Experimental Estimation of Equivalent Damping Coefficient of Thrust Bearings

MR damper (magnetorheological damper) has broad application prospects, and equivalent damping coefficient is very important of its dynamic characteristic analysis. Based on the modified Bouc_Wen model, the performance of MR damper was analyzed and the equivalent linear damping coefficient of MR damper was calculated. Based on simulation date of the modified Bouc_Wen model, the relationships between the equivalent linear damping coefficient of MR damper and the parameters of control voltage and MR dampers movement amplitude were established by the curve fitting regression analysis method. Verification results prove that the equivalent linear damping coefficient model has higher accuracy. For the vibration systems using strongly nonlinear MR damper, new model can effectively improve the efficiency of calculating the vibration analysis and the stability of the system in a certain frequency. At the same time, the model provides a theoretical basis for the application of MR damper control.

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A new type of damper combining eddy current damping with rack and gear

Journal of Vibration and Control ◽

10.1177/1077546320937110 ◽

2020 ◽

pp. 107754632093711

Author(s):

Yafeng Li ◽

Shouying Li ◽

Jianzhong Wang ◽

Zhengqing Chen

Keyword(s):

Eddy Current ◽

Permanent Magnets ◽

Air Gap ◽

Damping Coefficient ◽

Apparent Mass ◽

Damping Force ◽

Equivalent Damping ◽

Eddy Current Damping ◽

New Type ◽

Equivalent Damping Coefficient

A new type of damper combining eddy current damping with rack and gear, which can simultaneously export damping and inertial forces, is proposed. Eddy current damping with rack and gear is supposed to be installed between the building superstructure and foundation to mitigate the seismic response of the building. First, the concept of eddy current damping with rack and gear is introduced in detail and its apparent mass and equivalent damping coefficient are both theoretically investigated. Second, a prototype of eddy current damping with rack and gear is manufactured, and a series of tests on the prototype are carried out to verify its structural parameters. The experimental and theoretical results of the apparent mass of the prototype agree well with each other. The experimental result of the equivalent damping coefficient of the prototype is slightly lower than the numerical results obtained from COMSOL Multiphysics and its maximum relative differences are 11.3% and 13.6% for α = 0° and 45°, respectively. Third, detailed parametric studies on the damping force, including the effects of the thickness of the conductor plate, air gap, and number and location of permanent magnets, are conducted. The results show that the damping force keeps a linear relationship with velocity if it is lower than 0.15 m/s, and with the increase of the velocity, a strong nonlinear relationship between the damping force and the velocity is observed. The available maximum damping force can be increased by decreasing the thickness of the conductor plate and the air gap, increasing the number of permanent magnets. There is an optimal location about the permanent magnets for the available maximum damping force. In addition, the hysteretic curves of the eddy current damping with rack and gear obtained from the test indicate that the ability of energy dissipation is considerable.

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

Mathematical Problems in Engineering ◽

10.1155/2019/9272751 ◽

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.

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Study on Dynamic Characteristics of Aerostatic Bearing with Elastic Equalizing Pressure Groove

Shock and Vibration ◽

10.1155/2018/6142386 ◽

2018 ◽

Vol 2018 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Xiao-long Zhao ◽

Hao Dong ◽

Zhou Fang ◽

Deng-di Chen ◽

Jun-an Zhang

Keyword(s):

Dynamic Characteristics ◽

Dynamic Stiffness ◽

Dynamic Performance ◽

Coupling Model ◽

Damping Coefficient ◽

Aerostatic Bearing ◽

Equivalent Damping ◽

New Type ◽

Equivalent Damping Coefficient ◽

Control Equation

Microvibration has an important influence on the dynamic performance of aerostatic bearings. Dynamic stiffness and equivalent damping coefficient are the main indexes to evaluate the dynamic characteristics of the aerostatic bearing. In order to study the dynamic characteristics of a new type of aerostatic bearing with the elastic equalizing pressure groove (EEPG), the dynamic characteristics of the new type of bearing are studied by theoretical calculation and experiment. First, the dynamic gas-solid coupling control equation is established. Then, the steady term and the perturbation term are decomposed by the perturbation method. By solving the coupling model, the dynamic characteristics of the bearing are calculated and analyzed. The calculation results show that the perturbation frequency has a significant effect on the dynamic stiffness and equivalent damping coefficient of the aerostatic bearing with EEPG. The dynamic stiffness increases with the increase of frequency, and the equivalent damping coefficient decreases with the increase of frequency. The experimental results are basically the same with the theoretical results, which effectively verify the correctness of the theoretical analysis.

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Research on the Vertical Vibration Characteristics of Hydraulic Screw Down System of Rolling Mill under Nonlinear Friction

Processes ◽

10.3390/pr7110792 ◽

2019 ◽

Vol 7 (11) ◽

pp. 792 ◽

Cited By ~ 1

Author(s):

Yongshun Zhang ◽

Wanlu Jiang ◽

Yong Zhu ◽

Zhenbao Li

Keyword(s):

Parameter Uncertainty ◽

Rolling Mill ◽

Pid Controller ◽

Vertical Vibration ◽

Damping Coefficient ◽

Practical Significance ◽

Nonlinear Friction ◽

Equivalent Damping ◽

Leakage Coefficient ◽

Equivalent Damping Coefficient

The rolling mill with hydraulic system is widely used in the production of strip steel. For the problem of vertical vibration of the rolling mill, the effects of different equivalent damping coefficient, leakage coefficient, and proportional coefficient of the controller on the hydraulic screw down system of the rolling mill are studied, respectively. First, a vertical vibration model of a hydraulic screw down system was established, considering the nonlinear friction and parameter uncertainty of the press cylinder. Second, the correlation between different equivalent damping coefficient, internal leakage coefficient, proportional coefficient, vertical vibration was analyzed. The simulation results show that, in the closed-loop state, when Proportional-Integral-Derivative (PID) controller parameters are fixed, due to the change of the equivalent damping coefficient and internal leakage coefficient, the system will have parameter uncertainty, which may lead to the failure of the PID controller and the vertical vibration of the system. This study has theoretical and practical significance for analyzing the mechanism of vertical vibration of the rolling mill.

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EVALUATIONS OF CLUSTER STRUCTURE AND MAGNETO-RHEOLOGY OF MR SUSPENSIONS

International Journal of Modern Physics B ◽

10.1142/s0217979205030414 ◽

2005 ◽

Vol 19 (07n09) ◽

pp. 1437-1442 ◽

Cited By ~ 6

Author(s):

HIDEYA NISHIYAMA ◽

KAZUNARI KATAGIRI ◽

KATSUHISA HAMADA ◽

KAZUTO KIKUCHI ◽

KATSUHIKO HATA ◽

...

Keyword(s):

Magnetic Field ◽

Cluster Formation ◽

Cluster Structure ◽

Mr Damper ◽

Magnetic Flux Density ◽

Equivalent Damping ◽

Damping Characteristics ◽

Mr Fluids ◽

Equivalent Damping Coefficient ◽

Particle Shapes

In the present study, we sysnthesize two types of MR fluids with different particle shapes and sizes. The magnetic functions are evaluated circulatingly by the analysis of cluster formation, rheological properties in the applied magnetic field and damping characteristics in the MR damper, comparing with those of commercial MR fluids. Final objective is to provide the fundamental data for the development of newly advanced MR fluids. The main topics consist of geographycal cluster formation depending on particle shapes and sizes, relating to the apparent viscosity and yield stress with magnetic flux density and further equivalent damping coefficient of two newly sysnthesised MR fluids comparing with those of LORD MR fluid.

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Fabrication and characterization of highly controllable magnetorheological material in compression mode

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x20930081 ◽

2020 ◽

Vol 31 (14) ◽

pp. 1641-1661 ◽

Cited By ~ 1

Author(s):

Amin Fereidooni ◽

Afonso Martins ◽

Viresh Wickramasinghe ◽

Afzal Suleman

Keyword(s):

Magnetic Fields ◽

Loss Factor ◽

Magnetorheological Fluid ◽

Loading Frequency ◽

Magnetorheological Elastomer ◽

Magnetorheological Elastomers ◽

Equivalent Damping ◽

Magnetorheological Effect ◽

Equivalent Damping Coefficient

This article is focused on the development and characterization of highly controllable magnetorheological materials for stiffness and damping control in semi-active control applications. Two types of magnetorheological materials are developed in-house: magnetorheological elastomer with soft base elastomer, and magnetorheological fluid encapsulated in regular elastomer, namely magnetorheological fluid-elastomer. In both cases of magnetorheological elastomers and magnetorheological fluid-elastomers, the samples are evaluated using in-house-developed shear and compression test rigs, which are equipped with electromagnets and Hall effect sensors for measuring the magnetic field. These features provide the capability to precisely control a wide range of magnetic fields during the experiments. In the case of magnetorheological elastomers, the experimental results of the in-house magnetorheological elastomers are compared with commercially available counterparts made of hard base elastomer. It is shown that the controllability of the material, that is, the relative magnetorheological effect, is significantly improved in the case of magnetorheological elastomer with soft base elastomer. In addition to various magnetic fields, the samples are subjected to a range of loading amplitudes and frequencies. A general trend is observed where the frequency and strain amplitude cause an opposite effect on both the shear and compressive moduli: the increase in frequency gives rise to a higher value of modulus whereas the increase in amplitude reduces the modulus. Furthermore, the effect of bonding on the performance of the magnetorheological elastomers in compression mode is evaluated and the results indicate a significant increase in the modulus and decrease in the loss factor. In all the cases, however, the change of loss factor does not exhibit a predictable trend as a function of magnetic fields. In order to investigate a magnetorheological-based solution for controlling the damping of a semi-active system, magnetorheological fluid-elastomer samples are made in-house. These samples are fabricated using three different iron concentrations, and are tested in compression (squeeze) mode. The results of these experiments confirm that the equivalent damping coefficient of the material rises with the increase in magnetic field, and this effect becomes stronger as the iron concentration of magnetorheological fluids increases. It is also demonstrated that the magnetorheological effect is highly dependent on the loading frequency and amplitude, where the equivalent damping coefficient decreases with the increase in loading frequency and amplitude. In all the aforementioned cases, the stiffness of magnetorheological fluid-elastomers exhibits minor changes, which offers the in-house-developed magnetorheological fluid-elastomers as a damping only control option, a development that is different from the magnetorheological fluid-elastomers reported in the literature.

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Numerical Investigation of Static and Dynamic Characteristics of Water Hydrostatic Porous Thrust Bearings

International Journal of Automation Technology ◽

10.20965/ijat.2011.p0773 ◽

2011 ◽

Vol 5 (6) ◽

pp. 773-779 ◽

Cited By ~ 6

Author(s):

Yuki Nishitani ◽

◽

Shigeka Yoshimoto ◽

Kei Somaya

Keyword(s):

Porous Material ◽

Dynamic Characteristics ◽

Machine Tools ◽

Measuring Equipment ◽

Load Capacity ◽

Damping Coefficient ◽

Static And Dynamic Characteristics ◽

Thrust Bearings ◽

Hydrostatic Bearings ◽

Aerostatic Bearings

A moving table supported by aerostatic bearings can achieve excellent accuracy of motion because of its noncontact support and, hence, it is used in various precision machine tools and measuring equipment. However, because of low viscosity of air, the damping coefficient of aerostatic bearings is not very high, causing vibration with nanometer-order amplitudes. The accuracy of machine tools and measuring equipment could deteriorate because of this vibration. It is expected that water hydrostatic bearings would have a higher damping coefficient than aerostatic bearings due to the higher viscosity of water. In addition, water, like air, does not pollute the environment. In this paper, the static and dynamic characteristics of water hydrostatic thrust bearings using porous material were numerically investigated and comparedwith conventional pocket hydrostatic bearings with a capillary restrictor. Hydrostatic porous bearings can be easily constructed because the porous material becomes a viscous restrictor itself. It was consequently found that water hydrostatic porous thrust bearings have higher maximum load capacity and slightly lower stiffness than water bearings with a capillary restrictor.

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Shafting Vibration Simulation for Hydro Turbine Generating Sets

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.444-445.1171 ◽

2013 ◽

Vol 444-445 ◽

pp. 1171-1176

Author(s):

Yun Zeng ◽

Li Xiang Zhang ◽

Jing Qian ◽

Cheng Li Zhang

Keyword(s):

Vibration Amplitude ◽

Angular Speed ◽

Transient Model ◽

Integrated Simulation ◽

Hydro Turbine ◽

Equivalent Damping ◽

Generating Sets ◽

Mass Eccentricity ◽

Equivalent Damping Coefficient ◽

Vibration Simulation

Based on the transient model of hydro turbine generating sets (HTGS), the integrated simulation system of HGTS is built to study shafting stability. Given different bearing stiffness, equivalent damping coefficient and mass eccentricity, the change characteristics of shafting vibration at rated angular speed in steady and maximum angular speed in transient are simulated, and which are applied to study inferences shafting parameters and angular speed on shafting vibration. Simulation results show that the relationship between shafting vibration amplitude and angular speed is linear. however, the vibration amplitude increment produced by angular speed error will be amplified while the shafting stiffness is weaker, mass eccentricity of the runner and rotor is larger.

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Dynamic investigation of a spatial multi-body mechanism considering joint clearance and friction based on coordinate partitioning method

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/09544062211025566 ◽

2021 ◽

pp. 095440622110255

Author(s):

Gao Hua ◽

Zhai Jingyu ◽

Zhang Hao ◽

Han Qingkai ◽

Liu Jinguo

Keyword(s):

Lagrange Equation ◽

Contact Point ◽

Stable State ◽

Constraint Equation ◽

Friction Model ◽

Dynamic Equations ◽

Joint Clearance ◽

Equivalent Damping ◽

Equivalent Damping Coefficient ◽

Coordinate Partitioning

The dynamic response of the model, which is the series connection of a planar four-bar mechanism and a spatial RSSR mechanism, is analyzed considering revolute joint clearance and friction. A non-holonomic constraint equation is proposed to solve the Euler angles. The dynamic equations are established by combining the Lagrange equation with the modified contact model and the LuGre friction model. A dynamic solution program based on the coordinate partitioning method is designed to solve the dynamic equations. The paper verifies the correctness and applicability of the solution program by comparing the numerical calculation results with Adams simulation. Compared with the results of eccentricity, it is found that the maximum penetration is very sensitive to the change of the slider speed rather than the clearance. The equivalent damping coefficient proposed by authors not only represents whether a collision occurs, but reflects the hysteresis caused by damping. The macroscopic manifestation of the up and down oscillation of eccentricity is the swing of the contact point. Besides, the system quickly changes from the collision into the stable state due to considering friction, and the peak value of each collision reduces greatly. Therefore, when the clearance is unavoidable, the clearance joint should be coated with a material with a large friction coefficient and not easy to wear.

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