Surface Effects Considerations for the Design of Casimir Actuated Nanoswitches

2011 ◽  
Vol 110-116 ◽  
pp. 1036-1043
Author(s):  
Jian Ming Bryan Ma ◽  
Samuel F. Asokanthan ◽  
Li Ying Jiang
Keyword(s):  
Surface Stress ◽  
Casimir Force ◽  
Numerical Solutions ◽  
Surface Elasticity ◽  
Surface Effects ◽  
Threshold Value ◽  
Design Parameters ◽  
Beam Model ◽  
Casimir Forces ◽  
Residual Surface Stress

New techniques that can control Casimir forces in nanosacle structures may soon ensure the physical realization of switchable Casimir-force devices. In order to provide useful insights into the behaviour of this class of switches, the idea of Casimir-force actuation window has been proposed here to assist in the design of such switches. The influence of surface effects including residual surface stress and surface elasticity on the pull-in parameters of Casimir actuated switches has been demonstrated. These effects, together with other currently known difficulties due to uncertainties such as surface roughness and trapped electric charge may hinder the realization of this class of devices. An Euler-Bernoulli beam model has been employed to demonstrate surface effects in a nanocantilever switch, and numerical solutions employing a finite difference approach have been obtained for the static bending of this switch. The results demonstrate that surface effects play a significant role in the selection of basic design parameters of Casimir actuated switches, such as static deflection and detachment length. Threshold value of residual surface stress is also studied for these switches. The predictions reveal that exclusion of surface effects in Casimir-force actuation window may result in non-functional switch designs.

Surface Effects on the Buckling of Piezoelectric Nanobeams

2012 ◽  
Vol 486 ◽  
pp. 519-523 ◽  
Author(s):  
Kai Fa Wang ◽  
Bao Lin Wang
Keyword(s):  
Shear Deformation ◽  
Electric Potential ◽  
Surface Stress ◽  
Surface Elasticity ◽  
Beam Theory ◽  
Surface Effects ◽  
Residual Surface Stress ◽  
Buckling Behavior ◽  
Stress Surface ◽  
Piezoelectric Nanobeam

In this paper, we analyze the influence of surface effects including residual surface stress, surface piezoelectric and surface elasticity on the buckling behavior of piezoelectric nanobeams by using the Timoshenko beam theory and surface piezoelectricity model. The critical electric potential for buckling of piezoelectric nanobeams with different boundary condition is obtained analytically. From the results, it is found that the surface piezoelectric reduces the critical electric potential. However, a positive residual surface stress increases the critical electric potential. In addition, the shear deformation reduces the critical electric potential, and the influence of shear deformation become more significant for a stubby piezoelectric nanobeam.

Surface Effects on Large Deflection of Nanobeams Subjected to a Follower Load

2020 ◽  
Vol 12 (06) ◽  
pp. 2050067
Author(s):  
Yun Xing ◽  
Yi Han ◽  
Hua Liu ◽  
Jialing Yang
Keyword(s):  
Large Deformation ◽  
Surface Stress ◽  
Large Deflection ◽  
Surface Effect ◽  
Surface Elasticity ◽  
Surface Effects ◽  
Surface Residual Stress ◽  
Residual Surface Stress ◽  
Deformation Problem ◽  
Cross Sectional Dimension

As a basic element of the micro/nanodevices, nanobeams have remarkable physical properties and have attracted considerable attention in the previous studies. However, previous publications did not study the large deformation problem of nanobeams under follower loading when the surface effect becomes significant and especially for the influence of surface effect on mechanical behaviors of the nanobeams under follower loading remains unclear. In this paper, we investigated the large deformation behavior of nanobeams subjected to follower loads in consideration of the surface effects. The mechanical model of large deflection of extensible cantilever nanobeams under follower loading is presented in combination with the surface elasticity and residual surface stress, and then a MATLAB program of shooting method with a technique for determining the initial value was developed to solve the problems. The results indicate that the surface effects have an important influence on the large deflection of nanobeams under follower loading: when the surface residual stress is positive, the maximums of displacement in horizontal and vertical directions and the rotation angle of the free end become lager, but the corresponding follower force related to those maximums becomes smaller. When the residual surface stress is negative, the results are the opposite. In addition, the influence of the cross-sectional dimension of the nanobeams under follower loading on surface effects was discussed. This work is beneficial to understand the mechanism of large deformation of nanobeams with surface effects subjected to follower loads, and can also provide inspirations to design advanced nanomaterials and nanoscaled devices.

POSTBUCKLING OF PIEZOELECTRIC NANOBEAMS WITH SURFACE EFFECTS

2012 ◽  
Vol 04 (02) ◽  
pp. 1250018 ◽  
Author(s):  
YUHANG LI ◽  
CHI CHEN ◽  
BO FANG ◽  
JIAZHONG ZHANG ◽  
JIZHOU SONG
Keyword(s):  
Electric Field ◽  
Significant Role ◽  
Energy Method ◽  
Material Properties ◽  
Surface Stress ◽  
Surface Elasticity ◽  
Surface Effects ◽  
Surface Material ◽  
Residual Surface Stress ◽  
Piezoelectric Nanobeam

Surface effects, including surface elasticity, surface piezoelectricity and residual surface stress, on the postbuckling of piezoelectric nanobeams due to an electric field are investigated using an energy method in this paper. The critical buckling voltage and amplitude are obtained analytically in terms of the bulk and surface material properties and geometric parameters. The results show that surface effects play a significant role in the postbuckling of piezoelectric nanobeams. It is found that the influences of surface piezoelectricity and residual surface stress are more prominent than the surface elasticity. These results might be helpful for designing piezoelectric nanobeam-based devices.

Surface Effects on the Buckling of Nanowires Based on Modified Core-Shell Model

2014 ◽  
Vol 901 ◽  
pp. 3-9
Author(s):  
Hai Yan Yao ◽  
Guo Hong Yun
Keyword(s):  
Critical Load ◽  
Surface Stress ◽  
Surface Elasticity ◽  
Surface Effects ◽  
Core Shell ◽  
Nanowire Diameter ◽  
Residual Surface Stress ◽  
Work Surface ◽  
Effective Elasticity ◽  
S Model

In this work, surface effects including surface elasticity and residual surface stress on the buckling of nanowires are theoretically investigated. Based on modified core-shell (MC-S) model, the effective elasticity incorporating surface elasticity effect of the nanowire is derived, and by using the generalized Young-Laplace equation the residual surface stress is accounted for. The ratio of critical load with and without surface effects are obtained for a nanowire loaded in uniaxial compression. Taking silver (Ag) nanowires as an example, the analyzed results demonstrate that the influence of surface effects on the critical load of buckling becomes more and more significant as the nanowire diameter decreases. Moreover, it is shown that the influence of residual surface stress on the critical load is more prominent than that of surface elasticity.

Dynamic Behavior of a Class of Casimir Actuated NEM Switches

2018 ◽  
Author(s):  
Mohamed Bognash ◽  
Samuel F. Asokanthan
Keyword(s):  
Dynamic Behavior ◽  
Casimir Force ◽  
Surface Elasticity ◽  
Intermolecular Forces ◽  
Dynamic Responses ◽  
Squeeze Film ◽  
Initial Contact ◽  
Beam Model ◽  
Closure Condition ◽  
Residual Surface Stress

Dynamic behavior of a cantilever type nano-switch actuated by pure Casimir force is investigated. Residual surface stress, surface elasticity and intermolecular forces are included in Euler–Bernoulli beam model. Knudsen number dependent squeeze-film air damping model and an asperity-based contact model are incorporated. The proposed model is inherently nonlinear due to interactions between the different nonlinear physics. An approximate analytical approach based on Galerkin’s method has been employed for predicting transient dynamic responses, since no exact solutions are available. Predicted responses show that the beam tip hits the substrate and bounces before making a permanent contact. Actuation of the switch via pure Casimir force is demonstrated for certain length and gap combinations. Initial contact time which governs the switch performance, and the deflections under non-closure condition are also quantified. This study is envisaged to provide useful insights for the future design of Casimir actuated NEM switches.

Asymmetric Bifurcation of Initially Curved Nanobeam

2015 ◽  
Vol 82 (9) ◽  
Author(s):  
X. Chen ◽  
S. A. Meguid
Keyword(s):  
Symmetry Breaking ◽  
Degrees Of Freedom ◽  
Surface Elasticity ◽  
Beam Theory ◽  
Surface Effects ◽  
Beam Model ◽  
Bernoulli Beam ◽  
Reduced Order ◽  
Euler Bernoulli Beam ◽  
Bifurcation Behavior

In this paper, we investigate the asymmetric bifurcation behavior of an initially curved nanobeam accounting for Lorentz and electrostatic forces. The beam model was developed in the framework of Euler–Bernoulli beam theory, and the surface effects at the nanoscale were taken into account in the model by including the surface elasticity and the residual surface tension. Based on the Galerkin decomposition method, the model was simplified as two degrees of freedom reduced order model, from which the symmetry breaking criterion was derived. The results of our work reveal the significant surface effects on the symmetry breaking criterion for the considered nanobeam.

Axisymmetric Boussinesq problem of a transversely isotropic half space with surface effects

2018 ◽  
Vol 24 (5) ◽  
pp. 1425-1437 ◽  
Author(s):  
Jing Jin Shen
Keyword(s):  
Half Space ◽  
Mixed Boundary ◽  
Contact Stiffness ◽  
Surface Elasticity ◽  
Transversely Isotropic ◽  
Surface Effects ◽  
Building Blocks ◽  
Material Anisotropy ◽  
Residual Surface Stress ◽  
Special Cases

A transversely isotropic half space with surface effects subjected to axisymmetric loadings is investigated in terms of the Lekhnitskii formulism. Surface effects including residual surface stress and surface elasticity are introduced by using the Gurtin–Murdoch continuum model. With the aid of the Hankel transforms, solutions corresponding to several different axisymmetic loadings are derived and used to determine the influence of surface effects on contact stiffness in nanoindentations. Numerical results are provided to show the influence of surface effects and material anisotropy on the material behaviours. Meanwhile, the obtained analytical Green’s functions for two special cases can be used as building blocks for further mixed boundary value problems.

scholarly journals The influence of surface effects in the problem of theory of elasticity for a circular hole in a half-plane

2020 ◽  
pp. 250-259
Author(s):  
D. V Gandilyan
Keyword(s):  
Fourier Series ◽  
Stress Concentration ◽  
Half Plane ◽  
Surface Stress ◽  
Surface Elasticity ◽  
Surface Effects ◽  
Theory Of Elasticity ◽  
Plane Boundary ◽  
Problem Solution ◽  
Stress Components

Surface effects are important for modeling structures, such as nanofilms, nanoporous materials, and other nanoscale constructions. In the current study, we consider the problem of the theory of elasticity - the problem of a half-plane containing a circular hole, stretched by constant stresses applied at infinity, and take into account surface effects such as surface elasticity and surface stresses. The problem solution has been obtained by expanding the Fourier series with the variables written in the bipolar coordinate system (which simplifies the problem solution because one of the coordinates becomes a constant on the hole contour), where the stress components are expressed through a bi-harmonic stress function. The parametric coefficients involved in the solution, namely in the Fourier series, are determined in order to satisfy the boundary conditions on the hole contour. To solve the problem, in addition to the equations of the theory of elasticity, the equations of surface elasticity were used, in particular, by applying the generalized Young-Laplace’s law and the Shuttleworth’s law; the surface stress on the hole contour has been calculated directly. Using recurrence relations for the stress components at the boundary, stress concentration values have been obtained. The resulting expressions can be considered as a generalized solution of the problem in case of the classical elasticity. The stress concentrations are compared for the cases with and without taking into account surface effects at various points on the hole contour. The contribution caused by the surface effects depending on the relative distance between the hole and the half-plane boundary is studied. It is shown that despite a quite simple geometry, owing to the fairly small distance between the hole and the half-plane boundary, the stress concentration with and without taking into account the surface stress are significantly different from each other, due to the significant contribution of surface effects.

Elastohydrodynamic Lubrication Line Contact Based on Surface Elasticity Theory

2020 ◽  
Vol 87 (8) ◽  
Author(s):  
Jie Su ◽  
Hong-Xia Song ◽  
Liao-Liang Ke
Keyword(s):  
Elastic Modulus ◽  
Film Thickness ◽  
Elasticity Theory ◽  
Surface Stress ◽  
Surface Effect ◽  
Surface Elasticity ◽  
Fluid Pressure ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Residual Surface Stress

Abstract Using surface elasticity theory, this article first analyzes the surface effect on the elastohydrodynamic lubrication (EHL) line contact between an elastic half-plane and a rigid cylindrical punch. In this theory, the surface effect is characterized with two parameters: surface elastic modulus and residual surface stress. The density and viscosity of the lubricant, considered as Newtonian fluid, vary with the fluid pressure. A numerical iterative method is proposed to simultaneously deal with the flow rheology equation, Reynolds equation, load balance equation, and film thickness equation. Then, the fluid pressure and film thickness are numerically determined at the lubricant contact region. Influences of surface elastic modulus, residual surface stress, punch radius, resultant normal load, and entraining velocity on the lubricant film thickness and fluid pressure are discussed. It is found that the surface effect has remarkable influences on the micro-/nano-scale EHL contact of elastic materials.

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