Engineering › Mechanics of Materials

Adhesion, Friction, and Surface Interactions

Works Count: 46267

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Description

This cluster of papers focuses on the mechanics of gecko foot adhesion, including the study of van der Waals forces, surface roughness, contact mechanics, and the development of biomimetic adhesives. It explores the nanoscale structures, frictional properties, and hierarchical designs inspired by gecko feet for potential applications in various fields.

Keywords

Gecko; Adhesion; Friction; Contact Mechanics; Biomimetic; Nanotubes; Surface Roughness; Elastic-Plastic Contact Analysis; Microstructures; Bioinspired

Surface forces and surface interactions

1977-01-01

D. Tabor

The effect of surface roughness on the adhesion of elastic solids

1975-09-30

K. N. G. Fuller , David Tabor

This paper describes a study of the adhesion between elastic solids and the effect of roughness in reducing the adhesion. The experiments were carried out between optically smooth rubber spheres … This paper describes a study of the adhesion between elastic solids and the effect of roughness in reducing the adhesion. The experiments were carried out between optically smooth rubber spheres and a hard smooth flat surface of Perspex which could be roughened to various degrees. The radius of the rubber spheres was varied by a factor of 8, their elastic modulus by a factor of 10, while the centre line average (c.l.a.)of the roughened Perspex surface was varied from 0.12 to 1.5 μm. The results show that c.l.a. roughnesses which are small compared with the overall deformation occurring at the region of the rubber-Perspex contact can produce an extremely large reduction in adhesion. The effect is more marked for rubbers of higher modulus. On the other hand the curvature of the sphere (over the range examined) has little influence. For this reason and because the analytical problem of a sphere on a rough flat is extremely complicated a theoretical analysis has been developed for the simpler case of a smooth flat in contact with a rough flat surface. As in Greenwood & Williamson (1966) the rough surface is modelled by asperities all of the same radius of curvature and with heights following a Gaussian distribution of standard deviation σ. The overall contact force is obtained by applying the contact theory of Johnson, Kendall & Roberts (1971) to each individual asperity. The theory predicts that the adhesion expressed as a fraction of the maximum value depends upon a single parameter, 1/Δ e ,which is the ratio between a and the elastic displacement δ C that the tip of an asperity can sustain before it pulls off from the other surface. The analysis shows that the adhesion parameter may also be regarded as representing the statistical average of a competition between the compressive forces exerted by the higher asperities trying to prize the surfaces apart and the adhesive forces between the lower asperities trying to hold the surfaces together. Although the theory is derived for two nominally plane surfaces it is found to fit the experimental results for a sphere on a flat reasonably well.

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Theory of rubber friction and contact mechanics

2001-08-22

B. N. J. Persson

When rubber slides on a hard, rough substrate, the surface asperities of the substrate exert oscillating forces on the rubber surface leading to energy “dissipation” via the internal friction of … When rubber slides on a hard, rough substrate, the surface asperities of the substrate exert oscillating forces on the rubber surface leading to energy “dissipation” via the internal friction of the rubber. I present a discussion of how the resulting friction force depends on the nature of the substrate surface roughness and on the sliding velocity. I consider in detail the case when the substrate surface has a self affine fractal structure. I also present a theory for the area of real contact, both for stationary and sliding bodies, with elastic or elastoplastic properties. The theoretical results are in good agreement with experimental observation.

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Critical Review: Adhesion in surface micromechanical structures

1997-01-01

Roya Maboudian , Roger T. Howe

We present a review on the state of knowledge of surface phenomena behind adhesion in surface micromechanical structures. After introducing the problem of release-related and in-use adhesion, a theoretical framework … We present a review on the state of knowledge of surface phenomena behind adhesion in surface micromechanical structures. After introducing the problem of release-related and in-use adhesion, a theoretical framework for understanding the various surface forces that cause strong adhesion of micromechanical structures is presented. Various approaches are described for reducing the work of adhesion. These include surface roughening and chemical modification of polycrystalline silicon surfaces. The constraints that fabrication processes such as release, drying, assembly, and packaging place on surface treatments are described in general. Finally, we briefly outline some of the important scientific and technological issues in adhesion and friction phenomena in micromechanical structures that remain to be clarified.

An Asperity Microcontact Model Incorporating the Transition From Elastic Deformation to Fully Plastic Flow

1999-05-19

Yongwu Zhao , David M. Maietta , L. Chang

This paper presents an elastic-plastic asperity microcontact model for contact between two nominally flat surfaces. The transition from elastic deformation to fully plastic flow of the contacting asperity is modeled … This paper presents an elastic-plastic asperity microcontact model for contact between two nominally flat surfaces. The transition from elastic deformation to fully plastic flow of the contacting asperity is modeled based on contact-mechanics theories in conjunction with the continuity and smoothness of variables across different modes of deformation. The relations of the mean contact pressure and contact area of the asperity to its contact interference in the elastoplastic regime of deformation are respectively modeled by logarithmic and fourth-order polynomial functions. These asperity-scale equations are then used to develop the elastic-plastic contact model between two rough surfaces, allowing the mean surface separation and the real area of contact to be calculated as functions of the contact load and surface plasticity index. Results are presented for a wide range of contact load and plasticity index, showing the importance of accurately modeling the deformation in the elastoplastic transitional regime of the asperity contacts. The results are also compared with those calculated by the GW and CEB models, showing that the present model is more complete in describing the contact of rough surfaces. [S0742-4787(00)01201-7]

Contact and Rubbing of Flat Surfaces

1953-08-01

J. F. Archard

The interpretation of certain phenomena occuring at nominally flat surfaces in stationary or sliding contact is dependent on the assumed distribution of the real area of contact between the surfaces. … The interpretation of certain phenomena occuring at nominally flat surfaces in stationary or sliding contact is dependent on the assumed distribution of the real area of contact between the surfaces. Since there is little direct evidence on which to base an estimate of this distribution, the approach used is to set up a simple model and compare the deduced theory (e.g., the deduced dependence of the experimental observables on the load) with the experimental evidence. The main conclusions are as follows. (a) The electrical contact resistance depends on the model used to represent the surfaces; the most realistic model is one in which increasing the load increases both the number and size of the contact areas. (b) In general, mechanical wear should also depend on the model. However, in wear experiments showing the simplest behavior, the wear rate is proportional to the load, and these results can be explained by assuming removal of lumps at contact areas formed by plastic deformation; moreover, this particular deduction is independent of the assumed model. This suggests that a basic assumption of previous theories, that increasing the load increases the number of contacts without affecting their average size, is redundant.

The Stress Field Created by a Circular Sliding Contact

1966-06-01

G. M. Hamilton , L. E. Goodman

Equations are obtained for the complete stress field due to a circular contact region carrying a “hemispherical” Hertzian normal pressure and a proportional distributed shearing traction. The equations are illustrated … Equations are obtained for the complete stress field due to a circular contact region carrying a “hemispherical” Hertzian normal pressure and a proportional distributed shearing traction. The equations are illustrated by graphs of a constant-yield parameter and graphs of maximum tensile stress.

Computational Contact Mechanics

2007-01-01

Peter Wriggers

Design and mechanical properties of insect cuticle

2004-07-01

Julian F. V. Vincent , Ulrike G. K. Wegst

<i>Sliding Friction: Physical Principles and Applications</i>

1999-01-01

B. N. J. Persson , Nicholas D. Spencer

1. Introduction.- 2. Historical Note.- 3. Modern Experimental Methods and Results.- 4. Surface Topography and Surface Contaminants.- 5. Area of Real Contact: Elastic and Plastic Deformations.- 6. Sliding on Clean … 1. Introduction.- 2. Historical Note.- 3. Modern Experimental Methods and Results.- 4. Surface Topography and Surface Contaminants.- 5. Area of Real Contact: Elastic and Plastic Deformations.- 6. Sliding on Clean (Dry) Surfaces.- 7. Sliding on Lubricated Surfaces.- 8. Sliding of Adsorbate Layers.- 9. Boundary Lubrication.- 10. Elastic Interactions and Instability Transitions.- 11. Stress Domains, Relaxation, and Creep.- 12. Lubricated Friction Dynamics.- 13. Dry Friction Dynamics.- 14. Novel Sliding Systems.- 15. Outlook.- References.

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The temperature of rubbing surfaces

1959-10-01

J. F. Archard

Contact Angle Hysteresis Explained

2006-06-03

Lichao Gao , Thomas J. McCarthy

A view of contact angle hysteresis from the perspectives of the three-phase contact line and of the kinetics of contact line motion is given. Arguments are made that advancing and … A view of contact angle hysteresis from the perspectives of the three-phase contact line and of the kinetics of contact line motion is given. Arguments are made that advancing and receding are discrete events that have different activation energies. That hysteresis can be quantified as an activation energy by the changes in interfacial area is argued. That this is an appropriate way of viewing hysteresis is demonstrated with examples.

The elastic contact of a rough surface

1975-11-01

A.W. Bush , R.D. Gibson , T. R. Thomas

Internal Friction in Solids. I. Theory of Internal Friction in Reeds

1937-08-01

Clarence Zener

In a vibrating reed opposite sides have dilations of opposite signs. Thus when one side is heated the other is cooled. At low frequencies the vibrations are isothermal. At high … In a vibrating reed opposite sides have dilations of opposite signs. Thus when one side is heated the other is cooled. At low frequencies the vibrations are isothermal. At high frequencies they are adiabatic. At intermediate frequencies they are of a hybrid type accompanied by internal friction. In this paper this internal friction is calculated solely from thermodynamical considerations. It is predicted that the internal friction associated with this hybrid type of vibration is of a larger order of magnitude than that due to all other causes.

Thin-film peeling-the elastic term

1975-09-11

K. Kendall

An energy balance shows that the force required to peel an elastic film from a rigid substrate depends not only on the adhesive surface energy but also on an elastic … An energy balance shows that the force required to peel an elastic film from a rigid substrate depends not only on the adhesive surface energy but also on an elastic deformation term. This elastic term, tending to reduce the adhesion force, can only be significant in two instances: for materials which can support stresses approaching the elastic modulus without fracturing, and for very small peel angles. Experiments using rubber peeling from glass over a range of peel angles support the theory.

Models and computational methods for dynamic friction phenomena

1985-09-01

J. Tinsley Oden , J. A. C. Martins

SOME FRACTAL CHARACTERS OF POROUS MEDIA

2001-09-01

Boming Yu , Jianhua Li

In this paper, a unified model for describing the fractal characters of porous media is deduced. The theoretical predictions from the proposed unified model are compared with those from the … In this paper, a unified model for describing the fractal characters of porous media is deduced. The theoretical predictions from the proposed unified model are compared with those from the previous models and from the box-counting method. The results from the proposed model are found to be in good agreement with both the previous models and box-counting method. The results also indicate that the proposed unified model is applicable to both the exactly and statistically self-similar fractal media. A statistical property of porous media is also described based on the basic fractal theory and technique. A criterion, for determining whether a porous medium can be characterized by fractal theory and technique or not, is proposed based on the fractal statistical property.

Adhesion of spheres: The JKR-DMT transition using a dugdale model

1992-04-01

D. Maugis

Introduction to Tribology

2003-01-01

Bharat Bhushan , Pak Lim Ko

1R19. Introduction to Tribology. - B Bhushan (Nanotribology Lab for Info Storage and MEMS/NEMS (NLIM), Ohio State Univ, Columbus OH 43210). Wiley, New York. 2002. 732 pp. ISBN 0-471-15893-3. $120.00.Reviewed … 1R19. Introduction to Tribology. - B Bhushan (Nanotribology Lab for Info Storage and MEMS/NEMS (NLIM), Ohio State Univ, Columbus OH 43210). Wiley, New York. 2002. 732 pp. ISBN 0-471-15893-3. $120.00.Reviewed by Pak Lim Ko (Integrated Manuf Tech Inst, W Lab, NRC, 3250 E Mall, Vancouver BC, V6T 1W5, Canada).In the Preface, the author states that this book is intended as a broad-based textbook for post-graduate students. Judging by its contents and the comprehensiveness in discussion, this book has succeeded amply in fulfilling the author's claim. It can be used as a stand-alone reference book for both researchers and practicing engineers. Despite its title, which seems to suggest that this book is an introductory text, the scope of the topics that are covered is, indeed, very broad. With the exception of one significant omission, topics that are directly or indirectly concerned with the engineering and science of tribology, from friction, wear, and lubrication to surface characterization, contacting surfaces, test methods and applications, are dealt with comprehensively. The contemporary topic of micro/nanotribology is also given a prominent position in this book. The author also describes the book as a condensed version of his other comprehensive book titled Principles and Applications of Tribology. With a few minor differences, such as the omission of an important topic on coatings and surface treatments, the present version is in every aspect just as excellent a reference volume as the earlier version and a worthy alternative.The book is well organized with a very descriptive table of contents. Each chapter contains an introduction, a closure, and a comprehensive list of references and suggested reading. The author has provided many examples to illustrate the application of some of the equations and principles in the text. The book has 12 chapters spanning 720 pages. The graphs and figures are clearly presented, and the reproduction of photo-micrographs is reasonably good. The book starts with a chapter that briefly describes the history and industrial significance of tribology. This first chapter also reviews and describes the significance of the emerging field of micro/nanotribology. The second and third chapters provide a detailed discussion on topics involving solid surfaces and their contacts, such as, physico-chemical characteristics of surface layers, the analyses and measurement techniques for surface roughness, and elastic and plastic contacts. Several illustrative examples are presented to help the reader better comprehend the analyses involved. Chapter 4 describes the adhesion mechanisms of solid-solid and liquid-mediated contacts. The following chapter on friction, like the one on adhesion, is also divided into solid-solid and liquid-mediated contacts. There is also a short discussion on static friction and stick-slip. Unfortunately, it would require a more in-depth discussion for frictional vibration and the associated friction characteristics to be properly explained. The section on friction of materials describes the friction characteristics of a broad range of materials and their combinations. The interface temperature rise due to frictional heating is discussed in Chapter 6. The analysis, which follows the fundamental heat conduction solutions and takes into consideration the partition of heat, is divided into frictional contacts that are subjected to high stress conditions or low stress conditions. Although there are two numerical examples to help illustrate the application of the derived equations, some readers may find it difficult to comprehend the concept of heat partition and the development of the temperature rise equations between two bodies in relative motion for the two stress conditions. This would be particularly true for practicing engineers who may not be familiar with this topic. Chapter 7 provides a general description of several types of commonly known wear mechanisms and types of wear particles that are the consequence of different wear mechanisms and wear processes. The section on wear of materials helps to further illustrate the wear processes and wear mechanisms involved. Chapters 8 and 9 are devoted to fluid film and boundary lubrication. The various regimes of lubrication, the theories of hydrostatic, hydrodynamic and elastohydrodynamic lubrication, as well as bearing designs are reviewed in Chapter 8, whereas in Chapter 9, the mechanisms of boundary lubrication, various liquid lubricants and additives, and greases are presented. The surface force apparatus (SFA), the scanning tunneling microscopes (STM), and the atomic force and friction force microscopes (AFM and FFM) are relatively modern devices developed in the last 40 years. They are widely used for studies of interfacial phenomena on a small scale, such as those in magnetic storage systems and micro-electromechanical systems (MEMS). Chapter 10 provides a comprehensive description of these devices and their applications in tribology. Chapter 11 discusses some friction and wear test methods. The last chapter describes a number of tribological components, such as, bearings, seals and gears; and microcomponents, such as MEMS, as well as tools used in material processing operations. In summary, Introduction to Tribology is a broad-based reference book which covers nearly every aspect of tribology from the fundamentals of friction, wear, lubrication, and surface contacts to the emerging field of micro/nanotribology. It is, as the author intended, an excellent text for post-graduate and senior-level undergraduate courses, and a useful reference for researchers and practicing engineers who are involved in tribology related studies or projects.

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A continuum theory of elastic material surfaces

1975-12-01

Morton E. Gurtin , A. Ian Murdoch

Contact of nominally flat surfaces

1966-12-06

J. A. Greenwood , J. B. P. Williamson

It is usually assumed that the real area of contact between two nominally flat metal surfaces is determined by the plastic deformation of their highest asperities. This leads at once … It is usually assumed that the real area of contact between two nominally flat metal surfaces is determined by the plastic deformation of their highest asperities. This leads at once to the result that the real area of contact is directly proportional to the load and independent of the apparent area—a result with many applications in the theories of electric contacts and friction. Archard pointed out that plastic deformation could not be the universal rule, and introduced a model which showed that, contrary to earlier ideas, the area of contact could be proportional to the load even with purely elastic contact. This paper describes a new theory of elastic contact, which is more closely related to real surfaces than earlier theories. We show how the contact deformation depends on the topography of the surface, and establish the criterion for distinguishing surfaces which touch elastically from those which touch plastically. The theory also indicates the existence of an ‘elastic contact hardness’, a composite quantity depending on the elastic properties and the topography, which plays the same role in elastic contact as the conventional hardness does in plastic contact. A new instrument for measuring surface topography has been built; with it the various parameters shown by the theory to govern surface contact can be measured experimentally. The typical radii of surface asperities have been measured. They were found, surprisingly, to be orders of magnitude larger than the heights of the asperities. More generally we have been able to study the distributions of asperity heights and of other surface features for a variety of surfaces prepared by standard techniques. Using these data we find that contact between surfaces is frequently plastic, as usually assumed, but that surfaces which touch elastically are by no means uncommon in engineering practice.

An Elastic-Plastic Model for the Contact of Rough Surfaces

1987-04-01

Wen-Ruey Chang , I. Etsion , David B. Bogy

An elastic-plastic asperity model for analyzing the contact of rough surfaces is presented. The model is based on volume conservation of an asperity control volume during plastic deformation. Numerical results … An elastic-plastic asperity model for analyzing the contact of rough surfaces is presented. The model is based on volume conservation of an asperity control volume during plastic deformation. Numerical results obtained from this model are compared with other existing models that are either purely elastic or purely plastic. It is shown that these models are limiting cases of the more general elastic-plastic model presented here. Some of the results obtained deviate appreciably from previous analyses which do not consider asperity volume conservation.

Finite-deformation irreversible cohesive elements for three-dimensional crack-propagation analysis

1999-03-30

M. Ortíz , Anna Pandolfi

We develop a three-dimensional finite-deformation cohesive element and a class of irreversible cohesive laws which enable the accurate and efficient tracking of dynamically growing cracks. The cohesive element governs the … We develop a three-dimensional finite-deformation cohesive element and a class of irreversible cohesive laws which enable the accurate and efficient tracking of dynamically growing cracks. The cohesive element governs the separation of the crack flanks in accordance with an irreversible cohesive law, eventually leading to the formation of free surfaces, and is compatible with a conventional finite element discretization of the bulk material. The versatility and predictive ability of the method is demonstrated through the simulation of a drop-weight dynamic fracture test similar to those reported by Zehnder and Rosakis. The ability of the method to approximate the experimentally observed crack-tip trajectory is particularly noteworthy. © 1999 John Wiley & Sons, Ltd.

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Evidence for van der Waals adhesion in gecko setae

2002-08-27

Kellar Autumn , Metin Sitti , Yiching A. Liang +7 more

Geckos have evolved one of the most versatile and effective adhesives known. The mechanism of dry adhesion in the millions of setae on the toes of geckos has been the … Geckos have evolved one of the most versatile and effective adhesives known. The mechanism of dry adhesion in the millions of setae on the toes of geckos has been the focus of scientific study for over a century. We provide the first direct experimental evidence for dry adhesion of gecko setae by van der Waals forces, and reject the use of mechanisms relying on high surface polarity, including capillary adhesion. The toes of live Tokay geckos were highly hydrophobic, and adhered equally well to strongly hydrophobic and strongly hydrophilic, polarizable surfaces. Adhesion of a single isolated gecko seta was equally effective on the hydrophobic and hydrophilic surfaces of a microelectro-mechanical systems force sensor. A van der Waals mechanism implies that the remarkable adhesive properties of gecko setae are merely a result of the size and shape of the tips, and are not strongly affected by surface chemistry. Theory predicts greater adhesive forces simply from subdividing setae to increase surface density, and suggests a possible design principle underlying the repeated, convergent evolution of dry adhesive microstructures in gecko, anoles, skinks, and insects. Estimates using a standard adhesion model and our measured forces come remarkably close to predicting the tip size of Tokay gecko seta. We verified the dependence on size and not surface type by using physical models of setal tips nanofabricated from two different materials. Both artificial setal tips stuck as predicted and provide a path to manufacturing the first dry, adhesive microstructures.

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A reversible wet/dry adhesive inspired by mussels and geckos

2007-07-01

Haeshin Lee , Bruce P. Lee , Phillip B. Messersmith

Role of Fractal Geometry in Roughness Characterization and Contact Mechanics of Surfaces

1990-04-01

Arun Majumdar , Bharat Bhushan

A proper characterization of the multiscale topography of rough surfaces is very crucial for understanding several tribological phenomena. Although the multiscale nature of rough surfaces warrants a scale-independent characterization, conventional … A proper characterization of the multiscale topography of rough surfaces is very crucial for understanding several tribological phenomena. Although the multiscale nature of rough surfaces warrants a scale-independent characterization, conventional techniques use scale-dependent statistical parameters such as the variances of height, slope and curvature which are shown to be functions of the surface magnification. Roughness measurements on surfaces of magnetic tape, smooth and textured magnetic thin film rigid disks, and machined stainless steel surfaces show that their spectra follow a power law behavior. Profiles of such surfaces are, therefore, statistically self-affine which implies that when repeatedly magnified, increasing details of roughness emerge and appear similar to the original profile. This paper uses fractal geometry to characterize the multiscale self-affine topography by scale-independent parameters such as the fractal dimension. These parameters are obtained from the spectra of surface profiles. It was observed that surface processing techniques which produce deterministic texture on the surface result in non-fractal structure whereas those producing random texture yield fractal surfaces. For the magnetic tape surface, statistical parameters such as the r.m.s. peak height and curvature and the mean slope, which are needed in elastic contact models, are found to be scale-dependent. The imperfect contact between two rough surfaces is composed of a large number of contact spots of different sizes. The fractal representation of surfaces shows that the size-distribution of the multiscale contact spots follows a power law and is characterized by the fractal dimension of the surface. The surface spectra and the spot size-distribution follow power laws over several decades of length scales. Therefore, the fractal approach has the potential to predict the behavior of a surface phenomenon at a particular length scale from the observations at other length scales.

The Contact of Two Nominally Flat Rough Surfaces

1970-06-01

J. A. Greenwood , J. H. Tripp

Most models of surface contact consider the surface roughness to be on one of the contacting surfaces only. The authors give a general theory of contact between two rough plane … Most models of surface contact consider the surface roughness to be on one of the contacting surfaces only. The authors give a general theory of contact between two rough plane surfaces. They show that the important results of the previous models are unaffected: in particular, the load and the area of contact remain almost proportional, independently of the detailed mechanical and geometrical properties of the asperities. Further, a single-rough-surface model can always be found which will predict the same laws as a given two-rough-surface model, although the required model may be unrealistic. It does not seem possible to deduce the asperity shape or deformation mode from the load-compliance curve.

From micro to nano contacts in biological attachment devices

2003-09-05

Eduard Arzt , Stanislav N. Gorb , Ralph Spolenak

Animals with widely varying body weight, such as flies, spiders, and geckos, can adhere to and move along vertical walls and even ceilings. This ability is caused by very efficient … Animals with widely varying body weight, such as flies, spiders, and geckos, can adhere to and move along vertical walls and even ceilings. This ability is caused by very efficient attachment mechanisms in which patterned surface structures interact with the profile of the substrate. An extensive microscopic study has shown a strong inverse scaling effect in these attachment devices. Whereas μm dimensions of the terminal elements of the setae are sufficient for flies and beetles, geckos must resort to sub-μm devices to ensure adhesion. This general trend is quantitatively explained by applying the principles of contact mechanics, according to which splitting up the contact into finer subcontacts increases adhesion. This principle is widely spread in design of natural adhesive systems and may also be transferred into practical applications.

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Microfabricated adhesive mimicking gecko foot-hair

2003-05-30

A. K. Geǐm , S. V. Dubonos , I. V. Grigorieva +3 more

Elastic deformation and the laws of friction

1957-12-24

J. F. Archard

This paper examines whether the hypothesis of elastic deformation of surface protuberances is consistent with Amontons’s law, that the friction is proportional to the applied load. For a single elastic … This paper examines whether the hypothesis of elastic deformation of surface protuberances is consistent with Amontons’s law, that the friction is proportional to the applied load. For a single elastic contact, the area of contact A is known to be proportional to the ⅔ power of the load W . Since the frictional force is generally assumed to be proportional to A , it has been thought that in elastic deformation Amontons’s law would not be obeyed. However, conforming surfaces usually touch at many points, and it is shown that in these circumstances A and W become nearly proportional. Experiments are described which show that the general law is that the friction is proportional to the true area of contact; whether or not Amontons’s law is obeyed depends upon the surface topography. For highly elastic materials such as Perspex, Amontons’s law is obeyed when contact is made at many points, and other relations between A and W are observed when the contacts are few. Experiments with lubricated brass specimens show that the same conclusions apply to carefully prepared or well run-in metal surfaces running in conditions where the damage is small.

Surface energy and the contact of elastic solids

1971-09-08

Kenneth L. Johnson , Kevin Kendall , A. D. Roberts

This paper discusses the influence of surface energy on the contact between elastic solids. Equations are derived for its effect upon the contact size and the force of adhesion between … This paper discusses the influence of surface energy on the contact between elastic solids. Equations are derived for its effect upon the contact size and the force of adhesion between two lightly loaded spherical solid surfaces. The theory is supported by experiments carried out on the contact of rubber and gelatine spheres.

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Fractal Model of Elastic-Plastic Contact Between Rough Surfaces

1991-01-01

Arun Majumdar , Bharat Bhushan

Roughness measurements by optical interferometry and scanning tunneling microscopy on a magnetic thin-film rigid disk surface have shown that its surface is fractal in nature. This leads to a scale-dependence … Roughness measurements by optical interferometry and scanning tunneling microscopy on a magnetic thin-film rigid disk surface have shown that its surface is fractal in nature. This leads to a scale-dependence of statistical parameters such as r.m.s height, slope and curvature, which are extensively used in classical models of contact between rough surfaces. Based on the scale-independent fractal roughness parameters, a new model of contact between isotropic rough surfaces is developed. The model predicts that all contact spots of area smaller than a critical area are in plastic contact. When the load is increased, these plastically deformed spots join to form elastic spots. Using a power-law relation for the fractal size-distribution of contact spots, the model shows that for elastic deformation, the load P and the real area of contact Ar are related as P~Ar(3−D)/2, where D is the fractal dimension of a surface profile which lies between 1 and 2. This result explains the origins of the area exponent which has been the focus of a number of experimental and theoretical studies. For plastic loading, the load and area are linearly related. The size-distribution of spots also suggests that the number of contact spots contributing to a certain fraction of the real area of contact remains independent of load although the spot sizes increase with load. The model shows that the load-area relation and the fraction of the real area of contact in elastic and plastic deformation are quite sensitive to the fractal roughness parameters.

The properties of random surfaces of significance in their contact

1970-03-31

David J. Whitehouse , J. F. Archard

In recent work it has been shown that many types of surfaces used in engineering practice have a random structure. The paper takes, as a representation of the profile of … In recent work it has been shown that many types of surfaces used in engineering practice have a random structure. The paper takes, as a representation of the profile of such a surface, the waveform of a random signal; this is completely defined by two parameters, a height distribution and an auto-correlation function. It is shown how such a representation can be transformed into a model, appropriate for the study of surface contact, consisting of an array of asperities having a statistical distribution of both heights and curvatures. This theory is compared with the results of an analysis of surface profiles presented in digital form. The significance of these findings for the theory of surface contact and for the measurement and characterization of surface finish is discussed.

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Elastic-Plastic Contact Analysis of a Sphere and a Rigid Flat

2002-08-16

Lior Kogut , I. Etsion

An elastic-plastic finite element model for the frictionless contact of a deformable sphere pressed by a rigid flat is presented. The evolution of the elastic-plastic contact with increasing interference is … An elastic-plastic finite element model for the frictionless contact of a deformable sphere pressed by a rigid flat is presented. The evolution of the elastic-plastic contact with increasing interference is analyzed revealing three distinct stages that range from fully elastic through elastic-plastic to fully plastic contact interface. The model provides dimensionless expressions for the contact load, contact area, and mean contact pressure, covering a large range of interference values from yielding inception to fully plastic regime of the spherical contact zone. Comparison with previous elastic-plastic models that were based on some arbitrary assumptions is made showing large differences.

Contact Angle, Wettability, and Adhesion

1964-01-01

Frederick M. Fowkes , W. A. Zisman

A review of the author's investigations of the equilibrium contact angles of pure liquids on low- and high-energy solid surfaces, both bare and covered with a condensed monomolecular adsorbed film, … A review of the author's investigations of the equilibrium contact angles of pure liquids on low- and high-energy solid surfaces, both bare and covered with a condensed monomolecular adsorbed film, includes the critical surface tension of wetting and the effect of homology on spreading by pure liquids, the causes of nonspreading on high-energy surfaces, and the existence and properties of autophobic liquids and oleophobic monolayers. Constitutive relationships are summarized in a table of critical surface tensions of wetting. The theory and application of the retraction method of preparing adsorbed monolayers from solution and the conditions for mixed films are presented. Studies of the wetting behavior of solutions of various surfactants and the resultant explanation of the function of a wetting agent are generalized to include nonaqueous systems. Following estimates of the reversible work of adhesion of liquids to solids, the part played by wetting in obtaining optimum adhesion by adhesives is outlined, and a fundamental explanation is given of constitutive effects in the development of strong adhesive joints. Future areas of research on wetting and adhesion are indicated.

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Relation of the Equilibrium Contact Angle to Liquid and Solid Constitution

1964-01-01

W. A. Zisman

Contact Mechanics and Friction

2010-01-01

Valentin L. Popov

Elastic Spheres in Contact Under Varying Oblique Forces

1953-09-01

R. D. Mindlin , H. Deresiewicz

Abstract An investigation is made of the phenomena occurring at the contact surfaces of like elastic spheres subjected to a variety of applied forces. Owing to the presence of slip, … Abstract An investigation is made of the phenomena occurring at the contact surfaces of like elastic spheres subjected to a variety of applied forces. Owing to the presence of slip, with its associated energy dissipation and permanent set, the changes in tractions and displacements depend not only upon the initial state of loading, but upon the entire past history of loading and the instantaneous relative rates of change of the normal and tangential forces. On the basis of three of the simplest cases of varying oblique forces, a set of rules of procedure is assembled and then applied to two types of problems. In the first, the initial tangential compliances are calculated for a variety of past histories and instantaneous rates of loading; in the other, a detailed history of a varying oblique force is investigated.

The impurity-drag effect in grain boundary motion

1962-09-01

John W. Cahn

Verwendung von Schwingquarzen zur W�gung d�nner Schichten und zur Mikrow�gung

1959-04-01

G. Sauerbrey

On the nature of surface roughness with application to contact mechanics, sealing, rubber friction and adhesion

2004-12-11

B. N. J. Persson , O. Albohr , U. Tartaglino +2 more

Surface roughness has a huge impact on many important phenomena. The most important property of rough surfaces is the surface roughness power spectrum C(q). We present surface roughness power spectra … Surface roughness has a huge impact on many important phenomena. The most important property of rough surfaces is the surface roughness power spectrum C(q). We present surface roughness power spectra of many surfaces of practical importance, obtained from the surface height profile measured using optical methods and the atomic force microscope. We show how the power spectrum determines the contact area between two solids. We also present applications to sealing, rubber friction and adhesion for rough surfaces, where the power spectrum enters as an important input.

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Roughness parameters

2002-04-01

E S Gadelmawla , M M Koura , T.M.A. Maksoud +2 more

The Theory of Branching Processes

1963-01-01

T. E. Harris

Computational Contact Mechanics

2006-01-01

Peter Wriggers

Friction and Wear of Materials

1966-06-01

E. Rabinowicz , R. I. Tanner

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The Friction and Lubrication of Solids

2001-02-08

Frank Philip Bowden , D. Tabor

Abstract This classic work, originally published in 1950, was a landmark in the development of the subject of tribology. When it was first published, one reviewer wrote that it 'marks … Abstract This classic work, originally published in 1950, was a landmark in the development of the subject of tribology. When it was first published, one reviewer wrote that it 'marks the beginning of a new epoch in the study of friction and lubrication .... The most interesting and comprehensive work on a single branch of physics I have ever read.' For the 1986 reprint David Tabor wrote a new preface, reviewing developments in the subject in the 36 years since the book first appeared. He has also added an appreciation of the life and work of F.P. Bowden, who died in 1968.

Contact, Adhesion and Rupture of Elastic Solids

2000-01-01

D. Maugis

Bio-inspired controllable adhesion for robotics: mechanisms, design, and future directions

2025-06-26

Tianhui Sun , Yunxiao Liu , Yu Tian | Robotica

Abstract Interfacial interactions, including adhesion and friction, directly affect the ability of the robot system to interact with the external environment, such as the realization of operation and motion functions. … Abstract Interfacial interactions, including adhesion and friction, directly affect the ability of the robot system to interact with the external environment, such as the realization of operation and motion functions. Bionics provides guidance for the active control of interface forces. Creatures such as geckos, tree frogs, octopuses, and beetles have developed delicate topological structures and smart control strategies during long-term evolution, facilitating their ability to adhere to, manipulate, capture, and traverse various surfaces across diverse environments. Inspired by the advantages of high strength, adaptability, controllability, durability, and no residue, biomimetic controllable adhesion structures, materials, and systems have been developed, showing a wide range of potential applications in reversible attachment, flexible locomotion, and dexterous grasping. In this paper, the mechanisms and theoretical models of various biological reversible adhesion systems in nature are summarized. Then the design criteria, optimization method, and preparation technology of the artificial adhesion structures based on van der Waals interaction, capillary force, negative pressure, and mechanical interlocking mechanisms are reviewed. In particular, the adhesion/load ratio and the switch ratio of adhesive materials and structures are highlighted to evaluate the adhesion ability and controllability of various designs. The applications of biomimetic controllable adhesion structures and systems in robotics manipulation and locomotion are presented. Finally, the conclusion and possible future direction are discussed.

A Touch of Stribeck - Finger-Pad Friction in Viscous Liquid Spreading

2025-06-25

Maja Fehlberg , Dominik S. Schmidt , Sairam Saikumar +3 more | Tribology Letters

Rubber Wear: History, Mechanisms, and Perspectives

2025-06-25

Rufeng Xu , Wei Sheng , Feng Zhou +1 more | Tribology Letters

Roughness-dependent scaling of the contact area and separation gap with pressure for glassy polymers

2025-06-24

Utkarsh Patil , Shubhendu Kumar , Stephen Merriman +1 more | Proceedings of the National Academy of Sciences

The contact between two rough surfaces has been a topic of significant interest since early studies on Coulombic friction and remains crucial for numerous technological applications. However, theoretical progress has … The contact between two rough surfaces has been a topic of significant interest since early studies on Coulombic friction and remains crucial for numerous technological applications. However, theoretical progress has outpaced experiments due to the challenges in measuring contact areas across scales ranging from subnanometers to macroscopic dimensions. Here, we demonstrate the use of commonly available infrared-based (IR) spectroscopy in combination with finite-difference time-domain (FDTD) optical simulations to measure separation gaps and contact areas for glassy polymers ranging in roughness over two orders in magnitude. With the combined IR and FDTD simulations, we can overcome the optical diffraction limits and take advantage of the chemical specificity of IR spectroscopy to overcome limitations due to scattering. The scaling of the contact area ratio as a function of pressure illustrated the limitations of using pure elastic or plastic deformation in explaining the results. At both low and high pressures, the contact area ratios scale linearly with pressure as expected for purely elastic deformations at low pressures or plastic deformations at high pressures. However, if analyzed over a broad range of pressure, the power laws we observe are much larger than 1, exemplifying the need to consider elastoplastic models in explaining results for softer polymer contacts compared to other brittle, glassy materials. In comparison, the separation gaps scale exponentially with pressure, as expected. These results have important implications for the interpretation of properties such as friction, adhesion, and conductivity for softer, glassy contact interfaces.

Cassie-to-Wenzel transition of liquid metal on laser-structured substrates via water evaporation for reducing thermal contact resistance

2025-06-23

Jingzhou Zhang , Zihan Liu , Ning Wang +3 more | Applied Physics Letters

Ga-based liquid metal has attracted widespread attention in thermal management owing to its high thermal conductivity. However, its ultrahigh surface tension hinders effective wetting on structured surfaces. Air gaps are … Ga-based liquid metal has attracted widespread attention in thermal management owing to its high thermal conductivity. However, its ultrahigh surface tension hinders effective wetting on structured surfaces. Air gaps are easily created at the solid/liquid interface, thereby increasing the thermal contact resistance. In this study, the wettability of liquid metal is controlled by laser irradiation and water evaporation. The real contact area of solid surface is improved by a femtosecond laser, and liquid metal is infiltrated into microstructures through negative pressure generated by water evaporation. The resultant surfaces exhibit a higher adhesion to liquid metal and a higher thermal conductivity compared to the original surfaces. This approach offers a promising pathway for advancing liquid metal-based thermal management systems.

A kernel average misorientation evaluation of surface alterations caused by angled droplet impingements

2025-06-23

Jakub Poloprudský , Alice Chlupová , Štěpán Gamanov +4 more | Engineering Science and Technology an International Journal

Adhesion- and friction-induced suppression of buckling in thin spherical shells in contact with a rigid wall

2025-06-23

Roohollah Nazari , Ramin Aghababaei , A. Papangelo +1 more | International Journal of Engineering Science

Physics-informed neural network approach to randomly rough surface contact mechanics

2025-06-23

Yunong Zhou , Hengxu Song | Tribology Letters

Laser surface texturing for enhancing wettability and mechanical properties in dissimilar material welding: A review

2025-06-23

Xiaoming He , Haichuan Shi , Peilei Zhang +5 more | Journal of Manufacturing Processes

Friction measurements with picoliter droplets using scanning probe microscopy

2025-06-23

NULL AUTHOR_ID | Physical Review Letters

Slippery or sticky? How the friction performance of footwear changes with lower temperatures

2025-06-20

Sarah C. Griffin , Henry Ing , Dimitri Ferré Sentis +2 more | Footwear Science

How much structure do you need? The impact of bottom package deconstruction and fit on multidirectional movement stability and performance

2025-06-20

Adam Luftglass , Daniel Feeney , Kathryn Harrison +1 more | Footwear Science

Does the midsole matter in the tribological performance of footwear?

2025-06-20

Kitti Csajbók , Alex Klein‐Paste , Viveca Wallqvist | Footwear Science

Predicting impact of shoe outsole material on traction using multiscale mechanics model

2025-06-20

Henry Ing , Vimanyu Chadha , Tevis D. B. Jacobs +2 more | Footwear Science

Thermal Simulation for Ultrafast Laser in Multilayered Sample for Heat-Assisted Magnetic Recording Application

2025-06-20

Haidar J. Mohamad , Basaad Hadi Hamza | Baghdad Science Journal

Pick‐and‐Place Grippers with Tunable Adhesion from Capped Soft Hollow Pillar Structure

2025-06-19

Yanbing Tang , F Goodarzi , Guangchao Wan +1 more | Advanced Materials Technologies

Abstract Dynamically tunable dry adhesion has numerous applications in biological systems and industrial processes. Soft hollow pillars (SHPs) have demonstrated to have exceptional adhesion tunability under pneumatic actuation through sidewall … Abstract Dynamically tunable dry adhesion has numerous applications in biological systems and industrial processes. Soft hollow pillars (SHPs) have demonstrated to have exceptional adhesion tunability under pneumatic actuation through sidewall buckling or bulging mechanisms. However, the adhesion strength of SHPs is significantly lower than that of solid elastomeric pillars, which can limit their practical use. In this study, mushroom‐shaped SHPs with a mushroom cap, or capped SHPs (C‐SHPs), are introduced to enhance the adhesion performance of soft grippers based on hollow pillar structures. Experiments and finite element modeling demonstrate that the cap significantly improves adhesion strength (1.8 to 2.9×) and adhesion tunability (∼1000×) by optimizing stress distribution and altering the crack initiation process at the contact interface. The effect of the cap size on the adhesion strength of C‐SHPs under various pressures is systematically investigated. Miniaturized SHPs and C‐SHPs are fabricated for pick‐and‐place manipulation of lightweight objects. An untethered device containing a C‐SHP is designed and assembled to highlight the energy‐efficient operation of C‐SHPs, with a ∼139 mJ energy consumption per pick‐and‐place cycle, showcasing their potential for applications in precision handling tasks. This work establishes C‐SHPs as a robust and adaptable solution for tunable dry adhesion systems.

Stress relaxation-related features of dynamic contact interaction of viscoelastic fluid-saturated and elastic bodies

2025-06-19

Evgeny V. Shilko , Aleksandr S. Grigoriev | Russian Physics Journal

Correction to “Contact Angle on Rough Curved Surfaces and Its Implications in Porous Media”

2025-06-19

Lei Liu , Liang Lei | Langmuir

Wettability transition methods for metal surface after laser processing

2025-06-19

Wang Ye , Gong Wang , Yunfei Li +7 more | Optics & Laser Technology

Stochastic Dynamics of Surfaces and Interfaces

2025-06-19

| Cambridge University Press eBooks

Measuring thermal contact resistances between metallic rods using laser spot heating and infrared thermography. Part 1

2025-06-18

Thomas Lahens , Alain Sommier , Marie-Marthe Groz +1 more | Quantitative InfraRed Thermography Journal

Uncertainty assessment of effective friction angle of non-cohesive materials combining data from cone penetration and shear tests

2025-06-17

Julia Sorgatz , Adam Janzen , Johan Spross | Canadian Geotechnical Journal

The effective shear strength is a critical parameter for evaluating the ultimate and serviceability limit state of geotechnical structures. To conduct a fully probabilistic assessment or to determine characteristic values … The effective shear strength is a critical parameter for evaluating the ultimate and serviceability limit state of geotechnical structures. To conduct a fully probabilistic assessment or to determine characteristic values according to the second generation of Eurocodes, it is essential to quantify the uncertainty of ground properties that arises due to inherent variability, measurement error, transformation and statistical uncertainty. However, unlike other ground properties, even in the laboratory, the shear strength parameters are not directly measured but are derived from the relationship between shear and normal stresses, making the uncertainty analysis non-trivial. This study applies two different regression approaches and the extended multivariate approach (EMA) to estimate the effective friction angle for non-cohesive soils. Firstly, an Ordinary Least Squares (OLS) and a Bayesian Linear Regression (BLR) approach are utilized to quantify the uncertainties inherent to data from direct shear and triaxial tests from an offshore wind project. Secondly, the EMA is utilized to integrate CPT and shear test data via Bayesian inference. The results are discussed based on characteristic values according to Eurocode 7 (EN 1997-1:2024) highlighting the importance of an accurate and precise mean and uncertainty estimation.

Analytical solutions to the shear-induced anisotropic area reduction in frictional elastomer contact

2025-06-17

Mingzhu Xu , Mengru Zhang , Weiting Chen +1 more | Science China Physics Mechanics and Astronomy

Mathematical Model of Friction

2025-06-17

Milan Jus , Lenka Bartošová | Key engineering materials

The article deals with the creation of a mathematical model that can be applied in the testing of various materials. These are testing cases where the measurement and subsequent evaluation … The article deals with the creation of a mathematical model that can be applied in the testing of various materials. These are testing cases where the measurement and subsequent evaluation of the value of the coefficient of friction in various tribological measurements is considered. The mathematical model considers the static and dynamic coefficient of friction. It started with the creation of a simpler mathematical model, which was subsequently modified to a more sophisticated one, considering the real situation, which is closer to the real case. With the mathematical model created in this way, various simulations were performed and evaluated for cases of (constant) permanent load, but also repetitive (periodic) load. In another case, an improvement of the mathematical model was carried out, which represented the addition of an option that allows considering the degradation of the investigated material. Degradation of the material represents only part of the surface of the material, which during testing is exposed to contact with another material with a higher hardness than the tested material.

Rényi entropy of single-character CFTs on the torus

2025-06-17

NULL AUTHOR_ID | Physical review. D/Physical review. D.

Roughness exponents of the liquid/vapor/solid contact line on surfaces with dilute random Gaussian defects: numerical study

2025-06-16

Stanimir Iliev , Nina Pesheva , Pavel Iliev | The European Physical Journal E

Momentum-dependent quantum Hall surface states in acoustic nodal line semimetals

2025-06-16

NULL AUTHOR_ID | Physical review. B./Physical review. B

Duplex Roughing Tool Selection Via Minimization of Specific Cutting Sound Level

2025-06-15

Dong-Hyeon Jo , Su-Been Park , Jong-Chul Huh +1 more | Journal of The Korean Society of Manufacturing Technology Engineers

Osteology and arthrology of the ankle and tarsometatarsus of anoles (Iguania: Anolidae): not convergent with geckos but divergent from the ancestral iguanian condition

2025-06-15

Anthony P. Russell , Lisa McGregor , Timothy E. Higham | Journal of Anatomy

Abstract The ankle joint of lizards has a complex structure, and its features help to define the Lacertilia. The configuration of this joint in its ancestral state entrains conjoint flexion‐extension … Abstract The ankle joint of lizards has a complex structure, and its features help to define the Lacertilia. The configuration of this joint in its ancestral state entrains conjoint flexion‐extension and long‐axis rotation of the pes relative to the long axis of the crus. In Gekko gecko these actions can be decoupled because of derived features of the ankle joint. The increased degrees of freedom of the motions of the pes are associated with the operation of the adhesive toe pads carried on the digits. Among iguanian lizards, the genus Anolis has independently acquired a digital adhesive system that employs toe pads. Geckos and anoles are thus regarded as being convergent in the possession of a digital adhesive apparatus. This raises the question of whether anoles exhibit a similar ankle structure to that of geckos to allow them to deploy their toe pads in a mechanically similar fashion. Comparative analysis reveals that this is not the case, and that Anolis retains an ankle structure very similar to that of its iguanian relatives and non‐gekkotan lizards in general. Some differences set its ankle and foot structure apart from those of its closest relatives, but these exaggerate the differences between geckos and anoles rather than lessen them: its ankle joint architecture is more sharply contoured than that of its close iguanian relatives; the ventral peg on the fourth distal tarsal is more extensive; its metatarsals are more gracile in form, relatively longer, and their distal joints are all unicondylar; its fifth metatarsal has a longer shaft and a less prominently sculpted ventral surface; and the meniscus that intervenes between the anterodistal extremity of the astragalocalcaneum and the more medial of the metatarsals is more extensive. These attributes combine to limit degrees of freedom at the ankle joint but provide the digits with greater mobility relative to the metatarsals. Such derived features may prove to be associated with enhanced capabilities for grasping narrow perches, sprinting and jumping, activities common to anoles but much less evident for geckos. The ways in which geckos and anoles negotiate their locomotor environments may be associated with the differences evident in their ankle and tarsometatarsus structure—anoles seemingly using the combination of their toe pads and claws to navigate along and between relatively narrow branches and geckos using broader, more expansive sectors of the substratum. Anoles and geckos have incorporated adhesive toe pads into their locomotor apparatus from structurally different starting points, with the former integrating the adhesive system into a pedal configuration that departs little from the ancestral lacertilian pattern. Beyond the possession of toe pads the pedal structure of anoles exhibits little in the way of convergence with that of geckos.

Modeling and Analyzing of Rolling Contact Behavior Between the Striped Roller and the Tow in Automated Fiber Placement

2025-06-14

Yan Li , Zhi Li , Chenggan Zheng +1 more | Polymer Composites

ABSTRACT The selection of roller types and feeding parameters is critical for the automated fiber placement. However, it has not been extensively explored. In this study, based on contact mechanics … ABSTRACT The selection of roller types and feeding parameters is critical for the automated fiber placement. However, it has not been extensively explored. In this study, based on contact mechanics and incorporating Fourier series theory, a theoretical model was developed to describe the contact behavior between different striped rollers and the tow in the feeding mechanism. The validity of the model was verified using Laser‐Doppler Anemometry. In addition, a numerical algorithm was proposed to calculate the contact behavior between different striped rollers and the tow. Using this algorithm, the contact behavior under various process parameters was obtained, and the influence of stripe geometric features on the contact behavior was analyzed. The proposed model and algorithm provide theoretical support for the selection of roller types and the optimization of parameters in the feeding mechanism.

Experimental observation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>k</mml:mi></mml:math> -dependent bulk-edge correspondence in sonic semimetals with high winding numbers

2025-06-13

NULL AUTHOR_ID | Physical Review Letters

A Rough Surface Contact Model Considering Microscale Strain-Hardening Effects

2025-06-13

Yuqin Wen , Yaobin Xu , Liu Gan-hua +1 more | Tribology Letters

Spectral Selectors and Contact Orderability

2025-06-13

Simon Allais , Pierre-Alexandre Arlove | Communications in Contemporary Mathematics

Nonlinear model of a porous body with fluid-driven fracture under cohesion contact conditions and fluid volume control

2025-06-13

Hiromichi Itou , Victor A. Kovtunenko , Κ. R. Rajagopal | Mathematical Models and Methods in Applied Sciences

Hysteresis in Approach-Retraction Frictional Contacts with Geometric and Material Nonlinearity

2025-06-12

Marco Ceglie , Guido Violano , L. Afferrante +1 more | Materials science forum

Classical linear contact mechanics, formulated with small strain and displacement assumption, struggles to accurately describe experiments involving rubbers and elastomers. Indeed, under high loads, these materials undergo large deformations and … Classical linear contact mechanics, formulated with small strain and displacement assumption, struggles to accurately describe experiments involving rubbers and elastomers. Indeed, under high loads, these materials undergo large deformations and exhibit constitutive behaviors that deviate from a linear relationship between stress and strain. In such cases, it is essential to move beyond linear elasticity to account for nonlinearity caused by large deformations and displacements. Despite efforts to develop numerical tools capable of incorporating these non-linearities in contact problems, our understanding of their impact on contact mechanical responses remains limited. In this study, we investigate the basic case of normal contact between a wavy rigid indenter and a flat, deformable substrate. We examine the influence of geometric non-linearities, arising from large deformations and displacements, alongside material non-linearities, under both frictionless and frictional interfacial conditions. To this end, we developed a finite element model, and we compared its predictions with those of Westergaard’s fully linear theoretical model. The results indicate that even in frictionless contact scenarios, non-linearities produce a mechanical response that differs significantly from predictions based on linear theory. This discrepancy becomes more pronounced as the aspect ratio of the wavy indenter increases, thereby invalidating the small-displacement assumption inherent in linear models. Moreover, the presence of friction, coupled with geometric non-linearities, induces contact hysteresis during loading and unloading cycles a phenomenon often attributed to other interfacial behaviors such as adhesion and plasticity.

Analysis of the influence of sample surface roughness on non-metallic dry coupled piezoelectric ultrasound

2025-06-12

Shi‐Qiang Wang , Sha He , Qiang Xu +3 more | Nondestructive Testing And Evaluation