Three-Dimensional Elastic-Plastic Fractal Analysis of Surface Adhesion in Microelectromechanical Systems

1998 ◽  
Vol 120 (4) ◽  
pp. 808-813 ◽  
Author(s):  
K. Komvopoulos ◽  
W. Yan
Keyword(s):  
Microelectromechanical Systems ◽  
Van Der Waals ◽  
Three Dimensional ◽  
Surface Adhesion ◽  
Restoring Force ◽  
Elastic Plastic ◽  
Surface Separation ◽  
High Adhesion ◽  
Interfacial Force ◽  
Asperity Deformation

High adhesion is often encountered at contact interfaces of miniaturized devices, known as microelectromechanical systems, due to the development of capillary, electrostatic, and van der Waals attractive forces. In addition, deformation of contacting asperities on opposing surfaces produces a repulsive interfacial force. Permanent surface adhesion (referred to as stiction) occurs when the total interfacial force is attractive and exceeds the micromachine restoring force. In the present study, a three-dimensional fractal topography description is incorporated into an elastic-plastic contact mechanics analysis of asperity deformation. Simulation results revealing the contribution of capillary, electrostatic, van der Waals, and asperity deformation forces to the total interfacial force are presented for silicon/silicon and aluminum/aluminum material systems and different mean surface separation distances. Results demonstrate a pronounced effect of surface roughness on the micromachine critical stiffness required to overcome interfacial adhesion.

scholarly journals Van der Waals and Capillary Adhesion of Microelectromechanical Systems

2006 ◽  
Author(s):  
Frank W. DelRio ◽  
Maarten P. de Boer ◽  
Leslie M. Phinney ◽  
Chris J. Bourdon ◽  
Martin L. Dunn
Keyword(s):  
Microelectromechanical Systems ◽  
Capillary Condensation ◽  
Van Der Waals ◽  
Dispersion Forces ◽  
Surface Adhesion ◽  
Surface Separation ◽  
Capillary Adhesion ◽  
Close Proximity ◽  
Large Roughness ◽  
Deposition Technology

Interfacial adhesion is an important factor in determining the performance and reliability of microelectromechanical systems (MEMS). Van der Waals dispersion forces are the dominant adhesion mechanism in the low relative humidity (RH) regime. At small roughness values, adhesion is mainly due to van der Waals dispersion forces acting across extensive non-contacting areas and is related to 1/Dave2, where Dave is the average surface separation. These contributions must be considered due to the close proximity of the surfaces, which is a result of the planar deposition technology. At large roughness values, van der Waals forces at contacting asperities become the dominating contributor to the adhesion. Capillary condensation of water has a significant effect on rough surface adhesion in the moderate to high RH regime. Above a threshold RH, which is a function of the surface roughness, the adhesion jumps due to meniscus formation at the interface and increases rapidly towards the upper limit of Γ=2 γcos θ=144 mJ/m2, where γ is the liquid surface energy and θ is the contact angle.

Three-Dimensional Dry/Wet Contact Analysis of Multilayered Elastic/Plastic Solids With Rough Surfaces

2005 ◽  
Vol 128 (1) ◽  
pp. 18-31 ◽  
Author(s):  
Shaobiao Cai ◽  
Bharat Bhushan
Keyword(s):  
Contact Area ◽  
Microelectromechanical Systems ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Multilayered Structure ◽  
Contact Analysis ◽  
Maximum Displacement ◽  
Elastic Plastic ◽  
Surface Displacements ◽  
Dry And Wet Conditions

Friction/stiction and wear are among the main issues in microelectromechanical systems (MEMS/NEMS) devices having contact interfaces. Relevant parameters, i.e., layers thickness, need to be optimized. The contact analyses of multilayered structure under both dry and wet conditions are necessary to optimize these parameters. This study presents a first attempt to perform three-dimensional contact analysis of multilayered solids with rough surfaces in both dry and wet conditions. The surface displacements and contact pressure distributions are obtained based on variational principle with fast Fourier transform scheme. The effective hardness is modeled and plays a role when the local displacement meets the maximum displacement criterion. Simulations are performed to obtain the contact pressures, fractional total contact area, fractional plastic contact area, surface/subsurface stresses. Relative meniscus forces are obtained with the presence of an ultrathin liquid film for different loads and layers properties. These contact statistics and meniscus forces are analyzed to study the effects of layer-to-substrate ratios of stiffness and hardness, and the layers thickness of rough, two-layered elastic/plastic solids. The methods to decrease friction/stiction and wear are investigated, and the optimum layer parameters are identified.

scholarly journals Superconducting contact and quantum interference between two-dimensional van der Waals and three-dimensional conventional superconductors

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Michael R. Sinko ◽  
Sergio C. de la Barrera ◽  
Olivia Lanes ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
...  
Keyword(s):  
Quantum Interference ◽  
Van Der Waals ◽  
Three Dimensional ◽  
Two Dimensional

Van der Waals Epitaxy of GaSe on GaAs(111)

1994 ◽  
Vol 340 ◽  
Author(s):  
L. E. Rumaner ◽  
F.S. Ohuchi
Keyword(s):  
Lattice Mismatch ◽  
Van Der Waals ◽  
Three Dimensional ◽  
Structured Materials ◽  
Lattice Matching ◽  
Molecular Beam Deposition ◽  
Crystal Films ◽  
Low Dimensional ◽  
Matching Constraints ◽  
Lattice Matched

ABSTRACTAlthough heteroepitaxy of lattice-matched and lattice-mismatched materials leading to artificially structured materials has resulted in impressive performance in various electronics devices, material combinations are usually limited by lattice matching constraints. A new concept for fabricating material systems using the atomically abrupt and low dimensional nature of layered materials, called van der Waals epitaxy (VDWE), has been developed. GaSe (Eg = 2.1 eV) has been deposited on the three dimensional surface of GaAs (111) using a molecular beam deposition system. GaSe was evaporated from a single Knudsen source, impinging on a heated substrate. Even with a lattice mismatch of 6% between the substrate and the growing film, good quality single crystal films were grown as determined by RHEED. The films have further been analyzed using a complementary combination of XPS and X-ray reflectivity.

Atomic Force Microscopic Observations of Diamond-like Carbon (DLC) Films Produced by Plasma Immersion and Fibroblasts Cultured on DLC

2005 ◽  
Vol 11 (S03) ◽  
pp. 82-85 ◽  
Author(s):  
E. T. Uzumaki ◽  
C. S. Lambert ◽  
A. R. Santos Jr. ◽  
C. A. C. Zavaglia
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Three Dimensional ◽  
Chemical Vapour ◽  
High Wear Resistance ◽  
Diamond Like Carbon ◽  
Good Adhesion ◽  
Dlc Coatings ◽  
High Adhesion

Diamond-like carbon (DLC) films have been intensively studied with a view to improving orthopaedic implants. Studies have indicated smoothness of the surface, low friction, high wear resistance, corrosion resistance and biocompatibility [1-4]. DLC coatings can be deposited using various techniques, such as plasma assisted chemical vapour deposition (PACVD), magnetron sputtering, laser ablation, and others [5]. However it has proved difficult to obtain films which exhibit good adhesion. The plasma immersion process, unlike the conventional techniques, allows the deposition of DLC on three-dimensional workpieces, even without moving the sample, without an intermediate layer, and with high adhesion [6], an important aspect for orthopaedic articulations. In our previous work, DLC coatings were deposited on silicon and Ti-13Nb-13Zr alloy substrates using the plasma immersion process for the characterization of microstructure, mechanical properties and corrosion behaviour [7-9]. Hardness, measured by a nanoindenter, ranged from 16.4-17.6 GPa, the pull test results indicate the good adhesion of DLC coatings to Ti-13Nb-13Zr, and electrochemical assays (polarization test and electrochemical impedance spectroscopy) indicate that DLC coatings produced by plasma immersion can improve the corrosion resistance [9].

Modeling of a One-Sided Bonded and Rigid Constraint Using Beam Theory

2008 ◽  
Vol 75 (3) ◽  
Author(s):  
Peter J. Ryan ◽  
George G. Adams ◽  
Nicol E. McGruer
Keyword(s):  
Boundary Conditions ◽  
Microelectromechanical Systems ◽  
Three Dimensional ◽  
Beam Theory ◽  
Rotational Stiffness ◽  
Element Analysis ◽  
Transverse Loads ◽  
Rigid Constraint ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In beam theory, constraints can be classified as fixed/pinned depending on whether the rotational stiffness of the support is much greater/less than the rotational stiffness of the freestanding portion. For intermediate values of the rotational stiffness of the support, the boundary conditions must account for the finite rotational stiffness of the constraint. In many applications, particularly in microelectromechanical systems and nanomechanics, the constraints exist only on one side of the beam. In such cases, it may appear at first that the same conditions on the constraint stiffness hold. However, it is the purpose of this paper to demonstrate that even if the beam is perfectly bonded on one side only to a completely rigid constraining surface, the proper model for the boundary conditions for the beam still needs to account for beam deformation in the bonded region. The use of a modified beam theory, which accounts for bending, shear, and extensional deformation in the bonded region, is required in order to model this behavior. Examples are given for cantilever, bridge, and guided structures subjected to either transverse loads or residual stresses. The results show significant differences from the ideal bond case. Comparisons made to a three-dimensional finite element analysis show a good agreement.

An Extension of CEB Elastic-Plastic Contact Model

2007 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Contact Force ◽  
Tangential Force ◽  
Three Dimensional ◽  
Tangential Direction ◽  
Asperity Contact ◽  
Force Component ◽  
Normal Contact ◽  
Elastic Plastic ◽  
Force Components ◽  
Plastic Parts

Three dimensional elastic-plastic contact of two nominally flat rough surfaces is by developing the equations governing the shoulder-shoulder contact of asperities based on the Chang, Etsion and Bogy (CEB) model of contact in which volume conservation is assumed in the plastic flow regime. Shoulder-shoulder asperity contact yields a slanted contact force consisting of both tangential (parallel to mean plane) and normal components. Each force component comprises elastic and elastic-plastic parts. Statistical summation of normal force components leads to the derivation of the normal contact force for the elastic-plastic contact akin to the CEB model. Half-plane tangential force due to elastic-plastic contact is derived through the statistical summation of tangential force component along an arbitrary tangential direction.

scholarly journals A Three-Dimensional Semianalytical Model for Elastic-Plastic Sliding Contacts

2007 ◽  
Vol 129 (4) ◽  
pp. 761-771 ◽  
Author(s):  
Daniel Nélias ◽  
Eduard Antaluca ◽  
Vincent Boucly ◽  
Spiridon Cretu
Keyword(s):  
Pressure Distribution ◽  
Contact Pressure ◽  
Computing Time ◽  
Three Dimensional ◽  
Gradient Methods ◽  
Reciprocal Theorem ◽  
Contact Pressure Distribution ◽  
Sliding Contacts ◽  
Elastic Plastic ◽  
Residual Strains

A three-dimensional numerical model based on a semianalytical method in the framework of small strains and small displacements is presented for solving an elastic-plastic contact with surface traction. A Coulomb’s law is assumed for the friction, as commonly used for sliding contacts. The effects of the contact pressure distribution and residual strain on the geometry of the contacting surfaces are derived from Betti’s reciprocal theorem with initial strain. The main advantage of this approach over the classical finite element method (FEM) is the computing time, which is reduced by several orders of magnitude. The contact problem, which is one of the most time-consuming procedures in the elastic-plastic algorithm, is obtained using a method based on the variational principle and accelerated by means of the discrete convolution fast Fourier transform (FFT) and conjugate gradient methods. The FFT technique is also involved in the calculation of internal strains and stresses. A return-mapping algorithm with an elastic predictor∕plastic corrector scheme and a von Mises criterion is used in the plasticity loop. The model is first validated by comparison with results obtained by the FEM. The effect of the friction coefficient on the contact pressure distribution, subsurface stress field, and residual strains is also presented and discussed.

Three-Dimensional Finite Element Analysis of Elastic-Plastic Layered Media Under Thermomechanical Surface Loading

2002 ◽  
Vol 125 (1) ◽  
pp. 52-59 ◽  
Author(s):  
N. Ye ◽  
K. Komvopoulos
Keyword(s):  
Finite Element ◽  
Layered Medium ◽  
Numerical Solutions ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
Layered Media ◽  
Thin Layers ◽  
Surface Loading ◽  
Elastic Plastic ◽  
Thermomechanical Surface

The simultaneous effects of mechanical and thermal surface loadings on the deformation of layered media were analyzed with the finite element method. A three-dimensional model of an elastic sphere sliding over an elastic-plastic layered medium was developed and validated by comparing finite element results with analytical and numerical solutions for the stresses and temperature distribution at the surface of an elastic homogeneous half-space. The evolution of deformation in the layered medium due to thermomechanical surface loading is interpreted in light of the dependence of temperature, von Mises equivalent stress, first principal stress, and equivalent plastic strain on the layer thickness, Peclet number, and sliding distance. The propensity for plastic flow and microcracking in the layered medium is discussed in terms of the thickness and thermal properties of the layer, sliding speed, medium compliance, and normal load. It is shown that frictional shear traction and thermal loading promote stress intensification and plasticity, especially in the case of relatively thin layers exhibiting low thermal conductivity.

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