i

CHARACTERIZATION OF MR FLUID USING A NOVEL

MPDC VISCOMETER TECHNIQUE

A REPORT

submitted by

JEYA GANESH N.

in partial fulfillment for the award of the degree

of

MASTER OF TECHNOLOGY

in

APPLIED MECHANICS

FLUID MECHANICS GROUP

DEPARTMENT OF APPLIED MECHANICS

INDIAN INSTITUTE OF TECHNOLOGY MADRAS

CHENNAI-600 036.

May 2009

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THESIS CERTIFICATE

This is to certify that the thesis titled CHARACTERIZATION OF MR FLUID USING

A NOVEL MPDC VISCOMETER TECHNIQUE submitted by JEYA GANESH N., Roll

no. AM07M004 to the Indian Institute of Technology, Madras, for the award of the degree of

Master of Technology, is a bonafide record of the work done by him under my supervision,

during the academic session 2007-2009. The contents of this thesis, in full or in parts, have

not been submitted to any other Institute or University for the award of any degree or

diploma.

Place: Chennai

Dr. B.S.V. Patnaik

Assistant Professor

Dept. of Applied Mechanics

IIT-Madras, 600 036

M. S. Siva kumar

Professor

Dept. of Applied Mechanics

IIT-Madras, 600 036

Prof. K. Ramesh

Head of the Department

Dept. of Applied Mechanics

IIT-Madras, 600 036

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ACKNOWLEDGMENTS

I express my deep sense of gratitude to Dr. B.S.V. Patnaik and Prof, M. S. Sivakumar for

their inspiring and inimitable guidance through thought provoking discussions and constant

encouragement throughout this project work. It was a great pleasure working under them and

I will take this memorable experience throughout my life. If they had not provided the kind of

freedom which they had extended then I would not have enjoyed accomplishing the project.

I express my sincere thanks to the Prof K. Ramesh, Head of Department for his excellent

support. I also would like to thank MEC members and other solid mechanics faculties support

and patience extended towards my work. It was only due to their periodic review and

criticism, the project work was shaped and has attended its final version.

I would like to thank Dr. Chandrasekaran for his valuable suggestions and motivation for

my project work. It was he who inspired me in the art of presentation which was really useful

in each and every stage of my work.

No experimental work can surface without the help of experts present in various

departments. I, in this juncture, would like to express my sincere thanks to Prof Ramachandra

Rao from Physics department for allowing me to use the DC electromagnet in his lab.

Without his support the final face would have just remained theoretical. I also like to thank

my friends Senthil and Krishnan from the physics department for introducing us to the lab

and helping in understanding those devices.

I thank my dear friend Maniprakash for his invaluable suggestions and his help during

MATLAB coding. The work of my other friend Venkateswara Rao is unquestionable as he

helped a lot during the initial stages. I would have faced lot more difficulty in the fabrication

of experimental set up had he was not there. The hard work exerted accomplishing the project

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would have gone in vain had it not properly documented and presented before others. I thank

my other friend Srinivasan for his help in this regard in various stages of the project.

Academic life in IITM would have been stressful without the comfort, confidence, and

consideration of friends who made my stay enjoyable. In this regard, I like to thank my

friends Jayabal, Kasimayan, Shajil, Muthukumaran, Elango, Jayavel, Srivatsan, France and

Raja.

I finally would like to thank my parents and brothers and sisters for their patience

extended towards me during entire graduate study. My parents blessings and wishes was a

great source of motivation throughout my stay in IITM. I would not have reached this height

without their nurturing and support extended to me in my early days.

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ABSTRACT

The fact that viscosity of a Magneto-Rheological fluid (MR fluid) can be varied by the

application of a magnetic field implies that there exists a lot of scope for development of

applications in which such a control on viscosity can be exercised by the application of a

magnetic field. The first step towards realizing such tunable mechanisms in specific

applications is therefore the establishment of a database and a method for characterization of

initial viscosity and its variation with applied magnetic field. In this project, the coefficient of

viscosity and yield strength of a magneto-rheological fluid containing different

concentrations of ferro-magnetic particles in the chosen carrier fluid have been determined as

a function of varying magnetic fields. An improved unique inexpensive experimental set-up

has been designed, fabricated and utilized for the viscosity characterization of MR fluids.

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TABLE OF CONTENTS

ACKNOWLEDGMENTS .................................................................................................................... III

ABSTRACT ........................................................................................................................................ V

LIST OF FIGURES .......................................................................................................................... VIII

NOTATIONS ..................................................................................................................................... XI

CHAPTER 1 .................................................................................................................................... 1

INTRODUCTION ................................................................................................................................ 1

1.1 Magneto-Rheological Fluid .................................................................................................... 1

1.2 Types of Fluids ....................................................................................................................... 2

1.3 Characterization of MR Fluids ................................................................................................ 3

1.4 The Present Study ................................................................................................................... 4

CHAPTER 2 .................................................................................................................................... 5

LITERATURE REVIEW ...................................................................................................................... 5

2.1 Interaction .............................................................................................................................. 5

2.2 Operational Modes ................................................................................................................. 5

2.3 Characterization of MR Fluid.................................................................................................. 6

2.4 Measurements on Non-Newtonian Fluids ................................................................................ 6

2.5 Conclusions from the Literature .............................................................................................. 7

2.6 Objective of Present Work ...................................................................................................... 7

2.7 Scope of the Work .................................................................................................................. 8

CHAPTER 3 .................................................................................................................................... 9

PRELIMINARY WORK AND REVIEW ................................................................................................. 9

3.1 Introduction ............................................................................................................................ 9

3.1 MR Fluid Preparation ............................................................................................................. 9

3.1.1 Carrier Fluid ................................................................................................................... 9

3.1.2 Surfactant ..................................................................................................................... 10

3.1.3 Ferromagnetic Particles................................................................................................. 11

3.1.4 Preparation Procedure ................................................................................................... 12

3.2 An Overview Earlier of Experimental Work ......................................................................... 13

3.3 Description of MDCV Instrument ......................................................................................... 14

3.4 MDCV Testing Procedure..................................................................................................... 18

3.4 MDCV Formulation.............................................................................................................. 18

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3.5 MDCV Result Review .......................................................................................................... 24

CHAPTER 4 ................................................................................................................................... 30

MASS AND PRESSURE –DETECTING CAPILLARY VISCOMETER (MPDCV) .................................... 30

4.1 Description of the Instrument ................................................................................................ 30

4.2 Testing procedure ................................................................................................................. 33

4.3 The Formulation ................................................................................................................... 35

4.3 The Formulation ................................................................................................................... 35

CHAPTER 5 .................................................................................................................................. 38

RESULTS AND DISCUSSION ............................................................................................................. 38

5.1 Test Result for Reference Fluids ........................................................................................... 38

CHAPTER 6 .................................................................................................................................. 49

CONCLUSIONS AND FUTURE WORK ............................................................................................... 49

6.1 Summary and Conclusions .................................................................................................... 49

6.2 Future Work ......................................................................................................................... 50

REFERENCES .................................................................................................................................. 51

APPENDIX ....................................................................................................................................... 53

1 MATLAB code ....................................................................................................................... 53

For MDCV Viscometer ......................................................................................................... 53

For MPDCV Viscometer ....................................................................................................... 57

2 Curve fitting results ................................................................................................................. 58

MDCV .................................................................................................................................. 58

MPDCV ................................................................................................................................ 60

3 Viscosity Table:....................................................................................................................... 62

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LIST OF FIGURES

Fig. 1-1 A demonstration illustrating the behavior of MR fluids with and without magnetic field. An

otherwise a simple near-Newtonian fluid with suspended particles tend to become an

anisotropic non-Newtonian plastic viscous fluid in the presence of a magnetic field. .......... 1

Fig. 1-2 Shear stress vs. shear strain rate for different types of fluids. The slope of these curves is

the viscosity of the fluid. Unlike the Newtonian and other simple fluids, the MR fluid

behavior is closer to plastic-viscous fluids generally termed Bingham plastic fluids. ............ 2

Fig. 2-1 The two basic operational modes of MR Devices, (a) Pressure driven flow mode – flow

occurs due to pressure difference, (b) Direct shear flow mode – flow occurs due to relative

motion between the plates [1] ........................................................................................... 6

Fig. 3-1 A micelle is an aggregate of particle and surfactant molecules that contain polar head and

non-polar tail [5] .............................................................................................................. 10

Fig. 3-3 Prepared MR fluid with different mass fractions ................................................................ 12

Fig. 3-2 SEM micrographs of carbonyl iron powder which shows irregular shape of iron particles and

the particle size is around 2- 10µm. .................................................................................. 12

Fig. 3-4 Schematic diagram of a MDCV ............................................................................................ 15

Fig. 3-5 Experimental setup of MDCV .............................................................................................. 15

Fig. 3-6 Front panel, acts as a user interface. The system response can be viewed online during

experiment in chart window. This enables the user to check other uncertainties during

experiments ..................................................................................................................... 16

Fig. 3-7 Block diagram of the virtual instrument. It shows the internal circuitry of the elements used

in the experiment. It helps to add necessary elements to filter the noise so that actual data

is obtained without any external disturbances. ................................................................. 17

Fig. 3-8 Plot of Time Vs Mass for Water by MDCV ........................................................................... 26

Fig. 3-9 Plot of Time Vs Mass flow rate for Water by MDCV ............................................................ 26

Fig. 3-10 Plot of Time Vs Pressure for Water by MDCV .................................................................... 27

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Fig. 3-11 Plot of Shear strain rate Vs Shear stress for Water by MDCV............................................. 27

Fig. 3-12 Plot of Time Vs Mass for Mineral oil by MDCV .................................................................. 28

Fig. 3-13 Plot of Time Vs Mass flow rate for Mineral oil by MDCV ................................................... 28

Fig. 3-14 Plot of Time Vs Pressure for Mineral oil by MDCV ............................................................. 29

Fig. 3-15 Plot of Shear strain rate Vs Shear stress for Mineral oil by MDCV...................................... 29

Fig. 4-1 Schematic diagram of the MPDCV. As can be seen, the tall falling tube in MDCV is dispensed

with and replaced by a simple cylinder with a pressure gauge attached to it. The load cell

measures the weight of the liquid collected. The spring is used for applying the force to

the piston to generate the required pressure. .................................................................. 31

Fig. 4-2 MPDCV Experimental Setup with Data accusation system .................................................. 32

Fig. 4-3 Variable Magnetic field DC Magnet power Supply controller and Magnetic flux density

Measurement (Gauss Meter) ............................................................................................ 32

Fig. 4-4 MPDCV Experimental Setup with DC Magnet...................................................................... 34

Fig. 5-1 Plot of Time Vs Mass for Water by MPDCV ......................................................................... 40

Fig. 5-2 Plot of Time Vs Mass flow rate for Water by MPDCV .......................................................... 40

Fig. 5-3 Plot of Time Vs Pressure for Water by MPDCV .................................................................... 41

Fig. 5-4 Plot of Shear strain rate Vs Shear stress for Water by MPDCV ............................................ 41

Fig. 5-5 Plot of Time Vs Mass for Mineral oil by MPDCV .................................................................. 42

Fig. 5-6 Plot of Time Vs Mass flow rate for Mineral oil by MPDCV ................................................... 42

Fig. 5-7 Plot of Time Vs Pressure for Mineral oil by MPDCV ............................................................. 43

Fig. 5-8 Plot of Shear strain rate Vs Shear stress for Mineral oil by MPDCV ..................................... 43

Fig. 5-9 Plot of Shear strain rate Vs Shear stress for corn flour with water by MPDCV ..................... 44

Fig. 5-10 Plot of Time Vs Mass for MRF by MPDCV .......................................................................... 46

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Fig. 5-11 Plot of Time Vs Mass flow rate for MRF by MPDCV ........................................................... 46

Fig. 5-12 Plot of Time Vs Pressure for MRF by MPDCV .................................................................... 47

Fig. 5-13 Plot of Shear strain rate Vs Shear stress for MRF by MPDCV ............................................. 47

Fig. 5-14 Plot of Shear strain rate Vs Shear stress for MRF under different Magnetic flux density by

MPDCV ............................................................................................................................. 48

Fig. 5-15 Plot of Magnetic flux density Vs Threshold Pressure for MRF by MPDCV........................... 48

xi

NOTATIONS

Nomenclature

- Capillary length (m)

m - Mass (kg)

- Mass flow rate (kg s_1)

n -power-law index (dimensionless)

P - Pressure (Pa)

Q - Volume flow rate (m3 s_1)

t - Time (s)

Greek symbols

- Density (kgm3)

- Capillary diameter (m)

- cylinder diameter (m)

-non-Newtonian viscosity (Pa s)

- Newtonian viscosity (Pa s)

xii

- shear rate (1/s)

- Shear stress (Pa)

Subscripts

- Capillary tube

- Entrance and exit

– Cylinder

- Wall

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CHAPTER 1

INTRODUCTION

1.1 MAGNETO-RHEOLOGICAL FLUID

Magneto-rheological fluid (MR fluid) is a fluid made up of a carrier fluid with added

surfactants that holds in suspension micron-sized magnetically polarizable particles. The

viscosity of this fluid depends on the concentration of the suspended particles and varies

under the influence of a magnetic field. However, the purely concentration related influence

on viscosity weak compared to the strong influence of the magnetic field.

In the presence of a magnetic field, the suspended particles in the fluid tend to align in the

direction of the magnetic field. The particles so aligned restrict the flow of the fluid

perpendicular to the direction of alignment or direction of flux. This increases the viscous

resistance of fluid perpendicular to the direction of flux. The properties of the MR fluid under

the action of magnetic field are anisotropic and it behaves like a non-Newtonian fluid (See

Fig. 1-1) that shows a simple demonstration of the same). This controllable viscous nature of

the MR fluids offers immense scope in its use in smart applications [2].

Fig. 1-1 A demonstration illustrating the behavior of MR fluids with and without magnetic field. An otherwise a simple near-Newtonian fluid with suspended particles tend to become an anisotropic

non-Newtonian plastic viscous fluid in the presence of a magnetic field.

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1.2 TYPES OF FLUIDS

Generally, for most of the fluids (like water) shear stress versus rate of strain curve is

linear and passes through the origin. The slope of the curve is known as viscosity. Fluids that

exhibit this behaviour have a constant viscosity value i.e. viscosity is independent of shear

rate of the fluid and these fluids are called Newtonian fluids.

For a non-Newtonian fluid, the relation between the shear stress and the strain rate is

nonlinear, i.e. viscosity is shear strain rate dependent (see Fig. 1-2). Therefore, a constant

viscosity cannot be defined for a non-Newtonian fluid.

In general, non-Newtonian fluid behavior is modeled by treating the fluid as a dilatants, a

pseudoplastic or a Bingham plastic fluid depending on the type of nonlinearity exhibited by

the fluid. Dilatant or shear thickening fluids are those whose viscosity increases with increase

in shear rate (Fig. 1-2). The dilatant effect occurs in a fluid-particle mixture when the liquid

fraction present in the mixture is much less than the solid fraction and is just enough to only

Fig. 1-2 Shear stress vs. shear strain rate for different types of fluids. The slope of these curves is the viscosity of the fluid. Unlike the Newtonian and other simple fluids, the MR fluid

behavior is closer to plastic-viscous fluids generally termed Bingham plastic fluids.

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fill the gap between the major fraction solid particles. At low velocities, the liquid acts as a

lubricant, and the dilatant flows easily. At higher velocities, the liquid is unable to fill the

gaps created between particles, and friction greatly increases, causing an increase in

viscosity. This can readily be seen in the case of a mixture of cornstarch and water.

Psedoplastic or shear thinning fluids exhibit a behavior opposite to that of dilatant fluids.

The viscosity of shear thinning fluid decreases with the increase in the shear rate (Fig. 1-2).

Examples of such fluids are ketchup, whipped cream, blood, paint, and nail polish..

Some fluids remain solid until the applied pressure reaches a threshold value. They then

behave as Newtonian fluids. Such fluids are known as Bingham plastic named after Eugene

C. Bingham who first proposed a mathematical formulation to model its behaviour [6]. It is

the commonly used mathematical model for analysis of mud flow in offshore engineering,

and the handling of slurries.

In the presence of a magnetic field, MR fluid behaves like a viscoelastic solid till a

particular threshold pressure is reached after which it behaves like shear thinning fluid (see

Fig. 1-2). The threshold pressure and viscosity increase with applied magnetic field strength.

The threshold pressure and viscosity can be varied depending on the requirement by

controlling the magnetic field.

1.3 CHARACTERIZATION OF MR FLUIDS

The usefulness of magneto-rheological fluids lies in their ability to act as simple, quiet

and rapid response media between electronic controls and mechanical systems. In order to

exploit this useful feature of the MR fluids and for effective implementation of its use as a

medium in various applications it is necessary to establish a database that will help in

understanding the fluid behavior under various conditions. Such a database will ensure better

design of devices like magneto rheological actuator system using MR fluids. The primary

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requirement for creating such a database is the preparation and characterization of MR fluids

by devising a reliable and reproducible method for measuring their viscosity under various

conditions including the application of a magnetic field.

1.4 THE PRESENT STUDY

In this work, a novel technique called the Mass and Pressure Detecting Capillary

Viscometer-(MPDCV) that is effective in characterizing the MR fluid is developed and

tested. The first cut results from the developed characterization system offers tremendous

scope for its use in MR fluid characterization. The ensuing chapters in this report that

describe the route adopted for such characterization of an MR fluid are organized as follows.

In Chapter 2, a review of existing literature is presented and the various techniques

adopted for measuring the viscosity of non-Newtonian fluid are analysed and their suitability

for characterization of an MR fluid examined. The reasons for the initial choice of MDCV

technique based on pressure driven mode together with the results of the initial attempt at

using the MDCV are presented, analysed in Chapter 3. It is shown in this chapter that the

MDCV technique is inadequate for a complete characterization of the MR fluid. In Chapter 4

the development of a novel technique (Mass and Pressure Detecting Capillary Viscometer-

MPDCV) that rectifies this fault and the fabrication of an apparatus based on this technique is

described. Results obtained by the use of this technique are presented in Chapter 5. The

results obtained are analyzed and are shown to be more reliable. The report ends with a

presentation of summary of the work and salient conclusions from the study in Chapter 6.

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CHAPTER 2

LITERATURE REVIEW

2.1 INTERACTION

The initial discovery and development of MR fluids and devices are to be attributed to

Jacob Rainbow at the US National Bureau of Standards in the late 1940s [1]. In spite of that,

real research efforts started only after 1991. While the commercial success of other smart

fluids remained elusive, MR fluids have performed better in that respect in recent times. A

number of MR fluids and various MR fluid- based systems have been commercialized

including an MR fluid brake for use in the exercise industry, a controllable MR fluid damper

for use in truck seat suspensions and an MR fluid shock absorber for oval track automobile

racing. The emphasis in the development of these devices has been more on the

characterization of the devices for various conditions of use rather than on the

characterization of the MR fluid used in these devices. A proper characterization of a MR

fluid has to take into account the operational modes of flow the fluid will be subjected to.

2.2 OPERATIONAL MODES

The two basic operational modes for MR fluid controllable devices are pressure driven

flow (PDF) and direct shear flow. Schematic diagrams illustrating these two basic

operational modes are shown in Fig. 2-1. Examples of pressure driven flow mode devices

include servo-valves, dampers and shock absorbers. Examples of direct-shear mode devices

include clutches, brakes, chucking and locking devices. A third mode of operation known as

squeeze-film mode has also been used in slow motion, high force applications (Jolly and

Carlson, 1996) [1].

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2.3 CHARACTERIZATION OF MR FLUID

MR fluid behaviour has been examined by a few research workers. Jolly et.al [1] have

reported measured viscosity values for a MR fluid. However, neither its composition nor the

mode in which the measurement has been carried out have been specified. Foister[3] obtained

values for the viscosity and yield strength of a MR fluid treating it as a non-Newtonian

Bingham plastic fluid. However, sufficient data related to the characterization of MR fluids

in both modes is not available in open literature.

2.4 MEASUREMENTS ON NON-NEWTONIAN FLUIDS

Studying non-Newtonian rheological properties is quite a challenge and many research

works are being carried out. The commercial rheometer to characterize non-Newtonian fluids

costs around Rs. 35 Lakhs. Further the rheometer has to be modified to incorporate magnetic

field which may be difficult. It is also available only in shear driven flow mode and not in

pressure driven mode. Some literature work suggests techniques for testing non-Newtonian

fluids in pressure driven flow mode. One such technique was proposed by Yamasaki and

Irvine[4] who developed a comparative capillary tube viscometer to measure the viscous

properties of Newtonian and Power-law fluids. The flow in this technique is achieved by

constant external pressure source. And we need to contact some many trails for getting the

shear stress in different strain rate. The flow in this technique is achieved by gravitational

Fig. 2-1 The two basic operational modes of MR Devices, (a) Pressure driven flow mode – flow occurs due to pressure difference, (b) Direct shear flow mode – flow occurs due to

relative motion between the plates [1]

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head. In order to get high strain rate, the pressure should be high which is difficult to achieve

in a gravity driven flow for high viscous fluids. Hence, it is difficult for this technique to be

implemented for Bingham and high viscous fluids. Another technique, mass-detecting

capillary viscometer (MDCV) was developed by Shin and Keum [5] for measuring viscosity

of non-Newtonian fluids for a wide range of viscosity and shear strain rate. However, the set

up has to under a major change even for one order variation in the magnitude of viscosity.

Besides, MDCV does not take care of sticking nature of MR fluid which can affect the

measuring of threshold pressure.

2.5 CONCLUSIONS FROM THE LITERATURE

The characterization of MR fluids is important for design and development of MR fluid

devices. Though the MR fluids can act in both the pressure driven flow mode and direct

shear flow mode, it is learnt from the literature that the characterization has been done

generally for the later mode. The behavior of MR fluids under pressure driven flow mode is

assumed to be the same as that of direct shear flow mode. However, there is no experimental

evidence to hold the above assumption. To the best of the knowledge of the author, the

expensive rheometers commercially available to characterize the behavior of non-Newtonian

fluids also measures only on direct shear flow mode.

2.6 OBJECTIVE OF PRESENT WORK

The objective, therefore, in this work is to prepare the magnetic rheological fluid with

different concentrations of micron sized Ferro-magnetic particles and to develop a simple

experimental setup to estimate and obtain the viscosity of MR fluids at different strain rates

under varying magnetic fields.

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2.7 SCOPE OF THE WORK

To this effect, the following is set as the scope of the work

Preparation of the MR fluid using mineral oil and carbonyl particles with various

mass fractions using white lithium based grease as surfactants.

Design, development and fabrication of a simple instrument (viscometer) for the

characterization of MR fluid in a pressure driven mode under varying magnetic fields.

Validation of the developed viscometer on a well known Newtonian fluid for a broad

range of shear strain rate and viscosity.

Obtaining shear strain rate vs. shear stress behavior of MR fluids experimentally for

various magnetic flux densities using the developed viscometer

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CHAPTER 3

PRELIMINARY WORK AND REVIEW

3.1 INTRODUCTION

This chapter deals with preparation of MR fluids and design and fabrication of MDCV

technique. This technique was used for measuring the behavior of well known fluids for a

wide range of shear strain rate. The comparison on the results shows that this technique

requires certain modifications to yield the correct results.

3.1 MR FLUID PREPARATION

Magneto-rheological fluid consists of micron-sized magnetically polarizable particles,

carrier fluid and surfactants.

3.1.1 Carrier Fluid

Carrier fluid can be a any low viscous liquid. If high viscous oil is used the prepared MR

fluid will be like grease without magnetic field. The following fluids are generally used as

carrier fluids for preparing the MR fluid.

Petroleum based oils

Silicone oils

Mineral oils

Synthetic hydrocarbon oils

Mineral oil is used in as carrier fluid in the study due to its various advantages. Mineral

oil or liquid petroleum is a by-product in the distillation of petroleum to produce gasoline and

other petroleum based products from crude oil. It has a density of around 0.8 g/cm3.[6] It is

low-toxic, non-reactive general purpose lubricant and coolant. In addition to that its price is

low and found in abundance. Hence, mineral oil is chosen as carrier fluid.

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3.1.2 Surfactant

In MF fluid Ferro-particles settle out of the suspension over time due to the inherent

density difference between the particles and their carrier fluid. The rate and degree to which

this occurs is one of the primary attributes considered in industry when implementing or

designing an MR device. Surfactants are typically used to offset this effect.

It is wetting agents that lower the surface tension of a liquid, allowing easier spreading,

and lower the interfacial tension between two liquids. Addition of a surfactant allows

micelles to form around the Ferro-particles. A micelle is an aggregate of surfactant

molecules. A surfactant has a polar head and non-polar tail (or vice versa), one of which

adsorbs to a particle, while the non-polar tail (or polar head) sticks out into the carrier

medium, forming an inverse or regular micelle, respectively, around the particle. This

increases the effective particle diameter.

Steric repulsion then prevents heavy agglomeration of the particles in their settled state,

which makes fluid remixing (particle redispersion) occur far faster and with less effort. For

example, magnetorheological dampers will remix within one cycle with a surfactant additive,

but are nearly impossible to remix without them. Surfactants are useful in prolonging the

Fig. 3-1 A micelle is an aggregate of particle and surfactant molecules that contain polar head and non-polar tail [6]

Non-Polar tail

Polar head

Carrier

medium

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settling rate in MR fluids. The generally used Surfactants for the preparation of MR fluid are

as follows.

Oleic acid

Tetramethylammonium hydroxide

citric acid

soy lecithin

white lithium based grease

3.1.3 Ferromagnetic Particles

Cobalt, Ferrite, Nickel, iron are ferromagnetic materials. Iron is one among very cheap

and fine particles can be easily produced by powdering it.

The various types of iron particles such as carbonyl iron, stainless steel flakes, hydrogen

reduced iron and magnetic iron oxide can be used for the preparation of MR fluid. Carbonyl

iron powder is the most popular choice for use in MR fluids

Carbonyl iron is a highly pure iron, prepared by chemical decomposition of purified iron

pentacarbonyl. It usually has the appearance of grey powder, composed of spherical

microparticles. Among the filler particles iron has one of the highest saturation magnetization

values of metallic elements with saturation magnetic field around 2.1Tesla. Permeability is a

material property that describes the ease with which a magnetic flux is established in a

component. And this permeability is large in iron. The magnetic induction that remains in a

material after removal of the magnetizing field is called remenant effect. This remenant effect

is low in the carbonyl iron particles. Due to high permeability and saturation magnetization

attraction between the filler particles will be large and thereby a high viscosity change is

possible. The need for low remanent magnetization is that the particles do not stick together

when the magnetic field is turned off. Therefore they will make the viscosity change

reversible which is a problem with highly remanent particles. Fig. 3.1 shows the SEM

12

micrographs of carbonyl iron particles taken from SEM FEI QUANTA 200. This shows that

approximately the particle size ranges from 2µm to 10µm with irregular shape.

3.1.4 Preparation Procedure

For the present work, micronsized magnetically polarizable Carbonyl iron particles are

considered. Mineral oil is used as a carrier fluid and lithium based Grease is used as a surface

acting agent. The amount of iron particles and the quantity of grease and oil to be mixed is

decided based on the desired properties of MR Fluid.

Fig. 3-3 Prepared MR fluid with different mass fractions

First, mix the grease and oil thoroughly. Mixing is most effectively accomplished with a

high-speed rotary mixer. Finally, add the iron powder to the oil and grease mixture. Start by

adding about half of the iron powder. You will need to use a stirring stick to get the dry iron

powder to mix with liquid. Once the mixture appears to be relatively uniform and no dry iron

Fig. 3-2 SEM micrographs of carbonyl iron powder which shows irregular shape of iron particles and the particle size is around 2- 10µm.

13

powder is visible, add the remainder of the iron powder and continue to stir. Continue to stir

with the stick until the mixture appears uniform without lumps. At this point you can

continue mix using the electric stirrer.

3.2 AN OVERVIEW EARLIER OF EXPERIMENTAL WORK

In order to measure the non-Newtonian behavior completely, its viscosity for various

shear strain rates can be obtained from relation between the shear stress and the shear strain

rate. The only possible way to achieve variable shear strain rate in a pressure driven flow

mode is by varying the pressure at source. This is achieved in MDCV. The set-up is

fabricated with the property ranges of MR fluid as constraints which is listed by Jolly et.al

and Foister (1997). [1] [2].

Density range (2700 Kg/m3 to 3500 Kg/m

3)

Viscosity range (.5 to 25 Ns/m2) or (5 to 250 Poise)

The effective magnetic field about 0.2 to 0.3 Tesla (N/m A)

Yield stress range (.5 to 1.5 k Pa).

The MDCV technique using capillary tube for viscosity measurements of both Newtonian

and non-Newtonian fluids over a range of shear rates was developed by Shin and Keum

(2003).[5]. The viscosity of any fluid at any instant can be found out by knowing the Flow

rate and pressure drop at that instant. In MDCV, the viscosity can be calculated just with a

measurement of liquid-mass variation with time. Using a precision balance, one can measure

the variation of fluid mass collected, m (t), from which the test fluid viscosity and shear rate

are mathematically calculated. The feasibility and accuracy of the mass-detecting technique

have been demonstrated for water and non-Newtonian fluids by comparing results against

established viscosity measurement techniques. The advantages of this design are simplicity

(i.e., ease of operation and no moving parts) low cost, and the ability to measure viscosity

14

over a relatively broad range of shear rates. The apparatus constructed based on the technique

is explained next section.

3.3 DESCRIPTION OF MDCV INSTRUMENT

Fig. 3-4 is a schematic diagram of a Mass Detection Capillary Viscometer, which consists

of a falling tube, capillary tube, receptacle, load cell, and computer data acquisition system.

The inside diameter of the falling tube was 9.05 mm. The inside diameter and length

of the capillary tube were 1.9 mm and 108.8 mm, respectively. The diameter and length

of the capillary tube were chosen to ensure that the friction loss in the capillary tube was

significantly greater than the loss in the other parts of the system (Cho et al.,1999) [7].

Energy losses at the end of a capillary are small due to fluid divergence in the original

technique and usually neglected but entrance losses can be very significant (Dervisoglu &

Kokini, 1986; Steffe, 1992) [8] [9]. In the fabricated set-up, the divergence portion is

removed but the exit losses and entrance losses were considered in the energy equation using

standard data available in Corvalis Forest Research Community [10]. This allows the easy

fabrication of set-up with a very little loss in accuracy.

In this setup, capillary end effects were accounted for during data reduction analysis by

adjusting the values of the length of the capillary tube. In addition, the capillary tube

dimensions were designed to finish one test with test fluid within few minutes.

15

Fig. 3-5 Experimental setup of MDCV

Fig. 3-4 Schematic diagram of a MDCV

16

The essential feature in a MDCV is the use of precision load cell to measure the fluid

collected in the receptacle for every 0.01 s with a resolution of 0.1 g. The instantaneous fluid

weights are recorded in a computer data file with an analog-to-digital data acquisition system

(National Instruments) with respect to time using Labview.

LabVIEW (Laboratory Virtual Instrumentation Engineering Workbench) is a platform

and development environment for a visual programming language from National Instruments

for data acquisition, instrument control, and industrial automation on a variety of platforms

including Microsoft Windows, various flavors of UNIX, Linux, and Mac OS.

Fig. 3-6 Front panel, acts as a user interface. The system response can be viewed online during experiment in chart window. This enables the user to check other uncertainties during experiments

17

Fig. 3-7 Block diagram of the virtual instrument. It shows the internal circuitry of the elements used in the experiment. It helps to add necessary elements to filter the noise so that actual data is obtained without any external disturbances.

Fig. 3-6 & Fig. 3-7 shows the front panel and block diagram of the virtual instrument

programmed using LabVIEW which is used to do the data acquisition. Various filters such as

DC filter, high pass filter, low pass filter, band pass filter, and band stop filter were studied in

order to remove the noise from the load cell. From this study the DC filter is chosen such that

the noise is less compare to the other filters.

18

3.4 MDCV TESTING PROCEDURE

Typical tests are conducted as follows: First, fill up the test fluid in the falling tube so that

the initial height of the fluid in the falling tube reaches a preset position. Once this condition

is achieved, start the test. At time t = 0, the data acquisition system is enabled and the falling

tube is opened to atmosphere, allowing the fluid to flow through the capillary and to be

collected in the receptacle as driven by the gravity head. When the fluid level in the falling

tube approaches the bottom of the falling tube, the test fluid stops flowing. Typically, it took

~1 min for the fluid level in the falling tube to reach an asymptote with water. The time to

complete a run should vary depending on type of liquid and size of the falling and capillary

tubes. If a larger-diameter falling tube is used, a longer run time is required. Nonetheless,

using a falling tube with a larger diameter resulted in more accurate data.

3.4 MDCV FORMULATION

The fluid mass data from the receptacle were analyzed in the following way to determine

the viscosity of Newtonian and non-Newtonian fluids. The mathematical equation of the flow

analysis began with the equation of the conservation of energy between cylinder and the

capillary exit. Assuming a quasi-steady flow behavior, one may write the governing

equations as follows

(1)

where is the static pressure, is the density of the test fluid, is the fluid velocity, is

the acceleration due to gravity, is the fluid level, is the pressure drop across the

19

capillary tube, is the pressure drop occurring at the entrance and exit of the capillary tube

and the subscripts 1 and 2 are at the falling tube and capillary tube exit, respectively. The

third term on the right hand side of Eq. (1) represents the residue height of the falling tube at

due to the surface tension effect.

With this experimental set-up, the pressure drop ( ) caused by secondary flow patterns

or eddies in the entrance and exit of the capillary tube may appear to be significant in a high

shear zone. One of the most accurate methods for determining is to make a Bagley plot

with at least two short capillaries of the same diameter (Middleman, 1968; Macosko, 1993)

[12] [11]. It turned out that the contribution from the second term on the right hand side of

Eq. (1) is negligibly small for relatively low viscosity fluids. However, the entrance effect

must be considered and corrected for viscosity measurements for relatively high viscosity

fluids. The detail correction method for the entrance effect can be found elsewhere (Steffe,

1992) [9]. Furthermore, effects of wall slip should be considered and corrected in viscosity

measurement of particle suspensions (Kokini & Dervisoglu, 1990; Adhikari & Jindal, 2001)

[14] [13]. This effect can be particularly important for highly concentrated suspensions and

higher shear rate measurements. However, for low concentrated suspensions and low shear

rate measurements including the present measurement, the slip effect can be assumed as

negligibly small (Macosko, 1993) [11].

In the fabricated set up the capillary end is left free for the reason mentioned in section

3.2. Hence the exit losses and entrance losses were considered in the energy equation using

20

standard datas available in Corvalis Forest Research Community [10]. This loss is expressed

as the velocity head reduced by a factor known as the entrance and exit head loss coefficient.

The summation of both the losses is considered in energy equation as Ke. The entrance loss

coefficient is chosen based on the nature of projected end of the tube which is square cut in

our case. The corresponding value for projected square end is 0.5 and the exit loss coefficient

is 1. The summation of the coefficient (Ke) is 1.5.

(2)

Since (static ambient pressure), and , Eq. (1) can be simplified as

where is the initial fluid level at , is the final fluid level at and

is the fluid level difference between and . In addition, Eq. (3) can be expressed as a

function of fluid mass collected in the receptacle as follows:

(4)

= (3)

21

where is the fluid mass at and is the fluid mass at . It is of note that

the volume flow rate is proportional to the rate of change of the mass of the fluid collected on

the load cell. Hence, the corresponding flow rate in the capillary tube can be expressed as

The shear rate dependent viscosity for a non-Newtonian fluid flowing in the capillary

tube is obtained from experimental data with some mathematical treatment; the necessary

equations can be found in any standard handbooks (Macosko, 1993) [11].

The shear rate at the capillary tube wall is obtained from the classic Weissenberg–

Rabinowitsch equation (Macosko, 1993) [11],

(6)

where is the apparent or Newtonian shear rate at the wall.

(7)

The shear stress at the wall is given by

(8)

(5)

22

Thus, the viscosity corresponding to the wall shear rate is calculated in the form of a

generalised Newtonian viscosity:

(9)

(10)

If there is enough data near the point of interest, it is possible to evaluate the

derivative , where n is simply the exponent of the power-law constitutive equation.

The typical number of data points in a MPDCV is about 10,000 over a range of shear rates.

Even though the power-law exponent is used in the above equations, this does not limit

the capability of the present measurement for power-law fluids. This rigorous approach can

still be taken to obtain a viscosity versus shear rate relationship for any fluid (Macosko, 1993)

[11]. Thus, Eq. (10) can be described in terms of the mass measured in the MDCV as follows:

(11)

23

The viscosity versus shear rate information can be obtained from Eqs. (4) to (12) by

measuring the mass of the collected fluid with respect to time, from which flow rate can be

calculated. The values of and must be obtained by calibration.

24

3.5 MDCV RESULT REVIEW

In order to implement the MDCV technique for finding viscosity of MR fluid, initial

experiments were conducted with water and mineral oil to know the advantages and

limitations of the technique. It is well known that the viscosity range of MR fluid is wide. In

order to know the limitations of the technique for wide ranges two fluids of viscosity of

different order of magnitude can be used for experiments. Water and Mineral oil was chosen

based on this criteria. The results for water and mineral oil are discussed below.

The only data to be measured from the experimenmt is mass collected in the basin. The

mass collected as a function of time is shown in Fig. 3-8. The collected data cannot be used

directly to calculate the massflow rate due to the effect of noise. The mass flow rate can be

calculated by calculating the derivative of the mass vs time data. The presence of even less

noise amplifies the error while calculating derivative. Hence derivative is claculated after

curve fitting. The Mass flow rate calculated from the curve fitted data is shown in Fig. 3-9.

The pressure Vs time obtained from the curve fitted data is shown in Fig. 3-10. The mass

flow rate and the Pressure is used to calculate the shear strain rate and shear stress as

explained in section. The obtained shear strain rate and shear stress data is plotted in Fig.

3-11.

Many things can be concluded from the results obtained. First, compare the mass

collected vs time plot for water and mineral oil. It was observed that curve fitting is difficult

for water whereas it was much more accurate for mineral oil. It tends to conclude that the

setup can be more accurate for viscosity of order of 0.01Nsm-2. Now, compare the shear

strain rate vs shear stress plot for both fluids. The same is reflected in terms of accuracy i.e.

mineral oil plots look exactly linear whereas the plot for water shows more irregularities.

Also observe that the range of shear strain rate obtained for water is of the order of 1000

whereas the one obtained for mineral oils is of the order of 100s. In order to perform

25

experiments on MR fluid we need to test not only for the varying order of viscosity but also

for wide range of shear strain rates. In order to achieve both throught the setup, falling tube

and capillary tube arrangements of various dimension range should be used. This asks for

falling tube of more than 1m in order to test high viscous fluids in high shear strain rates.

This is tedious, impractical and unnecessary. Hence a new technique is formulated

incorporating both the needs.

26

Fig. 3-8 Plot of Time Vs Mass for Water by MDCV

Fig. 3-9 Plot of Time Vs Mass flow rate for Water by MDCV

27

Fig. 3-10 Plot of Time Vs Pressure for Water by MDCV

Fig. 3-11 Plot of Shear strain rate Vs Shear stress for Water by MDCV

28

Fig. 3-12 Plot of Time Vs Mass for Mineral oil by MDCV

Fig. 3-13 Plot of Time Vs Mass flow rate for Mineral oil by MDCV

29

Fig. 3-14 Plot of Time Vs Pressure for Mineral oil by MDCV

Fig. 3-15 Plot of Shear strain rate Vs Shear stress for Mineral oil by MDCV

30

CHAPTER 4

MASS AND PRESSURE –DETECTING CAPILLARY

VISCOMETER (MPDCV)

To perform experiments on MR fluid with the varying order of viscosity and also for

wide range of shear strain rates the MDCV setup is modified. The falling tube is replaced by

spring, piston and cylinder arrangment for testing the high viscous fluids in high shear strain

rates. This alleviates the problem of using a tall falling tube and in achieving a compact

setup. The pressure sensor is used for measuring the pressure in the cylinder. The mass

collected in the basin with respect to time is measured as similar as done in MDCV. This

setup will, henceforth, be called mass and pressure detecting capillary viscometer (MPDCV).

In this chapter, the development of the MPDCV instrument is first described before

evolving at a test procedure to test the MR fluids.

4.1 DESCRIPTION OF THE INSTRUMENT

Fig. 4.1 is a schematic diagram of a Mass and Pressure Detection Capillary Viscometer,

which consists of a piston cylinder arrangement, compression spring, and capillary tube, glass

adapter, receptacle, load cell and computer data acquisition system. The inside diameter of

the piston cylinder is 30 mm. Two different capillary tubes are used to cater to the wide range

of strain rates: one capillary tube has inside diameter and length of 1.8mm and 132.2mm

respectively while the other has 3 mm and 105 mm, respectively. Fig. 4-2 shows a

photograph of the viscometer.

The required magnetic field is applied using variable magnetic flux density DC

electromagnet device. The variable magnetic field is achieved by controlling the current

supply to the variable DC source provided. The applied magnetic field is measured using a

Gauss meter.

31

The capillary tube, piston cylinder arrangement, compression spring dimensions are

designed so that the test could be carried out within a few minutes. The essential feature of

the MPDCV is the use of precision mass balance to measure the fluid collected in the

receptacle and the introduction of the pressure sensor to measure the cylinder pressure every

0.01seconds with a resolution of 0.1grams and 0.01kPa respectively. The instantaneous fluid

weights and pressure are recorded in a computer data file using an analog-to-digital data

acquisition system (National Instruments) with respect to time using Labview software.

Fig. 4-1 Schematic diagram of the MPDCV. As can be seen, the tall falling tube in MDCV is dispensed with and replaced by a simple cylinder with a pressure gauge attached to it. The load cell measures the weight of the liquid collected. The spring is used for applying the force to the piston to generate the required pressure.

32

Fig. 4-2 MPDCV Experimental Setup with Data accusation system

Fig. 4-3 Variable Magnetic field DC Magnet power Supply controller and Magnetic flux density Measurement (Gauss Meter)

33

4.2 TESTING PROCEDURE

Typical tests are conducted as follows: The piston cylinder arrangement sucks up the test

fluid from the reservoir when piston is lifted up. The lead screw lever attached to the spring

rod which in-turn connected to the piston is rotated to lift the piston. This also compresses the

spring in the spring rod. The spring rod is held in a position by the use of a dog clutch. The

dog clutch is released to apply the load on the piston by the released compression spring. At

time t =0, the data acquisition system is enabled and cylinder inlet is closed, the capillary tube

exit is opened to atmosphere, allowing the fluid to flow through the capillary and to be

collected in the receptacle as driven by the compression spring . When the piston in the

cylinder approaches the bottom of the cylinder, the test fluid stops flowing. Typically, it took

few min for the piston in the cylinder to reach an asymptote. The time to complete a run

should vary depending on type of liquid and size of the cylinder and capillary tubes. If a

larger-diameter the cylinder is used, a longer run time is required. Fig. 4.3 shows the

variable magnetic field DC magnet power Supply controller and the magnetic flux density

measurement meter – the Gauss meter. The entire setup with the DC magnet is shown in Fig.

4.4.

34

Fig. 4-4 MPDCV Experimental Setup with DC Magnet

35

4.3 THE FORMULATION

The mathematical model of the flow analysis began with the equation of the conservation

of energy between cylinder (1) and the capillary exit (2). Assuming a quasi-steady flow

behavior, one may write the governing equation as follows

(12)

The assumptions for wall slip effect, entrance and exit loss are similar to that followed in

MDCV as explained in Chapter 3. In the fabricated set up the capillary end is left free similar

to MDCV. The value for projected square end is 0.5 and the exit loss coefficient is 1. The

summation of the coefficient (Ke) is 1.5.

Since cylinder and static ambient pressure), and , Eq. (12) can be

simplified as Eq. (1) can be simplified as

(13)

is equal to the pressure measured in pressure sensor in the experiment. It is of

note that the volume flow rate is proportional to the rate of change of the mass of the fluid

collected on the load cell. Hence, the corresponding flow rate in the capillary tube can be

expressed as

The shear rate dependent viscosity for a non-Newtonian fluid flowing in the capillary

tube is obtained from experimental data with some mathematical treatment; the necessary

equations can be found in any standard handbooks.

(14)

36

The shear rate at the capillary tube wall is obtained from the classic Weissenberg–

Rabinowitsch equation (James F. Steffe ,1996) [19] ,

(15)

where is the apparent or Newtonian shear rate at the wall.

(16)

The shear stress at the wall is given by

(17)

Thus, the viscosity corresponding to the wall shear rate is calculated in the form of a

generalised Newtonian viscosity:

(18)

(19)

The viscosity versus shear rate information can be obtained from Eqs. (13) to (19) by

measuring the pressure and mass of the collected fluid with respect to time, from which flow

37

rate and pressure drop in capillary can be calculated. The values of and must be

obtained by calibration.

In MPDCV, the relation between the apparent shear strain rate and shear stress behavior

need not be modeled as in the case of MDCV. The actual (non-Newtonian) shear strain rate

can be obtained directly using the Weissenberg–Rabinowitsch equation (15).

38

CHAPTER 5

RESULTS AND DISCUSSION

5.1 TEST RESULT FOR REFERENCE FLUIDS

In order to verify the MPDCV technique for finding viscosity of MR fluid, initial

experiments were conducted with water and mineral oil to know the advantages and

limitations of the technique. Water and Mineral oil was chosen based on the criteria that

fluids of varoius order of magnitude of viscosity should be tested. The results for water and

mineral oil are discussed below.

The data to be measured from the experimenmt is mass collected in the basin and the

pressure inside the piston cylinder. The mass collected as a function of time is hown in Fig.

5-1. The collected data cannot be used directly to calculate the massflow rate due to the effect

of noise. The mass flow rate can be calculated by calculating the derivative of the mass vs

time data. The presence of even less noise amplifies the error while calculating derivative.

Hence derivative is claculated after curve fitting. The Mass flow rate calculated from the

curve fitted data is shown in Fig. The pressure Vs time obtained from the experiment is curve

fitted data to minimise the effect of noise. The original and curve fitted data is shown in Fig.

5-3. The mass flow rate and the Pressure is used to calculate the shear strain rate and shear

stress as explained in section 4.4. The obtained shear strain rate and shear stress data is

plotted in Fig. 5-4.

Many things can be concluded from the results obtained. First, compare the mass

collected vs time plot for water and mineral oil shown in Fig. 5-1 & Fig. 5-5. Many analysis

on curve fitting was carrie out and it was found that exponential and polynomial fit was found

to be more accurate. The same is seen in shear strain rate vs shear stress plot shown in Fig.

5-4& Fig. 5-8. Now apart from the accuracy of the curve fitting also observe the range of

39

shear strain rate in Fig. 5-4& Fig. 5-8. The range of shear strain rate that can be obtained in

this technique for mineral oil was 12000 when compared to 700 in MDCV as shown in Fig.

3-15. Hence huge range of strain rate can be achieved in this technique without loss of

accuracy. Initial comparison of strain rate vs shear stress plot for water in Fig. 5-4 & Fig.

3-11 for MPDCV & MDCV respectively tends to conclude that vast range of strain rate may

not be obtained for lower viscous fluids in MPDCV as strain rate obtained in the MPDCV

was only 2500 whereas it was 7000 for MDCV. It is to be noted here that this less range is

only due to the constraint in the spring used rather than in the technique. If the stiffness of the

spring in the set-up was varied then more strain rate than it could be imagined could have

been obtained. It was not attempted only due to the lack of time and certain facilities.

Hence, it is now proved that the technique is quite accurate for vast range of shear rates as

well as for various order of magnitude of viscosity. Therefore, experiments were conducted

in this technique for MRF.

40

Fig. 5-1 Plot of Time Vs Mass for Water by MPDCV

Fig. 5-2 Plot of Time Vs Mass flow rate for Water by MPDCV

41

Fig. 5-3 Plot of Time Vs Pressure for Water by MPDCV

Fig. 5-4 Plot of Shear strain rate Vs Shear stress for Water by MPDCV

42

Fig. 5-5 Plot of Time Vs Mass for Mineral oil by MPDCV

Fig. 5-6 Plot of Time Vs Mass flow rate for Mineral oil by MPDCV

43

Fig. 5-7 Plot of Time Vs Pressure for Mineral oil by MPDCV

Fig. 5-8 Plot of Shear strain rate Vs Shear stress for Mineral oil by MPDCV

44

Fig. 5-9 Plot of Shear strain rate Vs Shear stress for corn flour with water by MPDCV

Corn flour with water colloidal is chosen for validating MPDCV for measuring non

Newtonian behavior. First, apparent shear strain rate and shear stress is calculated from basic

equations. Then, using Weissenberg–Rabinowitsch equation, actual (non Newtonian) shear

strain rate is calculated with and without using power law model. The obtained shear strain

rate and shear stress data is plotted in Fig. 5-9.In this Fig. 5-9 the power law model is

perfectly fitted in experimental data. The actual (non Newtonian) shear strain rate vs. shear

stress curve for with and without using power law model are similar.

45

5.2 TEST Result for MR Fluids

The experiments for MRF were conducted in two phases. In the first phase, shear stress

vs. shear strain plot was obtained without applying magnetic field. In the second phase, the

same was obtained with the application of magnetic field. The procedure is same as followed

for water and mineral oil. The shear stress vs. shear strain plot obtained in the experiment for

various magnetic flux density is shown in . The nature of variation of threshold pressure with

magnetic field is shown in Fig. 5-15.

The nature of variation of viscosity with magnetic field can be obtained from the slope of

the curve in Fig. 5-14. The magnetic field applied for experiment is 0, 100, 200, 300 & 400

Gauss. The behaviour of MRF with magnetic field, as reported in the literature, is non-

Newtonian. It can be seen that the shear stress vs. shear strain plot shown in Fig. 5-13 is

almost linear. The much acclaimed non-Newtonian behavior is not obtained in the range in

which the experiment is conducted. But, if the behavior is observed only in very low strain

rates (0-250) then the plot is non linear.

Further, it can be seen that there is no threshold pressure when no magnetic field is

applied. The threshold pressure is slightly increased at 100 Gauss. Though the plot is linear it

intersects with that of 0 Gauss. It shows that the viscosity is decreased at 100 gauss than at 0

Gauss. The plot for 200 Gauss is almost parallel to that 0 Gauss with a high threshold

pressure. The plot for 300 Gauss and 400 Gauss are having high slopes and the slope is

increasing with increase in magnetic flux density. Thus, it can be concluded that viscosity is

increasing with increase in magnetic field. The variation of threshold pressure with magnetic

field is shown in Fig. 5-15 . It can be seen that till 100 Gauss there not much increase in

threshold pressure whereas after that the increase is steady and linear. It is also visible in

shear strain rate vs shear stress plot shown in Fig. 5-14.

46

Fig. 5-10 Plot of Time Vs Mass for MRF by MPDCV

Fig. 5-11 Plot of Time Vs Mass flow rate for MRF by MPDCV

47

Fig. 5-12 Plot of Time Vs Pressure for MRF by MPDCV

Fig. 5-13 Plot of Shear strain rate Vs Shear stress for MRF by MPDCV

48

Fig. 5-14 Plot of Shear strain rate Vs Shear stress for MRF under different Magnetic flux density by MPDCV

Fig. 5-15 Plot of Magnetic flux density Vs Threshold Pressure for MRF by MPDCV

49

CHAPTER 6

CONCLUSIONS AND FUTURE WORK

6.1 SUMMARY AND CONCLUSIONS

A literature review on the existing techniques for characterization of MR fluids was done.

From the literature, it was found that the experimental set up presently available are based on

direct shear flow mode. It was also learnt that no experimental set up is available for

measuring the viscosity of MR fluids under pressure driven flow mode. With that being the

motivation, an attempt was made to design and develop an instrument with a simple

technique for the same purpose. In that direction, initially one existing non-Newtonian fluid

measuring technique (MDCV) was fabricated and used to measure the response of standard

fluids. During the validation process, many difficulties were realized with MDCV. One such

difficulty is the requirement to modify the set up for variation in the viscosity of the

measuring fluid. Another difficulty experienced was the inefficiency of MDCV in measuring

the threshold pressure due to sticking nature of MR fluid.

To overcome those difficulties, a new technique named “Mass and Pressure Detecting

Capillary Viscometer” (MPDCV) was proposed in this work. The developed instrument was

first tested with a well known fluid to obtain the relationship between shear strain rate and

shear stress for a wide range of shear strain rate under pressure driven flow mode. The

obtained experimental results using the new instrument were well comparable with standard

results. Gaining confidence out of this, the instrument was then used for measuring the

response of MR fluids under pressure driven mode for a various magnetic flux densities. MR

fluids with various mass fractions using lithium based grease as surfactants was prepared and

used for validation of the proposed technique. Wide range of shear strain rates was achieved

for various magnitude of viscosity of MR fluids with the proposed MPDCV. Actual data

50

obtained from the experiments was curve fitted with high accuracy for further understanding

and improvement of the technique. The threshold pressure of the fluid was only marginal till

100 Gauss whereas it increases steadily after that. With varying magnetic field, the viscosity

was also found to be increasing. The reason for the observed Newtonian behavior of MR

fluid is also explained. From the above results, it is opined here that the proposed technique

may be attempted for any non-Newtonian fluid.

6.2 FUTURE WORK

It is to be noted that the experiment was not conducted for higher magnetic fields due to

the limitations in the existing facilities. Hence, an attempt can be made to perform the

experiments discussed in this work for higher magnetic fields to estimate the capability of the

proposed technique. The experiment can also be conducted for various proportions and

shapes of Ferro-magnetic particles in MR fluids. Since the proposed technique is not limited

to MR fluid alone, it can be tested for any other non-Newtonian fluids.

51

REFERENCES

1. Mark R. Jolly, Jonathan W. Bender, and J. David Carlson ”Properties and Applications of

Commercial Magnetorheological Fluids” Thomas Lord Research Center, Lord Corporation

2. Cvbbgkn df J.C. Ulicny, D. J. Klingenberg, D. Kittipoomwong, M. A. Golden, A. L. Smith, C.S.

Namuduri and Z.Sun, (2008) “Modeling of MR Fluids and Devices,” eds. S.M.Sivakumar, V.

Buravalla and A.R.Srinivasa, Smart Devices: Modeling of Material Systems, Amer. Inst. of Physics, CP

1029, pp. 127-139.

3. Foister,R.T.,(1997),”Magnetorheological Fluids,” US Patent 5,667,715

4. Tadao Yamasaki,Thomas F. Irvine (1990) “A Comparative Capillary Tube Viscometer to Measure

the Viscous Properties of Newtonian and Power-Law Fluids” Experimental Thermal and Fluid Science

1990; 3:458-462

5. Sehyun Shin and Do-Young Keum (2003 )„Viscosity measurement of non-Newtonian fluid foods with

a mass-detecting capillary viscometer‟ Journal of Food Engineering, 58, pp.5–10.

6. http://www.wikipedia.org/

7. Cho, Y. I., Kim, W. T., & Kensey, K. R. (1999). “A new scanning capillary tube viscometer”. Review

of Scientific Instruments, 70(5), 2421–2423.

8. C Dervisoglu, M., & Kokini, J. L. (1986). “Steady shear rheology and fluid mechanics of four semi-

solid foods”. Journal of Food Science, 51(3), 541–546, 625.

9. D Steffe, J. F. (1992).” Rheological methods in food process engineering”. Michigan: Freeman Press.

10. http://www.fsl.orst.edu/geowater/FX3/help/7_Culvert_Basics/Entrance_Loss_Coefficient.htm as on 04-

11-2008

11. G Macosko,C.W.(1993). “Rheology principles measurements andapplications”. New

York:VCH(Chapter 6).

12. Middleman, S. (1968). “The flow of high polymers”. New York: Interscience.

13. Adhikari, B., & Jindal, V. K. (2001). “Fluid flow of characterization with tube viscometer data”.

Journal of Food Engineering, 50, 229–234,

52

14. Kokini, J. L., & Dervisoglu, M. (1990). “Wall effects in the laminar pipe flow of four semi-solid

foods”. Journal of Food Engineering, 11(1), 29–42.

15. http://home.fnal.gov/~randy/tech_specs.html as on 29.03.09

16. Sung Taek Lim, Min Seong Cho, In Bae Jang, Hyoung Jin Choi (2004) “Magnetorheological

characterization of carbonyl iron based suspension stabilized by fumed silica” Journal of Magnetism

and Magnetic Materials 282, 170–173.

17. A. Roszkowski, M. Bogdan, W. Skoczynski1, B. Marek (2008)” Testing Viscosity of MR Fluid in

Magnetic Field” Measurement Science Review, Volume 8, Section 3, No.3.

18. Fernando D. Goncalves, Jeong-Hoi Koo and Mehdi Ahmadian (2006 )“A review of the state of the

Art in Magnetorheological Fluid Technologies-Part I: MR fluid and MR fluid models ” The Shock and

Vibration Digest,Vol.38,No.3.

19. James F. Steffe (1996) “Rheological processes in food process engineering” Book.

53

APPENDIX

1 MATLAB CODE

For MDCV Viscometer

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% For Mineral Oil

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

load Sheet1.txt

t=Sheet1(:,1);

x=Sheet1(:,2);

cftool;

dn=840;

dc=0.0019;

Lc=0.1088;

df=0.00905;

%Using cftool find out best fit for mass vs. time plot

%Using fitted mass date find out mass flow rate(mdt1) and pressure(pr1)

%Give final mass(mif)

mif=------;

pr1=(4*9.81/(3.1416*df^2))*(mif-m);

sr=(32*mdt1/(dn*3.1415*dc^3));

st=((pr1-(1.5*dn*(sr*dc/8).^2/2))*dc/(4*Lc));

plot (sr,st);

54

% Plot of Time Vs Mass

plot (t,x);

hold on;

plot (t,m,'r');

% xlim([0 10]);

ylim([0 .02]);

xlabel('Time in sec');

ylabel('Mass in Kg');

title('Plot of Time Vs Mass');

h = legend('act','exp fit',2);

grid on;

saveas(gcf,'Plot of Time Vs Mass.tif')

hold off

% Plot of Time Vs Mass flow rate

plot (t,mdt1);

% ylim([0 .02]);

xlabel('Time in sec');

ylabel('Mass flow rate in Kg/sec');

title('Plot of Time Vs Mass flow rate');

grid on;

saveas(gcf,'Plot of Time Vs Mass flow rate.tif')

hold off

% Plot of Time Vs Pressure

55

plot (t,pr1);

% xlim([0 10]);

ylim([0 3000]);

xlabel('Time in sec');

ylabel('Pressure in Pa');

title('Plot of Time Vs Pressure');

% h = legend('act','exp fit',2);

grid on;

saveas(gcf,'Plot of Time Vs Pressure.tif')

hold off

%Plot of Shear strain rate Vs Shear stress

plot (sr,st);

hold on;

plot (srsst(:,1),srsst(:,2),'r');

% xlim([0 10]);

ylim([0 10]);

xlabel('Shear strain rate in 1/s');

ylabel('Shear stress in Pa');

title('Plot of Shear strain rate Vs Shear stress');

h = legend('act','lin fit',2);

grid on;

saveas(gcf,'Plot of Shear strain rate Vs Shear stress.tif')

56

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% For Water

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

load Sheet1.txt

t=Sheet1(:,1);

x=Sheet1(:,2);

cftool;

dn=1000;

dc=0.0019;

Lc=0.1088;

df=0.00905;

%Using cftool find out best fit for mass vs. time plot

%Using fitted mass date find out mass flow rate(mdt1) and pressure(pr1)

%Give final mass(mif)

mif=-------;

pr1=(4*9.81/(3.1416*df^2))*(mif-m);

sr=(32*mdt1/(dn*3.1415*dc^3));

st=((pr1-(1.5*dn*(sr*dc/8).^2/2))*dc/(4*Lc));

57

For MPDCV Viscometer

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% For MR fluid

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

clear all;

clc;

Sheet1=1;

m=1;

mdt1=1;

pr1=1;

srsst=1;

dsrsst=1;

load Sheet1.txt;

t=Sheet1(:,1);

x=Sheet1(:,2)/1000;

y=Sheet1(:,3)*1000;

cftool;

%Using cftool find out best fit for mass vs. time and pressure vs. time plot

%Using fitted mass and pressure(pr1)date find out mass flow rate(mdt1)

%Give final mass(mif)

dn=1400;

dc=0.0018;

Lc=0.1322;

sr=(32*mdt1/(dn*3.1415*dc^3));

st=((pr1-(1.5*dn*(sr*dc/8).^2/2))*dc/(4*Lc));

plot (sr,st);

srn=(0.75+0.25*(dsrsst(:,1)./dsrsst(:,2))).*sr;

58

2 CURVE FITTING RESULTS

MDCV

MO 09-17-2008 test 03

Linear model Poly1:

f(x) = p1*x + p2

Coefficients (with 95% confidence bounds):

p1 = 0.01362 (0.01361, 0.01363)

p2 = -0.197 (-0.1994, -0.1946)

Goodness of fit:

SSE: 1.59

R-square: 0.9999

Adjusted R-square: 0.9999

RMSE: 0.03333

MO 09-17-2008 test 06

Linear model Poly1:

f(x) = p1*x + p2

Coefficients (with 95% confidence bounds):

p1 = 0.01362 (0.0136, 0.01364)

p2 = -0.3106 (-0.3164, -0.3048)

Goodness of fit:

SSE: 8.134

R-square: 0.9993

Adjusted R-square: 0.9993

RMSE: 0.07722

59

wat 09-10-08 test 01

Linear model Poly1:

f(x) = p1*x + p2

Coefficients (with 95% confidence bounds):

p1 = 0.001283 (0.001267, 0.001299)

p2 = -0.2267 (-0.2704, -0.1829)

Goodness of fit:

SSE: 4.457

R-square: 0.9941

Adjusted R-square: 0.9941

RMSE: 0.173

wat unknown test 03wf

Linear model Poly1:

f(x) = p1*x + p2

Coefficients (with 95% confidence bounds):

p1 = 0.001162 (0.001142, 0.001183)

p2 = -0.1026 (-0.158, -0.04726)

Goodness of fit:

SSE: 7.526

R-square: 0.9883

Adjusted R-square: 0.9882

RMSE: 0.2247

60

MPDCV

water 01 03-13-09 tr 4

Linear model Poly1:

f(x) = p1*x + p2

Coefficients (with 95% confidence bounds):

p1 = 0.001041 (0.001039, 0.001043)

p2 = 0.08132 (0.07845, 0.08419)

Goodness of fit:

SSE: 0.1864

R-square: 0.9993

Adjusted R-square: 0.9993

RMSE: 0.01585

MO 03-09-09 tr 03

Linear model Poly1:

f(x) = p1*x + p2

Coefficients (with 95% confidence bounds):

p1 = 0.01724 (0.01715, 0.01733)

p2 = -0.4407 (-0.579, -0.3025)

Goodness of fit:

SSE: 1716

R-square: 0.9952

Adjusted R-square: 0.9952

RMSE: 1.623

61

MO 04-30-09 tr 04

Linear model Poly1:

f(x) = p1*x + p2

Coefficients (with 95% confidence bounds):

p1 = 0.01672 (0.01668, 0.01677)

p2 = -0.1066 (-0.2073, -0.005891)

Goodness of fit:

SSE: 1249

R-square: 0.9987

Adjusted R-square: 0.9987

RMSE: 1.287

cowt 05-22-09 tr 02

General model Power2:

f(x) = a*x^b+c

Coefficients (with 95% confidence bounds):

a = 0.001565 (0.001531, 0.001599)

b = 1.343 (1.34, 1.345)

c = 0.9119 (0.89, 0.9337)

Goodness of fit:

SSE: 58.83

R-square: 0.9998

Adjusted R-square: 0.9998

RMSE: 0.2458

62

MRF 05-03-09 tr 09

Linear model Poly1:

f(x) = p1*x + p2

Coefficients (with 95% confidence bounds):

p1 = 0.03973 (0.03963, 0.03983)

p2 = 8.824 (8.723, 8.925)

Goodness of fit:

SSE: 6378

R-square: 0.9972

Adjusted R-square: 0.9972

RMSE: 1.944

3 VISCOSITY TABLE:

Fluid Trail

Viscosity in Ns/m2

MDCV MPDCV

Water

1 0.001283 0.001041

2 0.001162 ----------

Mineral oil

1 0.01362 0.01724

2 0.01362 0.01672

MR Fluide 1 ----------- 0.03973