Modeling the coupled effects of surface layer and size effect on the static and dynamic instability of narrow nano-bridge structure

2016 ◽  
Vol 39 (5) ◽  
pp. 1735-1744 ◽  
Author(s):  
Maryam Keivani ◽  
Ali Koochi ◽  
Abolfazl Kanani ◽  
Hossein M. Navazi ◽  
Mohamadreza Abadyan
Keyword(s):  
Surface Layer ◽  
Size Effect ◽  
Dynamic Instability ◽  
Bridge Structure ◽  
Static And Dynamic Instability

Static and dynamic instability of nanowire-fabricated nanoelectromechanical systems: effects of flow damping, van de Waals force, surface energy and microstructure

2016 ◽  
Vol 94 (6) ◽  
pp. 594-603 ◽  
Author(s):  
Maryam Keivani ◽  
Ali Koochi ◽  
Naeime Abadian ◽  
Morteza Rezaei ◽  
Mohamadreza Abadyan
Keyword(s):  
Surface Energy ◽  
Governing Equation ◽  
Dynamic Instability ◽  
Surface Elasticity ◽  
Circular Cross Section ◽  
Continuum Theory ◽  
Nanoelectromechanical Systems ◽  
Gas Damping ◽  
Static And Dynamic Instability ◽  
Lagrange Strain

Surface energy and microstructure-dependent size phenomena can play significant roles in physical performance of nanoelectromechanical systems (NEMS). Herein, the static and dynamic pull-in instability of cantilever and double-clamped NEMS fabricated from conductive cylindrical nanowires with circular cross section is studied. The Gurtin–Murdoch surface elasticity in combination with the couple stress continuum theory is employed to incorporate the coupled effects of surface energy and microstructure-dependent size phenomenon. Using Green–Lagrange strain, the higher order surface stress components are incorporated into the governing equation. The effect of gas damping is considered in the model as well as structural damping. The nonlinear governing equation is solved using analytical reduced order method. The effects of various parameters on the static and dynamic pull-in parameters, phase plans, and stability threshold of the nanowire-based structures are demonstrated.

Modeling of Two-Phase Flow Instabilities in Microchannels

2005 ◽  
Author(s):  
Niranjan S. Chavan ◽  
A. Bhattacharya ◽  
Kannan Iyer
Keyword(s):  
Linear Stability ◽  
Characteristic Equation ◽  
Dynamic Instability ◽  
Analytical Form ◽  
Flow Instabilities ◽  
Two Phase ◽  
Stability Curve ◽  
Analytical Stability ◽  
Static And Dynamic Instability ◽  
Stability Model

This paper addresses a non-dimensional analytical stability model aimed at predicting the occurrence of flow instabilities at micro-scale. In this context, linear stability model using homogenous flow was considered. Towards that, a linear stability model was developed using perturbation method. A characteristic equation (the response of pressure drop to a hypothetical perturbation in inlet velocity) obtained in this analysis, is shown to be a function of sub-cooling number, Zuber number, Froude number, friction number and inlet and outlet restriction coefficients. Then, a neutral dynamic stability curve is obtained using D-Partition approach. Similarly, static or excursive stability curve is also obtained from the characteristic equation. The derived analytical form for static and dynamic instability threshold is represented in the form of simplified correlations. The experimental data reported by other researchers agree well with these correlations. From the results, it is amply clear that for all practical purposes, two-phase cooling will be unstable. The question to be answered in future is, therefore, whether the oscillations that accompany can be tolerated from the application viewpoint.

Static and dynamic instability characteristics of curved laminates with internal damage subjected to follower loading

2011 ◽  
Vol 225 (7) ◽  
pp. 1589-1600 ◽  
Author(s):  
S Biswas ◽  
P K Datta ◽  
C D Kong
Keyword(s):  
Dynamic Instability ◽  
Shear Deformation Theory ◽  
Internal Damage ◽  
First Order ◽  
Static And Dynamic Instability ◽  
Element Approach ◽  
Formulation Analysis ◽  
Flutter Load ◽  
Doubly Curved ◽  
Curved Panels

This article deals with the study of vibration, buckling, and dynamic instability characteristics in damaged cross-ply and angle-ply curved laminates under uniform, uniaxial follower loading, using finite element approach. First-order shear deformation theory is used to model the doubly curved panels and is formulated according to Sandars' first approximation. Damage is modelled using an anisotropic damage formulation. Analysis is carried out on plate and three types of curved panels to obtain vibration, buckling, and dynamic instability (flutter) behaviour. The effect of damage on natural frequency, critical buckling load, flutter load, and flutter frequency is studied. The results show that the introduction of damage influences the flutter characteristics of panels more profoundly than the free-vibration or buckling characteristics. The results also indicate that, compared to undamaged panels, heavily damaged panels show steeper deviations in stability characteristics than mildly damaged ones.

scholarly journals Динамическая неустойчивость поверхности твердых тел под нагрузкой

2018 ◽  
Vol 60 (7) ◽  
pp. 1334
Author(s):  
Ю.А. Хон ◽  
H. Zapolsky ◽  
П.П. Каминский ◽  
А.Н. Пономарев
Keyword(s):  
Surface Layer ◽  
Electron Density ◽  
Solid Surface ◽  
Large Amplitude ◽  
Dynamic Instability ◽  
Interatomic Interaction

AbstractThe mechanism of dynamic instability of a solid surface under a load, determined by perturbations of the electron density and the change in the interatomic interaction, is considered. This instability is manifested upon the excitation of dynamic displacements of atoms in the surface layer, which can lead to formation of finite-lifetime structures in the form of waves with a large amplitude. Such structures were earlier observed experimentally on a stretched germanium (111) surface.

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