A View to the Energy Dissipation Mechanism of a Gas Foil Bearing’s Structure due to Dry Friction

2012 ◽  
Author(s):  
José A. Matute ◽  
Rafael O. Ruiz ◽  
Sergio E. Diaz
Keyword(s):  
Energy Dissipation ◽  
Dry Friction ◽  
Nonlinear Behavior ◽  
Excitation Amplitude ◽  
Equivalent Model ◽  
Stick Slip ◽  
Friction Forces ◽  
Energy Dissipation Mechanism ◽  
Variable Function ◽  
Dissipation Mechanism

The purpose of the present work consists on improving the understanding of the energy dissipation mechanism in the structure of a gas foil bearing. The analysis is based on an analytical model capable of predicting bumps deformation due to a load on the top coupled with dry friction forces at the top and bump ends. Models of mass-individual bump and mass-bump foil subject to a harmonic force are predicted numerically. The nonlinear behavior due to dry friction results in the possibility of stick-slip conditions over the surfaces in contact. The Variation of parameters such as excitation amplitude, mass magnitude, coefficient of friction, and bump geometry were considered. Equivalent dynamic coefficients of stiffness and damping are estimated through a least squares curve fitting, which constitutes a linearization of the system with dry friction. A computer program was developed in order to consider the effect of stick-slip. As a final product of this research the nonlinear model of the structure support was used to obtain a linear and simplified equivalent model. In most studied cases it is possible to represent the system with a linearized model of constant stiffness and viscous damping which is a variable function of the studied parameters and the frequency.

Active Control Comparison of Vibration in Flexible Spacecraft Using Different Active Friction Joints

2013 ◽  
Vol 446-447 ◽  
pp. 1160-1164
Author(s):  
Sahar Bakhtiari Mojaz ◽  
Hamed Kashani
Keyword(s):  
Energy Dissipation ◽  
Attitude Control ◽  
Vibration Suppression ◽  
Excitation Amplitude ◽  
Step Function ◽  
Flexible Spacecraft ◽  
Control Effort ◽  
Stick Slip ◽  
Control Comparison ◽  
Frictional Joints

Vibration properties of most assembled mechanical systems depend on frictional damping in joints. The nonlinear transfer behavior of the frictional interfaces often provides the dominant damping mechanism in structure and plays an important role in the vibratory response of it. For improving the performance of systems, many studies have been carried out to predict measure and enhance the energy dissipation of friction. This paper presents a new approach to vibration reduction of flexible spacecraft with enhancing the energy dissipation of frictional dampers. Spacecraft is modeled as a 3 degree of freedom mass-spring system which is controlled by a lead compensator and System responses to step function evaluated. Coulomb and Jenkins element has been used as vibration suppression mechanisms in joints and sensitivity of their performance to variations of spacecraft excitation amplitude and damper properties is analyzed. The relation between frictional force and displacement derived and used in optimization of control performance. Responses of system and control effort needed for the vibration control are compared for these two frictional joints. It is shown that attitude control effort reduces, significantly with coulomb dampers and response of system improves. On the other hand, due to stick-slip phenomena in Jenkins element, we couldn’t expect the same performance from Jenkins damper.

Analysis of Beam-Like Structures With Displacement-Dependent Friction Forces: Part I — Single-Degree-of-Freedom Model

1995 ◽  
Author(s):  
Wayne E. Whiteman ◽  
Aldo A. Ferri
Keyword(s):  
Dry Friction ◽  
Damping Ratio ◽  
Strong Dependence ◽  
Time Integration ◽  
Single Mode ◽  
Stick Slip ◽  
Friction Forces ◽  
Equivalent Damping ◽  
Damping Characteristics ◽  
Parameter Values

Abstract The dynamic behavior of a beam-like structure undergoing transverse vibration and subjected to a displacement-dependent dry friction force is examined. In Part I, the beam is modeled by a single mode while Part II considers multi-mode representations. The displacement dependence in each case is caused by a ramp configuration that allows the normal force across the sliding interface to increase linearly with slip displacement. The system is studied first by using first-order harmonic balance and then by using a time integration method. The stick-slip behavior of the system is also studied. Even though the only source of damping is dry friction, the system is seen to exhibit “viscous-like” damping characteristics. A strong dependence of the equivalent natural frequency and damping ratio on the displacement amplitude is an interesting result. It is shown that for a given set of parameter values, an optimal ramp angle exists that maximizes the equivalent damping ratio. The appearance of two dynamic response solutions at certain system and forcing parameter values is also seen. Results suggest that the overall characteristics of mechanical systems may be improved by properly configuring frictional interfaces to allow normal forces to vary with displacement.

scholarly journals Interfacial strength-controlled energy dissipation mechanism and optimization in impact-resistant nacreous structure

2019 ◽  
Vol 163 ◽  
pp. 107532 ◽  
Author(s):  
Kaijin Wu ◽  
Zhijun Zheng ◽  
Shuaishuai Zhang ◽  
Linghui He ◽  
Hongbin Yao ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Interfacial Strength ◽  
Energy Dissipation Mechanism ◽  
Dissipation Mechanism

scholarly journals Energy dissipative photoprotective mechanism of carotenoid spheroidene from the photoreaction center of purple bacteria Rhodobacter sphaeroides

2015 ◽  
Vol 17 (36) ◽  
pp. 23468-23480 ◽  
Author(s):  
Sundaram Arulmozhiraja ◽  
Naoki Nakatani ◽  
Akira Nakayama ◽  
Jun-ya Hasegawa
Keyword(s):  
Energy Dissipation ◽  
Rhodobacter Sphaeroides ◽  
Purple Bacteria ◽  
Minimum Energy ◽  
Intersystem Crossing ◽  
Triplet Energy ◽  
Energy Dissipation Mechanism ◽  
Dissipation Mechanism ◽  
Crossing Point

Triplet energy dissipation mechanism of a carotenoid: just bond twisting and stretching lead to minimum energy intersystem crossing point.

scholarly journals Numerical investigation of the turbulence characteristics and energy dissipation mechanism of baffle drop shafts

2021 ◽  
Author(s):  
Qinghua Yang ◽  
Qian Yang
Keyword(s):  
Energy Dissipation ◽  
Flow Rate ◽  
High Energy ◽  
Design Flow ◽  
Low Flow ◽  
Turbulence Characteristics ◽  
Energy Dissipation Mechanism ◽  
Dissipation Mechanism ◽  
Drop Flow ◽  
Free Drop

Abstract The baffle drop shaft is widely used in deep tunnel drainage system due to its fine applicability and high energy dissipation. To fully study the turbulence characteristics and energy dissipation mechanism of baffle drop shafts, a 1:25 scale physical model test and the numerical simulation based on the Realizable k-ε model and Volume of Fluid (VOF) method were performed. The results showed that a baffle spacing that is too dense or too sparse is not conducive to energy dissipation and discharge. The minimum baffle spacing is the optimal structural design at the design flow rate when the flow regime is free-drop flow. The energy dissipation calculation model established in this paper has high accuracy for calculating the energy dissipation rate on the baffles in free-drop flow. The energy dissipation modes of the shaft can be divided into inlet energy dissipation, baffle energy dissipation, and shaft-bottom energy dissipation. Baffles play a major role in the energy dissipation at low flow rates, and the proportions of inlet and shaft-bottom energy dissipation increase with the increase in flow rate.

Oxide layer delamination: an energy dissipation mechanism during high-velocity microparticle impacts

2021 ◽  
pp. 151673
Author(s):  
Ahmed A. Tiamiyu ◽  
Xi Chen ◽  
Edward L. Pangv ◽  
Yuchen Sun ◽  
Jasper Z. Lienhard ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Oxide Layer ◽  
High Velocity ◽  
Energy Dissipation Mechanism ◽  
Dissipation Mechanism
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