses the mechanisms of action, mucosal adhesion theories, and standard techniques for producing films. Key areas of study in buccal drug delivery systems include evaluating films for weight variation, thickness, folding endurance, surface pH, percentage of moisture absorption and loss, tensile strength, swelling index, content uniformity, and in vitro permeation studies.

Theoretical Background of Self-Healing in Asphalt Concrete

The article presents theoretical premises that can be used to describe the mechanism of self-healing of the state of the structure of asphalt concrete containing an encapsulated reducing agent. The article presents the main provisions of the Flory-Huggins theory, according to which the restorative effect can be realized due to the ability of organic binder molecules to spontaneously entangle with each other. The intensity of this process depends on the proximity of the molecules to each other and the rate of spontaneous motion, which increases with increasing temperature. And in accordance with the theory of adhesion, the restoration of the state of the structure of asphalt concrete can be due to the mechanisms of formation of adhesive bonds with the help of an encapsulated modifier. To describe the features of the formation of adhesive bonds during restoration, the approaches described in the mechanical, molecular, chemical, diffuse, relaxation theory of adhesion or the theory of weak boundary layers can be used.

Modeling and measuring the bonding strength of overmolded polymer parts

Overmolding a polymer onto a polymer substrate is a versatile plastic processing technique already widely used in industry and has a high potential to customize mass-produced polymer parts. Even though the industry is ready for this technology, there are still no engineering calculation methods to predict the strength of overmolded parts. None of the available engineering software packages contains the modeling of bonding strength between a polymer substrate and an overmolded element of the same material. This is because the complexity and interdisciplinary nature of bonding and the lack of a unified adhesion theory. In this study, we developed a unique modeling method that can accurately predict the bonding strength of the interface formed between a substrate and an overmolded element for acrylonitrile butadiene styrene (ABS). The method combines the analytical modeling of reptation, the numerical modeling of overmolding, the modeling of tensile tests, and the verification of the obtained modeling results with the tested ones. Our method has an average accuracy of over 90%.