Theoretical and Experimental Studies on Magnetorheological Fluid Damper With Dc Input

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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976

6340(Print), ISSN 0976 6359(Online) Volume 3, Issue 2, May-August (2012), IAEME

610

THEORETICAL AND EXPERIMENTAL STUDIES ON

MAGNETORHEOLOGICAL FLUID DAMPER WITH DC INPUT

Mukund A. Patil1, Swapnil Sapkale

2, Sagar Soni

3, Vijay Sarvaiya

4, Vishal Parekh

5

1, 2,3,4,5

Department of Mechanical Engineering, G. H. Raisoni Institute of Engineering andManagement, Jalgaon

Email:[email protected]

[email protected]

[email protected]

[email protected]

ABSTRACT

A magneto-rheological (MR) fluid brake is a device to transmit torque by the shear force of

an MR fluid. Magnetorheological fluids (MRF) are smart materials consisting of silicon oil

and very small soft-magnetic particles. In a magnetic field, the viscosity and the flow

behaviour of the fluid are considerably changed. MRF damper is a device to give damping by

the shear stress of MR fluids. A MRF damper has the property whose damping changes

quickly in response to an external magnetic field strength. The design method of a new MR

fluid damper is investigated theoretically and the structure is presented. The equation of the

damping by MR fluids within damper is derived to provide the theoretical foundations in the

design of the damper. Based on this equation, after mathematical manipulation, the

calculations of the volume, thickness and width of the annular MR fluids within the MR

fluids damper are yielded and discussed.

INTRODUCTION

Magneto-rheological fluids can be characterised as controllable fluids. They are

manufactured by suspending ferromagnetic particles in a carrier fluid. The latter is typically

some kind of oil. MR fluids exhibit a change in rheological properties when being exposed to

a magnetic field (this is known as the on-state). Rheology is defined as the study of the

deformation and flow of matter (typically materials such as rubber, molten plastics, magneto-

rheological fluids, blood, paint, etc) under the influence of an applied stress. The rheological

INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING ANDTECHNOLOGY (IJMET)

ISSN 0976 6340 (Print)

ISSN 0976 6359 (Online)

Volume 3, Issue 2, May-August (2012), pp. 610-619

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properties of a liquid are the dominant features that can be quantified to characterise its

behaviour. The properties that can be affected are elasticity, plasticity and viscosity. In the

on-state, ferromagnetic particles are magnetically induced and aggregate to form chain-like or

column-like structures parallel to the applied field. Due to this, MR fluids have the ability to

reversibly change from viscous liquids to semi-solids in milliseconds when being exposed to

a magnetic field. This feature enables a rapid response interface between electronic controlsand mechanical systems, making MRF technologies attractive for many applications (e.g.

dampers).

In this paper, the fundamental design method of the MR damper is investigated theoretically.

Bingham model is used to characterize the constitutive behavior of the MR fluids subject to

an external magnetic field strength. The theoretical method is developed to analyze the shear

stress by the MR fluid within the damper. An engineering expression for the shear stress is

derived to provide the theoretical foundations in the design of the damper. Based on this

equation, being algebraically manipulated, the volume and thickness of the annular MR fluid

within the damper is yielded.

OPERATIONAL PRINCIPLE

MR fluid damper is a device to give damping by the shear stress of MR fluid. A MR damper

has the property whose damping changes quickly in response to an external magnetic field

strength. The MR fluid is filled in the working gap between the fixed outer cylinder and inner

cylinder. The inner cylinder moves at a speed V. In the absence of an applied magnetic field,

the suspended particles of the MR fluid cannot restrict the relative motion between the fixed

outer cylinder and inner cylinder. However, in the course of operation, the magnetic flux path

is formed when the electric current puts through the solenoidal coil. As a result, the particles

are gathered to form the chain-like structures, with the direction of the magnetic flux path.

These chain-like structures restrict the motion of the MR fluid, thereby increasing the shear

stress of the fluid. The damper can be achieved by utilizing the shear force of MR fluid. The

damping values can be adjusted continuously by changing the external magnetic field

strength.

THEORETICAL APPROACH TO MR DAMPER DESIGN

The key question in the design of MR fluid damper is to establish the relation between the

damper and the parameters of the structure and magnetic field strength. As the magnetic field

is applied, the damping F developed by MR fluid can be calculated by

22

0

3

12

sgn( )B

K L rL r

F v f vRh h

= + +

.................................... (1)

Where v is the speed of piston; f is friction of piston and cylinder; 0K is a coefficient

(0.81.0); h is the thickness of the annular MR fluid between the piston and outer cylinder.

The value of h can be given by


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h R r= .... (2)

If it is assumed that the value of f is much smaller, Eqns. (1) and (2) can be mathematically

manipulated to yield

32 2

2 BLr v

F L rh

= + ..... (3)

Eqn. (3) shows that the damping developed in the cylindrical MR fluid damper can be divided into a

magnetic field dependent induced yield stress component BF and a viscous component F .

22B BF L r = ........ (4)

32 Lr v

F h

=

... (5)

The total damping F is the sum of BF and F .

The active volume of annular MR fluid in the cylindrical MR damper can be obtained

through the integration the radius of annular MR fluid as follows.

2

R

r

v L rdr = ..................................................................................................................... (6)

Therefore,

2v rLh= . (7)

Eqns. (4) (7) can be manipulated to yield

( )2B

B

B

Fv F v

F

=

....................................................................................................... (8)

Eqns. (4) and (5) can be algebraically manipulated to derive the thickness of annular MR fluid as

follows.

B

B

Fh rv

F

=

.... (9)


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Eqn. (9) gives the minimum active MR fluid volume that is necessary within the damper in order to

achieve the desired control damping ratio BF

F

at a given speed v and a specified controllable

dampingB

F .

The length L of the effective length of the MR fluid can be obtained from Eqns. (7) and (9).

The completed assembly of MR damper is as shown in figure 1.

Figure 1 Catia Model of Magnetorheological Damper

EXPERIMENTAL APPROACH TO MR DAMPER

An MR damper is to be analyzed as a 2-D axisymmetric model in ANSYS software package. For a

given current, we can determine the magnetic flux density at the Engine, MR Fluid and the damper

housing.

Figure 2. 2-D Flux Lines around the Electrical Coil


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Figure 2 shows the flux lines around the electrical coil which is placed in the MR damper. It is

concluded that, all the flux lines are passing through the annular part of the MR damper. This annular

part consists of Magnetorheological fluid. Therefore, the required magnetic field in the annular part of

the damper can be obtained.

Figure 3 (a) and (b) shows the magnetic flux density and magnetic fields generated in the electrical

coils. UTM (Universal testing machine) which was used in the testing of the damper was capable of

both compressive and tensile testing of the sample.

Figure 4 shows the experimental set up for testing of the MR damper. The compression test has been

carried out for testing the force and current characteristics of the damper.

(a) (b)Figure 3. (a) Magnetic flux density and (b) magnetic fields generated in electrical coil.


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Figure 4. Experimental set up for testing of MR damper.

Table 1.1 Magnetic induction for different current values

Current (A) Magnetic induction (T)

0.2 0.3108

0.4 0.5884

0.6 0.8511

0.8 1.0844

1.0 1.2596

1.2 1.4325

1.4 1.6047

1.6 1.7768

1.8 1.9488

2.0 2.1207

Table 1.1 shows the magnetic induction values for different current values. It has been concluded that,

as the input DC current increases, the magnetic induction in the MR damper increased. Table 1.2

shows the force exerted by the MR damper for different DC current values. From the table 1.2, it has

been seen that, as the current increases, the force exerted by the MR damper increased.

MR Damper

UTM

Machine

DC Power Supply

Computer

for UTM

Software


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Table 1.2 MR damper exerted force for different current values

Current (A) Force (N)

0.0 26

0.2 28

0.4 29

0.6 32

0.8 42

1.0 60

Figure 5. Force versus displacement characteristics of MR damper for 0.0 A and 0.5v = mm/min


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Figure 8 Force versus displacement characteristics of MR damper for 0.6 A and 0.5v = mm/min

Figure 9 Force versus displacement characteristics of MR damper for 0.8 A and 0.5v = mm/min


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CONCLUSION

Magnetorheological (MR) fluid dampers have provided technology that has enabled effective semi-

active control in a number of real world applications. Because of their simplicity, low input power,

scalability and inherent robustness, such MR fluid dampers are quite promising for civil engineering

applications. The geometric design method of a cylindrical MR fluid damper is investigated

theoretically. The damping developed by MR fluid within the damper under different magnetic fieldstrength conditions is analyzed and tested at the Indian Institute of Technology, Bombay. Theengineering design calculations of the volume, thickness and width of the annular MR fluid within the

damper are derived. The parameters of the thickness and width of the fluid in the damper can becalculated from the equations obtained, when the required mechanical power level, the speed of the

piston, and the desired control damping ratio are specified.

ACKNOWLEDGEMENT

This work was financially supported by a G. H. Raisoni Institute of Engineering and Management,

Jalgaon. I am very thankful to HOD of Mechanical engineering department of Indian Institute of

Technology, Bombay for allowed to do experimental work.

REFERENCES

1. J. D. Carlson, D. M. Catanizarite, K. A. Clair, "Commercial magneto-rheological fluiddevice," Proc. 5th International Conference on ER Fluids, MR Suspensions and Associated

Technology, Singapore, 2857-2865(1996).

2. J. H. Koo, F. D. Goncalves, Mehdi Ahmadian. "Investigation of the response time ofMagnetorheological fluid dampers," Proc. SPIE 5386, 63-71(2004).

3. Satsua Soda, Haruhide Kusumoto, et al., "Semi-active seismic response control of base-isolated building with MR damper," Proc. SPIE 5052, 460-467(2003).

4. Yang G. "Large-scale Magnetorheological fluid damper for vibration mitigation: modeling,testing and control," Notre Dame, Indiana. Ph.D. Dissertation University of Notre Dame,

2001.

5. Unsal M. Semi-active vibration control of a parallel platform mechanism usingMagnetorheological damping. Ph. D. Dissertation: University of Florida; 2006.

6. Jolly M.R., Bender J.W., and Carlson J.D. Properties and applications of commercialMagnetorheological fluids. In: Proceedings of the SPIE fifth annual international symposium

on smart structures and materials: San Diego, CA 1998.

7. Yang G, Spencer Jr. BF, Carlson JD, Sain MK. Large-scale MR fluid Dampers: modeling,and dynamic performance considerations. Engineering Structures 2002; 24(3):30923.

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Theoretical and Experimental Studies on Magnetorheological Fluid Damper With Dc Input