NONDIMENSIONAL ANALYSIS OF ANNULAR DUCT FLOW IN MAGNETORHEOLOGICAL/ELECTRORHEOLOGICAL DAMPERS

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1577-1583 ◽  
Author(s):  
JIN-HYEONG YOO ◽  
NORMAN M. WERELEY
Keyword(s):  
Quadratic Equation ◽  
Damping Coefficient ◽  
Viscous Damping ◽  
Uniform Field ◽  
Duct Flow ◽  
Equivalent Viscous Damping ◽  
Performance Metric ◽  
Annular Duct ◽  
Er Damper ◽  
Analytical Expressions

Approximate analytical expressions describing MR/ER damper performance for an axisymmetric annular duct under the assumption of uniform field are presented. The key performance metric is the damping coefficient, which is the ratio of the equivalent viscous damping constant, Ceq, to the Newtonian viscous damping constant, C. To develop these approximations, a quadratic equation was used to approximate the center of the plug location in the annular duct. This equation simplified the calculation of the annular duct solution without resorting to numerical methods to solve the boundary value problem. Approximations for the damping coefficient are developed on this basis.

Force Behavior of Parallel Double Coupling Beams with Different Width

2014 ◽  
Vol 578-579 ◽  
pp. 707-710
Author(s):  
Ming Li ◽  
Ji Guang Chen ◽  
Wei Jian Zhao ◽  
Li Guo Wang
Keyword(s):  
Finite Element ◽  
Energy Dissipation ◽  
Damping Coefficient ◽  
Viscous Damping ◽  
Coupling Beams ◽  
Equivalent Viscous Damping ◽  
Dissipation Coefficient ◽  
Finite Element Software ◽  
Double Coupling ◽  
Energy Dissipation Coefficient

The force behavior of parallel double coupling beams (PDCB) with different width is analyzed, based on which the feasibility of this kind of beams is discussed. The loading process of the PDCB is simulated by using finite element software ABAQUS. By analyzing the hysteretic loops, skeleton curves, energy dissipation coefficient, equivalent viscous damping coefficient and ductility coefficient,the bearing capacity and seismic performance of the PDCB is studied. Through simulation, it shows that the hysteretic loops is plump, and the energy dissipation coefficient, equivalent viscous damping coefficient and ductility coefficient of this double beams is high. It can be concluded that the PDCB has good force behavior, and the beams of PDCB can work in coordination.

scholarly journals Actively Controlled Bearing Dampers for Aircraft Engine Applications

1999 ◽  
Author(s):  
John M. Vance ◽  
Daniel Ying ◽  
Jorgen L. Nikolajsen
Keyword(s):  
Critical Speed ◽  
Aircraft Engine ◽  
Viscous Damping ◽  
Aircraft Engines ◽  
Equivalent Viscous Damping ◽  
Critical Speeds ◽  
Speed Range ◽  
Coulomb Type ◽  
Er Damper ◽  
San Andres

This paper describes some of the requirements for bearing dampers to be used in an aircraft engine and briefly discusses the pros and cons of various types of dampers that were considered as candidates for active control in aircraft engines. A disk type of electrorheological (ER) damper was chosen for further study and testing. The paper explains how and why the choice was made. For evaluating potential applications to aircraft engines, an experimental development engine (XTE-45) was used as an example for this study. Like most real aircraft engines, the XTE-45 ran through more than one critical speed in its operating speed range. There are some speeds where damping is desirable and other speeds where it is not. Thus, the concept of a damper with controllable forces appears attractive. The desired equivalent viscous damping at the critical speeds along with the available size envelope were two of the major criteria used for comparing the dampers. Most previous investigators have considered the ER damper to produce a purely Coulomb type of damping force and this was the assumption used by the present authors in this study. It is shown in a companion paper (Vance and San Andres, 1999), however, that a purely Coulomb type of friction cannot restrain the peak vibration amplitudes at rotordynamic critical speeds and that the equivalent viscous damping for rotordynamics is different from the value derived by previous investigators for planar vibration. Control laws for Coulomb damping are derived in Vance and San Andres, (1999) to achieve minimum rotor vibration amplitudes in a test rig while avoiding large bearing forces over a speed range that includes a critical speed. The type of control scheme required and its effectiveness was another criterion used for comparing the dampers in this paper.

Research in Testing of Loess Foundation Pile Hysteretic Property under Horizontal Cyclic Load

2012 ◽  
Vol 433-440 ◽  
pp. 202-206
Author(s):  
Ming Bo Ding ◽  
Xing Chong Chen
Keyword(s):  
Cyclic Load ◽  
Large Scale ◽  
Damping Coefficient ◽  
Scale Model ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Loess Area ◽  
Hysteretic Property ◽  
Large Scale Model ◽  
Foundation Pile

In this paper, by the large scale model test of pile-soil in remodeling loess foundation, authors research the basic discipline of pile-soil interaction plastic hysteretic property of pile foundation in loess area under horizontal cyclic load and obtain hysteretic curves, skeleton curves and relationship between equivalent viscous damping coefficient and displacement under pile-soil interaction. The paper also discusses the intensity components, plastic and other energy and equivalent viscous damping coefficient cycles occur with varying degrees of degradation of the variation.

Approximating Annular Duct Flow in ER/MR Dampers Using a Rectangular Duct

2003 ◽  
Author(s):  
Jin-Hyeong Yoo ◽  
Norman M. Wereley
Keyword(s):  
Plastic Material ◽  
Flow Mode ◽  
Uniform Field ◽  
Duct Flow ◽  
Rectangular Duct ◽  
Bingham Plastic ◽  
Analysis And Design ◽  
Mr Dampers ◽  
Annular Duct ◽  
The Impact

In general, ER/MR dampers have a cylindrical cross-section, for reasons of simplicity of design and maximum strength of the damper. Usually the ER/MR effect is activated by applying field across an annular valve. However, for simplicity of the analysis and design, a rectangular duct flow model is usually adopted. This paper compares analytical solutions of the rectangular and annular duct model under the assumption of uniform field across the valve gap. To compare errors between annular and rectangular duct models, a formulation for the error in the case of Bingham plastic material will be derived for flow mode dampers. This paper focuses on the errors of shear stress, velocity profile and equivalent viscous damping coefficient arising from the approximation of an annular duct as a rectangular duct. The impact of the small gap assumption, that is, the valve gap, d, is much smaller than the annular radius, R1, is thoroughly investigated. We conclude that the approximate rectangular duct model can accurately describe the annular valve behavior as long as d/R1 ≪ 1.

scholarly journals Study on Equivalent Viscous Damping Coefficient of Sucker Rod Based on the Principle of Equal Friction Loss

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Qin Li ◽  
Bo Chen ◽  
Zhiqiang Huang ◽  
Haipin Tang ◽  
Gang Li ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Friction Loss ◽  
Damping Coefficient ◽  
Theoretical Formula ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Equivalent Damping ◽  
Rod System ◽  
Sucker Rod ◽  
Equivalent Damping Coefficient

Equivalent viscous damping coefficient is an important parameter of wave equation for sucker rod string. In this paper, based on the principle of equal friction loss, when the viscous energy consumption and the local damping energy consumption are taken into account, effects of equivalent viscous damping coefficients are obtained. Through deducing energy consumption equation of oil and energy consumption equation of the coupling, theoretical formula for equivalent damping coefficient of sucker rods is received. Results show that the smaller the K is (K is the ratio of sectional area of tubing to sucker rod), the larger the proportion of damping coefficient caused by viscous energy consumption in the equivalent damping coefficient of sucker rod system is. When K< 0.095, the proportion of damping coefficient caused by viscous energy consumption is more than 90%. Reducing the sudden change of cross-section area at sucker rod coupling has remarkable effect on reducing damping force of the sucker rod system. The research provides a theoretical basis for the application and design of sucker rod and tubing.

scholarly journals Design analysis and performance evaluation of a novel Multi-Cantilever Foil Bearing

2021 ◽  
Vol 40 (3) ◽  
pp. 449-460
Author(s):  
M. Obaseki ◽  
P.T. Elijah ◽  
P.B. Alfred
Keyword(s):  
Performance Evaluation ◽  
Phase Angle ◽  
Design Analysis ◽  
Damping Coefficient ◽  
Viscous Damping ◽  
Maximum Deflection ◽  
Structural Stiffness ◽  
Equivalent Viscous Damping ◽  
Foil Bearing ◽  
And Performance

This study gives an explanation to design analysis and performance evaluation of a novel multi-cantilever foil bearing (MCFB). The aim of this study is to develop a theoretical model that will explain the working principles of the cantilever foil bearing. A theoretical derivation of structural and vibration models were developed to find structural stiffness, equivalent viscous damping and maximum deflection. Findings show that the theoretical results of structural models have an equivalent structural stiffness of 58.59kN/mm, equivalent viscous damping of 0.599kNs/m and maximum deflection of 0.5675mm. The equivalent viscous damping is computed at a near zero circumferential coordinate (0.0350). The results obtained from vibration models show an equivalent structural stiffness of 58.74kN/mm, equivalent viscous damping of 0.228kNs/m and maximum deflection of 0.5675mm. Theoretical viscous damping coefficient varies from 0.23kNs/m at 24Hz to 0.026kNs/m at 200Hz when determined at maximum deflection of 0.5675mm and phase angle of 0.0350. This means the higher the frequency, the lower the viscous damping coefficient. The validation was done over frequency range 24-200Hz and at amplitude of 50mm at a 450 phase angle. The models were found to have compared well with experimental results in the prediction of equivalent viscous damping coefficient. The models can be relied upon to analyze the behaviour of MCFB and it can also form a theoretical background for the design and manufacture of Multi-Cantilever Foil Bearing.

Force Behavior of Outer Annular-Stiffener Type Steel Castellated Beam-Concrete Filled Steel Tuber

2013 ◽  
Vol 405-408 ◽  
pp. 861-864
Author(s):  
Ming Li ◽  
Yong Liu ◽  
He Yuan
Keyword(s):  
Finite Element ◽  
Energy Dissipation ◽  
Simulation Method ◽  
Damping Coefficient ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Type Steel ◽  
Dissipation Coefficient ◽  
Castellated Beam ◽  
Energy Dissipation Coefficient

The force behavior of outer annular-stiffener type steel castellated beam (OATSCB) - concrete filled steel tube (CFST) is analyzed, and the feasibility of this kind of join is discussed. The loading process of the joint is simulated by using finite element software. By analyzing the hysteretic loops, skeleton curves, energy dissipation coefficient, equivalent viscous damping coefficient and ductility coefficient, the bearing capacity and seismic performance of this type of joint is studied. Before simulation, the validity of the simulation method is verified by using the previous experiment data of outer annular-stiffener type steel beam (OATSB) - CFST. It shows that the results from the finite element simulation method and the experiment are similar to each other, and the hysteretic loops is plump , the energy dissipation coefficient, equivalent viscous damping coefficient and ductility coefficient of this type of joint are high. It can be seen that this type of joint has good mechanical properties, and is easy to realize the yield mechanism of strong column weak beam.

Actively Controlled Bearing Dampers for Aircraft Engine Applications

2000 ◽  
Vol 122 (3) ◽  
pp. 466-472 ◽  
Author(s):  
John M. Vance ◽  
Daniel Ying ◽  
Jorgen L. Nikolajsen
Keyword(s):  
Aircraft Engine ◽  
Companion Paper ◽  
Viscous Damping ◽  
Aircraft Engines ◽  
Damping Force ◽  
Equivalent Viscous Damping ◽  
Experimental Development ◽  
Critical Speeds ◽  
Coulomb Type ◽  
Er Damper

This paper describes some of the requirements for bearing dampers to be used in an aircraft engine and briefly discusses the pros and cons of various types of dampers that were considered as candidates for active control in aircraft engines. A disk type of electrorheological (ER) damper was chosen for further study and testing. The paper explains how and why the choice was made. For evaluating potential applications to aircraft engines, an experimental development engine (XTE-45) was used as an example for this study. Like most real aircraft engines, the XTE-45 ran through more than one critical speed in its operating speed range. There are some speeds where damping is desirable and other speeds where it is not. Thus, the concept of a damper with controllable forces appears attractive. The desired equivalent viscous damping at the critical speeds along with the available size envelope were two of the major criteria used for comparing the dampers. Most previous investigators have considered the ER damper to produce a purely Coulomb type of damping force and this was the assumption used by the present authors in this study. It is shown in a companion paper, however, that a purely Coulomb type of friction cannot restrain the peak vibration amplitudes at rotordynamic critical speeds and that the equivalent viscous damping for rotordynamics is different from the value derived by previous investigators for planar vibration. The type of control scheme required and its effectiveness was another criterion used for comparing the dampers in this paper. [S0742-4795(00)00803-6]

Design and structural performance measurements of a novel multi-cantilever foil bearing

2014 ◽  
Vol 229 (10) ◽  
pp. 1830-1838 ◽  
Author(s):  
Kai Feng ◽  
Xueyuan Zhao ◽  
Zhiyang Guo
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Load ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Foil Bearing ◽  
Load Tests ◽  
Stiffness And Damping ◽  
Motion Amplitude

With increasing need for high-speed, high-temperature, and oil-free turbomachinery, gas foil bearings (GFBs) have been considered to be the best substitutes for traditional oil-lubricated bearings. A multi-cantilever foil bearing (MCFB), a novel GFB with multi-cantilever foil strips serving as the compliant underlying structure, was designed, fabricated, and tested. A series of static and dynamic load tests were conducted to measure the structural stiffness and equivalent viscous damping of the prototype MCFB. Experiments of static load versus deflection showed that the proposed bearing has a large mechanical energy dissipation capability and a pronounced nonlinear static stiffness that can prevents overly large motion amplitude of journal. Dynamic load tests evaluated the influence of motion amplitude, loading orientation and misalignment on the dynamic stiffness and equivalent viscous damping with respect to excitation frequency. The test results demonstrated that the dynamic stiffness and damping are strongly dependent on the excitation frequency. Three motion amplitudes were applied to the bearing housing to investigate the effects of motion amplitude on the dynamic characteristics. It is noted that the bearing dynamic stiffness and damping decreases with incrementally increasing motion amplitudes. A high level of misalignment can lead to larger static and dynamic bearing stiffness as well as to larger equivalent viscous damping. With dynamic loads applied to two orientations in the bearing midplane separately, the dynamic stiffness increases rapidly and the equivalent viscous damping declines slightly. These results indicate that the loading orientation is a non-negligible factor on the dynamic characteristics of MCFBs.

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