EXPERIMENTAL INVESTIGATIONS AND MODELING

OF BALL END MAGNETORHEOLOGICAL

FINISHING PROCESS

by

ANANT KUMAR SINGH

Submitted

in fulfillment of the requirements of the degree of

DOCTOR OF PHILOSOPHY

to the

DEPARTMENT OF MECHANICAL ENGINEERING

INDIAN INSTITUTE OF TECHNOLOGY DELHI

NEW DELHI – 110 016, INDIA

JANUARY 2013

Dedicated

To

“May almighty illuminate our intellect to the righteous path”

“Param Pujya Gurudev Pandit Sriram Sharma

Acharya a pioneer of spiritual renaissance

and Vandaniya Mata ji Bhagwati Devi

Sharma”

All World Gayatri Pariwar

Shantikunj, Haridwar

“When we reform ourselves the world will be reformed When we transform ourselves the world will be transformed”

"Self-refinement is the best service of the society"

i

CERTIFICATE

This is to certify that the thesis entitled, “Experimental Investigations and

Modeling of Ball End Magnetorheological Finishing Process” submitted by Mr. Anant

Kumar Singh to the Indian Institute of Technology Delhi, for the award of the degree of

Doctor of Philosophy, is a record of the original bonafide research work carried out by him

under my guidance and supervision. The results contained in it have not been submitted in

part or full to any other institute or university for the award of any degree or diploma.

Department of Mechanical Engineering

Indian Institute of Technology Delhi

New Delhi – 110 016, India

Dr. Pulak M. Pandey

Associate Professor

Dr. Sunil Jha

Associate Professor

ii

ACKNOWLEDGEMENTS

I am highly grateful to “Param Pujya Gurudev Pandit Sriram Sharma Acharya a pioneer of

spiritual renaissance and Vandaniya Mata ji Bhagwati Devi Sharma” Shantikunj, Haridwar

who gave me greatest opportunity in life as a research scholar to contribute some novel

research towards the global knowledgebase. Their blessing in all difficult moments during

my doctoral program enlightened my thinking and motivated to complete this work more

efficiently on righteous path.

Foremost, I express my deep sense of gratitude and sincere thanks to my thesis supervisors

Dr. Sunil Jha and Dr. P.M. Pandey for their excellent guidance, constant encouragement and

optimistic outlook. These have been constant source of motivation for me throughout this

work. Their expert guidance, constructive criticism and inspiring advices on the subject

enabled me to think in different dimensions of research and realize the value of hard work

and investigating approach. I am now able to see the wisdom in their ways. I thank them both

very much for their guidance and support which I got past four years during my research

work. The technical and personal lessons that I have learned by working under them are now

base supports for the rest of my life.

During the past four years I have learned a lot about motion controller, pneumatic circuits

design, electro pneumatic and PLC for automation in manufacturing during teaching

assistantship as well as more about magnetorheological finishing and magnetostatic

simulations under supervision of Dr. Sunil Jha. This knowledge helped me a lot during design

and development of my experimental setup. I was fortunate to work on our own developed

MR finishing setup. I am very appreciative of all the guidance received from the supervision

of Dr. Sunil Jha. He was one of the principal initiators of magnetorheological abrasive flow

iii

finishing process in India. I have learned a great pledge from him about the need base process

development and know that these lessons will continue to benefit me for the rest of my life.

Beyond the source of immense knowledge and experience Dr. P.M. Pandey is very kind

and caring with great compassion and love for the students. I am sincerely thankful to him.

I would like to express sincere thanks and acknowledge help provided by Dr. R. P. Pant

for his expert inputs during use of Magneto Rheometer for carrying out the rheological

characterization of synthesized MR polishing fluid at the National Physical Laboratory

(NPL), New Delhi, India.

I was fortunate to do my research at the Indian Institute of Technology Delhi would be

delighted and their generous financial support is appreciated.

I am thankful to my SRC chairman Prof. P. Venkateswara Rao and expert members Dr.

Sudarshan Gosh and Prof. J. Bijwe for their constructive criticism and valuable guidance

during course of my presentations. I am very thankful to Prof. N. Bhatnagar, O/I of PE lab for

proving SEM facility and to Mr. Vijay Tiwari for its operation.

A special thanks to the technical staff Mr. Tulsi Ram, Mr. Subash Chand and Mr.

Ayodhya Prasad for their support in completing the work in time.

I am sincerely thankful to all my friends and research scholars at IIT Delhi, Dr. Rahul S.

Mulik, Mr. Vineet Srivastava, Mr. Manoj Satyarthi, Mr. M.S. Niranjan, Ms. Sarswathi

Reddy, Mr. Mridul Singh Rajput, Mr. Pratik Kala, Mr. Dilshan Khan, Mr. Kanwaljeet Singh,

Mr. J.P. Singh, Ms. Harsha Goel, Ms. Sweta Tiwari, Mr. Satish S. Sonwane, Mr. Anand

Druv, Mr. Prashant Ambad, Mr. G. Kiran, Mr. Dinesh and co-research scholars who made

my life enjoyable and memorable on the campus.

I am indebted to my parents Shri. Jagannath Singh and Late Smt. Kamla Devi Singh and

elder brother Shri. Tarkeshwar Singh for their blessings, motivations, giving me freedom and

constant support throughout this period.

iv

I would like to thank my wife Sunita for her kind cooperation, great scarification, moral

support, inspiration, taking care of all the needs at home which helped me to focus on my

work all the time. Without her support this research contribution would have never been

possible. I express my lovely feelings for my beloved daughter Sunanda and son Yash Rishi,

who with their smiles showered love that wiped all the trace of tiredness day after day.

I would like to express my sincere thanks to “Ad. Dr. Pranav Pandya and Shraddheya

Shail Jiji” Shantikuj Haridwar (U.A.), Shri. Pradeep Dixit and Shri. J.P. Verma from Gayatri

Chetana Kendra Noida (U.P.), for their blessings and motivations to complete this work.

At last, but not the least, I am thankful to everyone at IIT Delhi or outside who helped me

directly or indirectly to complete this work.

(Anant Kumar Singh)

v

ABSTRACT

The nano-level surface finishing requirements on the components made of materials with

extraordinary properties, complex 3D surfaces and miniature surface features on complex

geometries etc. are highly demanded in today’s advanced engineering industries. This had

lead to the development of many advanced finishing technologies where forces acting on the

workpiece surface during the finishing operation can be controlled through external magnetic

field. Owing to this, components can be finished with close tolerances and without damaging

surface topography. From the literature review available, it has been found that mostly MR

polishing fluid ribbon on rotating wheel or polishing spots within a magnetorheological fluid

has been used as a finishing tool in the existing magnetorheological finishing (MRF)

processes. The surfaces such as grooves, in-depth pockets or projections at different angles

on a 3D workpiece are likely to be inaccessible by many of the existing MR finishing

processes due to rotating wheel size or mechanical interferences.

In the present research work a new ball end magnetorheological finishing (BEMRF)

process has been designed and developed where tool tip retains stiffened MR polishing

(MRP) fluid as a ball end shape of finishing spot. This can easily be made reachable for the

different 3D surface profiles and suitable to finish 3D free form features when it is integrated

with 3 axis CNC machine. In this process the novelty of the tool design is in flow of

pressurized MRP-fluid through central axis of the tool core and gets stiffened magnetically

controlled ball end shape of MRP-fluid at the tip surface of MR finishing tool. This is further

used as a finishing medium and guided to follow the surface to be finished through computer

controlled 3-axes motion.

The magnetostatic finite element analysis for study of variation in magnetic flux density

supported the design requirements of ball end shape of MR polishing fluid at the tip surface

vi

of the tool in BEMRF process. The initially designed MR finishing tool was rotated as a

whole during finishing operation. In this design there was no provision for cooling of

electromagnet coil due to its rotation. The limitations of initially developed BEMRF process

were relaxed by redesigning of MR finishing tool with rotating only central core and

stationary electromagnet coil wrapped by copper cooling coil to cool it continuously during

finishing operation. This has improved the stable rotational motion of central core and in-

process control of heat generation of electromagnet coil for smooth functionality of the

developed BEMRF setup.

The magnetorheological polishing (MRP) fluid was synthesized indigenously as per the

requirement of different experimental conditions. The preliminary experiments were

conducted using the synthesized MRP-fluid on ferromagnetic and nonferromagnetic

workpiece surfaces. The experimental results demonstrated the effectiveness of the developed

BEMRF process in nanofinishing of ferromagnetic as well as nonferromagnetic workpieces.

Process was found to be capable of nanofinishing on fused silica glass also.

The effect of process parameters on the percentage change in surface roughness surfaces

have been studied using design of experiments. The percentage change in surface roughness

was highly influenced by working gap followed by magnetizing current and rotational speed

of tool core during surface finishing of ferromagnetic workpieces (hardness 43.15 HRC). The

optimization of response surface regression model has been done to maximise the percentage

change in surface roughness. The optimal process parameters were captured in the

experimental range of variables at higher electromagnet magnetizing current, lower working

gap and lower rpm for maximum percentage change in surface roughness. The performance

of BEMRF process with different MRP-fluid compositions was analyzed. It has been found

from the experimental results that the process performance was influenced by varying the

abrasives size and concentration in MRP-fluid. The performance was also analyzed at

vii

microscopic level in terms of improvement in surface characteristics and texture using the

scanning electron microscopy and atomic force microscopy. For achieving the maximum

process performance in terms of % change in Ra, the optimal MRP-fluid composition was

found with 25% volume concentration abrasives of mesh number 400 for a given initial Ra

value.

The performance of BEMRF process was demonstrated on the typical 3D workpiece

surfaces in terms of percentage change in surface roughness. The effects of variation in

magnetic normal forces were observed in terms of variation in final surface roughness of the

3D finished surfaces.

A mathematical model has been developed to predict the magnetic field induced normal

force in the newly developed BEMRF process. The developed mathematical model has been

compared with the experimentally obtained magnetic normal forces using dynamometer

(Kistler Dynoware type 2825A). Both were found in close agreement. In order to understand

the material removal process and wear behaviour during finishing, different modes of

abrasive-workpiece interaction have been analysed with respect to measured magnetic normal

forces.

On whole, this thesis demonstrates that the design and development of a new BEMRF

process at various stages. This leads to significant improvement in process performance in

terms of percentage reduction in surface roughness, surface textures at microscopic level of

the flat and 3D workpieces. The applications of developed finishing process can be used in

industries such as die and mold manufacturing, automotive, aerospace, semiconductor and

optics machining etc. However, there are still detailed studies that need to be investigated to

complete the validation of present newly developed MR finishing process for a material like

fused silica glass and particularly for a very hard material like chrome steels etc.

viii

TABLE OF CONTENTS

CERTIFICATE i

ACKNOWLEDGEMENTS ii

ABSTRACT v

LIST OF FIGURES xiv

LIST OF TABLES xxvi

ABBREVIATIONS xxix

NOMENCLATURE xxx

1. INTRODUCTION AND LITERATURE REVIEW 1- 29

1.1 Introduction 1

1.2 Overview of traditional finishing processes 3

1.2.1 Grinding 3

1.2.2 Honing 4

1.2.3 Lapping 4

1.2.4 Superfinishing 6

1.2.5 Buffing 6

1.3 Advanced finishing processes 7

1.3.1 Advanced finishing processes without external control of forces 8

1.3.1.1 Abrasive Flow Machining (AFM) 8

1.3.1.2 Elastic Emission Machining (EEM) 10

1.3.1.3 Chemo-Mechanical Polishing (CMP) 11

1.3.2 Advanced finishing processes with external control of forces 12

1.3.2.1 Magnetic Abrasive Finishing (MAF) 12

1.3.2.2 Magnetic Float Polishing (MFP) 13

1.3.2.3 Magnetorheological Abrasive Flow Finishing (MRAFF) 14

ix

1.3.2.4 Magnetorheological Jet Finishing (MRJF) 16

1.3.2.5 Magnetorheological finishing (MRF) 16

1.4. Literature Review 18

1.5 Motivation of the present work 25

1.6 Objectives of the present work 27

1.6.1 Research objectives 27

1.7 Thesis organization 27

2. DESIGN AND DEVELOPMENT OF BALL END MAGNETORHEOLOGICAL

FINISHING (BEMRF) PROCESS 30-52

2.1 Initial design and fabrication of experimental setup 30

2.1.1. Electromagnetic modeling of MR finishing tool 35

2.1.2. Magnetostatic finite element analysis of MR finishing tool

with ferromagnetic workpiece surface 36

2.1.3. Magnetostatic finite element analysis of the MR finishing tool

with non ferromagnetic workpiece surface 38

2.1.4. Magnetostatic finite element analysis for MR finishing tool

with taper tip length 39

2.1.5. 3D model of the assembled MR finishing tool 42

2.1.6. Limitation on initial design of BEMRF process 44

2.2 Improved design and fabrication of experimental setup for BEMRF process 44

2.2.1. Finite element analysis of an improved MR finishing tool 50

2.2.2. Effect of cooling coil temperature 51

2.3. Conclusions 52

3. SYNTHESIS OF MRP-FLUID AND PRELIMINARY EXPERIMENTS 53 -74

3.1 Synthesis of MRP- fluid for finishing of ferromagnetic workpiece surfaces 54

x

3.1.1 Rheological characterization of synthesized MRP- fluid 56

3.2. Synthesis of different MRP- fluid compositions for finishing

of ferromagnetic workpiece surfaces 58

3.3 Synthesis of MRP- fluid for finishing of fused silica glass 59

3.4 Preliminary experiments on the initially developed BEMRF process 60

3.4.1 Finishing of ferromagnetic workpiece 60

3.4.1.1 Results and discussion for finishing

of ferromagnetic workpiece 61

3.4.2 Finishing of nonferromagnetic (diamagnetic) copper workpiece 64

3.4.2.1 Results and discussion for finishing

of nonferromagnetic copper workpiece 66

3.5 Finishing of diamagnetic nonferromagnetic fused silica glass using improved

BEMRF process 68

3.5.1 Experimentation 68

3.5.2 Results and discussion for finishing of fused silica glass 70

3.6 Conclusions 74

4. PARAMETRIC ANALYSIS OF BEMRF PROCESS 75 -115

4.1 BEMRF process variables 75

4.1.1 Rotational speed of tool core 76

4.1.2 Magnetizing current 76

4.1.3 Working gap 77

4.2. Design of experiments 77

4.3 Response surface regression analysis 82

4.4 Results and discussion 89

4.4.1 Effect of rotational speed of tool core 89

xi

4.4.2 Effect of magnetizing current 90

4.4.3 Effect of working gap 91

4.4.4. Confirmation experiments for validation of model 95

4.4.5 Optimization of developed process 96

4.5 Performance evaluation of BEMRF process with finishing time 97

4.6 Performance analysis of BEMRF process with MRP-fluid compositions 102

4.6.1 Experimentation 104

4.6.2 Results and discussion 105

4.6.2.1 Effect of volume % concentration of abrasives

in MRP-fluid on process performance 106

4.6.2.2 Effect of abrasive mesh number in MRP-fluid

on process performance 108

4.6.2.3 Microscopic study of the finished workpiece surfaces 110

4.6.3 Optimization of process performance with MRP-fluid compositions 113

4.7. Conclusions 114

5. FINISHING OF TYPICAL 3D FERROMAGNETIC WORKPIECE 116-134

5.1 Experimental set-up for finishing of typical 3D workpiece surfaces 116

5.2 Magnetostatic field simulation on differently inclined surfaces of a typical 3D

workpiece surfaces 118

5.2.1 Flat surfaces 118

5.2.2 30° inclined surface 119

5.2.3 45° inclined surface 121

5.2.4 Curved surface 122

5.3 Experimentation 123

5.4 Results and discussions 125

xii

5.4.1 Observations and discussions on finishing of flat surfaces 126

5.4.2. Observations and discussions on finishing of inclined

and curve surfaces 131

5.5 Conclusions 134

6. ANALYSIS OF MAGNETIC FIELD INDUCED NORMAL FORCE IN BEMRF

PROCESS 135-160

6.1 Experimental set-up for measuring the magnetic field induced normal force 136

6.2 Mechanism of material removal and surface finishing with respect to magnetic

normal force in BEMRF process 137

6.3 Analysis of magnetic field-induced normal force 140

6.3.1 Calculation of number of CIP chains in the working gap

with volume V of MRP-fluid 141

6.3.2 Calculation of number of active abrasives per chain of CIPs

on the workpiece surface 142

6.3.3 Modeling of magnetic field-induced normal force 144

6.3.3.1 Calculation of total flux flow in the equivalent

magnetic circuit of the BEMRF setup 145

6. 3.3.2 Calculation of magnetic flux density with respect

to variable working gap 146

6. 3.3.3 Calculation of average normal magnetic force

with respect to working gap 148

6.4 Experimentation 150

6.5 Results and discussions 152

6.5.1 Validation of mathematical model for magnetic normal force 152

6.5.2 Observations and discussions for the effect of magnetic normal

xiii

force on surface finishing 153

6.5.2.1 Observations and discussions on microscopic mechanism

of material removal with magnetic normal force 156

6.6 Conclusions 160

7. CONCLUSIONS AND SCOPE FOR FUTURE WORK 161-165

7.1 Conclusions 161

7.2 Scope for future work 164

REFERENCES 166

APPENDIX-A 173

2D drawing of the initial and updated MR finishing tool

Copper cooling coil wrapped over the stationary electromagnet

2D drawing of aluminium bracket for holding the MR finishing tool

APPENDIX-B 179

Preparation of base fluid

Preparation of oil base MRP- fluid

Preparation of water base MRP- fluid

APPENDIX-C 180

Computer controlled program using ACR1505 code for finishing of flat ferromagnetic

workpiece surfaces used in design of experiments chapter- 4

Computer controlled 3-axis program using ACR1505 code for finishing of 3D typical

workpiece surfaces by single pass in 10 min used in chapter-5

APPENDIX-D 182

LIST OF PATENTS AND PUBLICATIONS FROM THE PRESENT RESEARCH

WORK 183

AUTHOR BIOGRAPHY 185