scholarly journals Modeling the Response of Magnetorheological Fluid Dampers under Seismic Conditions

2019 ◽  
Vol 9 (19) ◽  
pp. 4189 ◽  
Author(s):  
Darson Dezheng Li ◽  
Declan Finn Keogh ◽  
Kevin Huang ◽  
Qing Nian Chan ◽  
Anthony Chun Yin Yuen ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Pressure Drop ◽  
Fluid Velocity ◽  
Pressure Profile ◽  
Inlet Pressure ◽  
Mr Fluid ◽  
Pressure Profiles ◽  
Efficiency And Effectiveness ◽  
Fluid Dampers ◽  
Mr Fluid Damper

Magnetorheological (MR) fluid is a smart material fabricated by mixing magnetic-responsive particles with non-magnetic-responsive carrier fluids. MR fluid dampers are able to provide rapid and reversible changes to their damping coefficient. To optimize the efficiency and effectiveness of such devices, a computational model is developed and presented where the flow field is simulated using the computational fluid dynamics approach, coupled with the magnetohydrodynamics model. Three different inlet pressure profiles were designed to replicate real loading conditions are examined, namely a constant pressure, a sinusoidal pressure profile, and a pressure profile mimicking the 1994 Northbridge earthquake. When the MR fluid damper was in its off-state, a linear pressure drop between the inlet and the outlet was observed. When a uniform perpendicular external magnetic field was applied to the annular orifice of the MR damper, a significantly larger pressure drop was observed across the annular orifice for all three inlet pressure profiles. It was shown that the fluid velocity within the magnetized annular orifice decreased proportionally with respect to the strength of the applied magnetic field until saturation was reached. Therefore, it was clearly demonstrated that the present model was capable of accurately capturing the damping characteristics of MR fluid dampers.

scholarly journals Parameter identification of Bouc-Wen model for Magnetorheological (MR) fluid Damper by a Novel Genetic Algorithm

2020 ◽  
Vol 12 (8) ◽  
pp. 168781402095054
Author(s):  
Birhan Abebaw Negash ◽  
Wonhee You ◽  
Jinho Lee ◽  
Kwansup Lee
Keyword(s):  
Genetic Algorithm ◽  
Parameter Identification ◽  
Mr Damper ◽  
Absolute Error ◽  
Mr Fluid ◽  
Fitness Evaluation ◽  
Damper Control ◽  
Fluid Dampers ◽  
Mr Fluid Damper ◽  
Crossover And Mutation

In this research, novel genetic algorithm (nGA) is proposed for Bouc-Wen modle parameters esstimation for magnetorheological (MR) fluid dampers. The optimization efficiency is improved by modifying the crossover and mutation steps of a GA. In the crossover stage, the probability of reproducing offspring from the same parent (same mother and father chromosome) is done to be zero, which may happen in the standard GA, and the probability of a chromosome to be selected for mating is based on error rank weighting of the chromosomes. Additional fitness evaluation of chromosomes will take place in between the crossover and mutation steps to save the best chromosome found so far, which is not implemented in the standard genetic algorithm (GA). The model is validated by comparing its simulation output force ( Fsim) with experimentally generated MR damper force ( Fexp). The mean absolute error, standard deviation and number of generations for convergence are taken as a criterias for performance evaluation. With these ctriterias, the proposed novel GA outperform better than the other researches. The accuracy is improved by 46.67% compared to standard GA. The proposed novel GA for Bouc-Wen model parameter identification can be used for any MR damper control system with better accuracy.

Radiales Druckprofil in einem magnetoplasmadynamischen Wasserstoff-Lichtbogen

1970 ◽  
Vol 25 (8-9) ◽  
pp. 1332-1343
Author(s):  
W. L. Bohn ◽  
T. E. Mccann
Keyword(s):  
Magnetic Field ◽  
Ambient Pressure ◽  
Radial Pressure ◽  
Pressure Profile ◽  
Pressure Increase ◽  
Pressure Decrease ◽  
Mass Entrainment ◽  
Pressure Profiles ◽  
Flow Approximation ◽  
Characteristic Pressure

Abstract Within the framework of the five-moments approximation the radial pressure profile of an MPD-arc is calculated as a function of the ambient pressure and the superimposed magnetic field. In addition to the well known pressure increase due to ambipolar diffusion, the typical axi-symmetric MPD geometry provides further pressure increase or decrease by the interaction of current density (Hall-effect) or mass flow with the magnetic field. Characteristic pressure profiles for assumed current and flow fields and for various superimposed magnetic field strengths are shown in numerous diagrams and are discussed by use of the generalized Ohm's law. A significant pressure decrease due [to mass entrainment becomes evident. Deviations from LTE are considered in the frozen flow approximation. The theoretically predicted pressure decrease in the axial region of the plasma flow of an MPD-arc subjected to mass entrainment agrees qualitatively with experimental results.

Controllability of a Magnetorheological Fluid Squeeze Film Damper under Sinusoidal Magnetic Field

2007 ◽  
Vol 334-335 ◽  
pp. 1089-1092 ◽  
Author(s):  
Chang Sheng Zhu
Keyword(s):  
Magnetic Field ◽  
Squeeze Film ◽  
Field Frequency ◽  
Mr Fluid ◽  
Magnetic Field Frequency ◽  
Squeeze Film Damper ◽  
Fluid Damper ◽  
Sinusoidal Magnetic Field ◽  
Mr Fluid Damper ◽  
The Magnetic Field

The controllability of a magnetorheological(MR) fluid squeeze film damper under a sinusoidal magnetic field was experimentally studied on a flexible rotor. It is shown that the frequency of the excitation magnetic field has a great effect on the controllability of the MR fluid damper. As the magnetic field frequency increases, the controllability of the MR fluid damper significantly reduces. There is a maximum frequency of the magnetic field for a given magnetic field strength or a minimum strength of the magnetic field for a given magnetic field frequency to make the dynamic behavior of the MR damper be controllable. When the magnetic field frequency is over the maximum one or the magnetic field strength is less than the minimum one, the controllability of the MR fluid damper almost completely disappears and the dynamic behavior of the MR fluid damper with the sinusoidal magnetic field is the same as that without the magnetic field.

Radiales Druckprofil in einem magnetoplasmadynamischen Wasserstoff-Lichtbogen

1970 ◽  
Vol 25 (8-9) ◽  
pp. 1344-1353
Author(s):  
T. E. Mccann ◽  
W. L. Bohn
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Mass Flow ◽  
Radial Pressure ◽  
Pressure Profile ◽  
Pressure Increase ◽  
Higher Moments ◽  
Viscous Forces ◽  
Pressure Profiles ◽  
Quantitative Results

Abstract The calculation of the radial pressure profile of an MPD-arc as a function of the ambient pres-sure and the superimposed magnetic field as has been developed in a previous paper is extended to the 13-moments approximation. The higher moments approximation introduces additional thermomagnetic forces and changes significantly the structure of the velocity-dependant part of the external viscous forces. While the Hall-effect and the mass flow are practically unaffected by the higher approximation, as far as their influence on the radial pressure profile is concerned, the ambipolar diffusion leads to an appreciably smaller pressure increase than the 5-moments theory. Qualitative differences of the two approximations are discussed beyond the scope of pressure profiles via the generalized Ohm's law. Quantitative results for a partially as well as for a fully ionized plasma are shown in diagrams. The importance of thermomagnetic forces (especially the Nernst effect) for MPD-arcs is clearly pointed out.

Study of the Vibration Control of a Rotor System Using a Magnetorheological Fluid Damper

2005 ◽  
Vol 11 (2) ◽  
pp. 263-276 ◽  
Author(s):  
J. Wang ◽  
G. Meng
Keyword(s):  
Magnetic Field ◽  
Vibration Control ◽  
Control Method ◽  
Rotor System ◽  
Shear Mode ◽  
Rotor Vibration ◽  
Mr Fluid ◽  
Critical Speeds ◽  
Fluid Damper ◽  
Mr Fluid Damper

A shear mode magnetorheological (MR) fluid damper used for rotor vibration control is designed and manufactured, and the theoretical model of a cantilevered rotor system with the MR fluid damper is established. The response properties of the rotor system are studied theoretically and experimentally. It is found from the study that the Coulomb friction of the damper is increased as the magnetic field strength applied to the MR fluid increases. As a result, the vibration amplitude of the rotor system supported by the MR damper is decreased near the undamped critical speeds, but is increased in a rotating speed range between the first and the second undamped critical speeds. At the same time, the damped critical speed of the rotor system is increased with the increase of the applied magnetic field. Based on these characteristics, a simple on-off control method is used to suppress the rotor vibration across the critical speeds, and the results show that the method is very effective.

Researches of a Magneto-Rheological Fluid Damper with External Coil Based on Electromagnetic Finite Element Analysis

2012 ◽  
Vol 490-495 ◽  
pp. 3427-3431
Author(s):  
Xiao Mei Xu ◽  
Cai Min Zeng
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Element Analysis ◽  
Mr Fluid ◽  
Damping Characteristics ◽  
Fluid Damper ◽  
New Type ◽  
Fluid Dampers ◽  
Magneto Rheological ◽  
Mr Fluid Damper

In vibration control field magneto-rheological (MR) fluid dampers are semi-active control devices that have recently begun to receive more attention. This paper presents a new type of MR fluid damper with external coil. The new structure of the damper was optimized and analyzed based on a static magnetic analysis with the help of electromagnetic finite element analysis (FEA) using the software of ANSYS. The damping characteristics of the damper were theoretically researched. Research results show that the designed MR fluid damper with external coil has wider scope of damping adjustment and strong energy-dissipating ability. The study method in this paper and the obtained results will help designers to create more efficient and reliable MR fluid dampers.

BEHAVIOR OF MR FLUIDS AT HIGH VELOCITIES AND HIGH SHEAR RATES

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1395-1401 ◽  
Author(s):  
F. D. GONCALVES ◽  
M. AHMADIAN ◽  
J. D. CARLSON
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
High Speed ◽  
Fluid Velocity ◽  
Zero Field ◽  
High Shear ◽  
Mr Fluid ◽  
Shear Rates ◽  
High Shear Rates ◽  
Field Strengths

The objective of this work is to characterize the performance of MR fluid at high shear rates and high velocities. A slit-flow rheometer has been built which allows for high speed testing of MR fluid under varying field strengths. Fluid velocities range from 3.9 m/s to 27 m/s with resulting shear rates ranging from 0.23×105 s -1 to 1.6×105 s -1. In order to evaluate the performance of the fluid, the force required to drive the fluid through the slit is measured and force-velocity characteristics are generated. The zero-field viscosity is found and results indicate that shear thinning is still present even at these high shear rates. Two magnetic field strengths were considered for the field testing (50 kA/m and 100 kA/m). Results indicate that a yield stress is still being developed in the fluid. However, as fluid velocity increases, the yield stress being developed in the fluid decreases. This reduction in the yield stress could be attributed to the dwell time, or the amount of time the fluid spends in the presence of a magnetic field.

Investigation of ultrasonic properties of MR fluid under various sweep rates of magnetic field

2013 ◽  
Vol 49 (3-4) ◽  
pp. 430-433
Author(s):  
A. Isnikurniawan ◽  
Y. Fujita ◽  
S. Tanimoto ◽  
T. Sawada
Keyword(s):  
Magnetic Field ◽  
Mr Fluid ◽  
Ultrasonic Properties

scholarly journals Propagation of radiosonde pressure sensor errors to ozonesonde measurements

2014 ◽  
Vol 7 (1) ◽  
pp. 65-79 ◽  
Author(s):  
R. M. Stauffer ◽  
G. A. Morris ◽  
A. M. Thompson ◽  
E. Joseph ◽  
G. J. R. Coetzee ◽  
...  
Keyword(s):  
Pressure Sensor ◽  
Atmospheric Pressure ◽  
Pressure Profile ◽  
Mixing Ratio ◽  
Concentration Cell ◽  
Pressure Profiles ◽  
Dependent Variables ◽  
Sensor Errors ◽  
Subsequent Addition ◽  
Total Column

Abstract. Several previous studies highlight pressure (or equivalently, pressure altitude) discrepancies between the radiosonde pressure sensor and that derived from a GPS flown with the radiosonde. The offsets vary during the ascent both in absolute and percent pressure differences. To investigate this problem further, a total of 731 radiosonde/ozonesonde launches from the Southern Hemisphere subtropics to northern mid-latitudes are considered, with launches between 2005 and 2013 from both longer term and campaign-based intensive stations. Five series of radiosondes from two manufacturers (International Met Systems: iMet, iMet-P, iMet-S, and Vaisala: RS80-15N and RS92-SGP) are analyzed to determine the magnitude of the pressure offset. Additionally, electrochemical concentration cell (ECC) ozonesondes from three manufacturers (Science Pump Corporation; SPC and ENSCI/Droplet Measurement Technologies; DMT) are analyzed to quantify the effects these offsets have on the calculation of ECC ozone (O3) mixing ratio profiles (O3MR) from the ozonesonde-measured partial pressure. Approximately half of all offsets are > ±0.6 hPa in the free troposphere, with nearly a third > ±1.0 hPa at 26 km, where the 1.0 hPa error represents ~ 5% of the total atmospheric pressure. Pressure offsets have negligible effects on O3MR below 20 km (96% of launches lie within ±5% O3MR error at 20 km). Ozone mixing ratio errors above 10 hPa (~ 30 km), can approach greater than ±10% (> 25% of launches that reach 30 km exceed this threshold). These errors cause disagreement between the integrated ozonesonde-only column O3 from the GPS and radiosonde pressure profile by an average of +6.5 DU. Comparisons of total column O3 between the GPS and radiosonde pressure profiles yield average differences of +1.1 DU when the O3 is integrated to burst with addition of the McPeters and Labow (2012) above-burst O3 column climatology. Total column differences are reduced to an average of −0.5 DU when the O3 profile is integrated to 10 hPa with subsequent addition of the O3 climatology above 10 hPa. The RS92 radiosondes are superior in performance compared to other radiosondes, with average 26 km errors of −0.12 hPa or +0.61% O3MR error. iMet-P radiosondes had average 26 km errors of −1.95 hPa or +8.75 % O3MR error. Based on our analysis, we suggest that ozonesondes always be coupled with a GPS-enabled radiosonde and that pressure-dependent variables, such as O3MR, be recalculated/reprocessed using the GPS-measured altitude, especially when 26 km pressure offsets exceed ±1.0 hPa/±5%.

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