ENGINEERING DESIGN PROJECT BOOK_pagenumber.pdf

ISBN - 978-81-963578-7-0
Editor-in-Chief
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International Research and Reviews
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Dr P SENTHIL KUMAR
Professor
PGP College of Engineering and Technology
Namakkal India
IQAC and NAAC Coordinator &
Co-Ordinator for Research and Innovation Committee
ENGINEERING DESIGN
PG PROJECT BOOK
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I realize that this book will create a great deal of controversy. It has never been easy to challenge
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ness leaders, and scientists coming to the realization.
Dr N HARIHARAN
Founder and chief Editor Heduna Publications of
International Research and Reviews
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JOURNAL ADVISERS AND CHAPTER EDIOTRS
Dr P SENTHIL KUMAR
PROFESSOR
PGP COLLEGE OF ENGINEERING AND TECHNOLOGY, NAMAKKAL
IQAC AND NAAC COORDINATOR &
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SI
NO
CHAPTER TITLE AUTHOR PAGE NO
1 “EXPERIMENTAL ANALYSIS AND OPTIMIZA-
TION OF FRICTION STIR WELDING ON ALU-
MINIUM ALLOY”
Mr. N.KUMARESAN 7-65
2 “ANALYSIS AND OPTIMIZATION OF THE
EXHAUST PORT OF AN INTERNAL COM-
BUSTION ENGINE”
Mr. R SRI SAKTHI
66-93
3 “ANALYSIS ON HEAT TRANSFER IN CERAMIC
COATED I.C ENGINE PISTON”
Mr. S. MOWLIDHARAN 94-137
4 “ANALYSIS OF FUEL TANKER TO REDUCE
THE RATE OF FUEL EVAPORATION BY COM-
POSITE MATERIALS”
Mr. P.POOVARASAN 138-192
5 “DESIGN AND ANGLE CUTTING” Mr. M.PREMKUMAR 193-237
6 “WELDING EXPERIMENTAL ANALYSIS OF
FRICTION STIR
WELDING ON MAGNESIUM ALLOYS USING FI-
NITE”
Mr. N. K MOHAMED TANVEER 238-301
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CHAPTER -1
“EXPERIMENTAL ANALYSIS AND OPTIMIZATION OF FRICTION STIR
WELDING ON ALUMINIUM ALLOY”
N.KUMARESAN
REG NO: 621821408003
ME -ENGINEERINGDESIGN,
SECOND YEAR,
PGP COLLEGE OF ENGINEERING AND
TECHNOLOGY, NAMAKKAL.
ABSTRACT
Purpose of this paper is the investigation on the properties and micro
structural changes in Friction Stir Welds in the aluminum alloy in func-
tion of varying process parameters. Tensilestrength of the produced
joints was tested and the correlation with process parameter was as-
sessed. Microstructures of various zones of FSW welds are presented
and analyzed by means of optical microscopy and hardness measure-
ments.
Mechanical resistance of test welds increased with the increase of
travel (welding) speed with constant rotational speed. Softening of the
material in weld nugget and heat affected zone was observed, of entity
inferior that that of fusion welds. Origin of tunnel (worm hole) defects
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were found and analyzed. The increase of mechanical resistance with in-
creasing welding speed offers an immediate economic return, as the pro-
cess efficiency is increased.
Keywords: FSW; Aluminum alloys, HSS Tool
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INTRODUCTION
1.1 Introduction Of Friction-Stir Welding (FSW)
Friction stir processing is an emerging surface–engineeringtechnol-
ogy basedon the principles of friction stir welding (FSW). Friction stir welding is a relatively
new joining process, invented at The Welding Institute (Cambridge, UK) in 1991 and devel-
oped initially for aluminum alloys. Since then FSW has rapidly evolved and has opened up a
variety of research channels. It is a solid-state joining technique that is energy efficient, envi-
ronment friendly, and versatile. It is being touted as the most significant development in metal
joining in the last decade. Friction stir processing (FSP) uses the same methodology as friction
stir welding, but FSP is used to modify the local microstructure and does not join metals to-
gether. The basic concept of friction stir processing is remarkably simple. A rotating tool with
pin and shoulder is inserted in the material to be treated, and traversed along the line of interest
(Figure 1.1). During FSP, the area to be processed and the tool are moved relative to each other
such that the tool traverses with overlapping passes untilthe entire selected area is processed to
a fine grain size. The rotating tool provides a continualhot working action, plasticizing metal
within a narrow zone while transporting metal from theleading face of the pin to its trailing
edge. The processed zone cools without solidification, as there is no liquid a defect-free re-
crystallized fine grain microstructure is formed. Essentially, FSP is a local thermo-mechanical
metal working process with additional adiabatic heating from metal deformation that changes
the local properties without influencing properties in theremainder of the structure. A processed
zone is produced by movement of material from the front of the pin to the back of the pin. As
mentioned later, the pin and shoulder of the tool canbe modified in a number to ways to influ-
ence material flow and micro-structural evolution. Friction Stir Processing has opened up a
new process for inducing directed, localized, and controlled materials properties in any arbi-
trary location and pattern to achieve revolutionary capability in high value-added components.
Friction stir processing provides the ability to thermo-mechanically process selective locations
on the structure‘s surface and to some considerable depth (>25mm) to enhance specific prop-
erties. Research is being increasingly focused on this aspect of the technology for use with
automotive alloys. For example, Cast aluminum alloys, such as A319, are used for suspension
and drive line components inautomobiles. The microstructure of cast A319 contains coarse
eutectic and porous
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constituents. Research indicates that friction stir processing can refine the size of the eutectic
constituents, making the microstructure finer and therefore stronger. It also closes pores that
are open to the surface of the material.
FSP can be used to create super-plastic properties never achievable before. Very fine grain size
(<5 micron) yields high strain rate super-plasticity at lower temperatures.
Figure (1) Schematic diagram of the FSW process
In addition, super-plasticity can be created in thick section aluminum alloys or in a controlled
area for subsequent local forming. FSP can be applied selectively to a location in a material
or structure to tailor specific properties without altering the performance characteristics of other
structural parts. Therefore, the long-term goal is to use friction stir processing to controllocal
properties in structural metals including aluminum and other nonferrous and ferrous alloys.
During friction stir processing, the work piece is placed on a backup plate and clamped rigidly
by an anvil along the far side to prevent lateral movement. A specially designed cylindrical tool
with a pin protruding from the shoulder rotates with a speed of several hundreds rpm and is
slowly plunged into the work piece to start the process. The pin may have a diameter one-third
of the cylindrical tool and typically has a length slightly less than the thickness of the work
piece. The pin is forced or plunged into the work piece untilthe shoulder contacts the surface
of the work piece.
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Figure 1.1 Schematic of friction stir processing: (a) rotating tool prior to contact with the
plate; (b) tool pin contacts plate creating heat; (c) Shoulder of tool contacts plate restrict-
ing further penetration while expanding the hot zone; (d) plate moves relative to rotating
tool creating a fully re-crystallized, fine grain microstructure.
As the tool descends further, its shoulder surface touches the top surface of the work piece
and creates heat. As the temperature of the material under the tool shoulder elevates, the
strength of the material decreases. The tool then moves along the selected path on the work
piece. The pin of the rotating tool provides the ‗‗stir‘‘ action in the material of the work piece.
As the tool passes, the metal cools, thereby producing a processed zone. One of the keyelements
in the FSP process is the heat generated at the interface between the tool and the work piece
which is the driving force to make the FSP process successful. The heat flux must keep the
maximum temperature in the work piece high enough so that the material is sufficiently soft
for the pin to stir but low enough so that the material does not melt. The maximum temperature
created by FSP process ranges from 80% to 90% of the melting temperature of the work piece
material, as measured by Tang et al. [1] and Colegrove et al. [2], so that welding defects and
large distortion commonly associated with fusion welding areminimized or avoided. The heat
flux in friction stir processing is primarily generated by the friction and the deformation pro-
cess. This heat is conducted to both the tool and the work piece. The amount of the heat con-
ducted into the work piece dictates a successful process which is defined by the quality, shape
and microstructure of the processed zone, as well asthe residual stress and the distortion of
the work piece. The amount of the heat gone to the tool dictates the life of the tool and the
capability of the tool to produce a good processed zone. For instance, insufficient heat from the
friction could lead to breakage of the pin of the tool since the material is not soft enough.
Therefore, understanding the heat transfer aspect of the friction stir processing is extremely
important, not only for the science but also for improving the process. In addition, the overall
efficiency in energy transfer or energy consumption of FSP is of interest, since energy trans-
lates to cost in a production environment. Advantages of Friction Stir Processing a. Low
amount of heat generated. b. Extensive plastic flow of material. c. Very fine grain size in the
stirred region. d. Random disorientation of grain boundaries in stirred region. e. Mechanical
mixing of the surface layer.FSP generates a fine, equiaxed grain morphology having a banded,
bimodal grain size of 1 to 5 micron. The microstructure of friction stir processed aluminum
alloy is normally stable under super plastic conditions of high temperature and dynamic
strain. High-angle grain
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boundaries can enhance grain boundary sliding and related super plasticity. However, optimum
super plasticity requires a homogeneous distribution of equiaxed grains of minimum grain
size. Microstructures resulting from FSP do not have a uniform grain size distribution for any
one set of process parameters. Grain size varies from the top to thebottom as well as from the
advancing to the retreating side. The differences in grain size likely are associated with differ-
ences in both peak temperature and time of application of temperature. The ability of friction
stir processing to change the local microstructure via thermo-mechanical working has been
well established by many investigators. Despite significant advances in the application of FSW
as a relatively new welding technique for welding aluminum alloys, the fundamental
knowledge of such thermal impact and thermo- mechanical processes are still not completely
understood. Chao and Qi [3] published a three- dimensional heat transfer model, a constant
heat flux input from the tool shoulder and work piece interface was assumed. A trial-and-error
procedure was used to adjust the heat input until all the calculated temperatures matched with
the measured ones. Chao et al [3] also proposed a model to predict the thermal history and the
subsequent thermal stress and distortion of the work piece without involving the mechanical
effect of the tool. Chao et al [4]investigated the variations of heat energy and temperature pro-
duced by the FSW in both the work piece and the pin tool. All investigations show that the
FSW of aluminum alloys yield welds with low distortion, high quality and low cost. Conse-
quently, better structural performance is the primary advantage of this technology‘s applica-
tions. In the model by Chaoand Qi [5], the heat generation comes from the assumption of slid-
ing friction, where Coulomb‘s law is used to estimate the shear or friction force at the interface.
Furthermore, thepressure at the tool interface is assumed to be constant, thereby enabling a
radially dependent surface heat flux distribution as a representation of the friction heat gener-
ated by the tool shoulder, but neglecting that generated by the probe surface. Frigaard, Grong
and Midling [6, 7] developed a process model for FSW, the heat input from the tool shoulder
is assumed to bethe frictional heat. The coefficient of friction is continuously adjusted to keep
the calculated temperature from exceeding the material melting point. In principle, the FSW
process can be applied to join other alloy materials such as steels and titanium. But, it is well
known that current tool materials used in the FSW for aluminum are not adequate for produc-
tion applications in many of the harder alloy materials. However, when adequate wear resistant
tool materials become available, the benefits of the FSW may promote its rapid implementation
in the production of ferrous structures and structures made from other refractory materials.
While work to develop the necessary tool materials continues, it is also
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important to make progress in the development of the FSW process for steels. For instance,
experimental studies of austenitic stainless steels by Reynolds et al [8] revealed the microstruc-
tures, residual stresses and strength of the friction stir welds. To further understandthe funda-
mental mechanisms associated with the welding formation process and improve the welding
quality for the FSW of steels, numerical modeling and simulations of transient temperature and
residual stresses are valuable and necessarily needed. Colegrove [9] used an advanced analyti-
cal estimation of the heat generation for tools with a threaded probe to estimate the heat gener-
ation distribution. The fraction of heat generated by the probe is estimated to be as high as 20%,
which leads to the conclusion that the analytical estimated probe heat generation contribution
is not negligible. Song and Kovacevic [10] investigated the influence of the preheating/dwell
period on the temperature fields. They assume a sliding condition and used an effective friction
coefficient and experimental plunge force in the heat source expression. Chen and Kovacevic
[11] developed a three-dimensional thermo- mechanical model including the mechanical action
of the shoulder and the thermo- mechanical effect of the welded material for the FSW of an Al-
alloy. Schmidt et al [12] established an analytical model for heat generation by friction stir
welding, based on differentassumptions of the contact condition between the rotating tool
surface and the weld piece.The material flow and heat generation were characterized by the
contact conditions at the interface, and were described as sliding, sticking or partial slid-
ing/sticking. Zhu and Chao
[13] conducted Three-dimensional nonlinear thermal and thermo-mechanical numerical simu-
lations using finite element analysis code – WELDSIM on 304L stainless steel. An inverse
analysis method for thermal numerical simulation was developed. McClure et al [14] used
Rosenthal equations to calculate temperature fields in friction stir welding. The existence of
the thermocouples and holes containing thermocouples do not influence the temperature field.
Ulysse [15] used a three dimensional visco-plastic modeling to model friction stir welding pro-
cess. Forces applied on the tool were computed for various welding and rotational speeds. Pin
forces increase with increasing welding speeds, but the opposite effect is observed for increas-
ing rotational speeds. Soundararajan [16] developed a finite element thermo-mechanical model
with mechanical tool loading considering a uniform value for contact conductance and used for
predicting the stress at the work piece and backing plateinterface. These pressure distribution
contours are used for defining the non-uniform adaptivecontact conductance used in the ther-
mal model for predicting the thermal history in the work piece. The thermo-mechanical model
was then used to predict stress development in friction stir welding.
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1.2 FSW PRINCIPLE
In FSW, a cylindrical-shouldered tool, with a profiled threaded/unthreaded probe (nib or
pin) is rotated at a constant speed and fed at a constant traverse rate into the joint line between
two pieces of sheet or plate material, which are butted together. The parts have to be clamped
rigidly onto a backing bar in a manner that prevents the abutting joint faces from being forced
apart. The length of the nib is slightly less than the weld depth required and the tool shoulder
should be in intimate contact with the work surface. The nib is then moved against the work,
or vice versa.
Fig 1 : Diagram of FSW principle
Frictional heat is generated between the wear-resistant welding tool shoulder and nib, and the
material of the work pieces. This heat, along with the heat generated by the mechanical mixing
process and the adiabatic heat within the material, cause the stirred materials to softenwithout
reaching the melting point (hence cited a solid-state process), allowing the traversing of the
tool along the weld line in a plasticized tubular shaft of metal. As the pin is moved in
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the direction of welding, the leading face of the pin, assisted by a special pin profile, forces
plasticized material to the back of the pin while applying a substantial forging force to consol-
idate the weld metal. The welding of the material is facilitated by severe plastic deformation in
the solid state, involving dynamic recrystallization of the base material
1.3 FSW PROCESS
FSW uses a non-consumable tool to generate frictional heat at the point of welding,
inducing complex plastic deformation of the work piece along the joint line. Generally the
plates to be joined are placed on a rigid backing plate and clamped to prevent the faying joint
faces from separating. A shouldered cylindrical tool, with a specially shaped pin (probe), is
then rotated and slowly plunged between the faying surfaces. This causes frictional heating of
the plates, which in turn lowers their mechanical strength. After a certain dwell time weld trav-
erse starts whilst a relatively high axial load (z-force) is maintained (by a forwards rake angle)
on the tool shoulder behind the pin to support weld forging. After welding the tool extracts
from the plate to leave a characteristic keyhole.
During welding the tool profile is the primary cause of the mixing and recombining of
the plasticized material that forms the so-called weld ‗third-body‘ region. This region is also
termed the thermo-mechanically affected zone (TMAZ). The form of the tool geometry and
selection of process parameter settings are therefore essential starting points for development
of optimization strategies. Tool design improvement rests on measuring the forces exerted by
the third-body region on the tool during welding. Process parameters or tool geometries that
minimize these forces, whilst retaining mechanical properties, will increase process efficiency
and reduce the heat input required during welding. FSW process is divided in two famous pro-
cesses defined as lab joints and butt joints.
In this research the process of butt joints is investigated. These joints are when two
work pieces are clamped on a rigid back plate. The clamping prevents the work pieces from
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spreading apart or lifting during welding. The welding tool, consisting of a shank, shoulder and
pin, is then rotated to a prescribed speed and tilted with respect to the work piece normal.The
tool is slowly plunged into the work piece material at the butt line, until the shoulder of the tool
forcibly contacts the upper surface of the material and the pin is a short distance fromthe back
plate. A downward force is applied to maintain the contact and a short dwell time is observed
to allow for the development of the thermal fields for preheating and softening the material
along the joint line. At this point, a lateral force is applied in the direction of welding(travel
direction) and the tool is forcibly traversed along the butt line, until it reaches the end of the
weld; alternately, the work pieces could be moved, while the rotating tool remains stationary.
Upon reaching the end of the weld, the tool is withdrawn, while it is still being rotated. As the
pin is withdrawn, it leaves a keyhole at the end of the weld. Shoulder contact leaves in its wake
an almost semi-circular ripple in the weld track, as depicted schematically. The process of butt
joints is shown in Figure.
Fig 2: diagram of FSW process
1.3.1 HEAT GENERATION
During FSW, heat is generated by friction between the tool and the work-piece and via
plastic deformation. A fraction of the plastic deformation energy is stored within the thermo
mechanically processed region in the form of increased defect densities. In the weld, amixture
of recovery and recrystallization phenomena occur simultaneously.
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Fig. 3 : Schematic cross-section of a typical FSW weld showing four distinct zones:
(A) base metal, (B) heat-affected, (C) thermo mechanically affected and
(D) stirred (nugget) zone.
1.3.2 WELDING VARIABLES
The welding speed, the tool rotational speed, the vertical pressure on the tool, the tilt
angle of the tool and the tool design are the main independent variables that are used to control
the FSW process. The heat generation rate, temperature field, cooling rate, x-directionforce,
torque, and the power depend on these variables. The effects of several of the independent
variables on the peak temperature have been discussed in the previous section. Inshort, peak
temperature increases with increasing rotational speed and decreases slightly with welding
speed. Peak temperature also increases with increase in the axial pressure increase in peak tem-
perature with increase in rotational speed.
During FSW, the torque depends on several variables such as the applied vertical pres-
sure, tool design, the tilt angle, local shear stress at the tool material interface, the frictioncoef-
ficient and the extent of slip between the tool and the material. Measured torque values can
provide some idea about the average flow stress near the tool and the extent of slip between the
tool and the work-piece for certain conditions of welding, when other variables are kept con-
stant. The torque decreases with increase in the tool rotation speed due to increase in the heat
generation rate and temperature when other variables are kept constant. It becomes easier for
the material to flow at high temperatures and strain rates. However, torque
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is not significantly affected by the change in welding speed. The relative velocity between the
tool and the material is influenced mainly by the rotational speed. Therefore, the heat genera-
tion rate is not significantly affected by the welding speed. High traverse speeds tend to reduce
heat input and temperatures.
The torque increases only slightly with the increase in traverse speed because material
flow becomes somewhat more difficult at slightly lower temperatures. The torque on the tool
can be used to calculate the power required from P =ώM, where M is the total torque on the
tool. Excessive x-direction force can be an important indicator of potential for tool erosion and,
in extreme cases, tool breakage. Axial pressure also affects the quality of the weld. Very high
pressures lead to overheating and thinning of the joint while very low pressures lead to insuf-
ficient heating and voids. Power requirement also increases with the increase in axial pressure
1.4 TOOL DESIGN
Tool design influences heat generation, plastic flow, the power required, and the uni-
formity of the welded joint. The shoulder generates most of the heat and prevents the plasticized
material from escaping from the work-piece, while both the shoulder and the tool pin affect the
material flow. In recent years several new features have been introduced in the design of tools.
Several tools designed at TWI are shown in Table.
The Whorl and MX-Tri flute have smaller pin volumes than the tools with cylindrical
pins. The tapered threads in the whorl design induce a vertical component of velocity that fa-
cilitates plastic flow. The flute in the MX-Tri flute also increases the interfacial area between
tool and the work-piece, leading to increased heat generation rates, softening and flow of ma-
terial. Consequently, more intense stirring reduces both the traversing force for theforward tool
motion and the welding torque. Although cylindrical, Whorl and Tri flute designs are suitable
for butt welding, they are not useful for lap welding, where excessive thinning of the upper
plate can occur together with the trapping of adherent oxide betweenthe overlapping surfaces.
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Flared-Tri flute and A-skew tools were developed to ensure fragmentation of the inter-
facial oxide layer and a wider weld than is usual for butt welding. The Flared-Tri flute tool is
similar to MX-Tri flute with an expanded flute, while A-skew TM tool is a threaded tapered
tool with its axis inclined to that of the machine spindle. Both of these tools increase the swept
volume relative to that of the pin, thus expanding the stir region and resulting in a wider weld
and successful lap joints. Motion due to rotation and translation of the tool induces asymmetry
in the material flow and heating across the tool pin. It has been demonstrated that during FSW,
material flows primarily on the retreating side. To overcome this problem, TWI devised a new
tool, Re-stir, which applies periodic reversal of toolrotation. This reversal of rotation elimi-
nates most problems associated with inherent asymmetry of conventional FSW. With the ex-
ception of FSW with Re-stir tool, material flowis essentially asymmetric about joint interface.
Understanding the asymmetry in material flowis important for optimal tool design.
Fig Basic variants on the Whorl type probes
1.5 MICROSTRUCTURE CLASSIFICATION OF FSW
A schematic diagram is shown in the below Figure which clearly identifies the various
regions. The process not only generates a heat-affected zone (HAZ), but within this HAZ near
the weld nugget a thermo-mechanically affected zone (TMAZ) is also produced. TMAZ is a
result of the severe plastic deformation and the temperature rise in the plate from the friction
heating. The friction stir weld appears broad at the top surface with a smaller well-defined weld
nugget in the interior. The weld nugget corresponds to the tool probe that penetrates through
the plate thickness, whereas the broader surface deformation and subsequent recrystallization
are associated with the rotating tool shoulder.
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The system divides the weld zone into distinct regions as follows:
A. Unaffected material
B. Heat affected zone (HAZ)
C. Thermo-mechanically affected zone (TMAZ)
D. Weld nugget (Part of thermo mechanically affected zone)
A. Unaffected material or parent metal:
This is material remote from the weld, which has not been deformed, and which alt-
hough it may have experienced a thermal cycle from the weld is not affected by the heat in
terms of microstructure or mechanical properties
B.Heat affected zone (HAZ):
In this region, which clearly will lie closer to the weld centre, the material has experi-
enced a thermal cycle which has modified the microstructure and/or the mechanical properties.
However, there is no plastic deformation occurring in this area. In the previous system, this
was referred to as the "thermally affected zone". The term heat affected zone is now preferred,
as this is a direct parallel with the heat affected zone in other thermal processes, and there is
little justification for a separate name.
C.Thermo-mechanically affected zone (TMAZ):
In this region, the materialhas been plastically deformed by thefriction stir welding tool,
and the heatfrom the process will also have exertedsome influence on the material. In thecase
of aluminium, it is possible to get significant plastic strain without recrystallization inthis re-
gion, and there is generally a distinct boundary between the recrystallized zone and the de-
formed zones of the TMAZ. Aluminium behaves in a different manner to most other materials,
in that it can be extensively deformed at high temperature without recrystallization.In other
materials, the distinct recrystallized region (the nugget) is absent, and the whole of the TMAZ
appears to be recrystallized. This is certainly true of materials which have no thermally induced
phase transformation which will in itself induce recrystallization without strain, for example
pure titanium, b titanium alloys, austenitic stainless steels and copper. In
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materials such as ferrite steels and a-b titanium alloysunderstanding the microstructure is made
more difficult by the thermally induced phase transformation, and this can also make the
HAZ/TMAZ boundary difficult to identify precisely.
D.Weld Nugget:
The recrystallized area in the TMAZ in aluminium alloys has traditionally been called
the nugget. Although this term is descriptive, it is not very scientific. However, its use has
become widespread, and as there is no word which is equally simple with greater scientific
merit, this term has been adopted. It has been suggested that the area immediately below the
tool shoulder (which is clearly part of the TMAZ) should be given a separate category, as the
grain structure is often different here. The microstructure here is determined by rubbing by the
rear face of the shoulder, and the material may have cooled below its maximum. It is suggested
that this area is treated as a separate sub-zone of the TMAZ.
1.5.1 MICROSTRUCTURAL FEATURES
The solid-state nature of the FSW process, combined with its unusual tool and asymmetric
nature, results in a highly characteristic microstructure. While some regions are common to all
forms of welding some are unique to the technique. While the terminology is varied the fol-
lowing is representative of the consensus.
 The stir zone (also nugget, dynamically recrystallized zone) is a region of heavily de-
formed material that roughly corresponds to the location of the pin during welding. The
grains within the stir zone are roughly equiaxed and often an order of magnitude smaller
than the grains in the parent material. A unique feature of the stir zone is the common
occurrence of several concentric rings which has been referred to as an
‗onion-ring‘ structure. The precise origin of these rings has not been firmly established,
although variations in particle number density, grain size and texture haveall been sug-
gested.
 The flow arm is on the upper surface of the weld and consists of material that is dragged
by the shoulder from the retreating side of the weld, around the rear of the tool, and
deposited on the advancing side.
 The thermo-mechanically affected zone (TMAZ) occurs on either side of the stir
zone. In this region the strain and temperature are lower and the effect of welding on
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the microstructure is correspondingly smaller. Unlike the stir zone the microstructure
is recognizably that of the parent material, albeit significantly deformed and rotated.
Although the term TMAZ technically refers to the entire deformed region it is often
used to describe any region not already covered by the terms stir zone and flow arm.
 The heat-affected zone (HAZ) is common to all welding processes. As indicated by the
name, this region is subjected to a thermal cycle but is not deformed during welding.
The temperatures are lower than those in the TMAZ but may still have a significant
effect if the microstructure is thermally unstable. In fact, in age-hardened aluminium
alloys this region commonly exhibits the poorest mechanical properties.
1.6 IMPORTANT WELDING PARAMETERS
1.6.1 Tool rotation and traverse speeds:
There are two tool speeds to be considered in friction-stir welding; how fast the tool
rotates and how quickly it traverses the interface. These two parameters have considerable im-
portance and must be chosen with care to ensure a successful and efficient welding cycle. The
relationship between the welding speeds and the heat input during welding is complex but, in
general, it can be said that increasing the rotation speed or decreasing the traverse speed will
result in a hotter weld. In order to produce a successful weld it is necessary that thematerial
surrounding the tool is hot enough to enable the extensive plastic flow required and minimize
the forces acting on the tool. If the material is too cool then voids or other flaws may be present
in the stir zone and in extreme cases the tool may break.
At the other end of the scale excessively high heat input may be detrimental to the
final properties of the weld. Theoretically, this could even result in defects due to theliquation
of low-melting-point phases (similar to liquation cracking in fusion welds). These competing
demands lead onto the concept of a ‗processing window‘: the range of processing parameters
that will produce a good quality weld. Within this window the resulting weld will
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have a sufficiently high heat input to ensure adequate material plasticity but not so high that
the weld properties are excessively reduced.
1.6.2 Tool tilt and Plunge depth:
The plunge depth is defined as the depth of the lowest point of the shoulder below the
surface of the welded plate and has been found to be a critical parameter for ensuring weld
quality. Plunging the shoulder below the plate surface increases the pressure below the tool and
helps ensure adequate forging of the material at the rear of the tool. Tilting the tool by 2- 4
degrees, such that the rear of the tool is lower than the front, has been found to assist this forging
process. The plunge depth needs to be correctly set, both to ensure the necessary downward
pressure is achieved and to ensure that the tool fully penetrates the weld. Giventhe high
loads required the welding machine may deflect and so reduce the plunge depth compared to
the nominal setting, which may result in flaws in the weld. On the other hand an excessive
plunge depth may result in the pin rubbing on the backing plate surface or a significant under
match of the weld thickness compared to the base material. Variable load welders have been
developed to automatically compensate for changes in the tool displacement while TWI have
demonstrated a roller system that maintains the tool position above the weld plate.
1.6.3 Tool requirements:
Because the peak temperatures experienced during friction stir welding are lower than
those of fusion welding processes distortion may be reduced and micro structural changes as-
sociated with the welding thermal cycle are minimized. Characteristics such as these make
friction stir welding an attractive process for welding a variety of high temperature alloys and
metal matrix composites. For these alloys, however, the selection of materials for the rotating
non consumable tooling is crucial to successful deployment. Properties that are likely to be
important for tool materials include strength, fatigue resistance, wear resistance, thermal con-
ductivity, toughness, and chemical stability. High strength relative to base materials is an ab-
solute necessity for tools.
1.6.4 Welding forces:
During welding a number of forces will act on the tool:
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 A downwards force is necessary to maintain the position of the tool at or below the
material surface. Some friction-stir welding machines operate under load control but
in many cases the vertical position of the tool is preset and so the load will vary during
welding.
 The traverse force acts parallel to the tool motion and is positive in the traverse direc-
tion. Since this force arises as a result of the resistance of the material to the motion of
the tool it might be expected that this force will decrease as the temperatureof the ma-
terial around the tool is increased.
 The lateral force may act perpendicular to the tool traverse direction and is defined here
as positive towards the advancing side of the weld.
 Torque is required to rotate the tool, the amount of which will depend on the down force
and friction coefficient (sliding friction) and/or the flow strength of the material in the
surrounding region (sticking friction).
In order to prevent tool fracture and to minimize excessive wear and tear on the tool and asso-
ciated machinery, the welding cycle should be modified so that the forces acting on the tool are
as low as possible, and abrupt changes are avoided. In order to find the bestcombination of
welding parameters it is likely that a compromise must be reached, since the conditions that
favor low forces (e.g. high heat input, low travel speeds) may be undesirable from the point of
view of productivity and weld properties.
1.6.5 Flow of material:
Early work on the mode of material flow around the tool used inserts of a
different alloy, which had a different contrast to the normal material when viewed through a
microscope, in an effort to determine where material was moved as the tool passed. The data
was interpreted as representing a form of in-situ extrusion where the tool, backing plate and
cold base material form the ‗extrusion chamber‘ through which the hot, plasticized material is
forced. In this model the rotation of the tool draws little or no material around the front of the
pin instead the material parts in front of the pin and passes down either side. After the material
has passed the pin the side pressure exerted by the ‗die‘ forces the material back together and
consolidation of the join occurs as the rear of the tool shoulder passes overhead and the large
down force forges the material.
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More recently, an alternative theory has been advanced that advocates considerable material
movement in certain locations. This theory holds that some material does rotate around the pin,
for at least one rotation, and it is this material movement that produces the ‗onion-ring‘ struc-
ture in the stir zone. The researchers used a combination of thin Cu strip inserts and a
‗frozen pin‘ technique, where the tool is rapidly stopped in place. They suggested that material
motion occurs by two processes:
1. Material on the advancing front side of a weld enters into a zone that rotates and ad-
vances with the pin. This material was very highly deformed and sloughs off behindthe
pin to form arc-shaped features when viewed from above (i.e. down the tool axis). It
was noted that the copper entered the rotational zone around the pin, where it was bro-
ken up into fragments. These fragments were only found in the arc shaped featuresof
material behind the tool.
2. The lighter material came from the retreating front side of the pin and was dragged
around to the rear of the tool and filled in the gaps between the arcs of advancing side
material. This material did not rotate around the pin and the lower level of deformation
resulted in a larger grain size.
The primary advantage of this explanation is that it provides a plausible explanation for the
production of the onion-ring structure.
1.6.6 Generation and flow of heat:
For any welding process it is, in general, desirable to increase the travel speed and
minimize the heat input as this will increase productivity and possibly reduce the impact of
welding on the mechanical properties of the weld. At the same time it is necessary to ensure
that the temperature around the tool is sufficiently high to permit adequate material flow and
prevent flaws or tool fracture.
When the traverse speed is increased, for a given heat input, there is less time for heat
to conduct ahead of the tool and the thermal gradients are larger. At some point the speed will
be so high that the material ahead of the tool will be too cold, and the flow stress too high, to
permit adequate material movement, resulting in flaws or tool fracture. If the ‗hot zone‘ is too
large then there is scope to increase the traverse speed and hence productivity.
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The welding cycle can be split into several stages during which the heat flow and ther-
mal profile will be different:
 Dwell. The material is preheated by a stationary, rotating tool in order to achieve a
sufficient temperature ahead of the tool to allow the traverse. This period may also
include the plunge of the tool into the work piece.
 Transient heating. When the tool begins to move there will be a transient period
where the heat production and temperature around the tool will alter in a complex man-
ner until an essentially steady-state is reached.
 Pseudo steady-state. Although fluctuations in heat generation will occur the thermal
field around the tool remains effectively constant, at least on the macroscopic scale.
 Post steady-state. Near the end of the weld heat may ‗reflect‘ from the end of the plate
leading to additional heating around the tool.
Heat generation during friction-stir welding arises from two main sources: friction at
the surface of the tool and the deformation of the material around the tool. The heat generation
is often assumed to occur predominantly under the shoulder, due to its greater surface area,
and to be equal to the power required to overcome the contact forces betweenthe tool and
the work piece. The contact condition under the shoulder can be described by sliding friction,
using a friction coefficient μ and interfacial pressure P, or sticking friction, based on the inter-
facial shear strength &tor; at an appropriate temperature and strain rate. Mathematical approx-
imations for the total heat generated by the tool shoulder Qtotal have beendeveloped using both
sliding and sticking friction models:
(Sliding)
(Sticking)
where ω is the angular velocity of the tool, Rshoulder is the radius of the tool shoulder
and Rpin that of the pin. Several other equations have been proposed to account for factors such
as the pin but the general approach remains the same.
A major difficulty in applying these equations is determining suitable values for the
friction coefficient or the interfacial shear stress. The conditions under the tool are both
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extreme and very difficult to measure. To date, these parameters have been used as 'fitting
parameters' where the model works back from measured thermal data to obtain a reasonable
simulated thermal field. While this approach is useful for creating process models to predict,
for example, residual stresses it is less useful for providing insights into the process itself.
1.7 MECHANICAL PROPERTIES OF ALUMINIUM ALLOY
Property Value
Atomic Number 13
Atomic Weight (g/mol) 26.98
Melting Point (°C) 660.2
Boiling Point (°C) 2480
Mean Specific Heat (0-100°C) (cal/g.°C) 0.219
Thermal Conductivity (0-100°C) (cal/cms.
°C)
0.57
Thermal Expansion Coefficient
(× 10-6
/K)
20.4
Co-Efficient of Linear Expansion
23.5
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(0-100°C) (x10-6
/°C)
Electrical Resistivity at 20°C (µΩcm) 2.69
Density (g/cm3
) 2.6898
Modulus of Elasticity (GPa) 68.3
Poissons Ratio 0.34
Elastic Modulus (Gpa) 70
Tensile Strength (Mpa) 230
Yield Strength (Mpa) 215
Percent Elongation (%) 10
Table 2: mechanical properties of Aluminium Alloy
1.8 ADVANTAGES OF FSW PROCESSES
 Retain near-parent metal properties across the weld, good strength and ductility
 Join similar and dissimilar materials that can be easily welded.
 The weld quality is excellent (no porosity) compare to the other welding.
 Avoids the weaknesses caused by distortion and metallurgical reactions, because no
melting of materials
 Low residual stresses
 No consumables (filler material, shielding gases)
 Improved safety
1.9 FSW – APPLICATIONS
Shipbuilding and marine industries:
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The shipbuilding and marine industries are two of the first industry sectors which have
adopted the process for commercial applications.
The process is suitable for the following applications
Aerospace industry:
At present the aerospace industry is welding prototype and production parts by friction
stir welding. Opportunities exist to weld skins to spars, ribs, and stringers for use in military
and civilian aircraft. In which a high proportion of the rivets are replaced by friction stir weld-
ing, has made many certification flights. This offers significant advantages comparedto riveting
and machining from solid, such as reduced manufacturing costs and weight savings. Longitu-
dinal butt welds in Al alloy fuel tanks for space vehicles have been friction stir welded and
successfully used. The process could also be used to increase the size of commercially available
sheets by welding them before forming.
The friction stir welding process can therefore be considered for:
Railway industry:
The commercial production of high speed trains made from aluminium ex-
trusions which may be joined by friction stir welding has been published. Applications include.
Land transportation:
The friction stir welding process is currently being used commercially, and is also being
assessed by several automotive companies and suppliers to this industrial sector for its com-
mercial application. Existing and potential applications include
1.10 LIMITATIONS
However, FSW produces a heterogeneous microstructure in the weld zone, causing cor-
rosion problems. The variation of microstructure is caused by the different frictional heat input
determined by welding parameters, especially travel and spindle speeds. Steel can be friction
stir welded but the essential problem is that tool materials wear rapidly. Indeed, the wear debris
from the tool can frequently be found inside the weld. FSW uses forces, which
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are significantly higher relative to arc welding. Therefore, the design of the joint and the
fixture, as well as the rigidity of the equipment required, are factors to be considered.
However, the main limitations of the FSW process are at present:
 Work pieces must be rigidly clamped due to high forces involve in welding
 Backing bar required (except where self-reacting tool or directly opposed tools are
used)
 Keyhole at the end of each weld
 Cannot make joints which required metal deposition (e.g. fillet welds)
CHAPTER 2 LIT-
ERATURE REVIEW
2.1 Experimental study on the effect of rotational speed and tool pin profile on aa2024
aluminium friction stir welded butt joints
P. Bahemmat, A. Rahbari, M. Haghpanahi, M. K. Besharati.
Friction stir welding (FSW) is a novel solid state welding process for joining metallic
alloys and has been employed in several industries such as aerospace and automotive for join-
ing aluminium, magnesium and copper alloys. The various parameters such as rotational speed,
longitudinal speed, axial force and attack angle play vital roles in FSW process in order to
analysis the weld quality. The aim of this study is to investigate the effect of different rota-
tional speed and tool pin profile on the weld quality of AA2024 aluminium which has gathered
wide acceptance in the fabrication of light weight structures requiring a
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high strength-to-weight ratio. It must be said that the four flute and taper screw thread pin are
used as pin profiles in this research. The appearance of the weld is well and no obvious defect
is found using these tools. The grain of the weld nugget is very fine and the precipitation dis-
tributes equably. Consequently, the obtained results elucidate the variation of stress as a func-
tion of strain and the effect of different rotational speed and pin profiles on yield strengthand
elongation.
2.2 Recent advances in friction-stir welding – Process, weldment structure and
properties
R. Nandan a, T. DebRoy a, H.K.D.H. Bhadeshia.
Friction-stir welding is a refreshing approach to the joining of metals. Although origi-
nally intended for aluminium alloys, the reach of FSW has now extended to a variety of mate-
rials including steels and polymers. This review deals with the fundamental understanding of
the process and its metallurgical consequences. The focus is on heat generation, heat transfer
and plastic flow during welding, elements of tool design, understanding defect formation and
the structure and properties of the welded materials.
2.3 Friction stir welding of aluminium foam materials
H. Horn
The aim of the study was to examine the suitability of the welding technique Friction
Stir Welding (FSW) for welding aluminium foam materials in an un foamed condition. It could
be noticed that such materials can be welded both of the same type, with sandwich sheets and
also with conventional aluminium sheets. After the welding process the foaming process could
be carried out without difficulty. In opposite to the structure of the base materials, in the weld-
ing region a smaller grain size took place. The strength properties of theconnection are corre-
sponding to the requests.
2.4 Finite Element Modelling of Friction Stir Welding of Aluminium alloy Plates Inverse
Analysis using a Genetic Algorithm
T. De Vuyst1, L. D‘Alvise1, A. Simar2, B. de Meester2, S. Pierret1.
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This paper presents finite element simulation results of instrumented FSW experiments
on aluminium alloys 6005A-T6 and 2024-T3. The SAMCEF™ finite element code is used to
perform the simulations. The FE model involves a sequential thermal-mechanical analysis and
includes contact between the meshed tool, work piece and backing plate. The model takes into
account the pressure applied by the tool on the weld as well as theheat input. The heat transfers
such as convection in air and contact conductance with the backing plate are modeled. For each
experiment, the temperature time-histories were recorded at several locations in the work
piece. The heat input in the finite element model is identified by minimizing the objective func-
tion of a constrained problem using a genetic optimization algorithm. The objective function is
the square of the difference between the experimental measurements and the numerical predic-
tion of temperature. Finally, levels of residual stress predicted by simulation are presented.
2.5 Friction Stir Welding – Process Developments and Variant Techniques
By W M Thomas, I M Norris, D G Staines, and E R Watts.
Friction stir welding (FSW) is now extensively used in aluminium industries for joining
and material processing applications. The (FSW) technology has gained increasing interest and
importance since its invention at TWI almost 14 years ago. The basic principle and the contin-
uing development of the FSW technology are described and recent applicationsare reviewed.
The paper will introduce some of the variants of FSW, such as Twin-stir™ Skew-stir™, Re-
stir™, Dual-rotation stir and the Pro-stir™ near-net shape processing technique. Particular at-
tention will also be paid to tool probe/shoulder features, in relation to the joint geometry being
welded. In addition, this paper makes special reference to the mechanical and structural integ-
rity that can be expected from FSW technology.
2.6 Mechanical properties of friction stir welded joints of 1050 –H24 aluminium alloy
H. J. Liu, H. Fujii, M. Maeda and K. Nogi.
The friction stir welding (FSW) of 1050 –H24 aluminium alloy was performed to in-
vestigate the mechanical properties of the joints and determine the optimum FSW parameters.
The mechanical properties of the joints were evaluated via tensile tests. The experimental re-
sults showed that a distinct softened region located at the weld and heat affected zones occurred
in the joints. The degree of softening and tensile properties of the joints are significantly af-
fected by the welding process parameters, such as welding speed and
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rotation speed. The optimum FSW parameters can be determined from the relations between
the tensile properties and the welding parameters, and the maximum tensile strength of the
joints is equivalent to 80% of that of the base material. When the welding parameters deviate
from the optimum values, a crack like defect or significant softening is produced in the joints,
thus the tensile properties of the joints deteriorate and the fracture locations of the joints change.
All these results can be explained by the hardness distributions and welding defectsin the
joints.
2.7 Friction Stir Welding of 2219 Aluminum: Behavior of (Al2Cu) particles
BY G. CAO AND S. KOU.
An experimental study was conducted to determine if the maximum temperature in
the work piece can reach the lower bound of the melting temperature range and triggerliqua-
tion during friction stir welding (FSW) of aluminum alloys as some computer simulation has
suggested. Alloy 2219, which is essentially a binary Al-Cu alloy, was selected as the mate-
rial for study because of its clear lower bound of the melting temperature range, that is, the
eutectic temperature 548°C. In addition to FSW, gas metal arc welding (GMAW) ofAlloy
2219 was also conducted to provide a benchmark for checking liquation in FSW ofAlloy
2219. The microstructure of the resultant welds was examined by both optical andscanning
electron microscop particles
acted as in-situ micro sensors, clearly indicating the onset of liquation by reacting with the
surrounding aluminum matrix and forming distinct composite like eutectic particles upon
reaching -induced
suggesting that the eutectic temperature was not reached during FSW. However, in most
fric
–15 μm in length in both the
es appeared to
the particles in the work piece. No apparent correlation between the extent of agglomeration
and the welding condition was found.
2.8 Friction stir welding characteristics of 2017-T351 aluminum alloy sheet
H. J. LIU.
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Heat-treatable aluminum alloys are difficult to fusion weld because of easy formation
of some welding defects such as crack and porosity in the weld [1]. Friction stir welding (FSW)
is a solid state welding process in which the crack and porosity often associated with fusion
welding processes are eliminated [1, 2]. Therefore, the FSW process is being studied to weld
heat-treatable aluminum alloys in order to obtain high-quality joints [3–10].However,some
studies have indicated that FSW gives rise to the softening of heat-treatable aluminum alloys,
thus resulting in the degradation of the mechanical properties of the joints. The degradation
extent is related not only to the alloy type [9–11], but also to the alloy thickness [12–16]. 2017-
T351 aluminum alloy is one of the 2xxx-series heat-treatable aluminum alloys,and a 5-mm
thick 2017-T351 plate has been friction stir welded to examine the tensile properties and frac-
tion locations of the joints [9]. This letter aims to further demonstrate the FSW characteristics
of a 3-mm thick 2017-T351 sheet to comprehend the effect of alloy thickness
CHAPTER 3 EX-
PERIMENTAL WORK
The rolled plates of Aluminium alloy were machined to the required dimensions
(100 mm x 100 mm x 5 mm). Square butt joint configuration was prepared to fabricate the
joints. The plates to be joined were mechanically and chemically cleaned by acetone before
welding to eliminate surface contamination. The direction of welding was normal to the rolling
direction. Necessary care was taken to avoid joint distortion and the joints were made by se-
curing the base metal. A non-consumable, rotating tool made of high carbon steel was used to
fabricate FSW joints.
FSW – RADIAL DRILLING MACHINE SETUP
 Al alloy plates, and sheet metal each with a dimension of 100 x 100 x5 mm3
are butt
welded in an adapted Radial drilling machine for FSW. Figure shows the picture of the
whole setup used for FSW.
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 The tool made of High-speed steel consists of shank, shoulder, and pin with radius of
18, and 6 mm respectively (see Figure ).
FSW experiments are performed varying the tool rotation speed (900 rpm) and the traverse
speed of 70 mm/min. The setup consists of a fixture to clamp the two plates together. A vertical
force of 7KN is applied on the tool.
Friction Stir Welding tool
FIGURE 13 Thermocouple positions on welded workpiece AA 6061-T6
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Fixture arrangement for Friction stir Welding
 The plates are prepared to measure the temperature at 8 points using thermocouples.
On each plate, four 6mm diameter holes were drilled on one side of the plate.
 Type K thermocouples of 5 mm diameter are subsequently inserted into the holes and
glued so that the thermocouple ends are in intimate contact with the workpiece. The
locations of thermocouples in the workpiece are shown in figure 13.
Experimental set-up of FSW using Radial Drilling machine
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3.1 RADIAL DRILLING MACHINE SPECIFICATION
 Length of bed = 2 feet
 Power required = 3Ǿ, 440 v
 Change of speed = 4 speed
Speed 350 rpm -1440 rpm
Extra accessories :
 Electric motor and reverse & forward switch = 1.5HP
 Up and down electric motor = 0.5 HP
Fixture set-up
3.2 MATERIAL REQUIRMENT
Partially recrystallized IS 737 Gr 19000 condition O having the chemical composition
Si- 0.181%, Fe- 0.266%, Cu- 0.008%, Mn- 0.035%, Mg- 0.195%, Al-99.30% was used. The
dimensions of the aluminium alloy plates were 100 mm x 100 mm x 5 mm. A high-speed
steel tool was used for welding aluminium alloy having the shoulder diameter of 18 mm. The
tool had a pin height of 5 mm and a 6 mm pin diameter. And material heat affected zone tem-
perature measured by using temperature controller.
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Temperature controller
3.3 TOOL DESIGN
The design of the tool is a critical factor as a good tool can improve both the quality
of the weld and the maximum possible welding speed. It is desirable that the tool material is
sufficiently strong, tough and hard wearing, at the welding temperature. Further it should have
a good oxidation resistance and a low thermal conductivity to minimize heat loss and thermal
damage to the machinery further up the drive train. Hot-worked tool steel such as AISI H13
has proven perfectly acceptable for welding aluminium alloys within thickness ranges of 0.5 –
50 mm but more advanced tool materials are necessary for more demanding applications such
as highly abrasive or higher melting point materials such as steel or titanium.
Tool design Welded aluminium alloy plate
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4. RESULTS AND DISCUSSION
4.1 CHEMICAL ANALYSIS FOR ALUMINIUM ALLOY
In this project, 5 mm thick aluminium alloy plates were used for friction stir butt- weld-
ing trials. The chemical composition of the Al-alloy plate used in this study is given in Table
1. Table 2 shows the mechanical properties of the plate used. Friction stir welding ofthe plates
was conducted using a radial drilling machine.
Material specification : IS 737 Gr 19000 condition O
Si% Fe% Cu% Mn% Mg% Al%
0.181 0.266 0.008 0.035 0.195 99.30
Table 1 : Chemical Analysis For Aluminium Alloy
Aluminium alloy plate
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4.2HIGH SPEED STEELCOMPOSTION (AISI H13)
Element Weight %
C 0.32-0.45
Mn 0.20-0.50
Si 0.80-1.20
Cr 4.75-5.50
Ni 0.3
Mo 1.10-1.75
V 0.80-1.20
Cu 0.25
P 0.03
S 0.03
Mechanical Properties:
Properties
Conditions
T (°C) Treatment
Density
(×1000 kg/m3
)
7.76 25 -
Poisson's Ratio 0.27-0.30 25 -
Elastic Modulus
(GPa)
190-210
25
-
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Thermal Properties:
Properties
Conditions
T (°C) Treatment
Thermal Expansion
(10-6
/ºC)
10.4 20-100 more -
Thermal Conduc-
tivity (W/m-
K)
28.6 215 more -
4.3 THERMAL TESTING ON WELDING ALUMINIUM ALLOY
Thermal Stability:
The plates were fixed to the backing table, and then instrumented with 4 thermocouples,
Even though the weld length was rather short, the recorded thermal cycle shows that thermal
stability has been reached 30 mm from the beginning of the weld (thermocouple T5, T6), In
order to attain the necessary plasticity, a higher heat input is needed at the beginning of the
weld. This is obtained by reaching the welding speed througha ramp (continuous increase of
welding speed up to the actual value). A slower speed at the beginning guaranties a higher
heat input, and the right plasticity to start the weld, thereforethe first thermocouples register
higher temperatures than the others do. This observation is supported by the fact that all the
thermocouples recorded. The thermal profiles recorded on 100mm long welds produced for a
subsequent project, confirmed these results.
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Fig : Thermocouples setup
Thermocouples recorded heat affected zone starting on FSW
Time (sec) Advancing side T5 ( ºc) Retreating side T6 ( ºc)
0 36 36
15 84 88
30 91 99
45 102 101
60 104 98
75 96 91
90 87 82
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Graph:
Thermocouples recorded heat affected zone ending on FSW
TIME (sec) advancing side T7 ( ºC) retreating side T3 ( ºC)
0 36 36
15 58 54
30 85 83
45 103 101
60 146 142
75 160 155
90 184 180
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Graph:
4.4 MICROSTRUCTURE ANALYSIS
A tool rotational speed of 900 rpm was chosen for these trials. The plates were joined
employing three different traverse speeds, 70 mm/min. The joint performance was determined
by conducting optical microscopy, micro hardness measurements and mechanical testing (e.g.
tensile and bend tests).
The metallography specimens extracted from the joints were mounted in polyester at
room temperature to avoid the micro structural alterations which might take place during hot-
mounting. The specimens were then grounded with silicon carbide papers of 240, 400, 800,
1000 and 1200 grades followed by polishing on a rotating wheel with 1 and 0.3 micron alumina
suspension. All polished specimens were etched with a solution comprising 15 ml HNO3 and
10 ml HF in distilled water for optical microscopy.
A detailed micro structural observation was conducted for each welded plate using op-
tical microscopy to determine the presence of any weld defect.
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ISBN - 978-81-963578-7-0
4.5MICRO HARDNESS TEST
Micro hardness measurements were conducted on each welded plate to determine hard-
ness variations across the stirred zones. Vickers micro hardness measurement methodwas
employed with a load of 5kgf (loading time being 10 seconds) for micro hardness measure-
ments.
Vickers Hardness Test:
The Vickers hardness test method consists of indenting the test material with adiamond
indenter, in the form of a right pyramid with a square base and an angle of 136 degrees between
opposite faces subjected to a load of 1 to 100 kgf. The full load is normally applied for 10 to
15 seconds. The two diagonals of the indentation left in the surface of the material after removal
of the load are measured using a microscope and their average calculated. The area of the
sloping surface of the indentation is calculated. The Vickers hardness is the quotient obtained
by dividing the kgf load by the square mm area of indentation.
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ISBN - 978-81-963578-7-0
F= Load in kgf
d = Arithmetic mean of the two diagonals, d1 and d2 in mm
HV = Vickers hardness
When the mean diagonal of the indentation has been determined the Vickers hardness
may be calculated from the formula, but is more convenient to use conversion tables. The Vick-
ers hardness should be reported 43HV/5, which means a Vickers hardness of 43, was obtained
using a 5 kgf force. Several different loading settings give practically identical hardness num-
bers on base materials and weld materials.
Base metal:
d = Long diagonal length
(mm)
F = force Hardness (HV)
0.461 5 kgf 43HV
0.464 5 kgf 43HV
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ISBN - 978-81-963578-7-0
Weld metal: (weld line)
d = Long diagonal length
(mm)
F = force Hardness (HV)
0.530 5 kgf 33 HV
0.534 5kgf 32.5 HV
Tabulation for Distance VS Hardness:
Distance from weld centre,
mm
Hardness ( HV)
-20 43
-17.5 43
-15 43
-12.5 43
-10 42.5
-7.5 41
-5 39
-2.5 38
0 33
2.5 37
5 38
7.5 41.5
10 42.5
12.5 43
15 43
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ISBN - 978-81-963578-7-0
Graph for distance from the weld centre VS
hardness:
4.6 TENSILE STRENGTH TEST ON WELDED ALUMINIUM ALLOY
Furthermore, minimum three tensile specimens prepared according to EN 895 were
tested for each condition to determine the mechanical performances of the joints obtained as
explained in detail in an earlier publication.
The results were compared with those obtained from the base plate specimens. Moreo-
ver, two non-standard bending specimens (20 mm wide and 200 mm long) were also extracted
from each welded plate
Required TS : 70 N/mm² (min)
Thickness
mm
Width mm CSA mm²
Tensile Load
KN
Tensile
strength
N/mm²
Position of
fracture
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ISBN - 978-81-963578-7-0
4.70 19.30 90.71 7.31 81.00 Weld metal
Work piece setup in universal testing machine
Tensile specimen
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ISBN - 978-81-963578-7-0
Tabulation for load and tensile strength values :
Load (KN) tensile strength N/mm²
0 0
1 11.02
1.5 16.53
2 22.04
2.5 27.56
3 33.07
3.5 38.58
4 44.09
4.5 49.60
5 55.12
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ISBN - 978-81-963578-7-0
Graph for load VS tensile
strength:
4.7 BENDING TEST ON WELDED ALUMINIUM ALLOY
Both specimens were bended up to 180°, one specimen with weld root being outside
and the other with weld root inside, to determine whether cracking occurs or not in both
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ISBN - 978-81-963578-7-0
bending conditions. Thus, the effect of welding speed at a given rotational speed on the
mechanical performance was determined.
Specimen loaded on the bending machine
Bend test Weld metal
( 4t / 180° ) 5 x 30 x 200 mm
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ISBN - 978-81-963578-7-0
Tensile Strength
Sequential Model Sum of Squares [Type I]
Source
Sum of
Squares df
Mean
Square
F
Value
p-value
Prob > F
Mean vs Total 4626.08 1 4626.08 Suggested
Linear vs Mean 18.5 2 9.25 0.19 0.832
2FI vs Linear 35.88 1 35.88 0.71 0.4203
Quadratic vs 2FI 138.34 2 69.17 1.5 0.2804
Cubic vs Quadratic 198.73 2 99.37 3.49 0.0989
Residual 170.92 6 28.49
Total 5188.45 14 370.6
"Sequential Model Sum of Squares [Type I]": Select the highest order polynomial where the
additional terms are significant and the model is not aliased.
Lack of Fit Tests
Source
Sum of
Squares df
Mean
Square
F
Value
p-value
Prob > F
Linear 390.72 6 65.12 2.13 0.2127
2FI 354.84 5 70.97 2.32 0.1889
Quadratic 216.5 3 72.17 2.36 0.1885
Cubic 17.76 1 17.76 0.58 0.4807
Pure Error 153.15 5 30.63
"Lack of Fit Tests": Want the selected model to have insignificant lack-of-fit.
Model Summary Statistics
Source
Std.
Dev.
R-
Squared
Adjusted
R-Squared
Predicted
R-Squared
PRESS
Surface opening found along the weld
Observation :
54

ISBN - 978-81-963578-7-0
Linear 7.03 0.0329 -0.1429 -0.6983 955.08
2FI 7.13 0.0967 -0.1743 -1.3368 1314.15
Quadratic 6.8 0.3427 -0.0681 -3.1484 2332.94
Cubic 5.34 0.6961 0.3415 -2.9596 2226.74 Aliased
"Model Summary Statistics": Focus on the model maximizing the "Adjusted R-Squared"
and the "Predicted R-Squared".
Response 1 tensile strength
ANOVA for Response Surface Reduced Cubic Model
Analysis of variance table [Partial sum of squares - Type III]
Source
Sum of
Squares
df
Mean
Square
Value Prob > F
p-value
Model 77.08 5 15.42 0.25 0.9261 not significant
A-rotational speed 0.19 1 0.19 3.15E-03 0.9566
B-welding speed 1.13 1 1.13 0.019 0.895
AB 35.88 1 35.88 0.59 0.4639
A2 4 1 4 0.066 0.8038
A2B 18.7 1 18.7 0.31 0.5939
Residual 485.29 8 60.66
Lack of Fit 332.14 3 110.71 3.61 0.1002 not significant
Pure Error 153.15 5 30.63
Cor Total 562.37 13
The "Model F-value" of 0.25 implies the model is not significant relative to the noise.
There is a
92.61 % chance that a "Model F-value" this large could occur due to noise.
Values of "Prob > F" less than 0.0500 indicate model terms are significant.
In this case there are no significant model terms.
Values greater than 0.1000 indicate the model terms are not significant.
If there are many insignificant model terms (not counting those required to supporthier-
archy),
model reduction may improve your model.
The "Lack of Fit F-value" of 3.61 implies the Lack of Fit is not significant relative to the
pure
error. There is a 10.02% chance that a "Lack of Fit F-value" this large could occur due
55

ISBN - 978-81-963578-7-0
to noise. Non-significant lack of fit is good -- we want the model to fit.
Std.
Dev. 7.79 R-Squared 0.1371
Mean 18.18 Adj R-Squared -0.4023
C.V. % 42.85
Pred R-
Squared -5.541
PRESS 3678.43 Adeq Precision 2.35
A negative "Pred R-Squared" implies that the overall mean is a better predictor of your
response than the current model.
"Adeq Precision" measures the signal to noise ratio. A ratio of 2.35 indicates an inadequate
signal and we should not use this model to navigate the design space
Coefficient
Factor
Estimate
Standard
df
95%
CI
Error
95%
CI
Low High VIF
Intercept 17.71 1 2.75 11.37 24.06
A-rotational
speed
0.18 1 3.18 -7.15 7.51 1
B-welding
speed
0.75 1 5.51 -11.95 13.45 3
AB -2.99 1 3.89 -11.98 5.99 1
A2 1.08 1 4.21 -8.62 10.78 1
A2 B -3.74 1 6.75 -19.3 11.81 3
Final Equation in Terms of Coded Factors:
tensile strength = +17.71 +0.18 * A +0.75 * B -2.99 * A * B +1.08 * A2 -3.74 * A2 * B
Final Equation in Terms of Actual Factors:
tensile strength = +482.69466 -0.61152 * rotational speed -272.11392 * welding speed
+0.36028 * rotational speed * welding speed +2.00028E-004 * rotational speed2 -1.18513E-004
* rotational speed2 * welding speed
The Diagnostics Case Statistics Report has been moved to the Diagnostics Node.
In the Diagnostics Node, Select Case Statistics from the View Menu.
Proceed to Diagnostic Plots (the next icon in progression). Be sure to look at the:
56

ISBN - 978-81-963578-7-0
1) Normal probability plot of the studentized residuals to check for normality of residuals.
2) Studentized residuals versus predicted values to check for constant error.
3) Externally Studentized Residuals to look for outliers, i.e., influential values.
4) Box-Cox plot for power transformations.
If all the model statistics and diagnostic plots are OK, finish up with the Model Graphs
icon.
Design-Expert® Softw are
tensile strength
Color points by value of
tensile strength: 99
25.4
95
8.05
90
Normal Plot of Residuals
80
70
50
30
20
10
5
1
-1.66 -0.83 0.00 0.83 1.66
Internally Studentized Residuals
Normal
%
Probability
57

ISBN - 978-81-963578-7-0
tensile strength
Design Points
25.4
8.05
X1 = A: rotational speed
X2 = B: w elding speed
tensile strength
2.25
1.86
1.46
1.06
0.67
1400.00 1500.00 1600.00 1700.00 1800.00
A: rotational speed
Hardness Testing
Sequential Model Sum of Squares [Type I]
Source
Sum of
Squares
df
Mean
Square
F
Value
p-value
Prob > F
Mean vs Total 5.13E+06 1 5.13E+06 Suggested
Linear vs Mean 63.61 2 31.8 0.083 0.921
2FI vs Linear 67.24 1 67.24 0.16 0.6958
Quadratic vs 2FI 2310.69 2 1155.35 5.02 0.0387 Suggested
Cubic vs Quadratic 340.86 2 170.43 0.68 0.541 Aliased
Residual 1500.08 6 250.01
Total
5.13E+06
14
3.67E+05
"Sequential Model Sum of Squares [Type I]": Select the highest order polynomial where the
additional terms are significant and the model is not aliased.
18.9733
22.9667
20.97
16.9767
18.9733
16.9767
14.98
B:
welding
speed
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ISBN - 978-81-963578-7-0
Lack of Fit Tests
Source
Sum of
Squares df
Mean
Square
F
Value
p-value
Prob > F
Linear 2759.92 6 459.99 1.58 0.317
2FI 2692.68 5 538.54 1.85 0.2587
Quadratic 381.99 3 127.33 0.44 0.7367 Suggested
Cubic 41.13 1 41.13 0.14 0.7227 Aliased
Pure Error 1458.95 5 291.79
"Lack of Fit Tests": Want the selected model to have insignificant lack-of-fit.
Model Summary Statistics
Source
Std.
Dev.
R-
Squared
Adjusted
R-Squared
Predicted
R-Squared
PRESS
Linear 19.58 0.0149 -0.1643 -0.6555 7089.44
2FI 20.38 0.0306 -0.2603 -2.0221 12942.07
Quadratic 15.17 0.5701 0.3015 -0.3354 5718.71 Suggested
Aliased Aliased Aliased Aliased Aliased Aliased Aliased
"Model Summary Statistics": Focus on the model maximizing the "Adjusted R-Squared"
and the "Predicted R-Squared".
Response2 Hardness
ANOVA for Response Surface Reduced Cubic Model
Analysis of variance table [Partial sum of squares - Type III]
Source
Model
Sum of
Squares
2449.55
df
6
Mean
Square
408.26
F
Value
1.56
p-value
Prob > F
0.2862 not significant
A-rotational speed 47.6 1 47.6 0.18 0.6826
B-welding speed 0 1 0 0 1
AB 67.24 1 67.24 0.26 0.6279
A2 187.79 1 187.79 0.72 0.4251
B2 1308.63 1 1308.63 5 0.0605
A2B 8 1 8 0.031 0.8662
Residual 1832.93 7 261.85
Lack of Fit 373.98 2 186.99 0.64 0.5652 not significant
Pure Error 1458.95 5 291.79
Cor Total 4282.48 13
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ISBN - 978-81-963578-7-0
The "Model F-value" of 1.56 implies the model is not significant relative to the noise.
There is a
28.62 % chance that a "Model F-value" this large could occur due to noise.
Values of "Prob > F" less than 0.0500 indicate model terms are significant.
In this case there are no significant model terms.
Values greater than 0.1000 indicate the model terms are not significant.
If there are many insignificant model terms (not counting those required to supporthier-
archy),
model reduction may improve your model.
The "Lack of Fit F-value" of 0.64 implies the Lack of Fit is not significant relative to the
pure
error. There is a 56.52% chance that a "Lack of Fit F-value" this large could occur due
to noise. Non-significant lack of fit is good -- we want the model to fit.
Std. Dev. 16.18 R-Squared 0.572
Mean 605.29 Adj R-Squared 0.2051
C.V. % 2.67 Pred R-Squared -1.4904
PRESS 10665.1 Adeq Precision 2.98
A negative "Pred R-Squared" implies that the overall mean is a better predictor of your
response than the current model.
"Adeq Precision" measures the signal to noise ratio. A ratio of 2.98 indicates an inadequate
signal and we should not use this model to navigate the design space.
Coefficient
Factor
Estimate
Standard
df
95%
CI
Error
95%
CI
Low High VIF
Intercept 617.99 1 6.21 603.31 632.66
A-rotational speed -2.82 1 6.61 -18.44 12.8 1
B-welding speed 0 1 11.44 -27.06 27.06 3
AB 4.1 1 8.09 -15.03 23.23 1
A2 -8.14 1 9.61 -30.87 14.59 1.21
B2 -21.49 1 9.61 -44.22 1.24 1.21
A2 B -2.45 1 14.01 -35.59 30.69 3
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Final Equation in Terms of Coded Factors:
hardness = +617.99 -2.82 * A +0.000 * B +4.10 * A * B -8.14 * A2 -21.49 * B2 -
2.45 * A2 * B
Final Equation in Terms of Actual Factors:
hardness = +396.48069 +0.23710 * rotational speed -139.44843
* welding speed +0.27405 * rotational speed * welding speed -9.03332E-005 * rotational speed2
-34.43547 * welding speed2 -7.75316E-005 * rotational speed2 * welding speed
The Diagnostics Case Statistics Report has been moved to the Diagnostics Node.
In the Diagnostics Node, Select Case Statistics from the View Menu.
Proceed to Diagnostic Plots (the next icon in progression). Be sure to look at the:
1) Normal probability plot of the studentized residuals to check for normality of residuals.
2) Studentized residuals versus predicted values to check for constant error.
3) Externally Studentized Residuals to look for outliers, i.e., influential values.
4) Box-Cox plot for power transformations.
If all the model statistics and diagnostic plots are OK, finish up with the Model Graphs
icon.
61

ISBN - 978-81-963578-7-0
hardness
Color points by value of
hardness:
645.6
580.7
Normal Plot of Residuals
99
95
90
80
70
50
30
20
10
5
1
-1.62 -0.75 0.11 0.98 1.85
Internally Studentized Residuals
hardness
Design Points
645.6
580.7
X1 = A: rotational speed
X2 = B: w elding speed
2.25
1.86
hardness
1.46
1.06
0.67
1400.00 1500.00 1600.00 1700.00 1800.00
A: rotational speed
595. 332 601.055 595.332
606.779
612.502
606.779
601.055 595.332
589. 609
B:
welding
speed
Normal
%
Probability
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ISBN - 978-81-963578-7-0
4.8 BILL OF MATERIAL
SL.NO COMPONENTS QUANTITY COST
1
Aluminium alloy plate
5x100x100
10 900
2 Tool, (High speed steel) 1 1000
3 Tool, Lathe works - 350
4 Tool, Sleeve 1 150
5 Plate cutting and drilling - 200
6 Chemical composition test - 800
7 Tensile strength test - 500
8 Bend test - 400
9 Micro hardness test - 225
10 Micro structure analysis - 400
11 Transport charges - 1500
12 Report and others 7 800
13 Thermo controller 4 2500
Total 9725
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ISBN - 978-81-963578-7-0
CHAPTER 5
CONCLUSIONS
The aluminium alloy can be readily friction stir welded in radial drilling machine, but
a softened region composed of the weld and HAZ evidently occurred in the joints. The degree
of softening of the joints is significantly affected by the welding parameters such as welding
speed and rotation speed. The optimum FSW parameters can be determined from the relations
between the tensile properties and the welding parameters, and the maximum tensilestrength
of the joints is equivalent to 80% of that of the base material.
Hardness drop was observed in the weld region. That softening was most evident in the
heat affected zone on the advancing side of the welds, that corresponded to the failure location
in tensile tests. An initial stage of a tunnel defect was found at the intersection of weld nugget
and thermo-mechanically affected zone.
The radial drilling machine 1.5 Hp motor used to weld the material the tensilestrength
is 81 N/mm² and hardness is 33 HV. The weld material is compare to the base material slightly
less. So the radial drilling machine motor capacity increased 3 HP, the load can be increased
so the weld quality and strength increase to achieve.
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ISBN - 978-81-963578-7-0
CHAPTER 6 REF-
ERENCES
[1] W. Tang, X. Guo, J.C. McClure, L.E. Murr, A. Nunes, ‗‗Heat Input and Temperature Dis-
tribution in Friction Stir Welding,‘‘ Journal of Materials Processing and Manufacturing Sci-
ence, 1988, 163–172.
[2] P. Colegrove, M. Painter, D. Graham, and T. Miller, ‗‗3 Dimensional Flow and Thermal
Modeling of the Friction Stir Welding Process,‘‘ Proceedings of the Second International Sym-
posium on Friction Stir Welding, 2000, June 26–28, Gothenburg, Sweden.
[3] Y.J. Chao, X. Qi, ―Thermal and thermo-mechanical modeling of friction stir welding of
aluminum alloy - 6061-T6‖, Journal of Materials Processing & Manufacturing Science, 1998.
[4] Y.J. Chao, X. Qi, W. Tang, ―Heat Transfer in Friction Stir Welding—Experimental and
Numerical Studies, ASME J. Manufacturing Science and Engineering‖, 2003 138–145.
[5] Y.J. Chao and X. Qi, ― Heat Transfer and Thermomechanical Analysis of Friction Stir
Joining of AA6061-T6‖, First International. Symposium on Friction Stir Welding (Thousand
Oaks, CA, USA), 1999.
[6] Ø. Frigaard, Ø. Grong, O.T. Midling, ―Modeling of the Heat Flow Phenomena in Friction
Stir Welding of Aluminum Alloys‖, Proceedings of the Seventh International Conference Joints
in Aluminum— INALCO ‘98, Cambridge, UK, April 15-17, 1998.
[7] Ø. Frigaard, Ø. Grong, O.T. Midling, ―A Process Model for Friction Stir Welding of Age
Hardening Aluminum Alloys‖, Metallurgical and Materials Transactions A 32A, 2001.
[8] A.P. Reynolds, W.D. Lockwood, T.U. Seidel, ―Processing – Property Correlation in
Friction Stir Welds‖, Material Science Forum 331–337 (2000) 1719–1724.
[9] P. Colegrove Second International Symposium on Friction Stir Welding (Gothenburg,
Sweden), 2000
[10] Song M and R. Kovacevic, ―Thermal Modeling of Friction Stir Welding in a Moving
Coordinate System and its Validation‖, International Journal of Machine Tools & Manu-
facture 43, 605–15, 2003
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ISBN - 978-81-963578-7-0
[11] C.M.Chen, R. Kovacevic, ―Finite Element Modeling of Friction Stir Welding – Thermal
and Thermo-Mechanical Analysis‖, International Journal of Machine Tools & Manufacture
43 (2003) 1319–1326
[12] H Schmidt, J Hattel and J Wert, ―An Analytical Model for the Heat Generation in
Friction Stir Welding‖, Modelling and Simulation in Material Science Engineering 12 143–
157, 2004
[13] X.K. Zhu, Y.J. Chao, ―Numerical Simulation of Transient Temperature and Residual
Stresses in Friction Stir Welding of 304L Stainless Steel‖, Journal of Materials Processing
Technology 146, 263–272, 2004
[14] J.C. McClure, W. Tang, L.E. Murr, X. Guo, Z.Feng, J.E. Gould, ―A Thermal Model of
th
Friction Stir Welding‖, International Conference on Trends in Welding Research 5 ; Pine
Mountain, GA, 1998
[15] P. Ulysse, ―Three Dimensional Modeling of Friction Stir Welding Process, Interna-
tional Journal of Machine Tools and Manufacture 42 , 1549-1557, 2002
[16] Vijay Soundararajan, Srdja Zekovic, Radovan Kovacevic, Thermo-mechanical model
with adaptive boundary conditions for friction stir welding of Al 6061, International Jour-
nalof Machine Tools & Manufacture 45, 1577–1587, 2005
17) P. Bahemmat, A. Rahbari, M. Haghpanahi, M. K. Besharati Experimental study on
the effect of rotational speed and tool pin profile on aa2024 aluminium friction stir
welded butt joints.
18) R. Nandan a, T. DebRoy a, H.K.D.H. BhadeshiaRecent advances in friction-stir weld-
ing – Process, weldment structure and properties.
19) H. Horn Friction stir welding of aluminium foam materials.
66

ISBN - 978-81-963578-7-0
CHAPTER -2
“ANALYSIS AND OPTIMIZATION OF
THE EXHAUST PORT OF AN INTERNAL COMBUSTION ENGINE”
SRI SAKTHI R
REG NO: 621821408008
ME -ENGINEERINGDESIGN,
SECOND YEAR,
PGP COLLEGE OF ENGINEERING AND
TECHNOLOGY, NAMAKKAL.
ABSTRACT
The purpose of this work focuses on the reduction of Exhaust valve stem
diameter with the same port diameter in order to exhaust the burnt gases from the
cylinder bore so that efficiency of the vehicle can be increased. The various pa-
rameters that influence the Exhaust valve stem diameter were selected. The pa-
rameters are angle of valve with Top Dead Center (TDC) and angle of valve with
Bottom Dead Center (BDC).
For this experiment Taguchi method was used as a tool. Levels were as-
signed to the parameters selected and an orthogonal array of experiment is de-
signed using Taguchi technique. This experimentation focused on the selectionof
optimum levels of the controllable design parameters.
Keywords: Exhaust valve, Taguchi Method, Orthogonal Array, ANOVA
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ISBN - 978-81-963578-7-0
CHAPTER 1 INTRODUCTION
The internal combustion engine is a heat engine that converts chemical energy in a fuel
into mechanical energy, usually made available on a rotating output shaft. Chemical energy of
the fuel is first converted to thermal energy by means of combustion or oxidation with air inside
the engine. This thermal energy raises the temperature and pressure of the gases within the
engine and the high-pressure gas then expands against the mechanical mechanisms of the en-
gine. This expansion is converted by the mechanical linkages of the engine to a rotating crank-
shaft, which is the output of the engine.
Figure 1.1 Cross-section of four-stroke cycle SI engine showing engine components;
(A) block, (B) camshaft, (C) combustion chamber, (D) connecting rod, (E)crankcase, (F) crankshaft,
(G) cylinder, (H) exhaust manifold, (I) head, (J) intake manifold, (K) oil pan, (L) piston, (M) piston rings, ( N)
push rod, (O) spark plug, (P)valve, (Q) water jacket
The crankshaft, in turn, is connected to a transmission and/or power train to transmit the ro-
tating mechanical energy to the desired final use. For engines this will often be the propulsionof
a vehicle.
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ISBN - 978-81-963578-7-0
1.1 Engine Valves
Poppet valves are used in most piston engines to open and close the intake and exhaust
ports in the cylinder head. The valve is usually a flat disk of metal with a long rod known as
the valve stem out one end. The stem is used to push down on the valve and open it, with a
spring generally used to close it when the stem is not being pushed on. On high performance
engines, the camshaft is movable and the cams have a varying height, so by axially moving the
camshaft in relation with the engine RPM, also the valve lift varies. See variable valve timing.
Figure1. 2 Valve timing diagram
The cross-section of four stroke SI engine and the valve timing diagram are shown in
Figure 1 & 2 respectively. Although better heat conductors, aluminum cylinder heads require
steel valve seat inserts while cast iron cylinder heads often used integral valve seats in the past.
Because the valve stem extends into lubrication in the cam chamber it must be sealed against
blow-by to prevent cylinder gases from escaping into the crankcase. A rubber lip-type seal
ensures that excessive amounts of oil are not drawn in from the crankcase on the induction
stroke and that exhaust gas does not enter the crankcase on the exhaust stroke. Worn valve
seals are characterized by a puff of blue smoke from the exhaust when pressing back down on
the accelerator pedal after allowing the engine to over-run, such as when changing gears.
1.2 Valve position
Modern designs have the camshaft on top of the cylinder head, pushing directly on the
valve stem (again through cam followers, also known as tappets), a system known as overhead
camshaft; if there is just one camshaft, this is termed as a single overhead cam or SOHC
engine.
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ISBN - 978-81-963578-7-0
Figure1. 3 Valve Position Diagram
Often there are two camshafts, one for the intake and one for exhaust valves, creating
the dual overhead cam, or DOHC. The camshaft is driven by the crankshaft - through gears,
a chain or a timing belt.
Because of exposure to hot exhaust gases and its effects on engine performance and
volumetric efficiency, the valves of an internal combustion engine is one of the most critical
parts. The design of valves depends on many parameters, such as fluid dynamics of the inlet
and exhaust gas, fatigue strength of the valve material, oxidation characteristics of the valve
material, exhaust gas behavior of the material at high temperature, the configuration of the
cylinder head, the coolant flow, the shape of the port, etc. The valve position diagram is shown
in Figure 3. The most significant factor in the performance of a valve is its operatingtempera-
ture. The importance of temperature can best be appreciated by its effect on the physical prop-
erties of the valve steel. The exhaust valve of an internal combustion engine operates under
severe conditions of thermal, fatigue, and mechanical stresses. Large temperature gradients in
the Valve bodies are responsible for thermal stresses. Knowledge of the temperature field in
different parts of an internal combustion engine is important in order to ascertain the points of
highest thermal stress.
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LITERATURE REVIEW
Radek et al [1] evaluated the steady-state heat transfer analysis of a diesel engine head
assembly. The valve or seat interface is responsible for sealing of a combustion chamber and
is subject to a high thermal, mechanical and chemical load. These loads may have the conse-
quences on both the life of the valves and the operation of an engine. A method for obtaining
information about the behavior of the valve or seat interface during an engine operation is the
analysis of contact pressure between the valve and valve seat. The FE model must involve
both a thermal and mechanical load. The evaluation of the seat or valve interactionshows the
different influence of valve and seat deformation. Valve head deformation by thetempera-
ture field moves the contact into the outer edge, while applying pure pressure leads tocontact
along the inner one. Seat deformation due to the head stiffness
and heating causes the non-uniformity of contact pressure distribution along the contact area.
Nurten Vardar et al [2] discussed the different failure modes affect the valve failure. The
combination of impact and sliding during the valve closing can lead to valve seat wear. Another
failure mode of valves is fatigue, which may cause the valve to break. Valves usually fail as a
result of different failure modes like fatigue, corrosion, wearing and impact. Since fatigue stri-
ations and beach marks did not appear on the fracture surfaces, the fatigue was not a possible
cause of failure in the valve and the valve was broken down before its expected service life.
Y.M.Puri et al, [12] have developed parametric optimization and various supportive
techniques for simultaneous optimization of multiple quality characteristics. LucianDascalescu
et al, [6] have described Taguchi’s experimental design technique as simultaneouscontrol of
various electrical and mechanical factors. [5] have employed this technique for deriving a math-
ematical model capable of reflecting the effects of a large number of factors like the character-
istic of granular mixtures to be sorted, the feed rate the configuration of the electrode system,
the applied high voltage and the environmental conditions, as well as their main interactions,
[6] have optimized this factors of electrostatic separation process.
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ISBN - 978-81-963578-7-0
selected by [17] P.R.Thyla et al, for assessing the thermal behavior of worm gear drives [16]
have optimized the numerical parameters by the Taguchi’s orthogonal array technique.
B.R.Rolfe et al, [15] have developed a shape error metric for measuring spring back effect in
U-channel of sheet metal. [15] have selected three parameters like blank holder force, die radii
and tool gap having three levels each. It was observed that combined springback increases
when the blank holder force is increased and the combined springback marginally decreases
when the radii is increased.
Avani Gandhi [3] has described Taguchi Design of Experiment technique as problem
solving method and [3] has conducted a case study of identifying and modifying the critical
parameters causing variation in end play on 2nd
gear side of 4-speed main shaft main assembly.
[3] has successfully implemented DOE for the identification of problem of groove profile and
solved by analysis.
K.Palanikumar et al, [9] have analyzed the cutting characteristics of glass fiber rein-
forced plastics using sintered carbide cutting tool inserts. [9] have obtained the optimal para-
metric combination for achieving accurate machining of composites using Taguchi method, a
powerful tool in the DOE for quality. N.V.R. Naidy et al, [7] have compared three methods of
DOE for quality improvement by robust design. The three methods of DOE includeclassical
DOE, Taguchi DOE and Shainin DOE. The study shows that Dr. Taguchi’s methodsoffers the
best capability to improve the quality of product or process. Delphina [4] has developed a test
matrix based on the orthogonal array of Taguchi DOE approach. Experimentswrer conducted
fir the V- bending process using 0022-T4AA to study the variation ofspringback due to both
process and material parameters such as bend radius, sheet thickness, grain size, plastic anisot-
ropy, heat treatment, punching speeds and time. The DOE was used toevaluate the predominant
parameters for a specific lot of sheet metal. It was observed tha the bend radius has greatest
effect on springback, Next, [4] conducted finite element simulation ofspringback using ANSYS
implicit code to explore the limits regarding process control by boundry values versus material
parameters, 2-D finite element modeling was considered in thespringback simulations. Experi-
mental results compare with the simulated predictions.
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6
CHAPTER 3 DE-
SIGN OF VALVES
Here we design the inlet and exhaust valve of a S.I engine having the maximum rpm of 6000.
Effective area of valve opening
A = π [di.h.cosѳ+h2
cos2
ѳsinѳ] (3.1)
Here, h,
Valve lift = [d i
+ w];
di, Inlet port diameter = 6h-6w,
w, face width of valve = 3 mm,
ѳ = 45°for the considered engine.Us-
ing the above,
A=2.2dih+1.1h2
From the valve timing diagram
α1=α2= 10° to 15°
Similarly,
β1=β2=45°to 50°
Total angle of inlet valve opening ǿ = α1+β1+180
Duration of valve opening, t = Φ/360
sec
N/60
= 6.528 milli secs
From the engine specification, N = 6000 rpm
For a flow of 10,000 cm/sec air-fuel mixture through port, Average volume of gas mixture
entering through the inlet port = [0.65 ×A × t× 10000] (3.2)
Total gas mixture admitted when inlet valve opens = Total Engine cc
No. of cylinders
= 299.25 cc (3.3)
Equating (2) and (3) and employing (1) in the above,
14.3h2
-3.96h-7.05 = 0
Now solve this quadratic equation;
h = 8.54mm & A= 7.05 cm2
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Other valve parameters are determined as follows:
Inlet port diameter, (di) = 33.25mm
Inlet valve stem diameter (dsi) = 8.13mm
Inlet valve head diameter (Hi) = 37.49mm
Exhaust port diameter (de) = 26.60mm
Exhaust valve stem diameter (dse) = 6.651mm
Exhaust valve head diameter (He) = 30.84mm
Check: Hi + He < 0.95B
0.95B = 0.95*73=69.35mm;
68.33 < 69.35, Hence, Design is safe
The following table shows the dimensions of the valves for various values of α and ß.
Table 3.1: Design parameters of various values of α and ß
Sl.No α β
Inlet stem
diameter
(mm)
Inlet valve
head diame-
ter (mm)
Exhaust
Valve stem
diameter
(mm)
Exhaust
Valve
head di-
ameter
(mm)
Valve lift
height
(mm)
1 10 45 8.31389999 37.49759994 6.65111999 30.84648 8.54259999
2 11 46 8.27020252 37.3228101 6.61616202 30.70665 8.51346835
3 12 47 8.22706159 37.15024635 6.58164927 30.5686 8.48470773
4 13 48 8.18446558 36.9798623 6.54757246 30.43229 8.45631038
5 14 49 8.14240322 36.81161288 6.51392258 30.29769 8.42826881
6 15 50 8.10086357 36.6454543 6.48069086 30.16476 8.40057572
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ISBN - 978-81-963578-7-0
CHAPTER 4
TAGUCHI DESIGN OF EXPERIMENTS
4.1INTRODUCTION
Quality is a matter of continuous process improvement. Improper design of prod-
uct/process quality will result in loss to the manufacturer as well as the customer. A merequality
product will have a minimum loss to the society as it goes through its life cycle. Therehave
been various traditional methods to minimize the quality loss. They are merely used for detect-
ing the trouble. These techniques are also known as the on-line (during the manufacture)quality
control techniques. To overcome this problem off-line quality control tool called Designof ex-
periment is used. Design of experiment (DOE) is a body of knowledge and technique forplan-
ning a set of experiments, analyzing the data and drawing conclusions from the analysis. Sta-
tistical Design of experiment (SDOE) plays a powerful role in many organizations today in
terms of improving process efficiency, product quality, product capability and reducing process
variability, cost of poor quality such as scrap, rework and other failure costs. This powerful
technique has proven to be one of the most effective and reliable weapons in the twenty-first
century arsenal of globally competitive organizations. It was initially developed by R.A. Fisher
at Rothamsted Agricultural Station, London, England (Fisher, 1935). However the person who
is seen to have most influenced the development of SDOEs (SDOE) in the industrial world is
Dr. Genichi Taguchi. He is a Japanese engineer and quality consultant who have promoted the
use of statistical design of experiments for improving process/product quality at minimal costs.
Taguchi Design of Experiments is a system of cost-driven quality engineering that em-
phasizes the effective applications of engineering strategies rather than advanced statistical
techniques. Dr. Taguchi has been very successful in integrating statistical methods into the
powerful engineering processes for achieving greater process stability, capability and yield.
Taguchi emphasized the importance of designing quality into products and processes right from
the design stage through to the entire product development cycle. The SDOE methodology
developed and promoted by Taguchi has accentuated the importance of making products func-
tional performance or process performance insensitive to various sources of noise conditions
relative humidity fluctuations, equipment or machine performance degrading, tool wear, prod-
uct to product variation, etc. This is also known as Robust Parameter Design (RPD),RPD is
essentially a part of Taguchi’s SDOE.
Taguchi proposes an off-line strategy for quality improvement in place of an attempt to
inspect quality into a product on the production line. He observes that no amount of inspection
can put quality back into the product; it merely treats a symptom. To achieve desirable product
75

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