scholarly journals INVESTIGATION ON EFFECT OF SURFACE ROUGHNESS PATTERN TO DYNAMIC PERFORMANCE OF MEMS RESONATORS IN VARIOUS TYPES OF GASES AND GAS RAREFACTION

2021 ◽  
Vol 59 (5) ◽  
Author(s):  
Nguyen Chi Cuong ◽  
Lam Minh Thinh ◽  
Phan Minh Truong ◽  
Trinh Xuan Thang ◽  
Ngo Vo Ke Thanh ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Effective Viscosity ◽  
Dynamic Performance ◽  
Squeeze Film ◽  
Molecular Gas ◽  
Q Factor ◽  
Squeeze Film Damping ◽  
Mems Resonators ◽  
Quality Factor Q ◽  
Effect Of Surface

The average modified molecular gas lubrication (MMGL) equation, which is modified with pressure flow factors and effective viscosity, is utilized to analyze the squeeze film damping (SFD) on micro-beam resonators considering effect of surface roughness pattern in various types of gases and gas rarefaction. Then, effect of surface roughness pattern (film thickness ratio and Peklenik number) is discussed on the quality factor (Q-factor) of micro-beam resonators in various types of gases and gas rarefaction. Thus, effect of surface roughness pattern is significantly reduced as effective viscosity of gas decreases in higher mode of resonator and higher gas rarefaction.

Effect of random surface roughness on squeeze film damping characteristics in damper of linear rolling guide with a fractal-based method

2015 ◽  
Vol 67 (6) ◽  
pp. 549-556 ◽  
Author(s):  
Linlin Li ◽  
Jiajun Yang ◽  
Wenwei Liu
Keyword(s):  
Surface Roughness ◽  
Rough Surface ◽  
Squeeze Film ◽  
Roughness Effect ◽  
Random Surface ◽  
Content Type ◽  
Damping Characteristics ◽  
Squeeze Film Damping ◽  
Rolling Guide ◽  
Effect Of Surface

Purpose – The purpose of this paper is to explore the effect of surface roughness characterized by fractal geometry on squeeze film damping characteristics in damper of the linear rolling guide, which has not been studied so far. Design/methodology/approach – The stochastic model of film thickness between rail and damper is established by using the two-variable Weierstrass–Mandelbrot function defining multi-scale and self-affinity properties of the rough surface topography. The stochastically averaged Reynolds equation is solved by using the variables separation method to further derive the film pressure distribution, the damping coefficient, the damping force and squeeze film time. The effect of surface roughness on squeeze film damping characteristics of the damper is analyzed and discussed through simulation. Findings – By comparing cases of the rough surface for different fractal parameters and the smooth surface, it is shown that for the isotropic roughness structure, the presence of surface roughness of the damper decreases the squeeze film damping characteristics. It is found that roughness effect on the damping coefficient is associated with the film thickness. In addition, the vibration amplitude effect is negligible for the damper of the linear rolling guide. Originality/value – To investigate the random surface roughness effect, the rough surface topography of damper of the linear rolling guide is characterized by using the fractal method instead of the traditional mathematical statistics method.

Effect of surface roughness on couple stress squeeze film lubrication of long porous partial journal bearings

2006 ◽  
Vol 58 (4) ◽  
pp. 176-186 ◽  
Author(s):  
N.M. Bujurke ◽  
N.B. Naduvinamani ◽  
Syeda Tasneem Fathima ◽  
S.S. Benchalli
Keyword(s):  
Surface Roughness ◽  
Couple Stress ◽  
Journal Bearings ◽  
Squeeze Film ◽  
Film Lubrication ◽  
Effect Of Surface

Surface Roughness Effect on the Performance of 3-lobe Symmetric Hole Entry Hybrid Journal Bearings

2014 ◽  
Vol 592-594 ◽  
pp. 1190-1194
Author(s):  
Prashant B. Kushare ◽  
Satish C. Sharama
Keyword(s):  
Surface Roughness ◽  
Journal Bearing ◽  
Dynamic Performance ◽  
Flow Equation ◽  
Longitudinal Roughness ◽  
Transverse Isotropic ◽  
Offset Factor ◽  
Rotor Dynamic ◽  
Selection Of ◽  
Effect Of Surface

The present paper, evaluates the effect of surface roughness on the performance characteristics of capillary compensated 3-lobe symmetric hole entry hybrid journal bearing. The effect of surface roughness patterns viz; transverse, isotropic, longitudinal and smooth, on bearing performance is presented for different values of offset factor. A modified form of Reynold’s equation in conjunction with restrictor flow equation is solved by using Galerkin’s technique of FEM. The numerically simulated results of the study indicate that the surface roughness orientation patterns affect the performance of 3-lobe hybrid journal bearing system significantly. Further, it is noticed that the longitudinal roughness pattern provides enhanced value of rotor dynamic coefficient.To have an improved dynamic performance, a judicious selection of offset factor and surface roughness pattern parameter is essential.

scholarly journals Combined Effect of Slip Velocity and Surface Roughness on a Magnetic Squeeze Film for a Sphere in a Spherical Seat

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
G. M. Deheri ◽  
Sejal J. Patel
Keyword(s):  
Surface Roughness ◽  
Slip Velocity ◽  
Type Equation ◽  
Velocity Slip ◽  
Performance Characteristics ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Slip Model ◽  
Load Carrying ◽  
Effect Of Surface

This investigation analyzes the performance of a magnetic fluid based squeeze film for a sphere in a rough spherical seat with slip velocity. The slip model of Beavers and Joseph has been deployed to study the effect of velocity slip while the stochastic model of Christensen and Tonder has been used to calculate the effect of surface roughness. The concerned statistically averaged Reynolds’ type equation is solved to derive the pressure distribution which results in the calculation of load carrying capacity. The results presented in graphical forms confirm that the adverse effect of slip velocity can be overcome to a large extent at least in the case of negatively skewed roughness. However, lower values of slip may be preferred for enhancing the performance characteristics of the bearing system. Besides, variance (−ve) provides a little support to improve the performance characteristics.

A Fully Coupled FEM Model of Electromechanically Actuated MEMS With Squeeze Film Damping

2009 ◽  
Author(s):  
Stephan D. A. Hannot ◽  
Daniel J. Rixen
Keyword(s):  
Rf Mems ◽  
Squeeze Film ◽  
Fem Model ◽  
Mems Switch ◽  
Squeeze Film Damping ◽  
Air Damping ◽  
Mems Resonators ◽  
Fluid Damping ◽  
Frequency Behavior ◽  
Damping Model

A specific type of Microsystems or MEMS is the so called RF-MEMS switch. In contrast to MEMS resonators switches generally do not operate in a vacuum. Therefore at the small scales of MEMS fluid (or air) damping is the most dominant damping form. This means that if one is interested in transient or frequency behavior a proper damping model is required. This paper presents a way of using the non-linear Reynolds equation to model the squeeze film damping that is often the type of fluid damping present in these switches. The formulation is provided ready for FEM implementation. Also the tangent matrices required for linearized eigen frequencies are derived. The equations are tested on a model of simple micro switch. The results show that with this model it is possible to predict the damped motion as well as the frequency behavior. The frequency results also show that damping shifts the zero frequency point away from the pull-in point. With a simple mechanical contact model it is also possible to model the closing and opening transient of a microsystem.

A Novel Expression for the Effective Viscosity to Model Squeeze-Film Damping at Low Pressure

2013 ◽  
Vol 390 ◽  
pp. 76-80 ◽  
Author(s):  
Maria F. Pantano ◽  
Salvatore Nigro ◽  
Franco Furgiuele ◽  
Leonardo Pagnotta
Keyword(s):  
Experimental Data ◽  
Effective Viscosity ◽  
Squeeze Film ◽  
Navier Stokes ◽  
Fluid Viscosity ◽  
The Novel ◽  
Mems Devices ◽  
Navier Stokes Equation ◽  
Experimental Procedure ◽  
Squeeze Film Damping

The Navier-Stokes equation is currentlyconsidered for modelling of squeeze-film damping in MEMS devices, also when the fluid flow associated to it is rarefied.In order to include rarefaction effects in such equation, a common approach consists of replacing the ordinary fluid viscosity with a scaled quantity, known as effective viscosity.The literature offers different expressions for the effective viscosity as a function of the Knudsen number (Kn). Such expressions were shown to work well whenKn<1, but theyresulted to be lessaccurate in case ofKn>1. In this paper a new expression is proposed to evaluate the effective viscosity for 1<Kn<40with increased reliability. Such anexpression was derivedfrom an optimized numerical-experimental procedure,developed in MATLAB® environment, using a finite element code and experimental data extracted from the literature. A comparison is finally reported and discussed between the results, in terms of damping coefficient, obtained considering previously reported effective viscosity expressions and the novel one,with reference to different squeeze film damping layouts, for which experimental data are already available.

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