MAGNETO-RHEOLOGICAL FLUID

AND ITS APPLICATION IN VEHICLE

SUSPENSION SYSTEM: A REVIEW

Vinayak Nyamagoudara , Shankar

Bhaumika

aR and DE (Engineers), Dighi, Pune, 411015, Maharashtra, India Abstract: Magneto rheological (MR) fluids are smart fluids whose flow characteristics can be changed rapidly by the application of magnetic field. Control of automobile vibration represents a wide area of research which is growing rapidly. Hydraulic fluid based passive suspension system is most commonly used vehicle suspension system because of their simple fail-safe design and zero-power requirement. However, these dampers cannot change their characteristics with change in road profile. MR fluid based semi-active systems provide an alternate to passive suspension system with controllable damping characteristics, delivering excellent ride comfort and vehicle handling. Over the past two decades MR fluid based suspension systems have gained popularity and are being used in large number of passenger and defence vehicles. This article provides an understanding of properties of MR fluid and its application in vehicle suspension. The topic discussed here includes modes of operation of MR fluid devices, constituents of MR fluid and their effect, operational principle of MR fluid, drawback of using MR fluid based devices in different applications and use of MR fluid in semi-active suspension system of passenger and defence vehicles in off-road conditions.

Keywords: MR fluid, operation modes, MR

fluid application

1. Introduction

Magneto rheology is a study of materials under an applied magnetic field that flows

and deforms. In 1948 Jacob Rabinow [1] discovered the effects of magneto rheological fluid at United States national bureau of standards and acquired an application device (clutch).

The vibration control technique has classically been classified into passive, active, hybrid and semi- active controls, depending on the degree of energy required and the type of devices employed. The semi active control system has advantages over passive system for desirable performance compared with active control, it demands less power consumption and the system is more stable. During the past decade study of semi active vibration control has been used by several researchers [2-4]. MR fluid devices are adaptive or smart devices that have been the case of intense research for several applications mainly centered around the structural vibration control under wind [5] or earthquake excitation [6, 7]. The automotive industry has been concerned with growing applications of these materials, for example engine mounts, shock absorbers, clutches and seat dampers [8, 9]. MR fluid devices use MR fluid to produce controllable damping force. Magneto-Rheological fluids have had significant interest due to the rapid response, fail-safe, low power requirement, simple interface between electronic controls and MR devices [10]. These are some characteristics of magneto-rheological fluid that have contributed to substantial research interest in using them as a semi active control device in several applications. When an external magnetic field is applied, the magneto rheological fluid particles form columnar, chain like structures parallel to the applied magnetic field (as depicted in Fig. 1. a and Fig. 1. b) by polarization effect. The energy needed to organize a chain like structures increases as the magnetic field strength applied to the fluid increases, which generates field dependent yield stress. This increase is not linear since the particles are ferromagnetic and the magnetization in different part of the particles occurs non uniformly [11]. The

chain like structures restricts the flow of the magneto-rheological fluid, which results in the increase of the viscosity of the fluid. This opposition to the flow imparts yield strength to the fluid. When no magnetic field exists, the magneto-rheological fluid behaves like a Newtonian fluid. When a magnetic field is applied the MR fluid is modeled as Bingham plastic that has controllable yield stress. The change of MR fluid from a free flowing liquid to a semi solid when exposed to the magnetic field is reversible and instantaneous.

(a) No magnetic field (b) Magnetic field

Fig. 1: Characteristics of MR fluid under

magnetic field [12]

2. Magneto Rheological Fluid Modes of Operation

Magneto rheological fluid devices use one of the three basic modes of operation of magneto-rheological fluids or any combination of them depending on the function of the system. These three modes of operations are valve mode, direct shear mode and squeeze mode [13, 14]. The rheological magnetic properties and the working style of the magneto-rheological fluid should be considered before designing any magneto-rheological fluid devices.

Valve mode is one of the operating modes in the MR devices where the stream of the MR fluid between the motionless plates is created by the pressure drop (Fig. 2.a). The magnetic field, which is applied perpendicular to the direction of the flow, is used to change the viscosity of the MR fluid in order to control the flow. Examples of

valve mode are servo valve, dampers, shock absorbers etc. In shear mode magneto-rheological fluid is located between two surfaces, whereby just one surface slide or rotates in relation to the other, with a magnetic field applied perpendicular to the direction of movement of these shear surfaces. Shear mode (as indicated in Fig. 2. b) is useful due to the characteristics of the shear stress vs. shear rate which can be manipulated by the magnetic field force. Examples of shear mode include clutches, brakes, chucking and locking devices, dampers and structural components.

Squeeze mode operates when force is applied to the plates in the same direction of the magnetic field to reduce or expand the distance between the parallel plates causing a squeeze flow. In squeeze mode (Fig. 2. c) the MR fluid is subjected to dynamic or static loading.

(a) Valve (b) Direct Shear (c) Squeeze

Fig. 2 Basic operation modes for controllable

fluid [15]

As the magnetic field charges the molecules, the particle chains formed between the walls become semi solid with an addition in the viscosity. The displacements engaged in squeeze mode are relatively very small (few millimeters) but requires great force. The squeeze mode has been utilized in some small amplitude vibration damper.

3. Components of MR Fluid and Their Effects

MR fluid is generally made up of three components: ferromagnetic particles, a

carrier fluid and a stabilizer.

The ferromagnetic particles are made of Iron or Iron based soft materials [10, 16 and 17]. These particles are typically of carbonyl iron and are usually spherical in shape. However, iron alloy particles, including Iron nickel and Iron cobalt alloys are found to perform much better than the original carbonyl iron [18]. Carbonyl iron particles are much used as suspensions because of their high magnetic permeability, low remnant magnetization and also these are magnetically multi domain. These alloys tend to cost a lot more than the iron carbonyl and hence not commonly used. The particle sizes are preferred to be between 1 and 10 microns although; successful use of particles as small as 0.1 microns and as big as 100 microns has been found [10]. Reducing the size of the particles can increase the stability of the fluid but may also, lead to Brownian motion of MR fluid. However, reducing the size of the particle can also lead to decrease in yield stress as compared to yield stress of MR fluid with higher particle size [19]. The concentration of iron particles is preferably between 20- 40 % by volume of the MR fluid [21, 22]. The Scanning Electron Microscope (SEM) image [20] of carbonyl iron particles employed in magneto-rheological fluid used is shown in Fig. 3. As the volume of carbonyl iron is increased the stability is improved [23] but at the same time the viscosity of magneto-rheological fluid in the off state will also be higher under these conditions [24]. The strength of these structures formed by the application of the field is judged through the yield stress. The change in viscosity and subsequent yield stress is due to the ferromagnetic particles forming chains in the fluid when a magnetic field is present [25, 26].

Fig. 3 SEM image of carbonyl iron [20].

It can be seen in Fig. 4, as the magnetic domain (in milliTesla) is used with increasing magnitude the chains become more and more evident [27]. The strength of these chains is also dependent on the intensity of the magnetic field. These chains can only be broken when the necessary amount of shear stress is present. This value is known as the yield stress of the magnetic chain structures [25].

The Carbonyl Iron Particles (CIPs) are suspended in some sort of medium normally chosen based upon their rheological properties and temperature stability. Common carrier liquids include petroleum base oils, silicone, mineral oils, synthetic hydrocarbon oils and others [25]. The carrier fluid serves as a dispersed medium and ensures the homogeneity of the carbonyl particles in the fluid.

(a) No field (b) 10mT

(c) 15 mT (d) 20 mT Fig. 4 Polarization and alignment of CIPs in

MR Fluid [27].

Carrier fluid (50-80 %) by volume is the major constituents of the MR fluid. Carrier fluid greatly influences the rheological properties of MR fluids. Its primary function is to offer a medium for magnetically active particulates to remain suspended during the absence of magnetic field and to facilitate realignment once the magnetic field is applied. But the type of carrier liquid used in a magneto-rheological fluid may differ. Some of the carrier fluids are poly vinyl-n-butyl, naphthol thickened kerosene, honge oil [28], silicon oil [29, 30], white and light grade mineral oils [31], a combination of synthetic oils, water, organic liquid [32] etc. The additives include stabilizers and surfactants [33]. Additives are suspending agents, thixotropes, friction modifiers and anti-corrosion/wear components. High viscous materials such as grease or thixotropic additives are applied to improve settling stability [1]. Ferrous napthanate or ferrous olecate can be used as dispersants and metal soaps such as lithium stearate or sodium stearate as thixotropic additives [34]. Additives are required to control the viscosity of the liquid and sedimentation rate of the particles. As shown in Fig. 5, the settling rate decreases for MR fluid with additives. Additives reduce the friction between the particles and avoid the in use thickening for a defined number of duty cycles, the stabilizers serve to keep the particles suspended in the fluid.

Fig. 5 Sedimentation vs time for MR fluid

[23].

Whilst the surfactants form a layer on surface of the magnetic particles to enhance the polarization induced in the suspended particles upon the application of magnetic domain.

4. Operational Principle of Magneto-Rheological Fluid In the presence of an applied magnetic field, the iron particles acquire a di-pole moment which causes particles to form linear chains aligned with the magnetic field. This phenomenon can solidify the suspended iron particles and limit the fluid movement. Thus the yield strength is made within the fluid. The point of alteration is related to the magnitude of the applied magnetic field and can take place in a few milliseconds. Typical magneto rheological fluid can achieve yield strength of up to 50-100 kPa at a magnetic field intensity of approximately 150-250 kA/m. It was found that wall roughness on contact with the fluid is important for yield strength, especially in the magnetic field. For low strains prior to yield, the shear modulus of a magneto-rheological fluid also shows a very large step-up in an applied magnetic field. Magneto rheological materials eventually reach a saturation point where the increment of the magnetic field does not increase the yield strength of the magneto rheological material. This phenomenon typically occurs around 300 kA/m. The effect of magnetic saturation on the strength of magneto

rheological material can be examined by applying finite element analysis. The magneto rheological effect is immediately reversible if the magnetic field is removed.

5. Comparisons of MR and ER Fluid Controllable fluids are materials that respond to an applied electric or magnetic field with a change in their rheological behavior. These materials are commonly referred to as electro-rheological (ER) or magneto rheological fluid. MR fluid is regarded to be an attractive alternate to the ER fluid for use in controllable fluid damper [38]. This can be seen in table 1, which compares the physical properties of both MR and ER fluids [39]. In contrast to ER fluids, MR fluids are 20 to 50 times stronger. Furthermore, because the magnetic polarization mechanism is unaffected by temperature, the performance of MR based devices are comparatively insensitive to temperature over a full temperature range [40]. In fact, MR fluids can operate at temperatures from -40 to 150 °C with only slight fluctuations in the yield stress [41], in contrast to ER fluids which are restricted to a range of 10 to 90°C. Table 1 Summary of the properties of a typical MR fluid and ER fluid [39]

Property

MR Fluid

ER Fluid

Initial

viscosity

– -

– -

C)

Density 3-4 g/cm3

1-2 g/cm3

Magnetic

field strength

150-250

[kA/m]

3-4

kV/mm

Yield point 50 -100 kPa 2-5 kPa

Reaction

time

Few

milliseconds

Few

millisecon

ds

Typical

supply

voltage and

Current

intensity

2-25 V, 1-2 A 2000-5000

V, 1-10 A

Work

temperature

-

C

MR fluids are significantly less sensitive to impurities or contaminants commonly encountered during manufacturing and usage [42]. MR technology can offer flexible control capabilities in designs that are far less complicated and more reliable than those based on ER technology [43]. Yet, in contrast to ER fluids, MR fluids can be readily run from a low voltage (12– 24 V), current-driven power supply output of only 1– 2 A.

6. Hysteresis Loop A hysteresis loop carries a lot of information on the magnetic properties of a material and can be represented by the relationship between magnetic flux density B and magnetic field intensity H and is normally called the B-H curve [44]. A material with a wide hysteresis loop has low permeability and high remanence, coercivity, reluctance and residual magnetism. On the contrary, a material with a narrower loop has the opposite characteristics. An example of a hysteresis loop for a ferromagnetic material is shown in Fig. 6.

Fig. 6 Magnetic flux density versus magnetic

field strength [44].

The ferromagnetic hysteresis loop is generated by measuring the magnetic flux B

as the magnetizing force H is changed. Initially, magnetization for a ferromagnetic material will follow the dashed line, in Fig. 6, until it reaches magnetic saturation. Points S and S’ represent the saturation values at positive and negative sides, respectively. When the value of H is reduced to zero, the

curve moves from point S to point instead of returning back to its original point. At this point some of the magnetic flux density still exists and the residual field is called the magnetic remanence. When the value of H is placed in the negative side or as H is reversed, the curve further moves to

point - (coercivity or coercive force) at

zero value of B. With further increase of H in the negative direction, the material will become magnetically saturated reaching the point S’ as the magnetizing force is increased in the negative direction.

On the other hand, when the value of H is increased back to zero, the curve moves from point S’ to point which has

the same value as in the other direction. This is because they have the same amount of the residual magnetism. The curve

moves to when is given a positive value at zero value of B. Further increases of H will result the curve to move back to point S, where the curve completes the loop [45].

7. Advantages of MR Fluid The role of MR fluids is advantageous in many different regards. The response time of the particles upon the diligence of a magnetic domain is in milliseconds. However, in order to fully utilize this aspect, one must have an electromagnet that will react quicker than the fluid itself [20]. The material is controllable and very compliant. As long as it is stable, the material will invariably return the same result, repeatedly. The material’s change in viscosity is also completely reversible with no sign of artifacts or material memory [46]. The magnetic field required is in the milliTesla (mT) range, and the power

required to apply that amount is minimal [20].

Another advantage is that MR fluid’s stability through a range of temperatures. This robustness to change in temperature as well as its lack of history dependency was tested and ascertained by various research studies.

8. Limitation in the Application of MRF

8.1. Sedimentation The frequent problem in any MR fluid application is due to the tendency of the active magnetic particles to aggregate and settle down, that disturbs the homogeneity of MR fluid and could influence its properties. It is because magnetic particles are denser than liquid carrier [47, 48] and under gravity settle and form a hard ”cake”, what makes them impossible to redisperse. This phenomenon is called as sedimentation. The rate at which the ferrous particles move down is called sedimentation rate. The rheological character of the carrier liquid, the surface properties of the particles and the presence of additives mainly determine this sedimentation rate (Fig. 5). It is reduced by additives like thixotropic agents and surfactants such as xantham gum, silica gel, stearates and carboxylic acids.

8.2. In-Use thickening This phenomenon leads to a progressive increase of the base viscosity when the fluid is subjected to high stresses and shear rates [49]. The origin of this problem is attributed to the splitting of the brittle surface layer of the particles. These smaller, secondary particles have a larger surface-volume ratio, through which even a diminished number of these atoms have a larger influence on the rheology of the MR fluid [50]. Each MR fluid exhibits a sure measure of ageing. In practical applications, shear thickening can be prevented by reducing the particle size.

8.3 Shear thinning Most of the MR fluids exhibit the shear thinning effect, wherein the fluid’s apparent viscosity decreases at high shear rates. MR fluids exhibit shear thinning behavior due to the influence of temperature and shear rate on the viscosity of the carrier liquid [51, 52, 53]. The influence of shear rate on viscosity is as shown in Fig.7.

Fig. 7 Shear thinning behavior of MRF-

132LD [54]

9. Influence of Temperature The temperature has an effect on the properties exhibited by MR fluids. The most obvious property affected by temperature is viscosity, which decreases as temperature increases. The dynamic yield strength also decreases with an increase in temperature, the reason for the decrease in strength is that the yield stress is directly proportional to the volume fraction of particles in the fluid [55, 56], and since the carrier liquid volume expands with the increase of temperature, the volume fraction of the particles decreases. MR dampers can experience large variation in temperature due to self heating of the damper as well as heat addition to the MR fluid because of the magnetic coil on the piston head. The change in fluid temperature results in a decay in fluid

viscosity and hence a reduction in the post-yield damping of the damper. Temperature rise mainly causes shifts of resonant frequency and large amplification factors at resonance. As the temperature increases, the pressure in the gas chamber increases, which in turn increases the damping force. On the other hand, when the temperature decreases, the pressure in the gas chamber decreases and hence the damping force deviates from the desired value. Temperature variations affect the operation of the damper by causing changes in the gas pressure, which in turn affects the maximum rebound damping force [57].

10. Effect of Pressure One of the most significant design

parameters of MR fluids is the yield shear

stress, which is the maximum stress the fluid

can withstand before shear occurs. This

value is fundamental in the design of the

MRF devices because the higher is the stress

the higher is the dissipated power of the

system. The behaviour of Lord 140-CG

commercial fluid was investigated under

several magnetic field and pressure values in

order to verify the influence of the variables

statistically and to offer an empirical

relationship to link pressure, applied field

and yield stress [58].

A MR fluid compressed along the

direction of the magnetic field, according to

Tang et al. [59] shows an increment of shear

stress by nearly ten times [58]. The shear

stress values under pressure were found to

be more than two times the values reached

with no pressure.

11 TYPES OF MR DAMPER

MR damper typically consists of a

piston, magnetic coils, accumulator, bearing,

seal and damper reservoir filled with MRF

[60].

Fig. 8: Cross-section of typical MR fluid

damper [60]

Figure 8 shows a cross section of the MR

fluid damper. In this damper, as the piston

rod enters the housing, MR fluid flows from

the high pressure chamber to the low

pressure chamber through orifices in the

piston head. The accumulator contains a

compressed gas (usually nitrogen) and its

piston provides a slightly movable barrier

between the MRF and the gas.

The accumulator serves three functions:

i. It provides a degree of softening by

providing an additional adjustment

for the volume changes that take

place when the piston rod enters the

housing.

ii. It accommodates thermal expansion

of the fluid.

iii. It prevents cavitation in the MRF

during piston movement.

There are two major types of MRF damper

used in vehicle suspension mono-tube and

twin tube.

Mono-tube MRF dampers have only

one reservoir and accumulator as shown in

Fig. 9

Fig. 9: Mono-tube MR damper [61]

This type of damper is commonly used in

car seat suspension [61].

The twin tube MR damper is one that

has two fluid reservoirs, one inside of the

other, as shown in Fig. 10. In this

configuration, the damper has an inner and

outer housing, which are separated from

each other by a foot value. The inner

housing guides the piston rod assembly, in

precisely the same way as in a mono tube

damper. The volume enclosed by the inner

housing is referred to as the inner reservoir.

Fig. 10: Schematic illustration of the twin

tube MR damper with accumulator [62]

A value assembly called “f v lue” i

attached to the bottom of the inner housing

to regulate the flow of fluid between the two

reservoirs.

The final type of MR damper is

called a double-ended damper since a piston

rod of equal diameter protrudes from both

ends of the damper housing. Fig. 11

illustrates a section view of the typical

double ended MR damper. Since there is no

change in volume as the piston rod moves

relatively to the damper body, the double

ended damper does not require an

accumulator mechanism. Double ended MR

dampers have been used for gun recoil

application [63], bicycle application [64]

and for controlling building sway motion

caused by wind gust and earthquakes [65].

Fig. 11: Double-ended MR damper [66]

12. Application in Vehicle Suspension System A vehicle suspension helps in reducing the

vertical acceleration of the sprung mass

caused due to irregularities on the road

surface, thus providing a good ride comfort

along with increased vehicle durability. The

main objective of a suspension system is to

provide comfortable ride and quality handling

along with good riding performance. These

conflicting requirements can be satisfied with

the use of active/semi active suspension based

on their control strategy. Passive suspension system (spring combined

with a hydraulic damper) is the most widely

used suspension systems as these are simple in

design and do not have high power

requirement, however these suspension

systems are incapable of adjusting their

characteristics based on variable road profile.

The performance limitation of passive

suspension can be overcome by fully

active/semi active suspension system. Semi-active suspension system uses

small amount of power to obtain variable

damping rate. This is achieved by using i)

Position control valves such as solenoid valve

ii) ER fluid iii) MR fluid iv) Piezoelectric

actuators.

Fig. 12: Body control system of the 2014

Mercedes-Benz S-Class

Among these MR fluid/Position control valves

are most widely used for vehicle suspension.

Position control valves requires a controllable

valve, the maximum operating pressure of this

valve must correspond to maximum operating

pressure of a passive damper. This

controllable valve should have fast response.

Fast response, linearity and efficiency could

be obtained by servo-valves but these valves

are expensive. Solenoid valves provide an

alternate to servo-valves. Solenoid valve based

dampers result in a better ride quality but these

dampers are not very accurate [67]. A semi-

active suspension system works similar to a

passive system but based on the profile of the

road the characteristics of MR fluid can be

controlled and hence semi-active suspension

system works adaptively unlike a passive

suspension system. These devices are fail-safe

i.e. if the control fails (due to mechanical,

electrical or software failure) the system will

not fail catastrophically but the performance

degrades.

MR fluid based dampers have been used in

more than 1000000 vehicles [60]. General

Motor in collaboration with Delphi

Corporation developed MR fluid based shock

absorber feature for passenger vehicles in

2002 as Magnetic Selective Ride Control

(MSRC). Many major automobile companies

like Ferrari, Audi, Land Rover, etc. use semi-

active based suspension system. Like fully

active suspension systems MR dampers also

use control strategy. MR dampers are non-

linear devices with hysteric response. Several

parametric and non-parametric models have

been developed to overcome these drawbacks.

Parametric models such as Bingham visco-

plastic model, Bouc-Wen model, etc. have

been studied by many researchers [68]. To

accurately predict the behaviour of MR

damper Genetic Algorithm (GA) was used to

determine the parameters of modified Bouc-

Wen model [69]. Non-parametric model such

as Chebyshev polynomial fit was used and it

was found that the predicted response of this

model resembled the corresponding

experimental data but this model is

computationally exhaustive. Neural network

based models [70] have also been used for

predicting any complicated multi input/multi

output continuous function of suspension

system.

13. Conclusion In the recent past MR fluid technology has gained lot of attention and some devices with exceptional efficiency have been developed based on MR fluid. Researchers have developed bio-degradable MR fluids which are environmentally safe and much cheaper than synthetic fluid. Hence more investigation has to be done to use this as carrier fluid. There are many problems faced by MR fluids as discussed earlier that needs to be addressed. Study into the degree of effect of temperature on the rheology of MR fluid has to be done. The durability of MR fluid devices has to be increased. All these improvements can make MR fluid technology a sustainable technology for future.

REFERENCE [1] Rabinow, J. The magnetic fluid

clutch. AIEE Trans., 1948, 67, pp 1308–1315.

[2] Y.S Kim, et.al, “Feedback control of ER-fluid-based structures for Vibration suppression”, Smart Materials and Structures, Vol. 1,1992, pp. 139-145.

[3] W.Taniwangsa and J.M. Kelly, “Experimental testing of a semi-active control scheme for vibration suppression”, Proceedings of SPIE Conference on Smart Structures and Materials: Passive Damping and isolation, SPIE Vol. 3045, 1997, pp.130-139.

[4] F.Sadek and B.Mohraz, ”Semiactive control algorithms for structures with variable dampers”, Journal of Engineering Mechanics, Vol. 124(9), 1998, pp. 981-990.

[5] Liu, M, et.al, “Non-Model-Based Semi-Active Vibration Suppression of Stay Cables Using Magneto-Rheological Fluid Dampers,” Smart Mater. Struct., 16, 2007, pp 1447–1452.

[6] Dyke, S., and Spencer, B., “A Comparison of Semi-Active Control Strategies for the MR Damper,” Proceedings of the IASTED International Conference, Intelligent Information Systems, Bahamas, 1997.

[7] Dyke, S., Spencer, B., Sain, M., and Carlson, J., “Modeling and Control of Magnetorheological Dampers for Seismic Response Reduction,” Smart Mater. Struct., 5, 1996, pp. 565–575.

[8] Yi, K., and Song B. S., “A New Adaptive Sky-Hook Control of Vehicle Semi-Active Suspensions,” Proc. Inst. Mech. Eng., Part D (J. Automob. Eng.), 213(3) , 1999, pp. 293–303.

[9] Karnopp. D, et.al, “Vibration Control Using Semi-Active Force

Generators,” ASME J. Eng. Ind., 96, 1974, pp. 619–626.

[10] Ginder, J. M., et.al. “Rheology of Magnetorheological Fluids: Models and Measurements,” Int. J. Mod. Phys. B, 10, 1996, pp. 3293–3303.

[11] Ginder, J.M. & Davis, L.C. “Shear stresses in magnetorheological fluids: role of magnetic saturation”. App. Phy. Lett. 1994, 65, pp 3410-412.

[12] Lord Corporation, Dr. Dave’s Do-It-Yourself MR Fluid, Designing with MR Fluid, Magnetic Circuit Design, FAQs, Fluid specifications, 2006, www.lord.com.

[13] Carlson, J. D. “Magnetorheological fluid actuators”. In Adaptronics and Smart Structures (Ed. H. Janocha) 1999, pp. 180–195 (Springer-Verlag, Berlin, Heidelberg).

[14] Bolter, R. and Janocha, H, “Design rules for MR fluid actuators in different working modes”. In Proceedings of the SPIE Conference of the International Society for Optical Engineers (Ed. L. P. Davis), Vol. 3045, 1997, pp. 148–159 (SPIE, Washington).

[15] Wang, J. & Meng, G, “Magnetorheological fluid devices: principles, characteristics and applications in mechanical engineering”, 2001, Proceedings of the Institution of Mechanical Engineers; Part B; Journal of Engineering Manufacture Volume: 215 (3), pp 165- 174.

[16] Ashour, O., et.al, “Magnetorheological Fluids: Materials, Characterization, and Devices.”Journal of Intelligent Material Systems and Structures. 7(2) , 1996, pp. 123-130.

[17] Rosensweig, R. E. “Directions in Ferrohydrodynamics”. Proceedings of the Thirtieth Annual Conference on Magnetism and Magnetic Materials, Nov. 1984, Journal of Applied Physics. San Diego, CA, USA.

[18] CARLSON J D, WEISS K D, “Magnetorheological materials based on alloy particles”, USA: Lord Corporation, 1995.

[19] Nicholos Rosenfeld, et.al, “Behaviour Of Magneto-Rheological Fluids Utilizing Nanopowder Iron”, International Journal of Modern Physics B, Vol. 16, Nos. 17 & 18, 2002, pp 2392-2398.

[20] Wook-Bae Kim, et.al, “Surface Finishing and Evaluation of Three Dimensional Silicon Microchannel Using Magnetorheological Fluid”, Journal of Manufacturing Science and Engineering, Vol. 126, 2004, pp 772-778.

[21] Carlson, J.D., Weiss, K.D., “A growing attraction to magnetic fluids,” Machine Design, Vol. 66, No. 15, 1994, pp. 61-64.

[22] Weiss, K.D. et.al, “High strength magneto - and electro - rheological fluids,” Society of Automotive Engineers, Vol. 932451, 1993.

[23] R. Turczyn, M. Kciuk, “Preparation and study of model magnetorheological fluids”, Volume 27, Issue 2, Journal of Achievements in Materials and Manufacturing Engineering, April 2008.

[24] O. Ashour, C. A. Rogers and W. Kordonsky, Magnetorheological Fluids: Materials, Characterization, and Devices, Journal of Intelligent Material Systems and Structures, Vol. 7, No. 2, 1996, 123-130.

[25] Farjoud, Alireza. "Mathematical Modeling of Magnetorheological (MR) Rotary Brakes." Thesis. Nanyang Technological University, 2007.

[26] Lord Materials Division, “Designing with MR Fluids,” Engineering Note, pp. 1-5, 199927.

[27] Ahn, Y.K., et.al. “A Small-sized Variable-damping Mount Using Magnetorheological Fluid,” International Journal of Vehicle

System Dynamics, Vol. 16, 2005, pp. 127-133.

[28] B. Gangadhara Shetty and P.S.S. Prasad, “Rheological Properties of a Honge Oil-based Magnetorheological Fluid used as Carrier Liquid”, Defence Science Journal, Vol. 61, No. 6, , November 2011 pp. 583-589.

[29] Genc, S. & Phule, P.P, “Rheological properties of magnetorheological fluids”. Smart Mater. and Struct., 11, 2002, pp 140-146.

[30] Shivaram, A.C. & Gangadharan, K.V “Statistical modeling of a magnetorheological fluid damper using the design of experiments approach”. Smart Mat. Struct., 2007, 16, pp 1310-1314.

[31] Lim S.T., et.al., “Magnetorheological characterisation of carbonyl iron-based suspension stabilised by fumed silica”. J. Magnet. Magnetic Mater, 282, 2004, pp 170-73.

[32] Vieira, S.L.; Ciocanel, C.; Kulkarni, P.; Agrawal, A. & Naganathan, N., “Behavior of MR fluids in squeeze mode”, Int. J. Veh. Des., 2003, 33, pp 1-3.

[33] J. Huang, et.al., “Analysis and design of a cylindrical magnetorheological fluid brake”, Journal of Materials Processing Technology 129 (2002), pp 559-562

[34] W. Wislow, “Field Responsive Fluid Couplings”, US Pat. No. 2.886.151, (1959)

[35] P. Domínguez-García, S. Melle, J.M. Pastor, M.A. Rubio, “Scaling in the aggregation dynamics of a magneto rheological fluid”, Physical Review E76 (2007), pp 13-20.

[36] J.H. Park, B.D. Chin, O.O. Park,” Rheological properties and dispertion stability of magnetorheological suspensions”, Rheologica Acta 40 (2001), pp 211-219

[37] Carlson, J.D. What Makes A Good MR Fluid? Technical report, Lord Corporation, July 2001.

[38] Barnes, H.A. “Shear-Thickening (’Dilatancy’) in Suspensions of Nonaggregating Solid Particles Dispersed in Newtonian Liquids”. Technical report, Port Sunlight Laboratory.

[39] Carlson, J.D., Catanzarite, D.M. and Clair, K.A.St. Commercial Magneto-Rheological Fluid Devices. Technical report, Lord Corporation, July 2001.

[40] Marin, L., Nicolae, C. P., Cornel, V., & Ladislau, N. V., “Investigations of a magnetorheological fluid damper”, IEEE Transactions on Magnetics, 2004, Volume: 40, (2), pp 469-472.

[41] Carlson, J. D. & Weiss, K. D. “A growing attraction to magnetic fluids”, 1994, Machine design 66 (August) 61–66.

[42] Wang, D. H., & Liao, W. H., “Modeling and control of magnetorheological fluid dampers using neural Networks”, 2005, Journal of Smart Materials and Structures, Volume: 14

[43] Dyke, S. J. “Acceleration feedback control strategies for active and semi-active control systems: modeling, algorithm development, and experimental verification”, 1996, PhD Thesis, Department of Civil and Geological Sciences, Notre Dame, Indiana.

[44] W. D. Callister Jr., Materials Science

and Engineering: An Introduction, 3rd

Ed., John Wiley and Sons, Inc., New York, 1994.

[45] J. D. Kraus, Electromagnetics,

International Edition, 4th

Edition, Mc-Graw-Hill Inc., Singapore, 1991.

[46] Bossis G., Lacis S., Meunier A., Volkova O.,2002,Magnetorheological fluids, Journal of Magnetism and Magnetic Materials, 252, 224–228.

[47] P. Domínguez-García, S. Melle, J.M. Pastor, M.A. Rubio, “Scaling in the aggregationdynamics of a magneto rheological fluid”, Physical Review E76 (2007), pp 13-20.

[48] J.H. Park, B.D. Chin, O.O. Park,” Rheological properties and dispertion stability of magnetorheological suspensions”, Rheologica Acta 40 (2001), pp 211-219

[49] Carlson, J.D. What Makes A Good MR Fluid? Technical report, Lord Corporation, July 2001.

[50] Barnes, H.A. “Shear-Thickening (’Dilatancy’) in Suspensions of Nonaggregating Solid Particles Dispersed in Newtonian Liquids”. Technical report, Port Sunlight Laboratory.

[51] Carlson, J.D., Catanzarite, D.M. and Clair, K.A.St. Commercial Magneto-Rheological Fluid Devices. Technical report, Lord Corporation, July 2001.

[52] Dimock, G.A., Lindler, J.E., Wereley, N.M., “Bingham Biplastic Analysis of Shear Thinning and Thickening in Magnetorheological Dampers”, Technical report, Alfred Gessow Rotorcraft Center, Department of Aerospace Engineering, University of Maryland, March 2000.

[53] Guangqiang Yang, B.S. “Larg-Scale Magnetorheological Fluid Damper for Vibration Mitigation: Modeling, Testing and Control”. Master’s thesis, University of Notre Dame, Department of Civil Engineering and Geological Sciences, Notre Dame, Indiana, December 2001.

[54] Phillips, R. W., 1969, "Engineering Applications of Fluids with a Variable Yield Stress", Ph.D. Thesis,University of California, Berkeley .

[55] Breese D. G., Ericksen E. O. and Gordaninejad F., Heat generation of magneto-rheological fluid dampers, Proc. SPIE 3988, 450, 2000.

[56] Chen Guang and Yeo Song Huat, “Research on MR Fluids and its Applications”, Applied Research Project Report RG63/96; Nanyang Technological University, Singapore: 1996.

[57] İsmail Şahin, et. al, “Investigation of The Effects of Temperature Variations On The Magnetorheological Damper Behaviour”, 15th International Research/Expert Conference, “Trends in the Development of Machinery and Associated Technology”, TMT 2011, Prague, Czech Republic, 12-18 September 2011, pp 63-66.

[58] Lord Corporation, Cary, NC http://www.lordfulfillment.com/upload/DS7012.pdf.

[59] X. Tang, X. Zhang, R. Tao, Y. Rong, J. Appl. Phys., 87 (2000) 2634.

[60] Lord Corporation Website http://www.lord.com/products-and-solutions/active-vibration-control systems/industrial-suspension systems/magneto-rheological-(mr)-fluid

[61] Choi, S. B., Nam, M. H., & Lee, B. K, “Vibration control of a MR seat damper for commercial vehicles”, 2000, Journal of Intelligent Material Systems and Structures, Vol. 11 (12), pp 936-944.

[62] Lee, H. S. & Choi, B. S, “Control and response characteristics of a magnetorheological fluid damper for passenger vehicles”, 2000, Intelligent Material Systems and Structures, Volume: 11, pp 80-87.

[63] Ahmadian, M., Poynor, J.C., Gooch, J.M. "Application of Magneto Rheological Dampers for Controlling Shock Loading", American Society of Mechanical Engineers, Dynamics Systems & Control Division (Publication) DSC-Volume 67, 1999, pp. 731-735.

[64] Ahmadian, M., "Design and Development of Magneto Rheological Dampers for Bicycle Suspensions", American Society of Mechanical Engineers, Dynamic Systems & Control Division Publication, DSC-Volume 67, 1999, pp. 737-741.

[65] S.J. Dyke, B.F. Spencer Jr., M.K. Sain, and J.D. Carlson, "Seismic Response Reduction Using Magnetorheological Dampers", Proceedings of the IFAC World Congress; San Francisco, CA; June 30-July 5, 1996.

[66] "Rheonetic RD-1005-3 MR damper", Lord Corporation product bulletin, Cary, NC, ©2001.

[67] A. Kim, T. Gillespie, N. Eslaminasab, “Evaluation of Existing Active-valve Technologies for Use in Semi-active Shock Absorbers”, University of Waterloo Department of Mechanical Engineering, Internal Technical Report, 2004.

[68] B.F. Spencer Jr., S.J. Dyke, M.K. Sian, J.D. Carlson, “Phenomenological model for magnetorheological dampers”, J. Eng. Mech., pp. 230–238, 1997.

[69] N.M. Kwok, Q.P. Ha, J. Li, B. Samali, S.M. Hong, “Parameter identification for a magnetorheological fluid damper: An evolutionary computation approach”, Proceedings of the Sixth International Conference on Intelligent Technologies, Phuket Thailand, pp. 115–122, 2005.

[70] R.C. Ehrgott, S.F. Masri, “Modeling the oscillatory dynamic behavior of electrorheological materials in shear”, Smart Materials and Structures, 1, pp. 275-285, 1992.