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The Effect Of Interfacial Conformity On The Contact Adhesion And Sliding Friction Of Surfaces With Small Roughness
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Book Synopsis The Effect of Interfacial Conformity on the Contact, Adhesion, and Sliding Friction of Surfaces with Small Roughness by : Herbert Mark Stanley
Download or read book The Effect of Interfacial Conformity on the Contact, Adhesion, and Sliding Friction of Surfaces with Small Roughness written by Herbert Mark Stanley and published by . This book was released on 1993 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Surface effects in adhesion, friction, wear, and lubrication by : Donald H. Buckley
Download or read book Surface effects in adhesion, friction, wear, and lubrication written by Donald H. Buckley and published by Elsevier. This book was released on 1981-01-01 with total page 643 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface effects in adhesion, friction, wear, and lubrication
Book Synopsis Contact Mechanics Modeling of Homogeneous and Layered Elastic-Plastic Media by : Zhichao Song
Download or read book Contact Mechanics Modeling of Homogeneous and Layered Elastic-Plastic Media written by Zhichao Song and published by . This book was released on 2012 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this dissertation was to analyze surface contact interaction at different length scales and to elucidate the effects of material properties (e.g., adhesion and mechanical properties), normal and shear (friction) surface tractions, and topography parameters (e.g., roughness) on contact deformation. To accomplish this objective, a surface adhesion model based on an interatomic potential was incorporated into finite element contact models of rough surfaces exhibiting multi-scale roughness described by statistical and fractal geometry models. The problem of a rigid sphere in contact with an elastic-plastic half-space was first examined in the light of finite element simulations. Four post-yield deformation regimes were identified and the boundaries of neighboring regimes were obtained by curve-fitting of finite element results. Material hardness was shown to significantly deviate from the similarity solution with decreasing elastic modulus-to-yield strength ratio and the logarithmic dependence of the mean contact pressure on the indentation depth was found to hold only when the plastic zone was completely surrounded by elastic material. Constitutive equations were first derived for elastic-perfectly plastic half-spaces from curve-fitting finite element results and were then extended to isotropic, power-law hardening half-spaces, using the concept of the effective strain, which correlates the indentation depth with the indenter size. Finite element simulations of unloading process and repetitive normal contact were used to correlate the residual indentation depth and the dissipated plastic energy with the maximum indentation depth. Elastic shakedown, plastic shakedown, and ratcheting were identified by tracking the accumulation of plasticity for different values of maximum contact load and elastic modulus-to-yield strength ratio. The semi-infinite half-space was characterized by three different regions, named ratcheting region, shakedown region and elastic region, as the distance to contact surface increases. The obtained results have direct implication in material property measurements obtained with indentation method, particularly for materials exhibiting strain hardening behavior, and provide insight into the accumulation of plasticity due to repetitive contact loading, which is important in the understanding of the contact fatigue life of contact-mode devices. Sliding contact between a rigid fractal surface exhibiting multi-scale roughness and an elastic-plastic half-space was examined to elucidate rough-surface deformation due to small-amplitude reciprocating sliding (fretting). Stick-slip at the asperity scale was analyzed based on Mindlin's theory and a friction model that accounts for both adhesion and plowing effects. Numerical results yield insight into the effects of surface roughness, contact pressure, oscillation amplitude, elastic modulus-to-yield strength ratio, and interfacial adhesion on the friction force, slip index, and energy dissipation. The results of this study illustrate the important role of the contact load and surface topography on the energy dissipation and fretting wear of small-amplitude oscillatory contacts. Surface adhesion modeled as surface traction obeying the Lennard-Jones (LJ) potential was incorporated into the contact analysis of a rigid sphere indenting an elastic half-space to study contact instabilities associated with instantaneous surface contact (jump-in) and detachment (jump-out). This surface traction was introduced into a finite element contact model in the form of nonlinear spring elements and the jump-in/jump-out condition obtained analytically was confirmed by finite element results. Then, adhesive contact between a rigid sphere and an elastic-plastic half-space was analyzed and the effect of plasticity on the pull-off force and the commencement of contact instabilities was interpreted in terms of a modified Tabor parameter. The developed finite element model with nonlinear spring elements representing adhesive surface interaction provides a physics-based, computationally-efficient technique for studying adhesive contacts. The obtained results provide explanation for the contact instabilities encountered during surface probing with microprobe tips and stiction (permanent adhesion) in contact-mode microdevices. Adhesive contact between a rigid sphere and a layered medium analyzed with the finite element method shed light into adhesion-induced contact deformation. Two modes of surface detachment were observed for perfect bonding of the film to the substrate - brittle- and ductile-like surface detachment. Simulation results illustrate the effects of the maximum surface separation, film thickness, film-to-substrate elastic property mismatch, and substrate yield strength on the mode of surface detachment and residual deformation. Introducing a cohesive model that allows for crack formation and growth along the film/substrate interface in the previous finite element model, a residual cohesive zone was found at the crack tip after complete unloading. Contact instabilities and interface delamination were interpreted by the competing effects of surface adhesion and interfacial cohesion. Crack closure and crack-tip opening displacement (CTOD) were studied by performing a parametric study of the cohesive strength, interfacial energy, surface energy, surface adhesive strength, substrate yield strength, and initial defect size. The obtained results can be used to explain thin-film failure in contact systems due to the effect of adhesion and to improve the endurance of thin-film media subjected to surface tractions. Adhesive contact of two elastic rough surfaces was analyzed by integrating asperity-scale constitutive equations into the model of Greenwood and Williamson (1966) to account for the effect of contact instabilities at asperity level on the macroscopic contact response. The strength of adhesion was found to be mostly affected by the Tabor parameter and the surface roughness. The widely used adhesion parameter of Fuller and Tabor (1977) was shown to be appropriate only for contact systems characterized by a high Tabor parameter. Therefore, a new adhesion parameter that governs the strength of adhesion of contact systems with a low Tabor parameter was introduced. Finally, a generalized adhesion parameter was derived by using the concept of the effective interatomic separation, defined as the ratio of the elastic stretch due to adhesion and the equilibrium interatomic distance. The research carried out in this dissertation provides fundamental understanding of the evolution of the stress and strain fields in contacting surfaces, the evolution of plasticity in indentation, the development of friction and dissipation of energy in fretting contacts, the occurrence of adhesion-induced contact instabilities and interfacial delamination, and the factors affecting the strength of adhesion for rough surfaces in normal contact. The results of this thesis have direct implications in various technologies, including high-efficiency gas turbines, magnetic storage devices, and microelectromechanical systems.
Book Synopsis How Surface Roughness Affects Adhesion by : Antoine Sanner
Download or read book How Surface Roughness Affects Adhesion written by Antoine Sanner and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: At atomic scales, all molecules attract each other, but macroscopic objects usually do not stick.The explanation for this apparent paradox is that most surfaces are rough, so that elastically stiff objects only touch on the top of their asperities. Geckos and insects have compliant fibrillar structures or soft pads at the tip of their feet that conform to surface roughness, sustaining enough adhesion to climb vertical walls. Understanding the role of surface roughness in adhesion is a challenge because surfaces exhibit roughness down to the atomic scale. In this thesis, my collaborators and I investigate the effect of surface roughness on adhesion in both stiff and compliant contact systems. I model adhesion theoretically, and I help experimentalists analyze surface topography over multiple scales. The combination of my new models and of the comprehensive surface topography characterization by Abhijeet Gujrati (University of Pittsburgh), allows us to unravel the role of surface roughness in adhesion experiments. Stiff materials do not stick because roughness prevents most of the surfaces to come into the range of molecular attraction. A recent theory quantifies this effect based on an approximate expression for the distribution of interfacial gaps near the contact edge. Joe Monti (Johns Hopkins University) and I benchmark this expression against gap distributions extracted from finely resolved numerical simulations. The theory is valid provided that adhesive stresses are weak and act over a range shorter than a geometrical parameter determined by small-scale roughness. Elastically soft (jelly-like) objects stick because the elastic penalty to deform into intimate contact is small compared to the gain in surface energy. However, theories based on this simple thermodynamic argument cannot explain the fact that in experiments, the force measured during retraction is often much higher than during indentation. This adhesion hysteresis can be caused by material specific irreversibility or elastic instabilities triggered by surface roughness. The role of these instabilities in adhesion hysteresis remains poorly understood because existing numerical and theoretical models cannot account for realistic roughness in soft contacts. I introduce an efficient crack-perturbation model for the contact of rough spheres, enabling large scale simulations with realistic surface roughness. By clarifying the link between adhesion hysteresis and classic pinning problems (for example fracture of heterogeneous materials and wetting angle hysteresis), this model allows me to derive a simple theoretical model linking adhesion hysteresis to surface roughness. In combination with the characterization of surface roughness over multiple scales, my models shed light on the role of elastic instabilities in adhesion experiments. Surfaces are rough from the macroscopic scale down to the atomic scale, and the lack of comprehensive roughness characterization is the major obstacle towards bringing theory and experiments together. Abhijeet Gujrati and collaborators measured the roughness of four diamond coatings over eight decades of length scales, enabling the application of adhesion theories on experiments performed with these samples. Besides the experimental challenge of determining roughness down to the atomic scale, an additional obstacle to the documentation of roughness is the technical complexity of established multiscale roughness measures such as the power spectral density. My collaborators and I address this problem by introducing the scale-dependent roughness parameters (SDRPs), a new analysis framework that is easy to interpret and to implement. This new analysis, together with several established techniques, is available to use through our web-service contact.engineering. We thereby encourage the community to measure, analyze and publish roughness over multiple length scales. The SDRP analysis computes the fluctuations of slopes and curvatures as a function of the lateral length scale. Slopes and curvatures are important ingredients for rough contact theories, but it remains unclear at which scales they matter. Luke Thimons (University of Pittsburgh) and I show that in macro-scale contacts between ruby spheres and diamond coatings, the roughness that critically affects adhesion is between lateral length scales of 43~nm to 1.8~μm. The large-scale cutoff is related to the finite radius of the spherical indenter, while the unimportance of small scales is due to plastic deformations and the long range of the adhesive interaction (5~nm). To determine the critical range of length scales, as well as the parameters of the adhesive interaction, we analyzed the experimental pull-off forces by combining surface topography characterization and numerical simulations. Adhesion is critical in applications such as microelectromechanical systems (MEMS), soft robotics and skin adhesives. Our insights provide guidance for practitioners which scales of roughness to control in order to tune adhesion, and our framework for surface topography characterization will allow a better overall understanding of surface topography across the community
Book Synopsis Modification of Adhesion and Friction by Surface Structuring by : Ying Bai
Download or read book Modification of Adhesion and Friction by Surface Structuring written by Ying Bai and published by . This book was released on 2014 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: Enhanced and selective adhesion, and controlled friction between contact surfaces are highly desirable mechanical properties for high-level functional materials. There are many instances in nature where such properties have been obtained by design of near-surface architecture. Inspired by many highly functional biological systems, we have explored bio-mimetic materials with different surface patterning, with the goal of designing surfaces that have unique combinations of contact mechanical properties. In the studies presented here, we show how: (a) highly selective adhesion can be achieved by complementarity of patterned charge and shape, and (b) how friction can be modulated by spatial variation in stiffness, and how structured surfaces interact with surface roughness. We consider how adhesion selectivity can be accomplished by complementarity of shape and inter-surface forces. We have studied an example each of charge and shape complementarity for selective adhesion between extended surfaces. First, we studied theoretically how surfaces patterned with stripes of charge interact with each other, and exhibit strong selectivity on rigid surfaces. However, deformability of the surfaces plays a crucial role in modulating adhesion by accommodating mismatches. To achieve shape complementarity, we designed and fabricated patterned elastomeric surfaces with lines of channels and complementary ridges with dimensions at the micrometer scale. We show that such surfaces have highly enhanced effective adhesion for shape complementary pairs and low adhesion between surfaces with a shape mismatch. We find that the pillar/channel combinations form defects to accommodate interfacial misalignment. These defects are interfacial dislocations. Adhesion between complementary surfaces is enhanced by crack trapping and friction, and attenuated due to the energy released by dislocation structures. In addition to enhanced adhesion, we studied the deliberate control of friction through near-surface micro-structures. Friction measurements on elastomeric surfaces patterned with periodic variation in stiffness show that it undergoes an "auto-roughening" transition under shear and this process can strongly attenuate overall sliding friction. Friction reduction is due to reduction of real contact area, as the initially full contact breaks up into partial contact at the interface. Finite element analysis demonstrates how auto-roughening depends on the modulus mismatch, frictional stress and normal displacement. A surface with random roughness is used to study sliding friction against micro-channel structures under fixed normal force. In contrast to a smooth surface, against which structured surfaces all have highly reduced sliding friction, the roughened surface can exhibit significantly larger frictional force on a structured surface. The enhancement of sliding friction is governed by channel depth, spacing and applied normal force.
Book Synopsis Understanding Contact Mechanics and Friction on Rough Surfaces by : Siddhesh Narayan Dalvi
Download or read book Understanding Contact Mechanics and Friction on Rough Surfaces written by Siddhesh Narayan Dalvi and published by . This book was released on 2020 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the mechanism of adhesion and friction in soft materials is critical to the fields of transportation (tires, wiper blades, seals etc.), prosthetics and soft robotics. Most surfaces are inherently rough and the interfacial area between two contacting bodies depends largely on the material properties and surface topography of the contacting bodies. Johnson, Kendall and Roberts (JKR) derived an equilibrium energy balance for the behavior of smooth elastic spherical bodies in adhesive contact that predicts a thermodynamic work of adhesion for two surfaces in contact. The JKR equation gives a reversible work of adhesion value during approach and retraction. However, viscoelastic dissipation, surface roughness and chemical bonding result in different work of adhesion values for approach and retraction. This discrepancy is termed adhesion hysteresis. Roughness is undermined as a cause of hysteresis in adhesion studies. Recently, a continuum mechanics model has been developed that predicts the work of adhesion on rough surfaces with known roughness in the form of power spectral density (PSD) function. To test the above mentioned theoretical model, we have conducted JKR experiments between highly cross-linked smooth polydimethylsiloxane (PDMS) of four different elastic moduli and diamond surfaces of four different crystal sizes and roughness.The rough diamond surfaces are characterized for topography using stylus profilometry, atomic force microscopy and in-situ transmission electron microscopy combined to give a comprehensive PSD. Results suggest that the observed work of adhesion during approach is equivalent to energy required to stretch the PDMS network at the surface and in the bulk to form the real rough contact area. However, in retraction work of adhesion is found to be proportional to the ratio of excess energy spent in the loading-unloading cycle and the true contact area obtained from topography indicating conformal contact matching fracture mechanics behavior. Thus, the study resolves adhesion hysteresis discrepancy on rough surfaces.It is known that adhesion hysteresis increases interfacial friction on rough surfaces. However, an experimentally proven quantitative model is still missing. Previous studies on smooth surfaces have shown that shear stress increases with velocity initially, reaching a maximum and then either plateaus out or decreases depending upon the modulus of the sliding elastomer. We have performed shear measurements with velocities ranging from nm/sec to cm/sec between PDMS elastomers and diamond surfaces. Data suggests higher shear stresses at lower velocities for rough surfaces and thus a shift for the peak previously observed on smooth surfaces. Additionally, there are states such as steady-state sliding, stick-slip and detachment waves with increasing stress in the same order. These states are found to occur at a critical stress and their onset is linearly proportional to the elastic modulus of the sliding rubber. The stress predictions using existing theories do not decouple adhesion and deformation energy losses during friction observed ex- perimentally on rough surfaces and further investigation is required in order to obtain a better friction model.
Book Synopsis Interfacial Phenomena by : J.T. Davies
Download or read book Interfacial Phenomena written by J.T. Davies and published by Academic Press. This book was released on 2012-12-02 with total page 507 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interfacial Phenomena examines the fundamental properties of various liquid interfaces. This book discusses the physics of surfaces; electrostatic and electrokinetic phenomena; and adsorption at liquid interfaces. The properties of monolayers; reactions at liquid surfaces; diffusion through interfaces; and disperse systems and adhesion are also deliberated. Other topics include the vapor pressures over curved surfaces; electrical capacity of the double layer; applications of electrophoresis; and thermodynamics of adsorption and desorption. The experimental methods of spreading films at the oil-water interface; penetration into monolayers; experiments on dynamic systems; and spontaneous emulsification are likewise covered in this text. This book is beneficial to chemical engineers and students concerned with interfacial phenomena.
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1992 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Optimization of Hard Disk Drive Components by : Matthew Arnold O'Hara
Download or read book Optimization of Hard Disk Drive Components written by Matthew Arnold O'Hara and published by . This book was released on 1997 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effect of Interfacial Friction on Adhesion by : Bi-min Zhang Newby
Download or read book Effect of Interfacial Friction on Adhesion written by Bi-min Zhang Newby and published by . This book was released on 1998 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventionally, the energy required to fracture an interface is predicted to be directly proportional to the thermodynamic work of adhesion. It has been observed, however, that on some low energy surfaces, the fracture energy of an adhesive deviates significantly from this rule. In viscoelastic systems, it is well known that most of the energy is dissipated by the viscous bulk materials near the crack tip region. What is, perhaps, not so widely known is that for a crack propagating at an asymmetric interface, a substantial amount of energy can be dissipated through a frictional mechanism near the crack tip region. This energy dissipation due to friction at and near the crack tip is being proposed to account for the discrepancies observed with adhesion on low energy surfaces. The objective of this research is to investigate the contribution of interfacial friction and associated slip processes to the total fracture energy.
Book Synopsis Fundamentals of Adhesion and Interfaces by : Lawrence P Demajo
Download or read book Fundamentals of Adhesion and Interfaces written by Lawrence P Demajo and published by CRC Press. This book was released on 2000-10-31 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: The understanding of adhesion and interfacial effects has benefited from various technological advances in recent years. Advances in laboratory equipment, analytical tools such as the nanoindentor, SIMS, and ESCA, and improvements in computing technology have greatly expanded the relevant body of knowledge. Rapid progress in adhesion and interfacial science has made dissemination of results in a timely fashion more important than ever. Accordingly, the editors of this book organized an ACS symposium, sponsored by the Division of Polymer Chemistry, entitled Fundamentals of Adhesion and Interfaces. The papers in this volume were selected from those presented at the symposium.
Book Synopsis International Encyclopedia of Ergonomics and Human Factors by : Waldemar Karwowski
Download or read book International Encyclopedia of Ergonomics and Human Factors written by Waldemar Karwowski and published by CRC Press. This book was released on 2001 with total page 712 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Contact Angle, Wettability and Adhesion by : K. L. Mittal
Download or read book Contact Angle, Wettability and Adhesion written by K. L. Mittal and published by BRILL. This book was released on 2008-08-31 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume chronicles the proceedings of the "5th International Symposium on Contact Angle, Wettability and Adhesion" Toronto, Canada, June 2006. Wettability is of pivotal importance in many and varied arenas, ranging from mundane to micro-and nanofluidics to lithography to biomedical. It should be underscored that in the last years there has been burgeoning interest in replicating the so-called a oeLotus Leaf Effecta to create superhydrophobic surfaces. This volume contains a total of 19 papers covering many facets of contact angle, wettability and adhesion. All manuscripts were rigorously peer-reviewed and revised and edited before inclusion in this book. Concomitantly, this volume represents an archival publication of the highest standard. This book (5th volume in the series) is divided into three parts: Part 1: Contact Angle Measurements and Solid Surface Free Energy; Part 2: Relevance of Wetting in Cleaning and Adhesion; Part 3: Superhydrophobic Surfaces. The topics covered include: Fundamental aspects of contact angle and its measurement; solidification contact angles of micro-droplets; microscopic wettability of wood call walls; dynamic vapor-liquid interfacial tension; surface free energy of polymeric materials; surface cleanliness evaluation from wettability measurements; wettability parameters affecting surface cleanability of stainless steel and textiles; wetting and adhesion in fibrous materials; wettability and adhesion of coatings; adhesion of hydrophobizing agents; modulation of surface properties of polymers; graft efficiency and adhesion; relevance of interfacial free energy in cell adhesion; various approaches to create superhydrophobic surfaces; adsorption of surfactants on hydrophobic and superhydrophobic surfaces.
Book Synopsis International Encyclopedia of Ergonomics and Human Factors - 3 Volume Set by : Informa Healthcare
Download or read book International Encyclopedia of Ergonomics and Human Factors - 3 Volume Set written by Informa Healthcare and published by CRC Press. This book was released on 2000-12-14 with total page 1980 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first encyclopedia in the field, the International Encyclopedia of Ergonomics and Human Factors provides a comprehensive and authoritative compendium of current knowledge on ergonomics and human factors. It gives specific information on concepts and tools unique to ergonomics. About 500 entries, published in three volumes and on CD-ROM, are pre
Book Synopsis Roughness and Adhesion Effects on Pre-sliding Friction by : Mohammad Bazr Afshan Fadafan
Download or read book Roughness and Adhesion Effects on Pre-sliding Friction written by Mohammad Bazr Afshan Fadafan and published by . This book was released on 2019 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Interfacial Mechanics by : Jane Wang
Download or read book Interfacial Mechanics written by Jane Wang and published by CRC Press. This book was released on 2019-12-06 with total page 1005 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the characteristics of material contact and lubrication at tribological interfaces is of great importance to engineering researchers and machine designers. Traditionally, contact and lubrication are separately studied due to technical difficulties, although they often coexist in reality and they are actually on the same physical ground. Fast research advancements in recent years have enabled the development and application of unified models and numerical approaches to simulate contact and lubrication, merging their studies into the domain of Interfacial Mechanics. This book provides updated information based on recent research progresses in related areas, which includes new concepts, theories, methods, and results for contact and lubrication problems involving elastic or inelastic materials, homogeneous or inhomogeneous contacting bodies, using stochastic or deterministic models for dealing with rough surfaces. It also contains unified models and numerical methods for mixed lubrication studies, analyses of interfacial frictional and thermal behaviors, as well as theories for studying the effects of multiple fields on interfacial characteristics. The book intends to reflect the recent trends of research by focusing on numerical simulation and problem solving techniques for practical interfaces of engineered surfaces and materials. This book is written primarily for graduate and senior undergraduate students, engineers, and researchers in the fields of tribology, lubrication, surface engineering, materials science and engineering, and mechanical engineering.
Book Synopsis Contact, Adhesion, and Static Friction of Metallic Rough Surfaces by : Wen-Ruey Chang
Download or read book Contact, Adhesion, and Static Friction of Metallic Rough Surfaces written by Wen-Ruey Chang and published by . This book was released on 1986 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
