A New Numerical Approach for Adhesive Contacts of Real Engineering Surfaces

2010 ◽  
Vol 44-47 ◽  
pp. 1251-1257 ◽  
Author(s):  
Yu Qi Zheng ◽  
San Min Wang
Keyword(s):  
Elastic Deformation ◽  
Meshless Method ◽  
Adhesive Contact ◽  
Adhesive Force ◽  
Viscous Force ◽  
Rigid Spheres ◽  
Dugdale Model ◽  
Nano Scale ◽  
D Model ◽  
Tabor Parameter

Microelectromechanical system (MEMS) and nanotechnology are important directions on the development of the science in twenty-first century. Some of the effects, such as viscous force, surface force, electrostatic force, friction etc., which can be usually ignored on the traditional scale, have become noticeable when the scale has turn to micro or nano scale. Nanotribology is one of the main areas of the indispensable researches on the basic theory and methodology of the effects. The micro/nano adhesive contact which is the foundation of nanotribology is studied in this paper. The earliest study on adhesive contact was done by Bradley. He presented an expression of adhesive force of two contacting rigid spheres. Derjaguin, Muller and Toprov (DMT) gave the relation of the contact area and the applied load of the adhesive contact of two spheres, but they did not consider the elastic deformation due to the adhesive force of the bodies. Johnson, Keudall and Roberts (JKR) provided a theory of the adhesive contact of two elastic spheres. Tabor gave a parameter (Tabor parameter) to interpret the ratio of the elastic deformation with the adhesive force of two contacting bodies. That is to say the DMT model corresponding to small Tabor parameter(<0.1) and the JKR model to large Tabor parameter(>5). Maguis gave a DMT-JKR transition using the Dugdale model in fracture mechanics (M-D model) in the intermediate region between the DMT model and the JKR model. A numerical algorithm of elastic adhesive contact based on the meshless method is presented in this paper. This make it possible to solve the adhesive contact with more complex surface topography and to consider more intricate factors, such as thermal stress, friction, elasto-plastic deformation etc. in the further studies on micro/nano scale adhesive contact problems. The meshless method seems to be a promising approach for contact analyses because of its flexibility in domain descritization and versatility in node arrangements. It can be used to solve a variety of complicated engineering problems. A numerical example of adhesive contact between a micro elastic cylinder and a rigid half-space is carried out to show the feasibility of the algorithm. In the simulation, an effective method of the M-D model is used to save the cost of computation. Compared with the existed solutions, the results solved by the presented algorithm are reasonable.

Influence of the Tabor Parameter on the Roughness-Induced Adhesion Hysteresis

2012 ◽  
Vol 157-158 ◽  
pp. 1233-1237
Author(s):  
Le Feng Wang ◽  
Wei Bin Rong ◽  
Bing Shao ◽  
Li Ning Sun
Keyword(s):  
Rough Surface ◽  
Rough Surfaces ◽  
Adhesive Contact ◽  
Contact Model ◽  
Dissipation Energy ◽  
Dugdale Model ◽  
Relationship Of ◽  
Special Case ◽  
Tabor Parameter

Influence of the Tabor parameter on the roughness-induced adhesion hysteresis was investigated. To achieve this, the adhesive contact model of single asperities was considered by incorporating the Maugis-dugdale model and its corresponding extension firstly. Further more, the load-approach relationship of adhesive contact between a rough surface and a flat was analyzed. The dissipation energy during a load and unload cycle is derived for general values of the Tabor parameter. It was found that the adhesion hysteresis becomes weaker gradually with the increase of the adhesion parameter, and it becomes stronger with the decrease of the Tabor parameter at the same adhesion parameter. The adhesion hysteresis for a special case that rough surfaces with DMT(Deryagin-Muller-Toporov)-type asperities is also discussed.

Numerical Method of Analyzing Contact Mechanics between a Sphere and a Flat Considering Lennard-Jones Surface Forces of Contacting Asperities and Noncontacting Rough Surfaces

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Kyosuke Ono
Keyword(s):  
Numerical Method ◽  
Contact Mechanics ◽  
Rough Surfaces ◽  
Present Theory ◽  
Adhesive Contact ◽  
Adhesive Force ◽  
Surface Forces ◽  
Contact Theory ◽  
Magnetic Disk ◽  
Lennard Jones

A new numerical method of analyzing adhesive contact mechanics between a sphere and a flat with sub-nanometer roughness is presented. In contrast to conventional theories, the elastic deformations of mean height surfaces and contacting asperities, and Lennard-Jones (LJ) surface forces of both the contacting asperities and noncontacting rough surfaces including valley areas are taken into account. Calculated contact characteristics of a 2-mm-radius glass slider contacting a magnetic disk with a relatively rough surface and a 30-mm-radius head slider contacting a currently available magnetic disk with lower roughness are shown in comparison with conventional adhesive contact theories. The present theory was found to give a larger adhesive force than the conventional theories and to converge to a smooth sphere-flat contact theory as the roughness height approaches zero.

Robust Strategies for Automated AFM Force Curve Analysis—II: Adhesion-Influenced Indentation of Soft, Elastic Materials

2007 ◽  
Vol 129 (6) ◽  
pp. 904-912 ◽  
Author(s):  
David C. Lin ◽  
Emilios K. Dimitriadis ◽  
Ferenc Horkay
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Full Range ◽  
Soft Materials ◽  
Adhesive Contact ◽  
Colloid Interface ◽  
Inhomogeneous Materials ◽  
Dugdale Model ◽  
Normal Contact ◽  
Adhesive Interactions

In the first of this two-part discourse on the extraction of elastic properties from atomic force microscopy (AFM) data, a scheme for automating the analysis of force-distance curves was introduced and experimentally validated for the Hertzian (i.e., linearly elastic and noninteractive probe-sample pairs) indentation of soft, inhomogeneous materials. In the presence of probe-sample adhesive interactions, which are common especially during retraction of the rigid tip from soft materials, the Hertzian models are no longer adequate. A number of theories (e.g., Johnson–Kendall–Roberts and Derjaguin–Muller–Toporov), covering the full range of sample compliance relative to adhesive force and tip radius, are available for analysis of such data. We incorporated Pietrement and Troyon’s approximation (2000, “General Equations Describing Elastic Indentation Depth and Normal Contact Stiffness Versus Load,” J. Colloid Interface Sci., 226(1), pp. 166–171) of the Maugis–Dugdale model into the automated procedure. The scheme developed for the processing of Hertzian data was extended to allow for adhesive contact by applying the Pietrement–Troyon equation. Retraction force-displacement data from the indentation of polyvinyl alcohol gels were processed using the customized software. Many of the retraction curves exhibited strong adhesive interactions that were absent in extension. We compared the values of Young’s modulus extracted from the retraction data to the values obtained from the extension data and from macroscopic uniaxial compression tests. Application of adhesive contact models and the automated scheme to the retraction curves yielded average values of Young’s modulus close to those obtained with Hertzian models for the extension curves. The Pietrement–Troyon equation provided a good fit to the data as indicated by small values of the mean-square error. The Maugis–Dugdale theory is capable of accurately modeling adhesive contact between a rigid spherical indenter and a soft, elastic sample. Pietrement and Troyon’s empirical equation greatly simplifies the theory and renders it compatible with the general automation strategies that we developed for Hertzian analysis. Our comprehensive algorithm for automated extraction of Young’s moduli from AFM indentation data has been expanded to recognize the presence of either adhesive or Hertzian behavior and apply the appropriate contact model.

Adhesive Contact Modeling of Ultra-Low Flying Head-Disk Interfaces With and Without Roughness Effects

2005 ◽  
Author(s):  
A. Y. Suh ◽  
A. A. Polycarpou
Keyword(s):  
Adhesive Contact ◽  
Adhesive Force ◽  
Flying Height ◽  
Successful Implementation ◽  
Roughness Effects ◽  
Interfacial Forces ◽  
Disk Interface ◽  
Parallel Surface ◽  
Effect Of Surface ◽  
Adhesive Forces

The head-disk interface (HDI) designed for sub-5nm pseudo-flying to obtain extremely high areal recording (EHDR) density of 1 Tbit/in is susceptible to strong adhesive interfacial forces, and the accurate predictions of these interfacial forces are critical in ensuring successful implementation of ultra-low flying HDI’s. In this paper, the effect of surface roughness on the adhesive forces at sub-5 nm flying-height regimes is investigated through a comparison to a simple two flat parallel surface counterpart. It was found that the effect of roughness promotes adhesion at higher separations than if a two flat parallel surface configuration is adopted. Prior to the onset of contact (during flying), however, the total adhesive force for an interface with low roughness is comparable to the two flat parallel surface approximation, thus significantly simplifying the analysis.

A Scale-Dependent Model for Multi-Asperity Contact and Friction

2003 ◽  
Vol 125 (4) ◽  
pp. 700-708 ◽  
Author(s):  
George G. Adams ◽  
Sinan Mu¨ftu¨ ◽  
Nazif Mohd Azhar
Keyword(s):  
Real Contact Area ◽  
Asperity Contact ◽  
Adhesion Forces ◽  
Friction Forces ◽  
Dugdale Model ◽  
The Real ◽  
Nano Scale ◽  
Macro Scale ◽  
Asperity Contacts ◽  
Coefficient Versus

As loading forces decrease in applications such as MEMS and NEMS devices, the size of the asperity contacts which comprise the real contact area tend to decrease into the nano scale regime. This reduction in size of the contacts is only partially offset by the nominally increased smoothness of these contacting surfaces. Because the friction force depends on the real area of contact, it is important to understand how the material and topographical properties of surfaces contribute to friction forces at this nano scale. In this investigation, the single asperity nano contact model of Hurtado and Kim is incorporated into a multi-asperity model for contact and friction which includes the effect of asperity adhesion forces using the Maugis-Dugdale model. The model spans the range from nano-scale to micro-scale to macro-scale contacts. Three key dimensionless parameters have been identified which represent combinations of surface roughness measures, Burgers vector length, surface energy, and elastic properties. Results are given for the friction coefficient versus normal force, the normal and friction forces versus separation, and the pull-off force for various values of these key parameters.

Adhesive Contact of Elastic-Plastic Layered Media: Effective Tabor Parameter and Mode of Surface Separation

2013 ◽  
Vol 80 (2) ◽  
Author(s):  
Z. Song ◽  
K. Komvopoulos
Keyword(s):  
Layer Thickness ◽  
Material Properties ◽  
Layered Medium ◽  
Adhesive Contact ◽  
Rigid Sphere ◽  
Maximum Surface ◽  
Elastic Plastic ◽  
Surface Separation ◽  
Plasticity Parameter ◽  
Tabor Parameter

Adhesive contact of a rigid sphere with a layered medium consisting of a stiff elastic layer perfectly bonded to an elastic-plastic substrate is examined in the context of finite element simulations. Surface adhesion is modeled by nonlinear spring elements obeying a force-displacement relation governed by the Lennard–Jones potential. Adhesive contact is interpreted in terms of the layer thickness, effective Tabor parameter (a function of the layer thickness and Tabor parameters corresponding to layer and substrate material properties), maximum surface separation, layer-to-substrate elastic modulus ratio, and plasticity parameter (a characteristic adhesive stress expressed as the ratio of the work of adhesion to the surface equilibrium distance, divided by the yield strength of the substrate). It is shown that surface separation (detachment) during unloading is not encountered at the instant of maximum adhesion (pull-off) force, but as the layered medium is stretched by the rigid sphere, when abrupt surface separation (jump-out) occurs under a smaller force (surface separation force). Ductile- and brittle-like modes of surface detachment, characterized by the formation of a neck between the rigid sphere and the layered medium and a residual impression on the unloaded layered medium, respectively, are interpreted for a wide range of plasticity parameter and maximum surface separation. Numerical results illustrate the effects of layer thickness, bulk and surface material properties, and maximum surface separation (interaction distance) on the pull-off and surface separation forces, jump-in and jump-out contact instabilities, and evolution of substrate plasticity during loading and unloading. Simulations of cyclic adhesive contact demonstrate that incremental plasticity (ratcheting) in the substrate is the most likely steady-state deformation mechanism under repetitive adhesive contact conditions.

Fluorocarbon Films Deposited by Deep Reactive Ion Etching for Stiction Minimization of MEMS Structures

2005 ◽  
Author(s):  
Yan Xin Zhuang ◽  
Aric K. Menon
Keyword(s):  
Thermal Stability ◽  
Contact Angle ◽  
Surface Energy ◽  
Reactive Ion Etching ◽  
Adhesive Force ◽  
Measuring System ◽  
Ion Etching ◽  
Deep Reactive Ion Etching ◽  
Fluorocarbon Films ◽  
Nano Scale

Fluorocarbon films, which can be used to minimize stiction of silicon microstructures, have been deposited by passivation process in deep reactive ion etching tool. The wettability, surface energy, nano-scale adhesive force, and thermal stability have been investigated by contact angle measuring system, atomic force microscopy (AFM) and ellipsometry. The fluorocarbon films are good for anti-stiction applications due to their high water contact angle (110°), low surface energy (14.5mJ/m2), low nano-scale adhesive force (33 nN) and high thermal stability up to 300°C.

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