A New Approach to the Modeling of Magnetorheological Dampers and Application to Resonance Control

2021 ◽  
Author(s):  
Dennis A. Siginer ◽  
Mario Letelier ◽  
Juan Sebastián Stockle Henríquez
Keyword(s):  
Flow Pattern ◽  
Yield Stress ◽  
A Priori ◽  
Time History ◽  
Magnetorheological Damper ◽  
Mr Fluid ◽  
Variable Resistance ◽  
History Of ◽  
Displacement Pattern ◽  
Analytical Tools

Abstract A predetermined flow pattern in a magnetorheological damper providing continuously variable resistance to flow is required for efficient damping of a given load. The required predetermined flow pattern rests on the a priori determination of the constitutive properties of the magnetorheological (MR) fluid determined to generate variable resistance to flow. The inverse problem of constructing the predetermined response of the damper with a specific displacement pattern of the piston in the damper for efficient damping of a given load is solved. The magnetorheological (MR) fluid in the damper is modeled as a Bingham phase change material with time dependent yield stress offering continuously variable resistance to the flow in the piston to achieve the required specific displacement pattern. The governing equations are solved for any time history of the dimensionless yield stress of the fluid which in turn is determined from the imposed response of the damper. Analytical tools developed can be used in optimizing damper performance. The application of the method to resonance mitigation is illustrated.

An Inverse Method for Material Characterization of Magnetorheological Dampers

2007 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Jean-Paul Rouliez ◽  
Omar F. Corral
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
Time History ◽  
Field Variation ◽  
Mr Fluid ◽  
Bingham Plastic ◽  
Damper Design ◽  
Analytical Tools ◽  
Constitutive Parameters

Flow of magnetorheological (MR) fluids in dampers is investigated. The MR fluid flows through narrow passages in the damper subject to a magnetic field applied across the passages. The inverse problem of the determination of the required constitutive properties of the MR fluid together with the corresponding flow pattern for the efficient damping of a given load is solved. The fluid is modeled as a Bingham plastic with time-varying yield-stress. Flow is governed by the continuously adjustable constitutive parameters of the MR fluid which are determined to generate variable resistance to flow to dampen the selected load efficiently. The method developed leads to the determination of the magnetic field variation necessary to achieve a specific displacement of the piston in the damper. The governing equations are solved for any time history of the dimensionless yield stress of the fluid. Relationships that correlate damping load and magnetic field time variations are obtained. The analytical tools developed are helpful in damper design.

scholarly journals A priori estimation of memory effects in reduced-order models of nonlinear systems using the Mori–Zwanzig formalism

2017 ◽  
Vol 473 (2205) ◽  
pp. 20170385 ◽  
Author(s):  
Ayoub Gouasmi ◽  
Eric J. Parish ◽  
Karthik Duraisamy
Keyword(s):  
Evolution Equations ◽  
Nonlinear Dynamical Systems ◽  
A Priori ◽  
Time History ◽  
Original System ◽  
Memory Kernel ◽  
Nonlinear Dynamical ◽  
History Of ◽  
Consistent Basis ◽  
A Priori Estimation

Reduced models of nonlinear dynamical systems require closure, or the modelling of the unresolved modes. The Mori–Zwanzig procedure can be used to derive formally closed evolution equations for the resolved physics. In these equations, the unclosed terms are recast as a memory integral involving the time history of the resolved variables. While this procedure does not reduce the complexity of the original system, these equations can serve as a mathematically consistent basis to develop closures based on memory approximations. In this scenario, knowledge of the memory kernel is paramount in assessing the validity of a memory approximation. Unravelling the memory kernel requires solving the orthogonal dynamics, which is a high-dimensional partial differential equation that is intractable, in general. A method to estimate the memory kernel a priori , using full-order solution snapshots, is proposed. The key idea is to solve a pseudo orthogonal dynamics equation, which has a convenient Liouville form, instead. This ersatz arises from the assumption that the semi-group of the orthogonal dynamics is a composition operator for one observable. The method is exact for linear systems. Numerical results on the Burgers and Kuramoto–Sivashinsky equations demonstrate that the proposed technique can provide valuable information about the memory kernel.

Mathematical Modelling of Magneto-Hydrodynamic Dampers With Time-Varying Fluid Properties

2005 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Jean-Paul Rouliez ◽  
Omar F. Corral
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Yield Stress ◽  
Time History ◽  
Field Variation ◽  
Time Varying ◽  
Viscosity Change ◽  
Flow Equations ◽  
Fluid Properties ◽  
Analytical Tools

The fluid dynamics of dampers is investigated for the case where the damping fluid flows through passages in which a magnetic field is applied. This is a specific case of a new and promising field of applications that has emerged through the design of devices that take advantage of some properties of the so-called electrorheological fluids and magnetorheological fluids (ERF and MRF). These fluids are created when a base fluid is seed with very small dielectric or iron particles, so that it reacts to electric or magnetic fields by developing some non-Newtonian characteristics, most prominently a yield stress, viscosity change, and also viscoelasticity. These fluid properties can be controlled through control of the electric or magnetic fields’ strength. In this paper, a typical damping load is modeled and related to the required flow of a MRF inside the damper. To this end the fluid is modeled as a Bingham fluid with time-varying yield-stress. The analysis here developed makes it possible to determine the magnetic field variation necessary in order to achieve a specific displacement of the damper’s piston. The flow equations are analytically solved for any time-history of the dimensionless fluid’s yield-stress. Main results are some simplified relationships that correlate damping load and magnetic field time-variations. These results aim at providing analytical tools that may facilitate dampers’ design.

scholarly journals Viewing Angle and the Appearance of Superluminal Jets

1996 ◽  
Vol 175 ◽  
pp. 437-438
Author(s):  
H. D. Aller ◽  
M. F. Aller ◽  
P. A. Hughes ◽  
A. Mioduszewski
Keyword(s):  
Flow Pattern ◽  
Time History ◽  
Lorentz Factor ◽  
Helical Flow ◽  
Line Of Sight ◽  
Viewing Angle ◽  
Density Data ◽  
Bl Lacertae ◽  
Relativistic Flow ◽  
History Of

The time history of BL Lacertae has shown clear evidence of changes in jet orientation both in the plane of the sky and in the angle to the line of sight (see Figure 1). Models based on transverse shocks in a relativistic flow quantitatively fit the polarization and flux density data well and permit one to determine parameters of the flow such as the bulk Lorentz factor and the angle of the flow to the line of sight (Hughes, Aller and Aller 1989). The orientation of the jet flow to the line of sight changed by approximately 6° between the early 1980 bursts and one in 1991. There have been comparable changes in the orientation of the jet on the plane of the sky. Such changes in jet orientation may be due to a helical flow pattern arising from precession or instability.

An Inverse Approach to Magnetorheological Damper Design: Hershel-Bulkley Model

2008 ◽  
Author(s):  
Mario F. Letelier ◽  
Juan S. Stockle ◽  
Dennis A. Siginer
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
A Priori ◽  
Variable Magnetic Field ◽  
Magnetorheological Damper ◽  
Heavy Vehicles ◽  
Aircraft Landing ◽  
Self Powered ◽  
Damper Design ◽  
Constitutive Parameters

Magnetorheological fluids (MRF) are increasingly used for the design of dampers in many cases when a given response is critical for desired performance. Some recent examples are self-powered magnetorheological dampers, cable vibration control and wheeled vehicle dampers. Loads of this type can be very big, especially in the case of seismic-dampers as well as in heavy vehicles and aircraft landing gear. This problem can be more efficiently dealt with by using an inverse-problem strategy, where the required performance is specified a priori, and the fluid parameters are changed accordingly by means of a variable magnetic field. The effect on the flow of the time-variation of the parameters of the Herschel-Bulkley constitutive model is analyzed in this paper. In this way, the influence of a varying magnetic field on the unsteady flow of a magnetic fluid is explored. Yield stress, viscosity and power index are assumed time-dependent. In particular, linear variations in time of these parameters are considered, and the case where the yield stress and viscosity oscillate in time is explored in detail. The characteristics of the velocity field are analyzed for different values of the constants that determine the time structure of the constitutive parameters.

On Studying Comparative Religion

1975 ◽  
Vol 11 (2) ◽  
pp. 145-156 ◽  
Author(s):  
R. J. Zwi Werblowsky
Keyword(s):  
International Association ◽  
A Priori ◽  
Recent Contribution ◽  
Natural Scientist ◽  
History Of Religions ◽  
Similar Remark ◽  
History Of ◽  
Field Workers ◽  
Definition Of ◽  
Analytical Tools

The Dutch writer Menno ter Braak once observed that when there is no bacon in the larder you tend to spend your time sharpening your knives. In a different context a somewhat similar remark concerning his preoccupation with the sharpening of his analytical tools was made by the philosopher Husserl. Applying these remarks—without the least intent of facetiousness—to the comparative study of religions, we might say that concern with methodology should be an occasional pastime, in which we may indulge at moments when we take an occasional respite from our substantive labours—but with plenty of bacon, as it were, in the larder. The quinquennial congresses of the International Association for the History of Religions are undoubtedly an appropriate occasion for such critical and reflective introspection. In fact, some of the best methodological clarifications come not froma priorilegislators but from active researchers stepping back for a moment, putting some distance between their nose and the grindstone, and asking themselves what exactly they and their colleagues have been and are doing, and how they should best proceed. (I am thinking, e.g., of J. Schwab's penetrating and profound essay ‘What do Scientists do?’ as an outstanding example of such reflection by a natural scientist.) Whilst the sterility of abstract discussions about the definition of religion is generally admitted, it should be acknowledged that some exceedingly helpful suggestions have been made by practising field-workers and historians of religion. I am thinking of e.g., C. Geertz, M. Spiro, and Th. van Baaren. Other examples of the theoretical clarifications resulting from the interaction—addicts of the currently fashionable jargon would say ‘feedback’—between attempts at definition and the actualpraxisof historians of religion are H. Ch. Puech's short introduction and A. Brelich's majorProlégomènesin vol. i of the PléiadeHistoire des Religions(1970), as well as U. Bianchi's thoughtful and thought-provoking recent contribution. Clearly students of religion continue to be very much exercised by the double problem of the nature of their subject-matter and of the proper methods of studying it.

PROGRAM OF PREDICTION AND MANAGEMENT OF COINTEGED DYNAMIC ECONOMIC PROCESSES BASED ON THE CYBERNETIC APPROACH

2019 ◽  
Author(s):  
Olena Bundak ◽  
Nataliia Zubovetska
Keyword(s):  
Computer Program ◽  
Pair Correlation ◽  
Time History ◽  
Critical Area ◽  
Concrete Object ◽  
Graphic Arts ◽  
Ex Post ◽  
History Of ◽  
Successive Change ◽  
Rms Errors

A method and computer program ConRow, which prognostication of development of the dynamically CPLD economic transients is executed by, is described in the article. Such prognostication of economic processes is very important in the cases when their development can result in undesirable consequences, that to go out in the so-called critical area. Extrapolation in a critical area with the use of information about the conduct of the system at an area, near to it, allows to estimate to the lead through of experiment in the critical area of his consequence. For the imitation of conduct of object the function of review is set on entrance influence. For a concrete object this function can express, for example, dependence of change of level sale from time-history of charges on advertising and set as a numeral row. Statistics as a result of analysis of row are represented in a table, where the level of meaningfulness is set statistician, and also parameters of the handed over criteria. The graphic reflection of information is intended for visualization of analysis. Here represented on the points of graphic arts, the crooked smoothing which are calculated as полиномиальные regressions is added. The best approaching is controlled by sight on the proper graph, and also by minimization of their rms errors. Models of prognostication by sight and as formulas represented on graphic arts, the middle is here determined tailings and their chance is checked up on statistics of signs. After the got models determined also and prognosis values of influences and reviews. Establishing an order models of Сr(p) of co integrate regression is carried out separate custom controls. The coefficient of clay correlation of ruФ shows by itself pair correlation between lines with a successive change in relation to each other on a size to лагу of l = 1, 2, 3 . The program was tested on the example of ex-post prognosis at establishing an integration connection and possibility of prognostication of growth of nominal average monthly settlings on the basis of these statistical indexes of consumer inflation in Ukraine.

scholarly journals Comparison of Novel Seismic Protection Devices to Attenuate the Earthquake Induced Energy

Actuators ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 73
Author(s):  
Osman Hansu ◽  
Esra Mete Güneyisi
Keyword(s):  
Lateral Displacement ◽  
Time History ◽  
Seismic Protection ◽  
Base Shear ◽  
Seismic Demands ◽  
Nonlinear Time History Analyses ◽  
History Of ◽  
Protection Devices ◽  
Nonlinear Time History ◽  
Better Than

This study addresses an alternative use of viscous dampers (VDs) associated with buckling restrained braces (BRBs) as innovative seismic protection devices. For this purpose, 4-, 8- and 12-story steel bare frames were designed with 6.5 m equal span length and 4 m story height. Thereafter, they were seismically improved by mounting the VDs and BRBs in three patterns, namely outer bays, inner bays, and all bays over the frame heights. The structures were modeled using SAP 2000 software and evaluated by the nonlinear time history analyses subjected to the six natural ground motions. The seismic responses of the structures were investigated for the lateral displacement, interstory drift, absolute acceleration, maximum base shear, and time history of roof displacement. The results clearly indicated that the VDs and BRBs reduced seismic demands significantly compared to the bare frame. Moreover, the all-bay pattern performed better than the others.

scholarly journals Development of a Field Deployable Firebrand Flux and Condition Measurement System

2020 ◽  
Author(s):  
Simone Zen ◽  
Jan C. Thomas ◽  
Eric V. Mueller ◽  
Bhisham Dhurandher ◽  
Michael Gallagher ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Time History ◽  
Infrared Camera ◽  
Thermal Conditions ◽  
Particle Characterization ◽  
Fire Dynamics ◽  
Rate Of Spread ◽  
New Instrument ◽  
History Of

AbstractA new instrument to quantify firebrand dynamics during fires with particular focus on those associated with the Wildland-Urban Interface (WUI) has been developed. During WUI fires, firebrands can ignite spot fires, which can rapidly increase the rate of spread (ROS) of the fire, provide a mechanism by which the fire can pass over firebreaks and are the leading cause of structure ignitions. Despite this key role in driving wildfire dynamics and hazards, difficulties in collecting firebrands in the field and preserving their physical condition (e.g. dimensions and temperature) have limited the development of knowledge of firebrand dynamics. In this work we present a new, field-deployable diagnostic tool, an emberometer, designed to provide measurement of firebrand fluxes and information on both the geometry and the thermal conditions of firebrands immediately before deposition by combining a visual and infrared camera. A series of laboratory experiments were conducted to calibrate and validate the developed imaging techniques. The emberometer was then deployed in the field to explore firebrand fluxes and particle conditions for a range of fire intensities in natural pine forest environments. In addition to firebrand particle characterization, field observations with the emberometer enabled detailed time history of deposition (i.e. firebrand flux) relative to concurrent in situ fire behaviour observations. We highlight that deposition was characterised by intense, short duration “showers” that can be reasonably associated to spikes in the average fire line intensity. The results presented illustrate the potential use of an emberometer in studying firebrand and spot fire dynamics.

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