A Fast Deterministic Model to Study Adhesion in Rough Contacts

2012 ◽  
Author(s):  
Simon Medina ◽  
Daniele Dini
Keyword(s):  
Surface Roughness ◽  
Deterministic Model ◽  
Adhesion Forces ◽  
Jones Potential ◽  
Surface Separation ◽  
Low Elastic Modulus ◽  
Parallel Surfaces ◽  
Theoretical And Numerical Analysis ◽  
Net Load ◽  
Adhesive Forces

As two bodies come into contact, attractive forces occur wherever a gap exists between the two surfaces. The forces are significant at distances of atomic order but become negligible at much larger separations. Their effect is insignificant in most situations for which engineers wish to understand the state of the contact since the adhesive forces are usually much smaller than the net load applied and/or surface roughness results in non-contacting areas being far enough apart that the attractive force is negligible. There are, however, certain cases in which adhesion forces do contribute to the contact mechanics and must be accounted for in any valid analysis. Materials with low elastic modulus, such as rubber, may deform sufficiently around surface asperities such that the surface separation is small and adhesion is apparent. A model for arbitrary geometry (with surface roughness) that includes adhesive forces is reported here. It is based upon the multi-level method of contact analysis developed by Venner and Lubrecht [1]. Adhesion has been implemented using the Lennard-Jones potential as applied to two parallel surfaces, adding the requirement of specific negative pressures for the separated surface nodes [2]. The model is then compared to theoretical and numerical analysis of smooth spherical contacts and to rough contacts of different scales and material properties.

Adhesion and Pull-Off Forces for Polysilicon MEMS Surfaces Using the Sub-Boundary Lubrication Model

2002 ◽  
Vol 125 (1) ◽  
pp. 193-199 ◽  
Author(s):  
Allison Y. Suh ◽  
Andreas A. Polycarpou
Keyword(s):  
Surface Roughness ◽  
Boundary Lubrication ◽  
Intermolecular Forces ◽  
Contact Forces ◽  
Root Mean Square Roughness ◽  
Magnetic Storage ◽  
Smooth Surfaces ◽  
Adhesion Forces ◽  
Disk Interface ◽  
Adhesion Model

Miniature devices including MEMS and the head disk interface in magnetic storage often include very smooth surfaces, typically having root-mean-square roughness, σ of the order of 10 nm or less. When such smooth surfaces contact, or come into proximity of each other, either in dry or wet environments, then strong intermolecular (adhesive) forces may arise. Such strong intermolecular forces may result in unacceptable and possibly catastrophic adhesion, stiction, friction and wear. In the present paper, a model termed sub-boundary lubrication (SBL) adhesion model is used to calculate the adhesion forces, and an elastic-plastic model is used to calculate the contact forces at typical MEMS interfaces. Several levels of surface roughness are investigated representing polished and as-deposited polysilicon films that are typically found in MEMS. The SBL adhesion model reveals the significance of the surface roughness on the adhesion and pull-off forces as the surfaces become smoother. The validity of using the SBL adhesion model to estimate the pull-off forces in miniature systems is further supported by direct comparison with experimental pull-off force measurements performed on silicon and gold interfaces. Finally, the significance of the interfacial forces as relate to the reliability of MEMS interfaces is discussed.

scholarly journals Adhesion force mapping on wood by atomic force microscopy: influence of surface roughness and tip geometry

2016 ◽  
Vol 3 (10) ◽  
pp. 160248 ◽  
Author(s):  
X. Jin ◽  
B. Kasal
Keyword(s):  
Surface Roughness ◽  
Atomic Force Microscopy ◽  
Wood Surface ◽  
Adhesion Force ◽  
Data Interpretation ◽  
Natural Fibre ◽  
Force Distribution ◽  
Adhesion Forces ◽  
Force Microscopy ◽  
Atomic Force

This study attempts to address the interpretation of atomic force microscopy (AFM) adhesion force measurements conducted on the heterogeneous rough surface of wood and natural fibre materials. The influences of wood surface roughness, tip geometry and wear on the adhesion force distribution are examined by cyclic measurements conducted on wood surface under dry inert conditions. It was found that both the variation of tip and surface roughness of wood can widen the distribution of adhesion forces, which are essential for data interpretation. When a common Si AFM tip with nanometre size is used, the influence of tip wear can be significant. Therefore, control experiments should take the sequence of measurements into consideration, e.g. repeated experiments with used tip. In comparison, colloidal tips provide highly reproducible results. Similar average values but different distributions are shown for the adhesion measured on two major components of wood surface (cell wall and lumen). Evidence supports the hypothesis that the difference of the adhesion force distribution on these two locations was mainly induced by their surface roughness.

Adhesive Contact Between Atomistic Surfaces Using a Continuum Analysis

2009 ◽  
Author(s):  
Simon Medina ◽  
Daniele Dini ◽  
Andrew V. Olver
Keyword(s):  
Adhesive Contact ◽  
Atomic Scale ◽  
Local Surface ◽  
Total Surface Energy ◽  
Complete Representation ◽  
Surface Separation ◽  
Continuum Analysis ◽  
Pressure Profiles ◽  
Dynamics Simulations ◽  
Adhesive Forces

We have previously shown that, for non-adhesive conditions, an atomic scale contact can be adequately represented by a continuum analysis despite the physical shortcomings at this scale. Here we have extended the approach to include effects of the adhesive forces that become significant at this level of contact. Adhesive forces are obtained directly from the surface separation across the contact rather than through a total surface energy approach; this allows a complete representation of local surface features. The pull-off characteristics and pressure profiles have been obtained for several different atomistic AFM tip profiles and compared to those obtained from molecular dynamics simulations presented in the literature [1].

Adhesion Forces for Sub-10 nm Flying-Height Magnetic Storage Head Disk Interfaces

2004 ◽  
Vol 126 (2) ◽  
pp. 334-341 ◽  
Author(s):  
Sung-Chang Lee ◽  
Andreas A. Polycarpou
Keyword(s):  
Flying Height ◽  
Magnetic Storage ◽  
Adhesion Forces ◽  
Force Measurements ◽  
Lubricant Thickness ◽  
Magnetic Disks ◽  
Atomic Force ◽  
Adhesion Model ◽  
Different Levels ◽  
Adhesive Forces

A quasi-dynamic adhesion model is used to calculate the intermolecular adhesion forces present in ultra low flying Head Disk Interfaces (HDI’s). The model is a continuum-based micromechanics model that accounts for realistic surfaces with roughness, molecularly thin lubricants, and is valid under both static and dynamic sliding conditions. Several different levels of surface roughness are investigated ranging from extremely smooth surfaces having a standard deviation of surface heights σ=2 Å to rougher interfaces with several nanometer roughness. It is found that when the flying-height is greater than 5 nm, there are no significant adhesive forces, whereas for flying-heights less than 5 nm, adhesion forces increase sharply, which can be catastrophic to the reliability of low flying HDI’s. In addition to roughness, the apparent area of contact between the flying recording slider and the magnetic disk is also found to significantly affect the magnitude of the adhesion forces. The adhesion model is validated by direct comparisons with adhesion “pull-off” force measurements performed using an Atomic Force Microscope with controlled probe tip areas and magnetic disks having different lubricant thickness.

scholarly journals Insect wet steps: loss of fluid from insect feet adhering to a substrate

2013 ◽  
Vol 10 (78) ◽  
pp. 20120639 ◽  
Author(s):  
Alexander E. Kovalev ◽  
Alexander E. Filippov ◽  
Stanislav N. Gorb
Keyword(s):  
Surface Roughness ◽  
Fluid Flows ◽  
Solid Substrate ◽  
Fluid Loss ◽  
Adhesion Forces ◽  
Roughness Parameters ◽  
Fluid Absorption ◽  
Remarkable Effect ◽  
Adhesive Pads ◽  
Attachment Ability

Reliable attachment ability of insect adhesive pads is proposed to be due to pad secretion. It has been shown that surface roughness strongly reduces adhesion forces of insect pads. This effect has been explained by decreased contact area and rapid fluid absorption from the pad surface by rough surfaces. However, it remains unclear how the fluid flows on rough substrates having different roughness parameters and surface energy. In this paper, we numerically studied the fluid flow on rough substrates during contact formation. The results demonstrate that an increase in the density of the substrate structures leads to an increase in fluid loss from the pad: substrates with a fine roughness absorb pad fluid faster. Decreased affinity of the solid substrate to the fluid has a more remarkable effect on the fluid loss and leads to a decrease in the fluid loss. With an increase in the aspect ratio of the substrate irregularities (porosity), the fluid loss is decreased. The numerical results obtained agree well with previous observations on insects and experimental results on nanoporous substrata. The significance of the obtained results for understanding biological wet adhesives is discussed.

Integrating Dry Adhesives and Compliant Suspension for Track-Type Climbing Robots

2019 ◽  
Author(s):  
Matthew W. Powelson ◽  
Wesley A. Demirjian ◽  
Stephen L. Canfield
Keyword(s):  
Design Procedure ◽  
Light Weight ◽  
Adhesion Forces ◽  
Climbing Robots ◽  
Adhesive Material ◽  
Full Contact ◽  
Dry Adhesives ◽  
Track Surface ◽  
Vehicle Size ◽  
Adhesive Forces

Abstract Climbing robots using dry adhesives in the literature typically exhibit minimal payload and are considered useful for tasks involving light-weight sensors, such as surveillance or exploration. Existing designs demonstrate small payloads primarily because they either employ minimal adhesion area or fail to distribute the adhesion forces over the adhering region of these robots. Further, existing design methods do not demonstrate scalability of payload-to-vehicle size and, in fact, indicate that such robots are not scalable. However, dry adhesives routinely demonstrate adhering pressures in the range of 20–50 kPa which suggests that a 30 × 30 cm robot could have a payload on the order of 20–50 kg. This paper presents a step-by-step approach for designing track-type dry adhesive climbing robots to achieve high payloads. The aforementioned design steps are then experimentally validated, showing that high payloads should theoretically be possible when using dry adhesives to climb. By integrating a general adhesion model with a suspension system, this design procedure can be used to design climbing robots that distribute the payload over a large adhesive area. The models behind the design procedure (developed previously [1] but summarized here) simultaneously consider the behavior of both the adhesive material at the track-surface interface and the distribution of the adhesive forces over the full contact surface. When each of these criteria are satisfied, track-type climbing robots can be designed to carry high payloads, thus enabling applications previously thought to be impossible.

The Investigation of Energy Loss in Conformal Contact Mechanics of Carpal-Radial Components in Wrist Arthroplasty

2014 ◽  
Author(s):  
Mohammad Hodaei ◽  
Kambiz Farhang
Keyword(s):  
Surface Roughness ◽  
Energy Loss ◽  
Contact Mechanics ◽  
Contact Force ◽  
Rough Surfaces ◽  
Approximate Equation ◽  
Integral Function ◽  
Contact Model ◽  
Metal Debris ◽  
Surface Separation

The contact mechanics of Wrist prosthetic implant is considered in which the surface roughness of the implant is included. Total wrist replacements are developed to perform wrist function as near normal as possible. The main goal of wrist replacement surgery is to relieve patients from painful arthritis and to maintain function in the wrist and hand. The gradual wearing away of the cartilage covering on bones can lead to the most common form of arthritis, usually osteoarthritis. Wear is a very important issue in wrist implant. Metal debris caused by excessive wear in wrist implant can lead to toxicity and patient discomfort. Since implant wear can be the result of contact between surfaces of Carpal and Radial components, so the investigation of the effect of roughness between wrist components and establishing a model for interaction of surface roughness is very important. There are several different designs of wrist implant. Most of them have two components that are made of metal. A high quality plastic called polyethylene is used as a space between the two components. The purpose of this paper is to investigate the effect of roughness between interaction of these metal and polyethylene in wrist implants. This paper develops a contact model to treat the interaction of Carpal - Radial Components. The contact model describes the interaction of implant rough surfaces including both elastic and plastic deformations. In the model, surfaces are investigated as macroscopically conforming semi-Cylinder containing micron-scale roughness. The derived equations relate contact force on the implant and the minimum mean surface separation of the rough surfaces. Based on the distribution of asperity heights, the force is expressed using statistical integral function of asperity heights over the possible region of interaction of the roughness of the implant surfaces. Closed-form approximate equation relating contact force and minimum separation is used to obtain energy loss per cycle in a load-unload sequence applied to the implant.

scholarly journals Stick tight: suction adhesion on irregular surfaces in the northern clingfish

2013 ◽  
Vol 9 (3) ◽  
pp. 20130234 ◽  
Author(s):  
Dylan K. Wainwright ◽  
Thomas Kleinteich ◽  
Anja Kleinteich ◽  
Stanislav N. Gorb ◽  
Adam P. Summers
Keyword(s):  
Surface Roughness ◽  
Body Weight ◽  
Aspect Ratio ◽  
The Body ◽  
Intertidal Environment ◽  
Irregular Surfaces ◽  
Adhesive Disc ◽  
Suction Cups ◽  
Adhesive Forces

The northern clingfish, Gobiesox maeandricus , is able to adhere to slippery, fouled and irregular surfaces in the marine intertidal environment. We have found that the fish can adhere equally well to surfaces with a broad range of surface roughness, from the finest sandpaper ( R a = 15 µm) to textures suitable for removing finish from flooring ( R a = 269 µm). The fishes outperform man-made suction cups, which only adhere to the smoothest surfaces. The adhesive forces of clingfish correspond to pressures 0.2–0.5 atm below ambient and are 80–230 times the body weight of the fish. The tenacity appears related to hierarchically structured microvilli around the edges of the adhesive disc that are similar in size and aspect ratio to the setae found on the feet of geckoes, spiders and insects. This points to a possible biomimetic solution to the problem of reversibly adhering to irregular, submerged surfaces.

scholarly journals Influence of Surface Properties on Adhesion Forces and Attachment ofStreptococcus mutansto ZirconiaIn Vitro

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Pei Yu ◽  
Chuanyong Wang ◽  
Jinglin Zhou ◽  
Li Jiang ◽  
Jing Xue ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Surface Properties ◽  
Biofilm Formation ◽  
Adhesion Force ◽  
Contact Angles ◽  
Adhesion Forces ◽  
Force Microscopy ◽  
Early Attachment ◽  
Atomic Force ◽  
Initial Adhesion

Zirconia is becoming a prevalent material in dentistry. However, any foreign bodies inserted may provide new niches for the bacteria in oral cavity. The object of this study was to explore the effect of surface properties including surface roughness and hydrophobicity on the adhesion and biofilm formation ofStreptococcus mutans(S. mutans) to zirconia. Atomic force microscopy was employed to determine the zirconia surface morphology and the adhesion forces between theS. mutansand zirconia. The results showed that the surface roughness was nanoscale and significantly different among tested groups (P<0.05): Coarse (23.94±2.52 nm) > Medium (17.00±3.81 nm) > Fine (11.89±1.68 nm). The contact angles of the Coarse group were the highest, followed by the Medium and the Fine groups. Increasing the surface roughness and hydrophobicity resulted in an increase of adhesion forces and early attachment (2 h and 4 h) ofS. mutanson the zirconia but no influence on the further development of biofilm (6 h~24 h). Our findings suggest that the surface roughness in nanoscale and hydrophobicity of zirconia had influence on theS. mutansinitial adhesion force and early attachment instead of whole stages of biofilm formation.

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