scholarly journals Viscous damping and spring force in periodic perforated planar microstructures when the Reynolds’ equation cannot be applied

2010 ◽  
Vol 127 (3) ◽  
pp. 1288-1299 ◽  
Author(s):  
Dorel Homentcovschi ◽  
Ronald N. Miles
Keyword(s):  
Reynolds Equation ◽  
Viscous Damping ◽  
Spring Force

Anti-Vibration Tribometer Using Viscous Damping Effect Generated by Lateral Slip

2012 ◽  
Author(s):  
Ken Nakano ◽  
Chiharu Tadokoro ◽  
Naohiro Kado
Keyword(s):  
Friction Coefficient ◽  
Relative Velocity ◽  
Mean Value ◽  
Force Balance ◽  
Viscous Damping ◽  
Negative Dependence ◽  
Damping Effect ◽  
Spring Force ◽  
The Mean ◽  
Frictional Vibration

This paper proposes a simple and novel principle for suppressing frictional vibration using viscous damping effect generated by “lateral slip” given to a typical sliding system. This principle was applied to the measurement of friction coefficient and an anti-vibration tribometer (AVT) was developed. The AVT suppressed frictional vibration caused by the negative dependence of the friction coefficient on the relative velocity, and it enabled one to measure friction coefficient accurately in the force balance between the friction force and spring force. If using the mean value of oscillating spring force to calculate friction coefficient under frictional vibration, it was found that considerable errors (e.g., approximately 30%) appears.

A Note on Inelastic Response Spectra for Systems with Bilinear Spring Force and Kinematic Strain-Hardening

1992 ◽  
Vol 8 (2) ◽  
pp. 181-200 ◽  
Author(s):  
L. A. de Béjar ◽  
K. Ganapathi
Keyword(s):  
Strain Hardening ◽  
Response Spectra ◽  
Intermediate Frequency ◽  
Viscous Damping ◽  
Frequency Range ◽  
Inelastic Response ◽  
Design Spectra ◽  
Spring Force ◽  
Damped Systems ◽  
Inelastic Design

Parametric studies on inelastic response spectra for systems with bilinear spring resistance and kinematic strain-hardening, low-to-moderate viscous damping, and standing on firm soil, indicate that aseismic design of such systems based on the associated elasto-plastic spectra is not always conservative, in particular, for systems in the intermediate frequency range. By contrast, present understanding of the effect of viscous damping on inelastic spectra is thoroughly verified. In addition, mathematical expressions for a tripartite model of design spectra for inelastic systems are presented and tested for a ground motion record representative of a major destructive earthquake. These formulas provide generally conservative estimates of parameters of response for undamped systems, as compared with both numerically generated spectra and spectral upper bounds previously reported in the literature; however, for damped systems, the inelastic design spectra provide safe envelopes for most of the frequency range, but often make unconservative predictions over a small portion of the intermediate frequency range.

Coupled Bending and Torsion Effects on the Squeezed Film Air Damping in Torsional Micromirrors

2012 ◽  
Author(s):  
Hamid Moeenfard ◽  
Farzaneh Kaji ◽  
Mohammad Taghi Ahmadian
Keyword(s):  
Angular Velocity ◽  
Vertical Velocity ◽  
Reynolds Equation ◽  
Rotation Angle ◽  
Viscous Damping ◽  
Damping Force ◽  
Dynamical Modeling ◽  
Air Damping ◽  
Tilting Angle ◽  
Damping Torque

The current paper presents an analytical model for the problem of squeezed film damping in micromirrors considering the bending of the supporting torsion microbeams. At the first the nonlinear Reynolds equation governing the behavior of the squeezed gas underneath the mirror is linearized. The resulting linearized equation is then nondimensionalized and analytically solved for two cases of the infinitesimal and finite tiling angle of the mirror. The obtained pressure distribution from the solution of the Reynolds equation is then utilized for finding the squeezed film damping force and torque applied to the mirror. The results show that in the case of the infinitesimal tilting angle, the squeezed film damping can be modeled with a linear viscous damping in both torsional and lateral directions. It is also shown that when the mirror’s rotation angle is small, with increasing the length of the mirror, the damping force and damping torque are increased. For the case of the finite tilting angle it was observed that the applied damping torque highly depends on the tilting angle of the mirror as well as the ratio of its vertical to angular velocity and as a result the effect of the vertical velocity of the mirror on the squeezed film damping force and torque applied to the mirror cannot be simply neglected. The results of this paper can be used for accurate dynamical modeling of the micromirrors under the effect of the squeezed film damping.

Effect of guide rail profile errors on the motion accuracy for a heavy-duty hydrostatic turntable

2019 ◽  
Vol 233 (15) ◽  
pp. 5350-5362 ◽  
Author(s):  
Yongsheng Zhao ◽  
Hongchao Wu ◽  
Congbin Yang ◽  
Ligang Cai ◽  
Zhifeng Liu
Keyword(s):  
Machine Tool ◽  
Reynolds Equation ◽  
Machining Accuracy ◽  
Guide Rail ◽  
Heavy Duty ◽  
Motion Equations ◽  
Rotating Speed ◽  
Proposed Model ◽  
Reaction Forces ◽  
Profile Errors

The motion accuracy of hydrostatic turntable is the key in improving the machining accuracy of heavy-duty machine tool. However, the motion accuracy of hydrostatic turntable depends not only on the offset load but also on the rotating speed of the turntable as well as the profile errors of the guide rails. In this paper, a simulation model is developed to analyze the effect of guide rail profile errors on the motion accuracy of hydrostatic turntable. The reaction forces of preload thrust bearing and hydrostatic circular oil pads are obtained based on the Reynolds equation of the lubricant film. The motion equations of hydrostatic turntable are derived in which the profile errors of two guide rails are considered. The results show that the motion accuracy of hydrostatic turntable can be affected by wavelength, amplitude of profile errors and speed, and offset load of turntable. Finally, the motion accuracy of heavy-duty hydrostatic turntable used in XCKA28105 type turning and milling composite machine tool is obtained by using the presented method. Comparing with the experimental results, the proposed model can be used to predict the machining accuracy caused by the profile errors of guide rails for any heavy-duty hydrostatic turntable.

Optimal control of an elastic string with viscous damping

2001 ◽  
Vol 77 (1-2) ◽  
pp. 3-10 ◽  
Author(s):  
Boris Belinskiy ◽  
Suzanne Lenhart
Keyword(s):  
Optimal Control ◽  
Viscous Damping ◽  
Elastic String

Damping characteristics of a magneto-rheological damper with dual independent controllable ducts

2021 ◽  
pp. 1045389X2110188
Author(s):  
Jianqiang Yu ◽  
Xiaomin Dong ◽  
Tao Wang ◽  
Zhengmu Zhou ◽  
Yaqin Zhou
Keyword(s):  
Dynamic Range ◽  
Fluid Flows ◽  
Mr Damper ◽  
Viscous Damping ◽  
The Novel ◽  
The Finite Element Method ◽  
Damping Force ◽  
Damping Characteristics ◽  
Magneto Rheological ◽  
The Mathematical Model

This paper presents the damping characteristics of a linear magneto-rheological (MR) damper with dual controllable ducts based on numerical and experimental analysis. The novel MR damper consisting of a dual-rod cylinder system and a MR valve is used to reduce the influences of viscous damping force and improve dynamic range. Driven by the dual-rod cylinder system, MR fluid flows in the MR valve. The pressure drop of the MR valve with dual independent controllable ducts can be controlled by tuning the current of two independent coils. Based on the mathematical model and the finite element method, the damping characteristics of the MR damper is simulated. A prototype is designed and tested on MTS machine to evaluate its damping characteristics. The results show that the working states and damping force of the MR damper can be controlled by the two independent coils.

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