experimental investigations into rotary ultrasonic
TRANSCRIPT
VISHAL GUPTA
FEBRUARY 2017
v
DRILLING OF BONES - AN IN VITRO STUDY
by
Submitted
in fulfilment of the requirements of the degree of Doctor of Philosophy
to the
FEBRUARY 2017
For their love, support and encouragement
i
Certificate
This is to certify that the thesis entitled ‘Experimental Investigations into Rotary Ultrasonic
Drilling of Bones - An In Vitro Study’ submitted by Mr. Vishal Gupta 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/diploma.
(Prof. Pulak Mohan Pandey)
New Delhi, India
iii
Acknowledgements
This thesis symbolizes an important milestone in the journey of my life. I would like to express
my deep sense of gratitude and sincere thanks to my thesis supervisor Prof. Pulak Mohan
Pandey. His excellent guidance, constant encouragement and optimistic outlook have been a
source of inspiration for me throughout this work. His knowledge of the subject and wealth of
experience motivated me to complete the work. The last four years of my interaction with him
has been a great learning experience. I have benefited immensely by his devotion for the
research, his ability to see things that are not obvious and his perseverance to pursue creative
leads in the research. Besides being a source of immense knowledge and experience,
Dr. Pulak Mohan Pandey is very kind and compassionate towards his students. I will forever
cherish my close association with him.
I owe many thanks to Prof. Ravi Kumar Gupta, Department of Orthopaedics, Government
Medical College Hospital Chandigarh for providing the orthopaedic drill bit and his valuable
suggestions to carry out this work. Gratitude is also given to Dr. Asit Ranjan Mridha, Assistant
Professor, Department of Pathology, All India Institute of Medical Sciences (AIIMS) New
Delhi for the histopathological analysis and the preservation of bone specimen.
The author gratefully acknowledges the financial support provided by EPSRC-DST (INDO-
UK) project titled as “Modelling of Advanced Materials for Simulation of Transformative
Manufacturing Process” (MAST) for carried out this work.
Very special thanks to Prof. Vadim V Silberschmidt, Wolfson School of Mechanical, Electrical
and Manufacturing Engineering Loughborough University, Loughborough LE11 3TU, UK for
his valuable suggestions and comments to carry out this work.
I am also thankful to my SRC members especially, Dr. Sudarsan Ghosh and Dr. Jyoti Kumar
for their constructive suggestions and valuable guidance during course of presentations. I am
very much thankful to Prof. D. Ravi Kumar for his suggestions; smooth functioning of SRC
meetings and presentations. I am thankful to staff members for providing me essential aids to
complete experiments.
Gratitude is also given to Mr. Girish C. Verma for his enthusiastic assistance, unlimited support
during the preparation of this dissertation.
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Many thanks given to my friends and research scholars at IITD, Dr. K. S. Khas, Dr. M. S.
Rajput, Dr. Pratik Kala, Dr. Manoj Satyarthi, Dr. J. P. Singh, Dr. Dinesh Sethi, Dr. Gyanendra
Singh, Dr. P. K. Rathore, Ms. Harsha Goel, Mr. Virendra Mishra, Mr. Anil Jain, Mr. Vipin
Shukla, Mr. Jagtar Singh, Mr. Bikash Behra, Mr. Kheelraj Pandey, Ms. Meenakshi, Mr.
Chetan, Mr. Jaskaran Singh, Mr. Aviral Mishra, Mr. Varun Sharma, Mr. Pawan Sharma, Mr,
Hardik Berawala, Mr. Dilpreet Singh, Mr. Fitsum, Mr. Ravinder Pal Singh and co-research
scholars / friends at IIT Delhi who were always there to lend a helping hand when it mattered
most and for the camaraderie that took away all the pressures and made research work more
enjoyable.
I am also thankful to lab technician of production lab Mr. Tulsi Ram, and Mr. Vijay Tiwari for
providing me the essential aid to complete experiments. I am exceeding thankful to Mr.
Ramchandr and Mr. Satish Raja for assistance in performing the universal testing machine.
I am indebted to my mother, Ms. Prem Wati and father, Mr. Vinod Kumar for their blessings,
motivation, providing me moral support, taking care of many social responsibilities and
constant support throughout this period. I would like express appreciation to the most important
person of my life i.e., my beloved wife Ms. Apoorva Sharma who spent sleepless nights with
me and was always my support in the moments when there was no one to answer my queries.
I appreciate the love and support of my sister Ms. Tanu Gupta, which helped me to focus on
my work all the time.
Above all, I owe it all to Almighty God for granting me the wisdom, health and strength to
undertake this research task and enabling me to its completion.
(Vishal Gupta)
v
Abstract
Bone drilling is one of the steps in a typical surgical operation i.e. performed around the world
for reconstruction and repair of the fractured bone. Fracture of bones is a common problem due
to age factors, sports injuries, transport and industrial accidents, etc. One of the most common
methods to immobilise these fractured parts of bones is to repair and reconstruct by fixing them
with metal plate held by screws or locking plate, intramedullary nail, dynamic compression
screw-plate etc. Fixing these screws into the bone needs a predrilled hole. Therefore drilling
on bone is required in various medical surgeries like orthopaedic, dental and trauma surgical
operations.
These predrilled holes are done with the help of the drilling technique, where the traumatologist
applies axial force on the drilling tool for penetrating it through the bone. This process involves
drill force and torque during the bone drilling. High cutting force and torque lead to problems
such as delamination of the bone, increased crack levels, poor hole accuracy, stuck of drill bit
or even drill breakage, thermal necrosis and osteosynthesis etc. It is reported that, the implant
failure rate for lower leg due to osteosynthesis is around 2.1-7.1%. Hence, there is always a
necessity to minimize the magnitude of drilling force and torque during the bone drilling
process
In bone drilling process, mechanical work energy is converted into thermal energy which could
be the cause of continuous increase in the temperature of bone as well as drill tool. Direct
cutting contact between the bone and drill tool bit results in significant amount of heat is
produced during the bone drilling process because of material removal and coefficient of
friction between the drill bit and bone. Increase in the temperature near the drilling site during
the bone drilling process can cause serious problems like thermal necrosis, reduced
regeneration capacity of protein, and bone death. Permanent death of the bone cells occurred
due to rise in temperature beyond a threshold value (< 47° C) is known as thermal necrosis or
bone necrosis.
Various process parameters have been reported in the literature which influence the bone
drilling process like drill diameter, feed rate, rotation speed of the tool, drilling depth, drill
geometry, drill bit material and irrigation method. Over the last few decades, limited research
has been conducted to control the force and torque during the bone drilling process. Various
vi
techniques like two step drilling, ultrasonic assisted bone drilling, laser drilling etc. have been
introduced to control the level of forces, torque and temperature during the bone drilling.
In the previous published research, researchers tried to control the temperature, force and
torque during bone drilling process by using irrigation technique, designing new drill bits and
drilling technique. Using irrigation technique maximum heat generated could be reduced
during the bone drilling process, but it could be a further cause of infection near the treated.
But still there is a need to minimize the rise in temperature, force and torque during surgical
bone drilling process for more efficient and successful orthopaedic and trauma surgery.
To overcome the aforesaid problem a new noble bone drilling method has been introduced
recently named as RUBD. In the present research, a novel bone drilling technique i.e., rotary
ultrasonic bone drilling named as RUBD has been successfully attempted to minimize the
forces, torque temperature and microcracks during bone drilling. In order to perform the
experimental investigations to find out change in temperature, force, torque, temperature and
microcracks with RUBD using diamond coated hollow tool on bone, rotary ultrasonic tool
assembly was designed and fabricated in house.
The drilling experiments were planned and carried out on porcine bones using design of
experiments (Response Surface Methodology). Analysis of variance (ANOVA) was carried
out to find the effect of process factors such as rotational speed, feed rate, drill diameter and
ultrasonic vibrational amplitude on the force and torque. Statistical models were developed for
the force and torque with 95% confidential interval and confirmation experiments have been
carried out to validate the models. Microcracks developed during drilling process were
characterized by scanning electron microscopy (SEM). The results revealed that RUBD
process offered a lower force, torque, temperature and minimum microcracks, making it a
potential process for bone drilling in orthopaedic surgery.
Thermal necrosis was also examined by the histopathological examination for the RUBD and
results were compared with the conventional surgical bone drilling method (CSBD). It was
also found that RUBD generated a much lower temperature, force and torque as compared to
the CSBD. The effect of the drilling parameters on the microcracks and pullout strength was
also evaluated. The obtained results showed that the increase in the length of microcracks led
to decrease in the strength of the bone screw bond; hence, there is a strong correlation between
the microcracks and the pullout strength of the bone screw.
vii
So it is concluded that this process can be further used in the orthopaedic drilling operations to
avoid thermal necrosis, osteonecrosis and osteosynthesis.
Keywords: RUBD, RBD, CSBD, Porcine, Bone, Thermal necrosis, osteosynthesis,
Temperature, Force, Torque, Microcracks, Pull-out, Drill bit, Wear and ANOVA.
ix
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Contents
Contents XII
1.2 Types of bone fracture and its treatment methods 2
1.2.1 Conventional approach 3
1.2.2 Direct approach 4
1.3 Need of bone drilling and its drawbacks in surgical operations 5
1.3.1 Need of bone drilling 5
1.3.2 Problems associated with conventional surgical bone drilling
(CSBD) 6
1.4.1 Aim and motivation of the study 8
1.4.1.1 Rotary ultrasonic bone drilling (RUBD) 8
1.4.2 Major goal 9
Chapter 2: Literature review 13-38
2.1 Introduction 13
2.3.1 Influence of conventional bone drilling parameters on temperature 14
2.3.2 Influence of irrigation method on temperature 21
xii
2.3.3 Influence of conventional bone drilling parameters on force and
torque 23
roughness and hole quality 25
2.3.5 Influence of reused drill bit on temperature, cutting force and
torque 25
2.4.3 Water jet drilling on bone 28
2.4.4 Ultrasonic assisted drilling (UAD) on bone 28
2.5 Temperature, force and torque measurement methods in the bone drilling
process 30
2.6 Summary 31
2.7 Research gaps 31
Chapter 3: Fabrication of RUBD experimental set up and tools 39-76
3.1 Introduction 39
3.2 Details of design and fabrication of experimental setup and tools 39
3.2.1 Details of ultrasonic tool and generator unit 39
3.2.2 Design and fabrication hollow and solid tool to perform the bone
drilling in-vitro study 40
3.2.3.1 FE analysis of the designed RUD assembly with
hollow and solid tool 45
3.2.4 Details of RUBD experimental setup to perform in vitro study 47
3.3 Bone specimen details 48
3.4 Comparative experimental study of various bone drilling techniques and
tools 49
parameters 49
torque and temperature 59
3.4.2.2 Effect of feed rate on force, torque and temperature 64
3.4.2.3 Effect of drill diameter on force, torque and temperature 67
3.4.2.4 Effect of ultrasonic vibration amplitude on force, torque
and temperature 70
surface morphology 72
3.4.3 Material removal mechanism in RUBD, RBD and CSBD 74
3.5 Conclusions 75
force, torque and temperature rise in RUBD 77-117
4.1 Introduction 77
4.2.2 Selection of process parameters and design of experiments 79
4.3 Statistical modeling of force and torque 80
4.3.1 Precision of the proposed models 88
4.3.2 Effect of process parameters on the cutting force and torque 89
4.3.2.1 Effect of rotational speed on force and torque 89
4.3.2.2 Effect of feed rate on force and torque 93
4.3.2.3 Effect of drill diameter on force and torque 93
4.3.2.4 Effect of vibrational amplitude on force and torque 93
4.3.2.5 Interaction effects for the force and torque 93
4.3.3 Optimization of the process parameters for cutting force and
torque 96
4.4.1.1 Adequacy of the temperature models 105
4.4.1.2 Precision of the temperature developed models 105
xiv
4.4.2 Temperature modeling at the bone interface and drill tool (T0) 106
4.4.3 Effect of process parameters on the temperature and its distribution
from the drilled hole 107
4.4.3.1 Effect of rotational speed on change in temperature 110
4.4.3.2 Effect of feed rate on change in temperature 111
4.4.3.3 Effect of drill diameter on change in temperature 111
4.4.3.4 Effect of vibrational amplitude on change in temperature 112
4.4.3.5 Interaction effects for change in temperature 113
4.4.4 Optimization of process parameters for minimum change in the
temperature 114
5.1 Introduction 119
5.2 Experimentation 119
5.3.2 Tissue processing 121
5.3.3 Tissue embedding 123
5.3.4 Tissue sectioning 125
5.3.5 Slide staining and cover-slipping 126
5.4 Effect of RUBD and CSBD on temperature and statistical analysis for fixed
thermocouple 126
5.5.1 Gross observation 130
5.5.2 Histopathological observation 131
Chapter 6: Study of biomechanical pullout strength and microcracks in
rotary ultrasonic bone drilling 137-152
6.1 Introduction 137
6.2 Experimental procedure for pullout strength and microcracks analysis 138
xv
6.2.2 Measurement of biomechanical pullout strength 140
6.3 Effect of process parameters on microcracks, hole edge quality and pullout
strength 141
6.3.3 Pullout Strength 148
6.4 Conclusions 152
Chapter 7: In-situ tool wear monitoring and its effects on the performance
of porcine cortical bone drilling 153-164
7.1 Introduction 153
7.2 Materials and methods 153
7.3 Effect of reused drill tool on tool wear, force, torque, temperature and chip
morphology 156
7.3.2 Cutting force and torque 159
7.3.3 Temperature and chip morphology 160
7.3.4 Statistical analysis 162
8.1 Summary 165
8.2 Conclusions 166
Curriculum vitae 187
Figure 1.1 Structure of bone 1
Figure 1.2 Types of bone fractures 2
Figure 1.3 Methods to treat bone fracture 3
Figure 1.4 Repair of fractured parts of bone by conventional method (a)
orthopaedic cast, (b) plaster cast and (c) body cast
3
Figure 1.5 Repair of fractured parts of bone by external fixation method (a)
surgical pins and rods (b) X-ray image shows the fractured parts
of tibia bone (c) circular disc and plate
4
Figure 1.6 (a) X-ray image shows the fracture in the bone of forearm, (b)
image immediately after the surgical procedure and (c) X-ray
images after 10th month
Figure 1.8 Hole inaccuracy, drill wander and delamination during bone
drilling
7
Figure 1.10 Illustration of the RUM process 9
Figure 2.1 Effect of input parameters on the performance of CSBD process 14
Figure 2.2 (a) Temperature variation w.r.t time (b) Effect of applied force
on the temperature
16
Figure 2.3 (a) I) Classical and II) Two phase drill bit, (b) change in
temperature vs drill bit used for comparative study
17
Figure 2.5 2-step internally cooled drill bit 22
Figure 2.6 Images of three drill bits used (a) new (b) after drilling 600 holes
and (c) drill bit obtained from the operation theater
26
Figure 2.7 Microwave drilling of bone showed a visible thermal necrosis 28
Figure 2.8 Effect of rotational speed on (a) force (b) torque. Effect of feed
rate on force (c) and (d) effect of amplitude on force and torque
drilling with CD and UAD
29
31
xviii
Figure 3.1 (a) Ultrasonic tool and (b) ultrasonic generator 40
Figure 3.2 Drawing of the designed tool (a) hollow and (b) solid, all
dimensions are in mm
41
Figure 3.3 Actual images of fabricated tool along with their enlarged view of
tool end face (a) hollow and (b) solid
42
Figure 3.4 Microscopic image of the diamond abrasive coated tool on the
tool shank
Figure 3.6 Measurement of vibrational frequency using a PiezoView
software, of the designed RUD tool assembly with (a) hollow tool
and (b) solid tool
44
Figure 3.7 FE analysis of RUD assembly with hollow tool 45
Figure 3.8 FE analysis of RUD assembly with solid tool 46
Figure 3.9 CNC vertical milling 47
Figure 3.10 Modified set up to perform the RUBD 48
Figure 3.11 Fresh porcine bone sample 49
Figure 3.12 Fresh porcine bone specimen (a) specimen used for first set (b)
mid diaphysis (c) specimen used for second and third set of
experiments
49
Figure 3.13 Experimental Setup: (a) for first set, (b) for second set and (c) for
third set of experiments and (d) drill tools used for the
comparative study: I) hollow tool, II) solid tool, III) CSD bit
50
Figure 3.14 Fixture used for holding the bone sample (a) actual image and (b)
CAD model
51
Figure 3.15 (a) Position of thermocouples fixed from the main drilled hole and
(b) thermocouple probe
52
Figure 3.16 Change in chip morphology with increase in rotational speed.
First row shows chips in CSBD (a) at 500 rpm, (b) 2500 rpm,
second row shows chips in RUBD with hollow tool at (c) 500 rpm,
(d) 2500 rpm and third row corresponds to microscopic
morphology of RUBD process with hollow tool at (e) 500 rpm
and (f) 2500 rpm. [Figure from 3.16 (a) to (d) were captured
online during the bone drilling by Dino light microscope and
60
xix
Figure 3.16 (e) and (f) were obtained by the microscope (BX43,
Upright microscope, Olympus)]
Figure 3.17 Effect of rotational speed and different drilling techniques on (a)
Force and (b) torque. [Feed rate = 30 mm/min, drill diameter =
3.5 mm, Amplitude = 16 µm]
62
Figure 3.18 Effect of rotational speed and different drilling techniques on
change in temperature. [Feed rate = 30 mm/min, drill diameter =
3.5 mm, Amplitude = 16 µm]
63
Figure 3.19 Change in temperature and its distribution over the radial distance
from the drill site edge vs spindle speed. [Feed rate = 30 mm/min,
drill diameter = 3.5 mm, Amplitude = 16 µm]
64
Figure 3.20 Effect of feed rate and different drilling techniques on (a) Force
and (b) torque. [Rotational speed = 1500 rpm, drill diameter = 3.5
mm, Amplitude = 16 µm]
65
Figure 3.21 Effect of feed rate and different drilling techniques on
temperature. [Rotational speed = 1500 rpm, drill diameter = 3.5
mm, Amplitude = 16 µm]
66
Figure 3.22 Change in temperature and its distribution over the radial distance
from the drill site edge vs feed rate. [Rotational speed = 1500 rpm,
drill diameter = 3.5 mm, Amplitude = 16 µm]
67
Figure 3.23 Effect of drill diameter and different drilling techniques on (a)
Force and (b) Torque. [Rotational speed = 1500 rpm, Feed Rate =
30 mm/min, Amplitude = 16 µm]
68
Figure 3.24 Effect of drill diameter and different drilling techniques on
temperature. [Rotational speed = 1500 rpm, Feed Rate = 30
mm/min, Amplitude = 16 µm]
69
Figure 3.25 Change in temperature and its distribution over the radial distance
from the drill site edge vs drill diameter. [Rotational speed = 1500
rpm, Feed Rate = 30 mm/min, Amplitude = 16 µm]
70
Figure 3.26 Effect of vibration amplitude and RUBD with hollow and solid
tool on (a) Force, (b) Torque and (c) Temperature. [Rotational
speed = 1500 rpm, Feed Rate = 30 mm/min, drill diameter = 3.5
mm]
71
xx
Figure 3.27 Change in temperature and its distribution over the radial distance
from the drill site edge vs vibrational amplitude. [Rotational speed
= 1500 rpm, Feed Rate = 30 mm/min, drill diameter = 3.5 mm]
72
Figure 3.28 SEM images of inner surface of drilled hole in bone with
magnification of 500X drilling with (a) RUBD with hollow tool,
(b) RUBD with solid tool, (c) RBD with Hollow tool (d) RBD
with solid tool and (e) CSBD. [Rotational speed = 500 rpm, Feed
rate = 10 mm/min, Drill Diameter = 4.5 mm, Amplitude = 16µm
(only for RUBD)]
Figure 3.30 Chips produced by CSBD process 75
Figure 4.1 Schematic diagram of RUBD experimental setup for
measurement of cutting force and torque
78
Figure 4.2 Fresh porcine bone specimen (a) before experiments, (b) after
experiments
78
Figure 4.3 Measured Value of force and torque w.r.t. time using the
dynamometer. [Rotational speed = 1500, feed rate = 30 mm/min,
Drill diameter = 3.5 and amplitude = 12µm]
79
Figure 4.4 (a) Effect of input process parameters on the force and (b) %
contribution of the process parameters on the force
90
Figure 4.5 Microscopic images of chips obtained at rotational speed of (a)
500 (b) 1500 and (c) 2500. [F = 10 mm/min, D = 4.5 mm, A= 16
µm]
91
Figure 4.6 (a) Effect of input process parameters on the torque and (b) %
contribution of the process parameters on the torque
92
Figure 4.7 Interaction effect between the drill diameter and feed rate on the
force (a) response surface plot (b) variation of force with drill
diameter and feed rate. [R= 1500 rpm and A = 12 µm]
94
Figure 4.8 Interaction effect between the drill diameter and feed rate on the
torque (a) response surface plot (b) variation of force with drill
diameter and feed rate. [R= 1500 rpm and A = 12 µm]
94
xxi
Figure 4.9 Interaction effect between the rotational speed and feed rate on
the force (a) response surface plot (b) variation of force with
rotational speed and feed rate. [D= 3.5 mm and A = 12 µm]
95
Figure 4.10 Interaction effect between the rotational speed and feed rate on
the torque (a) response surface plot (b) variation of force with
rotational speed and feed rate. [D= 3.5 mm and A = 12 µm]
95
Figure 4.11 Interaction effect between the amplitude and feed rate on the force
(a) response surface plot (b) variation of force with amplitude and
feed rate. [R = 1500 rpm and D= 3.5 mm]
96
Figure 4.12 Interaction effect between the amplitude and feed rate on the
torque (a) response surface plot (b) variation of force with
amplitude and feed rate. [R = 1500 rpm and D= 3.5 mm]
96
Figure 4.13 Effect of process parameters on maximum change in the
temperature at distance of (a) 0.5 mm, (b) 1.0 mm, (c) 1.5 mm and
(d) 2.0 mm
Figure 4.14 Percentage contribution of significant process parameters on
maximum change in the temperature at distance of (a) 0.5 mm, (b)
1.0 mm, (c) 1.5 mm and (d) 2.0 mm
109
Figure 4.15 Effect of rotational speed on change in temperature for
thermocouples placed at locations 0.5 mm, 1.0 mm, 1.5 mm and
2.0 mm from the drill site. [F = 30 mm/min, D = 3.5 mm and A =
12 µm]
110
Figure 4.16 Effect of feed rate on change in temperature for thermocouples
placed at locations 0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm from the
drill site. [R = 1500 rpm, D = 3.5 mm and A = 12 µm]
111
Figure 4.17 Effect of drill diameter on change in temperature for
thermocouples placed at locations 0.5 mm, 1.0 mm, 1.5 mm and
2.0 mm from the drill site. [R = 1500 rpm, F = 30 mm/min and A
= 12 µm]
112
Figure 4.18 Effect of amplitude on change in temperature for thermocouples
placed at locations 0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm from the
drill site. [R = 1500 rpm, F = 30 mm/min and D = 3.5 mm]
113
xxii
Figure 4.19 Significant interaction between feed rate and rotational speed on
change in the temperature (Δt0.5 mm). (a) 3 – D response surface
and (b) 2 – D plot for variation of change in temperature with feed
rate and rotational speed. [D = 3.5 mm and A = 12 µm]
114
Figure 4.20 Significant interaction between feed rate and amplitude on change
in the temperature (Δt0.5 mm). (a) 3 – D response surface and (b) 2
– D, plot for variation of change in temperature with feed rate and
amplitude. [R = 1500 rpm and D = 3.5 mm]
114
Figure 5.2 Porous cassettes with specimen 122
Figure 5.3 Automatic tissue processing unit for the dehydration 122
Figure 5.4 Clearing processing unit 123
Figure 5.5 Tissue embedding unit 124
Figure 5.6 Tissue embedding procedure 124
Figure 5.7 Actual images of tissue embedded on the wax mould 125
Figure 5.8 Rotary microtome used for the sectioning 125
Figure 5.9 Automatic staining unit 126
Figure 5.10 Microscopic examination procedure for Haematoxylin and Eosin
(H & E)
127
Figure 5.11 Images of final slides for the microscope examination 128
Figure 5.12 The variation of average temperature in RUBD and CSBD with
respect to each trial
129
Figure 5.13 Photographs of (a) drill hole and (b) inner surface of RUBD
specimen shows regular peripheral border and smooth surface of
the of the bone without any discoloration. (c) CSBD specimen
shows uneven hole margin with presence of brownish and
yellowish-colored particles. Yellowish discoloration is present
around the hole and (d) on inner surface. [Rotational speed = 2500
rpm, Feed rate = 10 mm/min and Drill diameter 4.5 mm
(Vibrational amplitude and frequency = 16µm and 20 kHz
respectively only for RUBD]
130
Figure 5.14 The scanner view of (a) CSBD specimen tissue shows several
splits in bone and irregular cracks at the drilling edge are present
131
xxiii
[haematoxylin and eosin (H&E)] and (b) RUDB specimen shows
uniform sections with regular, smooth drilling edge (H&E).
[Rotational speed = 2500 rpm, Feed rate = 10 mm/min and Drill
diameter 4.5 mm (Vibrational amplitude and frequency = 16µm
and 20 kHz respectively only for RUBD]
Figure 5.15 Enlarged view of hole edge drilled with CSBD method [H & E] 132
Figure 5.16 Enlarged view of hole edge drilled with RUBD method [H & E] 132
Figure 5.17 Viable osteocytes are present in all lacunae even at the cutting
edge, and no crack is noted in the bone matrix of RUBD tissue
(arrows) (a, H&E; 100x, b, H&E; 400x). (c & d) Heat induced
diffuse osteocytes necrosis is seen in a wide zone around the hole
of CSBD specimens (arrows). The bone matrix also shows
frequent micro-fractures (block arrow) (e, H&E; 100x, f, H&E;
400x). [Rotational speed = 2500 rpm, Feed rate = 10 mm/min and
Drill diameter 4.5 mm (Vibrational amplitude and frequency =
16µm and 20 kHz respectively only for RUBD]
133
Figure 5.18 Histogram drilled sample for (a) CSBD and (b) RUBD 134
Figure 6.1
Porcine bone specimens used for in-vitro study: (a) bones, (b)
specimens for pullout strength and (c) specimens for microcrack
analysis
139
Figure 6.2 Sample preparation for SEM analysis (a) main drilled hole, (b)
section of the hole and (c) final specimen for the analysis
140
Figure 6.3 (a) Testing setup for biomechanical pullout strength and (b) CAD
model of bone-holding fixture. (1) grip, 2) cortical bone screw, 3)
bone sample and 4) bone holding fixture
140
Figure 6.4 Schematic diagram of screw inserted into bone 141
Figure 6.5 Effect of rotational speed on the microcracks. Left column is from
the RUBD group and right column is from the CSBD group. First
row [Figure 6.5 (a-b)] shows the effect of two drilling methods on
the microcracks with 500 rpm, second row [Figure 6.5 (c-d)] with
1500 rpm and third row [Figure 6.5 (e-f)] with 2500 rpm
respectively. [Feed rate = 10 mm/min, drill diameter = 4.5 mm,
(amplitude = 16 µm, frequency = 20, only for RUBD)]
143
xxiv
Figure 6.6 Effect of feed rate on the microcracks. Left column is from the
RUBD group and right column is from the CSBD group. First row
[Figure 6.6 (a-b)] shows the effect of two drilling methods on the
microcracks with 10 mm/min, second row [Figure 6.6 (c-d)] with
30 mm/min and third row [Figure 6.6 (e-f)] with 50 mm/min
respectively. [Rotational speed = 500, drill diameter = 4.5 mm,
(amplitude = 16 µm, frequency = 20, only for RUBD)]
144
Figure 6.7 SEM images of drilled hole quality made by (a) CSBD and (b)
RUBD at 50 X. [spindle speed = 500 rpm, feed rate = 10 mm/min
and drill diameter = 4.5 mm, (Vibrational amplitude = 16 µm and
frequency 20 kHz only for RUBD)]
146
Figure 6.8 SEM images of drilled hole quality made by (a) CSBD and (b)
RUBD at 50 X. [spindle speed = 500 rpm, feed rate = 50 mm/min
and drill diameter = 4.5 mm, (Vibrational amplitude = 16 µm and
frequency 20 kHz only for RUBD)]
147
Figure 6.9 Edge quality of holes drilled with RUBD (a) and CSBD (b) (black
arrows show delamination near drilled hole edge). [Rotational
speed = 500 rpm; feed rate = 10 mm/min; drill diameter 4.5 mm
for RUBD: (vibration amplitude = 16 µm and frequency = 20 kHz
only for RUBD)]
148
Figure 6.10 Force - displacement diagram for axial pullout of cortical bone
screw [Rotational speed = 1500 rpm; feed rate = 10 mm/min, drill
diameter = 4.0 mm (vibration amplitude = 16 µm; frequency = 20
kHz; only for RUBD)]
150
Figure 6.11 Effects of rotational speed (a) and feed rate (b) on axial pullout
force for two bone-drilling methods
150
Figure 6.12 Specimen after axial pullout: (a) RUBD hole (arrows shows
delamination area); (b) CSBD hole [Rotational speed =1500 rpm;
feed rate = 10 mm/min; drill diameter = 4.0 mm; (vibration
amplitude = 16 µm and frequency = 20 kHz; only for RUBD)]
151
Figure 6.13 (a) Drilling of bone with RUBD produced powdered chips and
cylindrical machined rod. (b) CSBD produced fragmented chips
152
xxv
Figure 7.1 Experimental setup and equipment's used for force, torque,
temperature and tool wear measurement. 1) CNC controller unit,
2) personal computer attached to microscope, 3) Dino light
microscope, 4) RUBD tool assembly, 5) Digital thermometer with
thermocouple, 6) Tool, 7) Bone holding fixture, 8) Bone, 9) 6-
axis dynamometer, 10) Ultrasonic generator unit and 11) personal
computer attached to dynamometer
154
Figure 7.2 Microscopic images of tip wear on conventional drill bit using a
Dino lite microscope (a) new drill bit (b) after 30 drills (c) after
50 drills (d) after 100 drills
156
Figure 7.3 Microscopic images of side wear on conventional drill bit using a
Dino lite microscope (a) new drill bit (b) after 30 drills (c) after
50 drills (d) after 100 drills
157
Figure 7.4 Effect of repeated drill tool on the wear area in CSBD 157
Figure 7.5 Microscopic images of hollow drill tool at first location using a
Dino lite microscope (a) new drill bit (b) after 30 drills (c) after
50 drills (d) after 100 drills
158
Figure 7.6 Microscopic images of hollow drill tool at second location using
a Dino lite microscope (a) new drill bit (b) after 30 drills (c) after
50 drills (d) after 100 drills
159
Figure 7.7 Effect of reused drill tool on maximum cutting (a) force and (b)
torque, for both the drilling techniques
160
Figure 7.8 Effect of repeated drill tool on maximum temperature, for both
the drilling techniques
161
Figure 7.9 Effect of tool wear on chip morphology for both the drilling
technique
161
xxvii
Table No. Caption Page No.
Table 2.1 Summary of CSBD parameters on change in temperature 33
Table 2.2 Summary of CSBD parameters on cutting force and torque 37
Table 3.1 Results of FE analysis 46
Table 3.2 Specification of drill tools used for the comparative study 51
Table 3.3 Input process parameters and their range 53
Table 3.4 Run order to perform the experiments 54
Table 3.5
technique
55
technique
56
technique
56
technique
58
Table 3.6 Data summary for force and torque corresponding to the mentioned
drilling technique
Table 4.2 Run order to perform the in-vitro experiments 81
Table 4.3 Data summary for cutting force and torque 82
Table 4.4 Data summary for temperature corresponding to thermocouples
fixed at four different positions
83
Table 4.5 ANOVA for forces with respect to equation 4.2 85
Table 4.6 ANOVA for torque with respect to equation 4.3 86
Table 4.7 Pooled ANOVA for the forces with respect to equation 4.4 87
Table 4.8 Pooled ANOVA for the torque with respect to equation 4.5 88
Table 4.9 Confirmation experiments for the force and torque for statistical
modelling
89
xxviii
Table 4.10 Optimized values of the process factors for the cutting force and
torque
97
Table 4.11 ANOVA for ΔT0.5 mm with respect to equation 4.7 99
Table 4.12 ANOVA for ΔT1.0 mm with respect to equation 4.8 100
Table 4.13 ANOVA for ΔT1.5 mm with respect to equation 4.9 101
Table 4.14 ANOVA for ΔT2.0 mm with respect to equation 4.10 102
Table 4.15 Pooled ANOVA for ΔT0.5 mm with respect to equation 4.11 103
Table 4.16 Pooled ANOVA for ΔT1.0 mm with respect to equation 4.12 103
Table 4.17 Pooled ANOVA for ΔT1.5 mm with respect to equation 4.13 104
Table 4.18 Pooled ANOVA for ΔT2.0 mm with respect to equation 4.14 104
Table 4.19 Run order and corresponding input value of process parameters to
perform the confirmation experiments for validate the predicted
models
105
Table 4.20 Data summary for confirmation experiments for validate the
predicted models
106
Table 4.21 Optimized value of the process parameters for the minimum
temperature generated in the bone drilling
115
Table 4.22 Output value of temperature corresponding to optimized input
process parameters
115
Table 4.23 Comparison of present results with previous findings in CD and
simulation
116
Table 4.24 Comparison of present results with previous findings in UAD 116
Table 5.1 Input process parameters used for the histopathological
examination in RUBD and CSBD
120
Table 5.2 Comparison between maximum heat generation in RUBD and
CSBD with respect to thermocouple positions
128
Table 5.3 t-test paired sample for mean 129
Table 6.1 Process parameters and their values for in-vitro experiment 139
Table 6.2 Specification of cortical bone screw used in this work 141
Table 6.3 Run order and process parameters in experiments for microcracks
analysis
142
Table 6.4 Maximum length of microcracks (in µm) from SEM images
corresponding to two drilling processes
145
xxix
Table 6.5 Run order and process parameters in experiments for
biomechanical pullout
Table 6.6 Data summary for the maximum pullout force 149
Table 7.1 Output data summary for force, torque and temperature 155
Table 7.2 ANOVA of force, torque and temperature for RUBD and CSBD 163
xxxi
Nomenclature
xxxiii
Abbreviations
ANOVA Analysis of variance
DF Degrees of freedom
DOE Design of experiments
LBM Laser beam machining
RBD Rotary bone drilling
RUM Rotary ultrasonic machining
RSM Response surface methodology
UAD Ultrasonic assisted drilling
SEM Scanning electron microscopy
TEZ Thermal effective zone
FEBRUARY 2017
v
DRILLING OF BONES - AN IN VITRO STUDY
by
Submitted
in fulfilment of the requirements of the degree of Doctor of Philosophy
to the
FEBRUARY 2017
For their love, support and encouragement
i
Certificate
This is to certify that the thesis entitled ‘Experimental Investigations into Rotary Ultrasonic
Drilling of Bones - An In Vitro Study’ submitted by Mr. Vishal Gupta 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/diploma.
(Prof. Pulak Mohan Pandey)
New Delhi, India
iii
Acknowledgements
This thesis symbolizes an important milestone in the journey of my life. I would like to express
my deep sense of gratitude and sincere thanks to my thesis supervisor Prof. Pulak Mohan
Pandey. His excellent guidance, constant encouragement and optimistic outlook have been a
source of inspiration for me throughout this work. His knowledge of the subject and wealth of
experience motivated me to complete the work. The last four years of my interaction with him
has been a great learning experience. I have benefited immensely by his devotion for the
research, his ability to see things that are not obvious and his perseverance to pursue creative
leads in the research. Besides being a source of immense knowledge and experience,
Dr. Pulak Mohan Pandey is very kind and compassionate towards his students. I will forever
cherish my close association with him.
I owe many thanks to Prof. Ravi Kumar Gupta, Department of Orthopaedics, Government
Medical College Hospital Chandigarh for providing the orthopaedic drill bit and his valuable
suggestions to carry out this work. Gratitude is also given to Dr. Asit Ranjan Mridha, Assistant
Professor, Department of Pathology, All India Institute of Medical Sciences (AIIMS) New
Delhi for the histopathological analysis and the preservation of bone specimen.
The author gratefully acknowledges the financial support provided by EPSRC-DST (INDO-
UK) project titled as “Modelling of Advanced Materials for Simulation of Transformative
Manufacturing Process” (MAST) for carried out this work.
Very special thanks to Prof. Vadim V Silberschmidt, Wolfson School of Mechanical, Electrical
and Manufacturing Engineering Loughborough University, Loughborough LE11 3TU, UK for
his valuable suggestions and comments to carry out this work.
I am also thankful to my SRC members especially, Dr. Sudarsan Ghosh and Dr. Jyoti Kumar
for their constructive suggestions and valuable guidance during course of presentations. I am
very much thankful to Prof. D. Ravi Kumar for his suggestions; smooth functioning of SRC
meetings and presentations. I am thankful to staff members for providing me essential aids to
complete experiments.
Gratitude is also given to Mr. Girish C. Verma for his enthusiastic assistance, unlimited support
during the preparation of this dissertation.
iv
Many thanks given to my friends and research scholars at IITD, Dr. K. S. Khas, Dr. M. S.
Rajput, Dr. Pratik Kala, Dr. Manoj Satyarthi, Dr. J. P. Singh, Dr. Dinesh Sethi, Dr. Gyanendra
Singh, Dr. P. K. Rathore, Ms. Harsha Goel, Mr. Virendra Mishra, Mr. Anil Jain, Mr. Vipin
Shukla, Mr. Jagtar Singh, Mr. Bikash Behra, Mr. Kheelraj Pandey, Ms. Meenakshi, Mr.
Chetan, Mr. Jaskaran Singh, Mr. Aviral Mishra, Mr. Varun Sharma, Mr. Pawan Sharma, Mr,
Hardik Berawala, Mr. Dilpreet Singh, Mr. Fitsum, Mr. Ravinder Pal Singh and co-research
scholars / friends at IIT Delhi who were always there to lend a helping hand when it mattered
most and for the camaraderie that took away all the pressures and made research work more
enjoyable.
I am also thankful to lab technician of production lab Mr. Tulsi Ram, and Mr. Vijay Tiwari for
providing me the essential aid to complete experiments. I am exceeding thankful to Mr.
Ramchandr and Mr. Satish Raja for assistance in performing the universal testing machine.
I am indebted to my mother, Ms. Prem Wati and father, Mr. Vinod Kumar for their blessings,
motivation, providing me moral support, taking care of many social responsibilities and
constant support throughout this period. I would like express appreciation to the most important
person of my life i.e., my beloved wife Ms. Apoorva Sharma who spent sleepless nights with
me and was always my support in the moments when there was no one to answer my queries.
I appreciate the love and support of my sister Ms. Tanu Gupta, which helped me to focus on
my work all the time.
Above all, I owe it all to Almighty God for granting me the wisdom, health and strength to
undertake this research task and enabling me to its completion.
(Vishal Gupta)
v
Abstract
Bone drilling is one of the steps in a typical surgical operation i.e. performed around the world
for reconstruction and repair of the fractured bone. Fracture of bones is a common problem due
to age factors, sports injuries, transport and industrial accidents, etc. One of the most common
methods to immobilise these fractured parts of bones is to repair and reconstruct by fixing them
with metal plate held by screws or locking plate, intramedullary nail, dynamic compression
screw-plate etc. Fixing these screws into the bone needs a predrilled hole. Therefore drilling
on bone is required in various medical surgeries like orthopaedic, dental and trauma surgical
operations.
These predrilled holes are done with the help of the drilling technique, where the traumatologist
applies axial force on the drilling tool for penetrating it through the bone. This process involves
drill force and torque during the bone drilling. High cutting force and torque lead to problems
such as delamination of the bone, increased crack levels, poor hole accuracy, stuck of drill bit
or even drill breakage, thermal necrosis and osteosynthesis etc. It is reported that, the implant
failure rate for lower leg due to osteosynthesis is around 2.1-7.1%. Hence, there is always a
necessity to minimize the magnitude of drilling force and torque during the bone drilling
process
In bone drilling process, mechanical work energy is converted into thermal energy which could
be the cause of continuous increase in the temperature of bone as well as drill tool. Direct
cutting contact between the bone and drill tool bit results in significant amount of heat is
produced during the bone drilling process because of material removal and coefficient of
friction between the drill bit and bone. Increase in the temperature near the drilling site during
the bone drilling process can cause serious problems like thermal necrosis, reduced
regeneration capacity of protein, and bone death. Permanent death of the bone cells occurred
due to rise in temperature beyond a threshold value (< 47° C) is known as thermal necrosis or
bone necrosis.
Various process parameters have been reported in the literature which influence the bone
drilling process like drill diameter, feed rate, rotation speed of the tool, drilling depth, drill
geometry, drill bit material and irrigation method. Over the last few decades, limited research
has been conducted to control the force and torque during the bone drilling process. Various
vi
techniques like two step drilling, ultrasonic assisted bone drilling, laser drilling etc. have been
introduced to control the level of forces, torque and temperature during the bone drilling.
In the previous published research, researchers tried to control the temperature, force and
torque during bone drilling process by using irrigation technique, designing new drill bits and
drilling technique. Using irrigation technique maximum heat generated could be reduced
during the bone drilling process, but it could be a further cause of infection near the treated.
But still there is a need to minimize the rise in temperature, force and torque during surgical
bone drilling process for more efficient and successful orthopaedic and trauma surgery.
To overcome the aforesaid problem a new noble bone drilling method has been introduced
recently named as RUBD. In the present research, a novel bone drilling technique i.e., rotary
ultrasonic bone drilling named as RUBD has been successfully attempted to minimize the
forces, torque temperature and microcracks during bone drilling. In order to perform the
experimental investigations to find out change in temperature, force, torque, temperature and
microcracks with RUBD using diamond coated hollow tool on bone, rotary ultrasonic tool
assembly was designed and fabricated in house.
The drilling experiments were planned and carried out on porcine bones using design of
experiments (Response Surface Methodology). Analysis of variance (ANOVA) was carried
out to find the effect of process factors such as rotational speed, feed rate, drill diameter and
ultrasonic vibrational amplitude on the force and torque. Statistical models were developed for
the force and torque with 95% confidential interval and confirmation experiments have been
carried out to validate the models. Microcracks developed during drilling process were
characterized by scanning electron microscopy (SEM). The results revealed that RUBD
process offered a lower force, torque, temperature and minimum microcracks, making it a
potential process for bone drilling in orthopaedic surgery.
Thermal necrosis was also examined by the histopathological examination for the RUBD and
results were compared with the conventional surgical bone drilling method (CSBD). It was
also found that RUBD generated a much lower temperature, force and torque as compared to
the CSBD. The effect of the drilling parameters on the microcracks and pullout strength was
also evaluated. The obtained results showed that the increase in the length of microcracks led
to decrease in the strength of the bone screw bond; hence, there is a strong correlation between
the microcracks and the pullout strength of the bone screw.
vii
So it is concluded that this process can be further used in the orthopaedic drilling operations to
avoid thermal necrosis, osteonecrosis and osteosynthesis.
Keywords: RUBD, RBD, CSBD, Porcine, Bone, Thermal necrosis, osteosynthesis,
Temperature, Force, Torque, Microcracks, Pull-out, Drill bit, Wear and ANOVA.
ix
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xi
Contents
Contents XII
1.2 Types of bone fracture and its treatment methods 2
1.2.1 Conventional approach 3
1.2.2 Direct approach 4
1.3 Need of bone drilling and its drawbacks in surgical operations 5
1.3.1 Need of bone drilling 5
1.3.2 Problems associated with conventional surgical bone drilling
(CSBD) 6
1.4.1 Aim and motivation of the study 8
1.4.1.1 Rotary ultrasonic bone drilling (RUBD) 8
1.4.2 Major goal 9
Chapter 2: Literature review 13-38
2.1 Introduction 13
2.3.1 Influence of conventional bone drilling parameters on temperature 14
2.3.2 Influence of irrigation method on temperature 21
xii
2.3.3 Influence of conventional bone drilling parameters on force and
torque 23
roughness and hole quality 25
2.3.5 Influence of reused drill bit on temperature, cutting force and
torque 25
2.4.3 Water jet drilling on bone 28
2.4.4 Ultrasonic assisted drilling (UAD) on bone 28
2.5 Temperature, force and torque measurement methods in the bone drilling
process 30
2.6 Summary 31
2.7 Research gaps 31
Chapter 3: Fabrication of RUBD experimental set up and tools 39-76
3.1 Introduction 39
3.2 Details of design and fabrication of experimental setup and tools 39
3.2.1 Details of ultrasonic tool and generator unit 39
3.2.2 Design and fabrication hollow and solid tool to perform the bone
drilling in-vitro study 40
3.2.3.1 FE analysis of the designed RUD assembly with
hollow and solid tool 45
3.2.4 Details of RUBD experimental setup to perform in vitro study 47
3.3 Bone specimen details 48
3.4 Comparative experimental study of various bone drilling techniques and
tools 49
parameters 49
torque and temperature 59
3.4.2.2 Effect of feed rate on force, torque and temperature 64
3.4.2.3 Effect of drill diameter on force, torque and temperature 67
3.4.2.4 Effect of ultrasonic vibration amplitude on force, torque
and temperature 70
surface morphology 72
3.4.3 Material removal mechanism in RUBD, RBD and CSBD 74
3.5 Conclusions 75
force, torque and temperature rise in RUBD 77-117
4.1 Introduction 77
4.2.2 Selection of process parameters and design of experiments 79
4.3 Statistical modeling of force and torque 80
4.3.1 Precision of the proposed models 88
4.3.2 Effect of process parameters on the cutting force and torque 89
4.3.2.1 Effect of rotational speed on force and torque 89
4.3.2.2 Effect of feed rate on force and torque 93
4.3.2.3 Effect of drill diameter on force and torque 93
4.3.2.4 Effect of vibrational amplitude on force and torque 93
4.3.2.5 Interaction effects for the force and torque 93
4.3.3 Optimization of the process parameters for cutting force and
torque 96
4.4.1.1 Adequacy of the temperature models 105
4.4.1.2 Precision of the temperature developed models 105
xiv
4.4.2 Temperature modeling at the bone interface and drill tool (T0) 106
4.4.3 Effect of process parameters on the temperature and its distribution
from the drilled hole 107
4.4.3.1 Effect of rotational speed on change in temperature 110
4.4.3.2 Effect of feed rate on change in temperature 111
4.4.3.3 Effect of drill diameter on change in temperature 111
4.4.3.4 Effect of vibrational amplitude on change in temperature 112
4.4.3.5 Interaction effects for change in temperature 113
4.4.4 Optimization of process parameters for minimum change in the
temperature 114
5.1 Introduction 119
5.2 Experimentation 119
5.3.2 Tissue processing 121
5.3.3 Tissue embedding 123
5.3.4 Tissue sectioning 125
5.3.5 Slide staining and cover-slipping 126
5.4 Effect of RUBD and CSBD on temperature and statistical analysis for fixed
thermocouple 126
5.5.1 Gross observation 130
5.5.2 Histopathological observation 131
Chapter 6: Study of biomechanical pullout strength and microcracks in
rotary ultrasonic bone drilling 137-152
6.1 Introduction 137
6.2 Experimental procedure for pullout strength and microcracks analysis 138
xv
6.2.2 Measurement of biomechanical pullout strength 140
6.3 Effect of process parameters on microcracks, hole edge quality and pullout
strength 141
6.3.3 Pullout Strength 148
6.4 Conclusions 152
Chapter 7: In-situ tool wear monitoring and its effects on the performance
of porcine cortical bone drilling 153-164
7.1 Introduction 153
7.2 Materials and methods 153
7.3 Effect of reused drill tool on tool wear, force, torque, temperature and chip
morphology 156
7.3.2 Cutting force and torque 159
7.3.3 Temperature and chip morphology 160
7.3.4 Statistical analysis 162
8.1 Summary 165
8.2 Conclusions 166
Curriculum vitae 187
Figure 1.1 Structure of bone 1
Figure 1.2 Types of bone fractures 2
Figure 1.3 Methods to treat bone fracture 3
Figure 1.4 Repair of fractured parts of bone by conventional method (a)
orthopaedic cast, (b) plaster cast and (c) body cast
3
Figure 1.5 Repair of fractured parts of bone by external fixation method (a)
surgical pins and rods (b) X-ray image shows the fractured parts
of tibia bone (c) circular disc and plate
4
Figure 1.6 (a) X-ray image shows the fracture in the bone of forearm, (b)
image immediately after the surgical procedure and (c) X-ray
images after 10th month
Figure 1.8 Hole inaccuracy, drill wander and delamination during bone
drilling
7
Figure 1.10 Illustration of the RUM process 9
Figure 2.1 Effect of input parameters on the performance of CSBD process 14
Figure 2.2 (a) Temperature variation w.r.t time (b) Effect of applied force
on the temperature
16
Figure 2.3 (a) I) Classical and II) Two phase drill bit, (b) change in
temperature vs drill bit used for comparative study
17
Figure 2.5 2-step internally cooled drill bit 22
Figure 2.6 Images of three drill bits used (a) new (b) after drilling 600 holes
and (c) drill bit obtained from the operation theater
26
Figure 2.7 Microwave drilling of bone showed a visible thermal necrosis 28
Figure 2.8 Effect of rotational speed on (a) force (b) torque. Effect of feed
rate on force (c) and (d) effect of amplitude on force and torque
drilling with CD and UAD
29
31
xviii
Figure 3.1 (a) Ultrasonic tool and (b) ultrasonic generator 40
Figure 3.2 Drawing of the designed tool (a) hollow and (b) solid, all
dimensions are in mm
41
Figure 3.3 Actual images of fabricated tool along with their enlarged view of
tool end face (a) hollow and (b) solid
42
Figure 3.4 Microscopic image of the diamond abrasive coated tool on the
tool shank
Figure 3.6 Measurement of vibrational frequency using a PiezoView
software, of the designed RUD tool assembly with (a) hollow tool
and (b) solid tool
44
Figure 3.7 FE analysis of RUD assembly with hollow tool 45
Figure 3.8 FE analysis of RUD assembly with solid tool 46
Figure 3.9 CNC vertical milling 47
Figure 3.10 Modified set up to perform the RUBD 48
Figure 3.11 Fresh porcine bone sample 49
Figure 3.12 Fresh porcine bone specimen (a) specimen used for first set (b)
mid diaphysis (c) specimen used for second and third set of
experiments
49
Figure 3.13 Experimental Setup: (a) for first set, (b) for second set and (c) for
third set of experiments and (d) drill tools used for the
comparative study: I) hollow tool, II) solid tool, III) CSD bit
50
Figure 3.14 Fixture used for holding the bone sample (a) actual image and (b)
CAD model
51
Figure 3.15 (a) Position of thermocouples fixed from the main drilled hole and
(b) thermocouple probe
52
Figure 3.16 Change in chip morphology with increase in rotational speed.
First row shows chips in CSBD (a) at 500 rpm, (b) 2500 rpm,
second row shows chips in RUBD with hollow tool at (c) 500 rpm,
(d) 2500 rpm and third row corresponds to microscopic
morphology of RUBD process with hollow tool at (e) 500 rpm
and (f) 2500 rpm. [Figure from 3.16 (a) to (d) were captured
online during the bone drilling by Dino light microscope and
60
xix
Figure 3.16 (e) and (f) were obtained by the microscope (BX43,
Upright microscope, Olympus)]
Figure 3.17 Effect of rotational speed and different drilling techniques on (a)
Force and (b) torque. [Feed rate = 30 mm/min, drill diameter =
3.5 mm, Amplitude = 16 µm]
62
Figure 3.18 Effect of rotational speed and different drilling techniques on
change in temperature. [Feed rate = 30 mm/min, drill diameter =
3.5 mm, Amplitude = 16 µm]
63
Figure 3.19 Change in temperature and its distribution over the radial distance
from the drill site edge vs spindle speed. [Feed rate = 30 mm/min,
drill diameter = 3.5 mm, Amplitude = 16 µm]
64
Figure 3.20 Effect of feed rate and different drilling techniques on (a) Force
and (b) torque. [Rotational speed = 1500 rpm, drill diameter = 3.5
mm, Amplitude = 16 µm]
65
Figure 3.21 Effect of feed rate and different drilling techniques on
temperature. [Rotational speed = 1500 rpm, drill diameter = 3.5
mm, Amplitude = 16 µm]
66
Figure 3.22 Change in temperature and its distribution over the radial distance
from the drill site edge vs feed rate. [Rotational speed = 1500 rpm,
drill diameter = 3.5 mm, Amplitude = 16 µm]
67
Figure 3.23 Effect of drill diameter and different drilling techniques on (a)
Force and (b) Torque. [Rotational speed = 1500 rpm, Feed Rate =
30 mm/min, Amplitude = 16 µm]
68
Figure 3.24 Effect of drill diameter and different drilling techniques on
temperature. [Rotational speed = 1500 rpm, Feed Rate = 30
mm/min, Amplitude = 16 µm]
69
Figure 3.25 Change in temperature and its distribution over the radial distance
from the drill site edge vs drill diameter. [Rotational speed = 1500
rpm, Feed Rate = 30 mm/min, Amplitude = 16 µm]
70
Figure 3.26 Effect of vibration amplitude and RUBD with hollow and solid
tool on (a) Force, (b) Torque and (c) Temperature. [Rotational
speed = 1500 rpm, Feed Rate = 30 mm/min, drill diameter = 3.5
mm]
71
xx
Figure 3.27 Change in temperature and its distribution over the radial distance
from the drill site edge vs vibrational amplitude. [Rotational speed
= 1500 rpm, Feed Rate = 30 mm/min, drill diameter = 3.5 mm]
72
Figure 3.28 SEM images of inner surface of drilled hole in bone with
magnification of 500X drilling with (a) RUBD with hollow tool,
(b) RUBD with solid tool, (c) RBD with Hollow tool (d) RBD
with solid tool and (e) CSBD. [Rotational speed = 500 rpm, Feed
rate = 10 mm/min, Drill Diameter = 4.5 mm, Amplitude = 16µm
(only for RUBD)]
Figure 3.30 Chips produced by CSBD process 75
Figure 4.1 Schematic diagram of RUBD experimental setup for
measurement of cutting force and torque
78
Figure 4.2 Fresh porcine bone specimen (a) before experiments, (b) after
experiments
78
Figure 4.3 Measured Value of force and torque w.r.t. time using the
dynamometer. [Rotational speed = 1500, feed rate = 30 mm/min,
Drill diameter = 3.5 and amplitude = 12µm]
79
Figure 4.4 (a) Effect of input process parameters on the force and (b) %
contribution of the process parameters on the force
90
Figure 4.5 Microscopic images of chips obtained at rotational speed of (a)
500 (b) 1500 and (c) 2500. [F = 10 mm/min, D = 4.5 mm, A= 16
µm]
91
Figure 4.6 (a) Effect of input process parameters on the torque and (b) %
contribution of the process parameters on the torque
92
Figure 4.7 Interaction effect between the drill diameter and feed rate on the
force (a) response surface plot (b) variation of force with drill
diameter and feed rate. [R= 1500 rpm and A = 12 µm]
94
Figure 4.8 Interaction effect between the drill diameter and feed rate on the
torque (a) response surface plot (b) variation of force with drill
diameter and feed rate. [R= 1500 rpm and A = 12 µm]
94
xxi
Figure 4.9 Interaction effect between the rotational speed and feed rate on
the force (a) response surface plot (b) variation of force with
rotational speed and feed rate. [D= 3.5 mm and A = 12 µm]
95
Figure 4.10 Interaction effect between the rotational speed and feed rate on
the torque (a) response surface plot (b) variation of force with
rotational speed and feed rate. [D= 3.5 mm and A = 12 µm]
95
Figure 4.11 Interaction effect between the amplitude and feed rate on the force
(a) response surface plot (b) variation of force with amplitude and
feed rate. [R = 1500 rpm and D= 3.5 mm]
96
Figure 4.12 Interaction effect between the amplitude and feed rate on the
torque (a) response surface plot (b) variation of force with
amplitude and feed rate. [R = 1500 rpm and D= 3.5 mm]
96
Figure 4.13 Effect of process parameters on maximum change in the
temperature at distance of (a) 0.5 mm, (b) 1.0 mm, (c) 1.5 mm and
(d) 2.0 mm
Figure 4.14 Percentage contribution of significant process parameters on
maximum change in the temperature at distance of (a) 0.5 mm, (b)
1.0 mm, (c) 1.5 mm and (d) 2.0 mm
109
Figure 4.15 Effect of rotational speed on change in temperature for
thermocouples placed at locations 0.5 mm, 1.0 mm, 1.5 mm and
2.0 mm from the drill site. [F = 30 mm/min, D = 3.5 mm and A =
12 µm]
110
Figure 4.16 Effect of feed rate on change in temperature for thermocouples
placed at locations 0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm from the
drill site. [R = 1500 rpm, D = 3.5 mm and A = 12 µm]
111
Figure 4.17 Effect of drill diameter on change in temperature for
thermocouples placed at locations 0.5 mm, 1.0 mm, 1.5 mm and
2.0 mm from the drill site. [R = 1500 rpm, F = 30 mm/min and A
= 12 µm]
112
Figure 4.18 Effect of amplitude on change in temperature for thermocouples
placed at locations 0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm from the
drill site. [R = 1500 rpm, F = 30 mm/min and D = 3.5 mm]
113
xxii
Figure 4.19 Significant interaction between feed rate and rotational speed on
change in the temperature (Δt0.5 mm). (a) 3 – D response surface
and (b) 2 – D plot for variation of change in temperature with feed
rate and rotational speed. [D = 3.5 mm and A = 12 µm]
114
Figure 4.20 Significant interaction between feed rate and amplitude on change
in the temperature (Δt0.5 mm). (a) 3 – D response surface and (b) 2
– D, plot for variation of change in temperature with feed rate and
amplitude. [R = 1500 rpm and D = 3.5 mm]
114
Figure 5.2 Porous cassettes with specimen 122
Figure 5.3 Automatic tissue processing unit for the dehydration 122
Figure 5.4 Clearing processing unit 123
Figure 5.5 Tissue embedding unit 124
Figure 5.6 Tissue embedding procedure 124
Figure 5.7 Actual images of tissue embedded on the wax mould 125
Figure 5.8 Rotary microtome used for the sectioning 125
Figure 5.9 Automatic staining unit 126
Figure 5.10 Microscopic examination procedure for Haematoxylin and Eosin
(H & E)
127
Figure 5.11 Images of final slides for the microscope examination 128
Figure 5.12 The variation of average temperature in RUBD and CSBD with
respect to each trial
129
Figure 5.13 Photographs of (a) drill hole and (b) inner surface of RUBD
specimen shows regular peripheral border and smooth surface of
the of the bone without any discoloration. (c) CSBD specimen
shows uneven hole margin with presence of brownish and
yellowish-colored particles. Yellowish discoloration is present
around the hole and (d) on inner surface. [Rotational speed = 2500
rpm, Feed rate = 10 mm/min and Drill diameter 4.5 mm
(Vibrational amplitude and frequency = 16µm and 20 kHz
respectively only for RUBD]
130
Figure 5.14 The scanner view of (a) CSBD specimen tissue shows several
splits in bone and irregular cracks at the drilling edge are present
131
xxiii
[haematoxylin and eosin (H&E)] and (b) RUDB specimen shows
uniform sections with regular, smooth drilling edge (H&E).
[Rotational speed = 2500 rpm, Feed rate = 10 mm/min and Drill
diameter 4.5 mm (Vibrational amplitude and frequency = 16µm
and 20 kHz respectively only for RUBD]
Figure 5.15 Enlarged view of hole edge drilled with CSBD method [H & E] 132
Figure 5.16 Enlarged view of hole edge drilled with RUBD method [H & E] 132
Figure 5.17 Viable osteocytes are present in all lacunae even at the cutting
edge, and no crack is noted in the bone matrix of RUBD tissue
(arrows) (a, H&E; 100x, b, H&E; 400x). (c & d) Heat induced
diffuse osteocytes necrosis is seen in a wide zone around the hole
of CSBD specimens (arrows). The bone matrix also shows
frequent micro-fractures (block arrow) (e, H&E; 100x, f, H&E;
400x). [Rotational speed = 2500 rpm, Feed rate = 10 mm/min and
Drill diameter 4.5 mm (Vibrational amplitude and frequency =
16µm and 20 kHz respectively only for RUBD]
133
Figure 5.18 Histogram drilled sample for (a) CSBD and (b) RUBD 134
Figure 6.1
Porcine bone specimens used for in-vitro study: (a) bones, (b)
specimens for pullout strength and (c) specimens for microcrack
analysis
139
Figure 6.2 Sample preparation for SEM analysis (a) main drilled hole, (b)
section of the hole and (c) final specimen for the analysis
140
Figure 6.3 (a) Testing setup for biomechanical pullout strength and (b) CAD
model of bone-holding fixture. (1) grip, 2) cortical bone screw, 3)
bone sample and 4) bone holding fixture
140
Figure 6.4 Schematic diagram of screw inserted into bone 141
Figure 6.5 Effect of rotational speed on the microcracks. Left column is from
the RUBD group and right column is from the CSBD group. First
row [Figure 6.5 (a-b)] shows the effect of two drilling methods on
the microcracks with 500 rpm, second row [Figure 6.5 (c-d)] with
1500 rpm and third row [Figure 6.5 (e-f)] with 2500 rpm
respectively. [Feed rate = 10 mm/min, drill diameter = 4.5 mm,
(amplitude = 16 µm, frequency = 20, only for RUBD)]
143
xxiv
Figure 6.6 Effect of feed rate on the microcracks. Left column is from the
RUBD group and right column is from the CSBD group. First row
[Figure 6.6 (a-b)] shows the effect of two drilling methods on the
microcracks with 10 mm/min, second row [Figure 6.6 (c-d)] with
30 mm/min and third row [Figure 6.6 (e-f)] with 50 mm/min
respectively. [Rotational speed = 500, drill diameter = 4.5 mm,
(amplitude = 16 µm, frequency = 20, only for RUBD)]
144
Figure 6.7 SEM images of drilled hole quality made by (a) CSBD and (b)
RUBD at 50 X. [spindle speed = 500 rpm, feed rate = 10 mm/min
and drill diameter = 4.5 mm, (Vibrational amplitude = 16 µm and
frequency 20 kHz only for RUBD)]
146
Figure 6.8 SEM images of drilled hole quality made by (a) CSBD and (b)
RUBD at 50 X. [spindle speed = 500 rpm, feed rate = 50 mm/min
and drill diameter = 4.5 mm, (Vibrational amplitude = 16 µm and
frequency 20 kHz only for RUBD)]
147
Figure 6.9 Edge quality of holes drilled with RUBD (a) and CSBD (b) (black
arrows show delamination near drilled hole edge). [Rotational
speed = 500 rpm; feed rate = 10 mm/min; drill diameter 4.5 mm
for RUBD: (vibration amplitude = 16 µm and frequency = 20 kHz
only for RUBD)]
148
Figure 6.10 Force - displacement diagram for axial pullout of cortical bone
screw [Rotational speed = 1500 rpm; feed rate = 10 mm/min, drill
diameter = 4.0 mm (vibration amplitude = 16 µm; frequency = 20
kHz; only for RUBD)]
150
Figure 6.11 Effects of rotational speed (a) and feed rate (b) on axial pullout
force for two bone-drilling methods
150
Figure 6.12 Specimen after axial pullout: (a) RUBD hole (arrows shows
delamination area); (b) CSBD hole [Rotational speed =1500 rpm;
feed rate = 10 mm/min; drill diameter = 4.0 mm; (vibration
amplitude = 16 µm and frequency = 20 kHz; only for RUBD)]
151
Figure 6.13 (a) Drilling of bone with RUBD produced powdered chips and
cylindrical machined rod. (b) CSBD produced fragmented chips
152
xxv
Figure 7.1 Experimental setup and equipment's used for force, torque,
temperature and tool wear measurement. 1) CNC controller unit,
2) personal computer attached to microscope, 3) Dino light
microscope, 4) RUBD tool assembly, 5) Digital thermometer with
thermocouple, 6) Tool, 7) Bone holding fixture, 8) Bone, 9) 6-
axis dynamometer, 10) Ultrasonic generator unit and 11) personal
computer attached to dynamometer
154
Figure 7.2 Microscopic images of tip wear on conventional drill bit using a
Dino lite microscope (a) new drill bit (b) after 30 drills (c) after
50 drills (d) after 100 drills
156
Figure 7.3 Microscopic images of side wear on conventional drill bit using a
Dino lite microscope (a) new drill bit (b) after 30 drills (c) after
50 drills (d) after 100 drills
157
Figure 7.4 Effect of repeated drill tool on the wear area in CSBD 157
Figure 7.5 Microscopic images of hollow drill tool at first location using a
Dino lite microscope (a) new drill bit (b) after 30 drills (c) after
50 drills (d) after 100 drills
158
Figure 7.6 Microscopic images of hollow drill tool at second location using
a Dino lite microscope (a) new drill bit (b) after 30 drills (c) after
50 drills (d) after 100 drills
159
Figure 7.7 Effect of reused drill tool on maximum cutting (a) force and (b)
torque, for both the drilling techniques
160
Figure 7.8 Effect of repeated drill tool on maximum temperature, for both
the drilling techniques
161
Figure 7.9 Effect of tool wear on chip morphology for both the drilling
technique
161
xxvii
Table No. Caption Page No.
Table 2.1 Summary of CSBD parameters on change in temperature 33
Table 2.2 Summary of CSBD parameters on cutting force and torque 37
Table 3.1 Results of FE analysis 46
Table 3.2 Specification of drill tools used for the comparative study 51
Table 3.3 Input process parameters and their range 53
Table 3.4 Run order to perform the experiments 54
Table 3.5
technique
55
technique
56
technique
56
technique
58
Table 3.6 Data summary for force and torque corresponding to the mentioned
drilling technique
Table 4.2 Run order to perform the in-vitro experiments 81
Table 4.3 Data summary for cutting force and torque 82
Table 4.4 Data summary for temperature corresponding to thermocouples
fixed at four different positions
83
Table 4.5 ANOVA for forces with respect to equation 4.2 85
Table 4.6 ANOVA for torque with respect to equation 4.3 86
Table 4.7 Pooled ANOVA for the forces with respect to equation 4.4 87
Table 4.8 Pooled ANOVA for the torque with respect to equation 4.5 88
Table 4.9 Confirmation experiments for the force and torque for statistical
modelling
89
xxviii
Table 4.10 Optimized values of the process factors for the cutting force and
torque
97
Table 4.11 ANOVA for ΔT0.5 mm with respect to equation 4.7 99
Table 4.12 ANOVA for ΔT1.0 mm with respect to equation 4.8 100
Table 4.13 ANOVA for ΔT1.5 mm with respect to equation 4.9 101
Table 4.14 ANOVA for ΔT2.0 mm with respect to equation 4.10 102
Table 4.15 Pooled ANOVA for ΔT0.5 mm with respect to equation 4.11 103
Table 4.16 Pooled ANOVA for ΔT1.0 mm with respect to equation 4.12 103
Table 4.17 Pooled ANOVA for ΔT1.5 mm with respect to equation 4.13 104
Table 4.18 Pooled ANOVA for ΔT2.0 mm with respect to equation 4.14 104
Table 4.19 Run order and corresponding input value of process parameters to
perform the confirmation experiments for validate the predicted
models
105
Table 4.20 Data summary for confirmation experiments for validate the
predicted models
106
Table 4.21 Optimized value of the process parameters for the minimum
temperature generated in the bone drilling
115
Table 4.22 Output value of temperature corresponding to optimized input
process parameters
115
Table 4.23 Comparison of present results with previous findings in CD and
simulation
116
Table 4.24 Comparison of present results with previous findings in UAD 116
Table 5.1 Input process parameters used for the histopathological
examination in RUBD and CSBD
120
Table 5.2 Comparison between maximum heat generation in RUBD and
CSBD with respect to thermocouple positions
128
Table 5.3 t-test paired sample for mean 129
Table 6.1 Process parameters and their values for in-vitro experiment 139
Table 6.2 Specification of cortical bone screw used in this work 141
Table 6.3 Run order and process parameters in experiments for microcracks
analysis
142
Table 6.4 Maximum length of microcracks (in µm) from SEM images
corresponding to two drilling processes
145
xxix
Table 6.5 Run order and process parameters in experiments for
biomechanical pullout
Table 6.6 Data summary for the maximum pullout force 149
Table 7.1 Output data summary for force, torque and temperature 155
Table 7.2 ANOVA of force, torque and temperature for RUBD and CSBD 163
xxxi
Nomenclature
xxxiii
Abbreviations
ANOVA Analysis of variance
DF Degrees of freedom
DOE Design of experiments
LBM Laser beam machining
RBD Rotary bone drilling
RUM Rotary ultrasonic machining
RSM Response surface methodology
UAD Ultrasonic assisted drilling
SEM Scanning electron microscopy
TEZ Thermal effective zone