MATERIAL OPTIMIZATION OF FLYWHEEL IN IC ENGINE PROJECT REPORT 2011-2012 Submitted by (Team name) Guided by: Submitted in partial fulfillment of the requirement for the Award of Diploma in ---------------------------------------- - COLLEGE LOGO
Dec 30, 2015
MATERIAL OPTIMIZATION OF FLYWHEEL IN IC ENGINE
PROJECT REPORT 2011-2012
Submitted by
(Team name)
Guided by:
Submitted in partial fulfillment of the requirement for the
Award of Diploma in -----------------------------------------
By the State Board of Technical Education Government of
Tamilnadu, Chennai.
DEPARTMENT:
COLLEGE NAME:
COLLEGE LOGO
PLACE:
COLLEGE NAME
PLACE
DEPARTMENT
PROJECT REPORT-2011-2012
This Report is certified to be the Bonafide work done by
Selvan/Selvi ---------------- Reg.No. ------------ Of VI Semester
class of this college.
Guide Head of the Department
Submitted for the Practical Examinations of the board of
Examinations,State Board of Technical Education,Chennai,
TamilNadu.On -------------- (date) held at the ------------
(college name),Coimbatore
Internal Examiner External Examiner
ACKNOWLEDGEMENT
At this pleasing movement of having successfully
completed our project, we wish to convey our sincere thanks
and gratitude to the management of our college and our
beloved chairman------------------------.who provided all the
facilities to us.
We would like to express our sincere thanks to our
principal ------------------for forwarding us to do our project and
offering adequate duration in completing our project.
We are also grateful to the Head of Department
prof…………., for her/him constructive suggestions
&encouragement during our project.
With deep sense of gratitude, we extend our earnest
&sincere thanks to our guide --------------------, Department of
Mechanical for her/him kind guidance and encouragement
during this project we also express our indebt thanks to our
TEACHING staff of MECHANICAL ENGINEERING DEPARTMENT,
---------- (college Name).
CONTENTS
CHAPTER
NO
TITLE
SYNOPSIS
1 INTRODUCTION
2 COMPOSITE MATERIALS
3 PRO-E & ANSYS
4 MODELLING COMMANDS USED IN PRO-E
5 ANALYSIS PROCEDURE
6 MATERIAL PROPERTIES
7 RESULTS
8 CONCLUSION
REFERENCE
SYNOPSIS
In this project we are doing the material optimization of flywheel
in an internal combustion engine. This project we are designed the
3D model of the flywheel by using pro-e software and the analysis
taken by different materials and also change the thickness and other
design parameters of the flywheel and the analysis taken by the
ansys software.
This project we are analyzed the rotational velocity and moment
acting on the flywheel by the three materials. Presently the flywheels
are made by the material of cast iron, this project we are testing the
same load under the three materials. The materials are cast iron, high
strength epoxy carbon and duralumin.
CHAPTER-I
INTRODUCTION
INTRODUCTION TO FLYWHEEL
A flywheel is a mechanical device with a significant moment of
inertia used as a storage device for rotational energy. Flywheels
resist changes in their rotational speed, which helps steady the
rotation of the shaft when a fluctuating torque is exerted on it by its
power source such as a piston-based (reciprocating) engine, or when
an intermittent load, such as a piston pump, is placed on it. Flywheels
can be used to produce very high power pulses for experiments,
where drawing the power from the public network would produce
unacceptable spikes.
FLYWHEEL IN THE INTERNAL COMBUSTION ENGINE
For internal combustion engine applications, the flywheel is a
heavy wheel mounted on the crankshaft. Its main function is to
maintain a fairly constant angular velocity of the crankshaft.
ADVANTAGES OF OPTIMIZATION OF THE FLYWHEEL
Avoid the deformation of flywheel in short time
Improve the performance of the flywheel by using alternate
materials
Increase the lifecycle of the flywheel
USES OF COMPOSITE FLYWHEELS
The faster we can spin a flywheel and the more massive we
can make it, the flywheel, and the more kinetic energy we can store in
it. However, at extreme speeds, even metal flywheels can literally
tear themselves apart from the shear forces which are generated.
Further, the energy storage characteristics of the flywheel are
influenced more strongly by its maximal rotational velocity than by its
mass.
MANUFACTURING OF COMPOSITE FLYWHEEL:
The flywheel rim and arbors are constructed using a
combination of Toray M30S intermediate modulus graphite, Toray
T700 standard modulus graphite, and Owens-Corning S2 fiberglass
(Table) the resin is a Fiberite 977-2 thermosetting epoxy resin system
toughened with thermoplastic additives.
IMPORTANCE OF EPOXY
Epoxy is a prominent resin used in manufacture of composite
flywheel.
MERITS OF COMPOSITE FLYWHEEL
· Compact
· Energy storage system more efficient
· Less weight
· Long life
· High efficiency
· Low maintenance
· No aerodynamic noise
DEMERITS
· Safety concerns
· High material costs
Expensive magnetic bearing
APPLICATIONS OF COMPOSITE FLYWHEEL
Composite Flywheels are not only used for Electric Vehicles
and Hybrid Electric but it also finds space applications.
ENERGY STORED IN FLYWHEEL
When flywheel absorbs energy as in the case of internal
combustion engines, velocity increases and the stored energy is
given out, the velocity or speed diminishes.
Total kinetic energy E = i ω 2 /2
i = mass moment of inertia of flywheel about the axis of rotation in
KgMts2.
ω = mean angular speed of the flywheel in Rad/ sec.
i = MK2 For rim type.
i = MK2 / 2 for disc type.
K = Radius of gyration of flywheel in mts.
M = Mass of fly wheel in kgs.
FLUCTUATION OF ENERGY
If the velocity of flywheel changes, energy it will absorb or gives
up is proportional to the difference between the initial and final
speeds, and is equal to the difference between the initial and final
speeds, and is equal to the difference between energies which could
give out, if brought to a full stop position that which is still stored in it
at the reduced velocity.
E1 = E D = MAXke - MINke
= i ω12 /2 - i ω2
2 /2
= i / 2 (ω12 - ω2
2 )
= i / 2(ω1 - ω 2) x (ω1 + ω2)
= i x ω (ω1 - ω2) ω= (ω1 + ω2)/2
= i x ω 2 (ω1 - ω2 )/ω
E1 = E = i x ω2 x Cs
R = Mean radius of rim.
Cs = Co-efficient of fluctuating speed.
K = Radiation of gyration.
K = R (Assumption)
E1 = E = Fluctuation of energy.
ω = Mean angular velocity of flywheel.
M = Mass of flywheel rim.
CHAPTER-II
COMPOSITE MATERIALS
COMPOSITE MATERIALS
A typical composite material is a system of materials composing
of two or more materials (mixed and bonded) on a macroscopic
scale. For example, concrete is made up of cement, sand, stones,
and water. If the composition occurs on a microscopic scale
(molecular level), the new material is then called an alloy for metals
or a polymer for plastics.
Generally, a composite material is composed of reinforcement
(fibers, particles, flakes, and/or fillers) embedded in a matrix
(polymers, metals, or ceramics). The matrix holds the reinforcement
to form the desired shape while the reinforcement improves the
overall mechanical properties of the matrix. When designed properly,
the new combined material exhibits better strength than would each
individual material.
COMPOSITE THEORY
In its most basic form a composite material is one, which is
composed of at least two elements working together to produce
material properties that are different to the properties of those
elements on their own. In practice, most composites consist of a bulk
material (the ‘matrix’), and a reinforcement of some kind, added
primarily to increase the strength and stiffness of the matrix. This
reinforcement is usually in fibre form. Today, the most common man-
made composites can be divided into three main groups:
· Polymer Matrix Composites (PMC’s) – These are the most
common and will be discussed here. Also known as FRP - Fibre
Reinforced Polymers (or Plastics) – these materials use a polymer-
based resin as the matrix, and a variety of fibres such as glass,
carbon and aramid as the reinforcement.
· Metal Matrix Composites (MMC’s) - Increasingly found in the
automotive industry, these materials use a metal such as aluminium
as the matrix, and reinforce it with fibres such as silicon carbide.
· Ceramic Matrix Composites (CMC’s) - Used in very high
temperature environments, these materials use a ceramic as the
matrix and reinforce it with short fibres, or whiskers such as those
made from silicon carbide and boron nitride.
POLYMER MATRIX COMPOSITES
Resin systems such as epoxies and polyesters have limited use
for the manufacture of structures on their own, since their mechanical
properties are not very high when compared to, for example, most
metals. However, they have desirable properties, most notably their
ability to be easily formed into complex shapes. Materials such as
glass, aramid and boron have extremely high tensile and
compressive strength but in ‘solid form’ these properties are not
readily apparent. This is due to the fact that when stressed, random
surface flaws will cause each material to crack and fail well below its
theoretical ‘breaking point’. To overcome this problem, the material is
produced in fibre form, so that, although the same number of random
flaws will occur, they will be restricted to a small number of fibres with
the remainder exhibiting the material’s theoretical strength. Therefore
a bundle of fibres will reflect more accurately the optimum
performance of the material. However, fibres alone can only exhibit
tensile properties along the fibre’s length, in the same way as fibres in
a rope.
It is when the resin systems are combined with reinforcing
fibres such as glass, carbon and aramid that exceptional properties
can be obtained. The resin matrix spreads the load applied to the
composite between each of the individual fibres and also protects the
fibres from damage caused by abrasion and impact. High strengths
and stiffnesses, ease of moulding complex shapes, high
environmental resistance all coupled with low densities, make the
resultant composite superior to metals for many applications. Since
PMC’s combine a resin system and reinforcing fibres, the properties
of the resulting composite material will combine something of the
properties of the resin on its own with that of the fibres on their own,
as surmised in Figure 1.
Figure: 1 – Illustrating the combined effect on Modulus of the
addition of fibres to a resin matrix.
Overall, the properties of the composite are determined by:
· The properties of the fibre
· The properties of the resin
· The ratio of fibre to resin in the composite (Fibre Volume
Fraction (FVF))
· The geometry and orientation of the fibres in the composite
The ratio of the fibre to resin derives largely from the manufacturing
process used to combine resin with fibre. However, it is also
influenced by the type of resin system used, and the form in which
the fibres are incorporated. In general, since the mechanical
properties of fibres are much higher than those of resins, the higher
the fibre volume fraction the higher will be the mechanical properties
of the resultant composite. In practice there are limits to this, since
the fibres need to be fully coated in resin to be effective, and there
will be an optimum packing of the generally circular cross-section
fibres. In addition, the manufacturing process used to combine fibre
with resin leads to varying amounts of imperfections and air
inclusions.
Typically, with a common hand lay-up process as widely used
in the boat-building industry, a limit for FVF is approximately 30-40%.
With the higher quality, more sophisticated and precise processes
used in the aerospace industry, FVF’s approaching 70% can be
successfully obtained.
The geometry of the fibres in a composite is also important
since fibres have their highest mechanical properties along their
lengths, rather than across their widths. This leads to the highly
anisotropic properties of composites, where, unlike metals, the
mechanical properties of the composite are likely to be very different
when tested in different directions. This means that it is very
important when considering the use of composites to understand at
the design stage, both the magnitude and the direction of the applied
loads. When correctly accounted for, these anisotropic properties can
be very advantageous since it is only necessary to put material where
loads will be applied, and thus redundant material is avoided.
It is also important to note that with metals the material supplier
largely determines the properties of the materials, and the person
who fabricates the materials into a finished structure can do almost
nothing to change those ‘in-built’ properties. However, a composite
material is formed at the same time, as the structure is itself being
fabricated. This means that the person who is making the structure is
creating the properties of the resultant composite material, and so the
manufacturing processes they use have an unusually critical part to
play in determining the performance of the resultant structure.
LOADING
There are four main direct loads that any material in a structure has
to withstand: tension, compression, shear and flexure.
TENSION
Figure 2 shows a tensile load applied to a composite. The response of a composite
to tensile loads is very dependent on the tensile stiffness and strength properties of the
reinforcement fibres, since these are far higher than the resin system on its own.
Figure 2 – Illustrates the tensile load applied to a composite body.
COMPRESSION
Figure 3 shows a composite under a compressive load. Here, the adhesive and
stiffness properties of the resin system are crucial, as it is the role of the resin to maintain
the fibres as straight columns and to prevent them from buckling.
Figure 3 - Illustrates the compression load applied to a composite
body.
SHEAR
Figure 4 shows a composite experiencing a shear load. This load is trying to slide
adjacent layers of fibres over each other. Under shear loads the resin plays the major role,
transferring the stresses across the composite. For the composite to perform well under
shear loads the resin element must not only exhibit good mechanical properties but must
also have high adhesion to the reinforcement fibre. The interlaminar shear strength
(ILSS) of a composite is often used to indicate this property in a multiplayer composite
(‘laminate’).
Figure 4 - Illustrates the shear load applied to a composite body.
FLEXURE
Flexural loads are really a combination of tensile, compression and shear loads.
When loaded as shown (Figure 5), the upper face is put into compression, the lower face
into tension and the central portion of the laminate experiences shear.
Figure 5 - Illustrates the loading due to flexure on a composite
body.
COMPARISON WITH OTHER STRUCTURAL MATERIALS
Due to the factors described above, there is a very large range
of mechanical properties that can be achieved with composite
materials. Even when considering one fibre type on its own, the
composite properties can vary by a factor of 10 with the range of fibre
contents and orientations that are commonly achieved. The
comparisons that follow therefore show a range of mechanical
properties for the composite materials. The lowest properties for each
material are associated with simple manufacturing processes and
material forms (e.g. spray lay-up glass fibre), and the higher
properties are associated with higher technology manufacture (e.g.
autoclave moulding of unidirectional glass fibre prepreg), such as
would be found in the aerospace industry.
For the other materials shown, a range of strength and stiffness (modulus) figures are
also given to indicate the spread of properties associated with different alloys, for example.
Figure 6 – Tensile Strength of Common Structural Materials
Figure 7 – Tensile Modulus of Common Structural Materials
The above Figures (6 and 7) clearly show the range of properties that different
composite materials can display. These properties can best be summed up as high strengths and
stiffnesses combined with low densities. It is these properties that give rise to the characteristic
high strength and stiffness to weight ratios that make composite structures ideal for so many
applications. This is particularly true of applications, which involve movement, such as cars,
trains and aircraft, since lighter structures in such applications play a significant part in making
these applications more efficient. The strength and stiffness to weight ratio of composite
materials can best be illustrated by the following graphs that plot ‘specific’ properties. These are
simply the result of dividing the mechanical properties of a material by its density. Generally, the
properties at the higher end of the ranges illustrated in the previous graphs (Figures 6 and 7) are
produced from the highest density variant of the material. The spread of specific properties
shown in the following graphs (Figures 8 and 9) takes this into account.
Figure 8 – Specific Tensile Strength of Common Structural
Materials
Figure 9 - Specific Tensile Modulus of Common Structural Materials
COMMON CATEGORIES OF COMPOSITE MATERIALS
Based on the form of reinforcement, common composite
materials can be classified as follows:
1. Fibers as the reinforcement (Fibrous Composites):
a. Random fiber (short fiber) reinforced composites
b. Continuous fiber (long fiber) reinforced composites
2. Particles as the reinforcement (Particulate composites):
3. Flat flakes as the reinforcement (Flake composites):
4. Fillers as the reinforcement (Filler composites):
BENEFITS OF COMPOSITES
Different materials are suitable for different applications. When
composites are selected over traditional materials such as metal
alloys or woods, it is usually because of one or more of the following
advantages:
COST
o Prototypes
o Mass production
o Part consolidation
o Maintenance
o Long term durability
o Production time
o Maturity of technology
WEIGHT
o Light weight
o Weight distribution
STRENGTH AND STIFFNESS
o High strength-to-weight ratio
o Directional strength and/or stiffness
DIMENSION
o Large parts
o Special geometry
SURFACE PROPERTIES
o Corrosion resistance
o Weather resistance
o Tailored surface finish
THERMAL PROPERTIES
o Low thermal conductivity
o Low coefficient of thermal expansion
ELECTRIC PROPERTY
o High dielectric strength
o Non-magnetic
o Radar transparency
Note that there is no one-material-fits-all solution in the
engineering world. Also, the above factors may not always be positive
in all applications. An engineer has to weigh all the factors and make
the best decision in selecting the most suitable material(s) for the
project at hand.
HISTORYOF COMPOSITE MATERIALS
Wood is a natural composite of cellulose fibers in a matrix of
lignin. The most primitive manmade composite materials were straw
and mud combined to form bricks for building construction; the
Biblical Book of Exodus speaks of the Israelites being oppressed by
Pharaoh, by being forced to make bricks without straw being
provided. The ancient brick-making process can still be seen on
Egyptian tomb paintings in the Metropolitan Museum of Art. The most
advanced examples perform routinely on spacecraft in demanding
environments. The most visible applications pave our roadways in the
form of either steel and aggregate reinforced portland cement or
asphalt concrete. Those composites closest to our personal hygiene
form our shower stalls and bath tubs made of fiberglass. Solid
surface, imitation granite and cultured marble sinks and counter tops
are widely used to enhance our living experiences.
Composites are made up of individual materials referred to as
constituent materials. There are two categories of constituent
materials: matrix and reinforcement. At least one portion of each type
is required. The matrix material surrounds and supports the
reinforcement materials by maintaining their relative positions. The
reinforcements impart their special mechanical and physical
properties to enhance the matrix properties. A synergism produces
material properties unavailable from the individual constituent
materials, while the wide variety of matrix and strengthening materials
allows the designer of the product or structure to choose an optimum
combination.
Engineered composite materials must be formed to shape. The
matrix material can be introduced to the reinforcement before or after
the reinforcement material is placed into the mold cavity or onto the
mold surface. The matrix material experiences a melding event, after
which the part shape is essentially set. Depending upon the nature of
the matrix material, this melding event can occur in various ways
such as chemical polymerization or solidification from the melted
state.
A variety of molding methods can be used according to the
end-item design requirements. The principal factors impacting the
methodology are the natures of the chosen matrix and reinforcement
materials. Another important factor is the gross quantity of material to
be produced. Large quantities can be used to justify high capital
expenditures for rapid and automated manufacturing technology.
Small production quantities are accommodated with lower capital
expenditures but higher labor and tooling costs at a correspondingly
slower rate.
Most commercially produced composites use a polymer matrix
material often called a resin solution. There are many different
polymers available depending upon the starting raw ingredients.
There are several broad categories, each with numerous variations.
The most common are known as polyester, vinyl ester, epoxy,
phenolic, polyimide, polyamide, polypropylene, PEEK, and others.
The reinforcement materials are often fibers but also commonly
ground minerals. The various methods described below have been
developed to reduce the resin content of the final product, or the fibre
content is increased. As a rule of thumb, lay up results in a product
containing 60% resin and 40% fibre, whereas vacuum infusion gives
a final product with 40% resin and 60% fibre content. The strength of
the product is greatly dependent on this ratio.
FAILURE OF COMPOSITE MATERIALS
Shock, impact, or repeated cyclic stresses can cause the
laminate to separate at the interface between two layers, a condition
known as delamination. Individual fibers can separate from the matrix
e.g. fiber pull-out. Composites can fail on the microscopic or
macroscopic scale. Compression failures can occur at both the macro
scale or at each individual reinforcing fiber in compression buckling.
Tension failures can be net section failures of the part or degradation
of the composite at a microscopic scale where one or more of the
layers in the composite fail in tension of the matrix or failure the bond
between the matrix and fibers.
Some composites are brittle and have little reserve strength
beyond the initial onset of failure while others may have large
deformations and have reserve energy absorbing capacity past the
onset of damage. The variations in fibers and matrices that are
available and the mixtures that can be made with blends leave a very
broad range of properties that can be designed into a composite
structure. The best known failure of a brittle ceramic matrix composite
occurred when the carbon-carbon composite tile on the leading edge
of the wing of the Space Shuttle Columbia fractured when impacted
during take-off. It led to catastrophic break-up of the vehicle when it
re-entered the Earth's atmosphere on February 1, 2003. Compared to
metals, composites have relatively poor bearing strength.
TESTING OF COMPOSITE MATERIALS
To aid in predicting and preventing failures, composites are
tested before and after construction. Pre-construction testing may use
finite element analysis (FEA) for ply-by-ply analysis of curved
surfaces and predicting wrinkling, crimping and dimpling of
composites. Materials may be tested after construction through
several nondestructive methods including ultrasonics, thermography,
shearography and X-ray radiography.
PRODUCTS MADE BY THE COMPOSITES
Composite materials have gained popularity (despite their
generally high cost) in high-performance products that need to be
lightweight, yet strong enough to take harsh loading conditions such
as aerospace components (tails, wings, fuselages, propellers), boat
and scull hulls, bicycle frames and racing car bodies. Other uses
include fishing rods, storage tanks, and baseball bats. The new
Boeing 787 structure including the wings and fuselage is composed
largely of composites. Composite materials are also becoming more
common in the realm of orthopedic surgery.
Carbon composite is a key material in today's launch vehicles
and spacecraft. It is widely used in solar panel substrates, antenna
reflectors and yokes of spacecraft. It is also used in payload
adapters, inter-stage structures and heat shields of launch vehicles.
In 2007 an all-composite military High Mobility Multi-purpose
Wheeled Vehicle (HMMWV or Hummvee) was introduced by TPI
Composites Inc and Armor Holdings Inc, the first all-composite
military vehicle. By using composites the vehicle is lighter, allowing
higher payloads. In 2008 carbon fiber and DuPont Kevlar (five times
stronger than steel) were combined with enhanced thermoset resins
to make military transit cases by ECS Composites creating 30-
percent lighter cases with high strength.
LOAD TRANSFER IN A COMPOSITE MATERIALS
The concept of load sharing between the matrix and the reinforcing constituent
(fibre) is central to an understanding of the mechanical behaviour of a composite. An
external load (force) applied to a composite is partly borne by the matrix and partly by
the reinforcement. The load carried by the matrix across a section of the composite is
given by the product of the average stress in the matrix and its sectional area. The load
carried by the reinforcement is determined similarly. Equating the externally imposed
load to the sum of these two contributions, and dividing through by the total sectional
area, gives a basic and important equation of composite theory, sometimes termed the
"Rule of Averages".
(1)
which relates the volume-averaged matrix and fibre stresses ( ),
in a composite containing a volume (or sectional area) fraction f of
reinforcement, to the applied stress sA. Thus, a certain proportion of
an imposed load will be carried by the fibre and the remainder by the
matrix. Provided the response of the composite remains elastic, this
proportion will be independent of the applied load and it represents
an important characteristic of the material. It depends on the volume
fraction, shape and orientation of the reinforcement and on the elastic
properties of both constituents. The reinforcement may be regarded
as acting efficiently if it carries a relatively high proportion of the
externally applied load. This can result in higher strength, as well as
greater stiffness, because the reinforcement is usually stronger, as
well as stiffer, than the matrix.
What happens when a Composite is Stressed?
Figure 1
Consider loading a composite parallel to the fibres. Since they are
bonded together, both fibre and matrix will stretch by the same
amount in this direction, i.e. they will have equal strains, e (Fig. 1).
This means that, since the fibres are stiffer (have a higher Young
modulus, E), they will be carrying a larger stress. This illustrates the
concept of load transfer, or load partitioning between matrix and
fibre, which is desirable since the fibres are better suited to bear high
stresses. By putting the sum of the contributions from each phase
equal to the overall load, the Young modulus of the composite is
found (diagram). It can be seen that a "Rule of Mixtures" applies.
This is sometimes termed the "equal strain" or "Voigt" case. Page
2 in the section covers derivation of the equation for the axial stiffness
of a composite and page 3 allows the effects on composite stiffness
of the fibre/matrix stiffness ratio and the fibre volume fraction to be
explored by inputting selected values.
What about the Transverse Stiffness?
Also of importance is the response of the composite to a load applied
transverse to the fibre direction. The stiffness and strength of the
composite are expected to be much lower in this case, since the
(weak) matrix is not shielded from carrying stress to the same degree
as for axial loading. Prediction of the transverse stiffness of a
composite from the elastic properties of the constituents is far more
difficult than the axial value. The conventional approach is to assume
that the system can again be represented by the "slab model". A
lower bound on the stiffness is obtained from the "equal stress" (or
"Reuss") assumption shown in Fig. 2. The value is an
underestimate, since in practice there are parts of the matrix
effectively "in parallel" with the fibres (as in the equal strain model),
rather than "in series" as is assumed. Empirical expressions are
available which give much better approximations, such as that of
Halpin-Tsai. There are again two pages in the section covering this topic, the first
(page 4) outlining derivation of the equal stress equation for stiffness and the second
(page 5) allowing this to be evaluated for different cases. For purposes of comparison, a
graph is plotted of equal strain, equal stress and Halpin-Tsai predictions. The Halpin-Tsai
expression for transverse stiffness (which is not given in the module, although it is
available in the glossary) is:
(2)
in which
Figure 2
The value of x may be taken as an adjustable parameter, but its
magnitude is generally of the order of unity. The expression gives the
correct values in the limits of f=0 and f=1 and in general gives good
agreement with experiment over the complete range of fibre content.
A general conclusion is that the transverse stiffness (and strength) of
an aligned composite are poor; this problem is usually countered by
making a laminate (see section on "composite laminates").
How is Strength Determined?
There are several possible approaches to prediction of the strength of
a composite. If the stresses in the two constituents are known, as for
the long fiber case under axial loading, then these values can be
compared with the corresponding strengths to determine whether
either will fail. Page 6 in the section briefly covers this concept. (More
details about strength are given in the section on "Fracture
Behavior".) The treatment is a logical development from the analysis
of axial stiffness, with the additional input variable of the ratio
between the strengths of fiber and matrix.
Such predictions are in practice complicated by uncertainties
about in situ strengths, interfacial properties, residual stresses
etc. Instead of relying on predictions such as those outlined above, it
is often necessary to measure the strength of the composite, usually
by loading parallel, transverse and in shear with respect to the fibres.
This provides a basis for prediction of whether a component will fail
when a given set of stresses is generated (see section on "Fracture
Behaviour"), although in reality other factors such as environmental
degradation or the effect of failure mode on toughness, may require
attention.
What happens with Short Fibres?
Short fibres can offer advantages of economy and ease of
processing. When the fibres are not long, the equal strain condition
no longer holds under axial loading, since the stress in the fibres
tends to fall off towards their ends (see Fig. 3). This means that the
average stress in the matrix must be higher than for the long fiber
case. The effect is illustrated pictorially in pages 7 and 8 of the
section.
Figure 3
This lower stress in the fibre, and correspondingly higher
average stress in the matrix (compared with the long fibre case) will
depress both the stiffness and strength of the composite, since the
matrix is both weaker and less stiff than the fibres. There is therefore
interest in quantifying the change in stress distribution as the fibres
are shortened. Several models are in common use, ranging from
fairly simple analytical methods to complex numerical packages. The
simplest is the so-called "shear lag" model. This is based on the
assumption that all of the load transfer from matrix to fibre occurs via
shear stresses acting on the cylindrical interface between the two
constituents. The build-up of tensile stress in the fibre is related to
these shear stresses by applying a force balance to an incremental
section of the fibre. This is depicted in page 9 of the section. It leads
to an expression relating the rate of change of the stress in the fibre
to the interfacial shear stress at that point and the fibre radius, r.
(3)
which may be regarded as the basic shear lag relationship. The
stress distribution in the fibre is determined by relating shear strains
in the matrix around the fibre to the macroscopic strain of the
composite. Some mathematical manipulation leads to a solution for
the distribution of stress at a distance x from the mid-point of the fibre which
involves hyperbolic trig functions:
(4)
where e1 is the composite strain, s is the fibre aspect ratio
(length/diameter) and n is a dimensionless constant given by:
(5)
in which nm is the Poisson ratio of the matrix. The variation of
interfacial shear stress along the fibre length is derived, according to
Eq.(3), by differentiating this equation, to give:
(6)
The equation for the stress in the fibre, together with the assumption
of a average tensile strain in the matrix equal to that imposed on the
composite, can be used to evaluate the composite stiffness. This
leads to:
(7)
The expression in square brackets is the composite stiffness. In
page 10 of the section, there is an opportunity to examine the
predicted stiffness as a function of fibre aspect ratio, fibre/matrix
stiffness ratio and fibre volume fraction. The other point to note about
the shear lag model is that it can be used to examine inelastic
behaviour. For example, interfacial sliding (when the interfacial shear
stress reaches a critical value) or fibre fracture (when the tensile
stress in the fibre becomes high enough) can be predicted. As the
strain imposed on the composite is increased, sliding spreads along
the length of the fibre, with the interfacial shear stress unable to rise
above some critical value, ti*. If the interfacial shear stress becomes
uniform at ti* along the length of the fibre, then a critical aspect ratio,
s*, can be identified, below which the fibre cannot undergo fracture.
This corresponds to the peak (central) fibre stress just attaining its
ultimate strength sf*, so that, by integrating Eq.(3) along the fibre half-length:
(8)
It follows from this that a distribution of aspect ratios between s*
and s*/2 is expected, if the composite is subjected to a large strain.
The value of s* ranges from over 100, for a polymer composite with
poor interfacial bonding, to about 2-3 for a strong metallic matrix. In
page 10, the effects of changing various parameters on the
distributions of interfacial shear stress and fibre tensile stress can be
explored and predictions made about whether fibres of the specified
aspect ratio can be loaded up enough to cause them to fracture.
Composite Laminates
High stiffness and strength usually require a high proportion of
fibres in the composite. This is achieved by aligning a set of long
fibres in a thin sheet (a lamina or ply). However, such material is
highly anisotropic, generally being weak and compliant (having a
low stiffness) in the transverse direction. Commonly, high strength
and stiffness are required in various directions within a plane. The
solution is to stack and weld together a number of sheets, each
having the fibres oriented in different directions. Such a stack is
termed a laminate. An example is shown in the diagram. The
concept of a laminate, and a pictorial illustration of the way that the
stiffness becomes more isotropic as a single ply is made into a
cross-ply laminate, are presented in page 1 of this section.
What are the Stresses within a Crossply Laminate?
The stiffness of a single ply, in either axial or transverse
directions, can easily be calculated. (See the section on Load
Transfer). From these values, the stresses in a crossply laminate,
when loaded parallel to the fibre direction in one of the plies, can
readily be calculated. For example, the slab model can be applied to
the two plies in exactly the same way as it was applied in the last
section to fibres and matrix. This allows the stiffness of the laminate
to be calculated. This gives the strain (experienced by both plies) in
the loading direction, and hence the average stress in each ply, for a
given applied stress. The stresses in fibre and matrix within each ply
can also be found from these average stresses and a knowledge of
how the load is shared. In page 2 of this section, by inputting values
for the fibre/matrix stiffness ratio and fibre content, the stresses in
both plies, and in their constituents, can be found. Note that,
particularly with high stiffness ratios, most of the applied load is borne
by the fibres in the "parallel" ply (the one with the fibre axis parallel to
the loading axis).
What is the Off-Axis Stiffness of a Ply?
For a general laminate, however, or a crossply loaded in some
arbitrary direction, a more systematic approach is needed in order to
predict the stiffness and the stress distribution. Firstly, it is necessary
to establish the stiffness of a ply oriented so the fibres lie at some
arbitrary angle to the stress axis. Secondly, further calculation is
needed to find the stiffness of a given stack. Consider first a single
ply. The stiffness for any loading angle is evaluated as follows,
considering only stresses in the plane of the ply The applied stress is
first transformed to give the components parallel and perpendicular to
the fibres. The strains generated in these directions can be calculated
from the (known) stiffness of the ply when referred to these axes.
Finally, these strains are transformed to values relative to the loading
direction, giving the stiffness.
Figure 4
These three operations can be expressed mathematically in
tensor equations. Since we are only concerned with stresses and
strains within the plane of the ply, only 3 of each (two normal and one
shear) are involved. The first step of resolving the applied stresses,
sx, sy and txy, into components parallel and normal to the fibre axis, s1,
s2 and t12 (see Fig. 4), depends on the angle, f between the loading
direction (x) and the fibre axis (1)
(9)
where the transformation matrix is given by:
(10)
in which c = cosf and s = sinf. For example, the value of s1 would be
obtained from:
(11)
Now, the elastic response of the ply to stresses parallel and
normal to the fibre axis is easy to analyse. For example, the axial and
transverse Young’s moduli (E1 and E2) could be obtained using the
slab model or Halpin-Tsai expressions (see Load Transfer section).
Other elastic constants, such as the shear modulus (G12) and
Poisson’s ratios, are readily calculated in a similar way. The
relationship between stresses and resultant strains dictated by these
elastic constants is neatly expressed by an equation involving the
compliance tensor, S, which for our composite ply, has the form:
(12)
in which, by inspection of the individual equations, it can be seen that
Application of Eq.(12), using the stresses established from Eq.
(9), now allows the strains to be established, relative to the 1 and 2
directions. There is a minor complication in applying the final stage of
converting these strains so that they refer to the direction of loading
(x and y axes). Because engineering and tensorial shear strains are not quite the same, a
slightly different transformation matrix is applicable from that used for stresses
(13)
in which,
and the inverse of this matrix is used for conversion in the reverse direction,
(14)
in which,
The final expression relating applied stresses and resultant strains can therefore be
written,
(15)
The elements of | |, the transformed compliance tensor, are
obtained by concatenation (the equivalent of multiplication) of the
matrices | T '|-1, | S | and | T |. The following expressions are obtained
(16)
Figure 5
The final result of this rather tedious derivation is therefore quite
straightforward. Eq.(16), together with the elastic constants of the
composite when loaded parallel and normal to the fibre axis, allows
the elastic deformation of the ply to be predicted for loading at any
angle to the fibre axis. This is conveniently done using a simple
computer program. The results of such calculations can be explored
using pages 4 and 5 in this section. As an example, Fig. 5 shows the
Young's modulus for the an polyester-50% glass fibre ply as the
angle, f between fibre axis and loading direction rises from 0° to 90°.
A sharp fall is seen as f exceeds about 5-10°.
How is the Stiffness of a Laminate obtained?
Once the elastic response of a single ply loaded at an arbitrary
angle has been established, that of a stack bonded together (i.e. a
laminate) is quite easy to predict. For example, the Young's modulus
in the loading direction is given by an applied normal stress over the
resultant normal strain in that direction. This same strain will be
experienced by all of the component plies of the laminate. Since
every ply now has a known Young's modulus in the loading direction
(dependent on its fibre direction), the stress in each one can be
expressed in terms of this universal strain. Furthermore, the force
(stress times sectional area) represented by the applied stress can
also be expressed as the sum of the forces being carried by each ply.
This allows the overall Young's modulus of the laminate to be
calculated. The results of such calculations, for any selected stacking
sequence, can be explored using pages 4 and 5.
Are Other Elastic Constants Important?
There are several points of interest about how a ply changes
shape in response to an applied load. For example, the lateral
contraction (Poisson ratio, n) behaviour may be important, since in a
laminate such contraction may be resisted by other plies, setting up
stresses transverse to the applied load. Another point with fibre
composites under off-axis loading is that shear strains can arise from
tensile stresses (and vice versa). This corresponds to the elements of
S which are zero in Eq.(12) becoming non-zero for an arbitrary
loading angle (Eq.(16)). These so-called "tensile-shear
interactions" can be troublesome, since they can set up stresses
between individual plies and can cause the laminate to become
distorted. The value of , for example, represents the ratio between
g12 and s1. Its value can be obtained for any specified laminate by
using page 6 of this section. It will be seen that, depending on the
stacking sequence, relatively high distortions of this type can arise.
On the other hand, a stacking sequence with a high degree of
rotational symmetry can show no tensile-shear interactions. When the
tensile-shear interaction terms contributed by the individual laminae
all cancel each other out in this way, the laminate is said to be
"balanced". Simple crossply and angle-ply laminates are not
balanced for a general loading angle, although both will be balanced
when loaded at f=0° (i.e. parallel to one of the plies for a cross-ply or
equally inclined to the +q and -q plies for the angle-ply case). If the
plies vary in thickness, or in the volume fractions or type of fibres they
contain, then even a laminate in which the stacking sequence does
exhibit the necessary rotational symmetry is prone to tensile-shear
distortions and computation is necessary to determine the lay-up
sequence required to construct a balanced laminate. The stacking
order in which the plies are assembled does not enter into these
calculations.
How do Composites Fracture?
Figure 6
Fracture of long fibre composites tends to occur either normal
or parallel to the fibre axis. This is illustrated on page 1 of this section
- see Fig. 6. Large tensile stresses parallel to the fibres, s1, lead to
fibre and matrix fracture, with the fracture path normal to the fibre
direction. The strength is much lower in the transverse tension and
shear modes and the composite fractures on surfaces parallel to the
fibre direction when appropriate s2 or t12 stresses are applied. In these
cases, fracture may occur entirely within the matrix, at the fibre/matrix
interface or primarily within the fibre. To predict the strength of a
lamina or laminate, values of the failure stresses s1*, s2* and t12* have
to be determined.
Can the Axial Strength be Predicted?
Understanding of failure under an applied tensile stress parallel
to the fibres is relatively simple, provided that both constituents
behave elastically and fail in a brittle manner. They then experience
the same axial strain and hence sustain stresses in the same ratio as
their Young's moduli. Two cases can be identified, depending on
whether matrix or fibre has the lower strain to failure. These cases
are treated in pages 2 and 3 respectively.
Figure 7
Consider first the situation when the matrix fails first (em*<ef*).
For strains up to em*, the composite stress is given by the simple rule of mixtures:
(17)
Above this strain, however, the matrix starts to undergo
microcracking and this corresponds with the appearance of a "knee"
in the stress-strain curve. The composite subsequently extends with
little further increase in the applied stress. As matrix cracking
continues, the load is transferred progressively to the fibres. If the
strain does not reach ef* during this stage, further extension causes
the composite stress to rise and the load is now carried entirely by
the fibres. Final fracture occurs when the strain reaches ef*, so that
the composite failure stress s1* is given by f sf*. A case like this is
illustrated in Fig. 7, which refers to steel rods in a concrete matrix.
[FB2, RHS, real system data, mild steel fibres, concrete matrix, fibre
fraction 40%, "strength v. fraction of fibres" clicked]
Figure 8
Alternatively, if the fibres break before matrix cracking has become sufficiently extensive
to transfer all the load to them, then the strength of the composite is given by:
(18)
where sfm* is the fibre stress at the onset of matrix cracking (e1=em*).
The composite failure stress depends therefore on the fibre volume
fraction in the manner shown in Fig. 8. The fibre volume fraction
above which the fibres can sustain a fully transferred load is obtained
by setting the expression in Eq.(18) equal to f sf*, leading to:
(19)
If the fibres have the smaller failure strain (page 3), continued
straining causes the fibres to break up into progressively shorter
lengths and the load to be transferred to the matrix. This continues
until all the fibres have aspect ratios below the critical value (see Eq.
(8)). It is often assumed in simple treatments that only the matrix is
bearing any load by the time that break-up of fibres is complete.
Subsequent failure then occurs at an applied stress of (1-f) sm*. If
matrix fracture takes place while the fibres are still bearing some load, then the composite
failure stress is:
(20)
where smf is the matrix stress at the onset of fibre cracking. In
principle, this implies that the presence of a small volume fraction of
fibres reduces the composite failure stress below that of the
unreinforced matrix. This occurs up to a limiting value f ' given by
setting the right hand side of Eq.(20) equal to (1-f) sm*.
(21)
The values of these parameters can be explored for various systems
using pages 2 and 3. Prediction of the values of s2* and t12* from
properties of the fibre and matrix is virtually impossible, since they are
so sensitive to the nature of the fibre-matrix interface. In practice,
these strengths have to be measured directly on the composite
material concerned.
How do Plies Fail under Off-axis Loads?
Failure of plies subjected to arbitrary (in-plane) stress states can be
understood in terms of the three failure mechanisms (with defined
values of s1*, s2* and t12*) which were depicted on page 1. A number of
failure criteria have been proposed. The main issue is whether or
not the critical stress to trigger one mechanism is affected by the
stresses tending to cause the others - i.e. whether there is any
interaction between the modes of failure. In the simple maximum
stress criterion, it is assumed that failure occurs when a stress parallel or normal to
the fibre axis reaches the appropriate critical value, that is when one of the following is
satisfied:
(22)
For any stress system (sx, sy and txy) applied to the ply, evaluation of
these stresses can be carried out as described in the section on
Composite Laminates (Eqs.(9) and (10)).
Figure 9
Monitoring of s1, s2 and t12 as the applied stress is increased allows
the onset of failure to be identified as the point when one of the
inequalities in Eq.(22) is satisfied. Noting the form of | T | (Eq.(10)),
and considering applied uniaxial tension, the magnitude of sx necessary
to cause failure can be plotted as a function of angle f between stress axis and fibre axis,
for each of the three failure modes.
(23)
(24)
(25)
The applied stress levels at which these conditions become satisfied
can be explored using page 5. As an example, the three curves
corresponding to Eqs.(23)-(25) are plotted in Fig. 9, using typical
values of s1*, s2* and t12*. Typically, axial failure is expected only for
very small loading angles, but the predicted transition from shear to
transverse failure may occur anywhere between 20° and 50°,
depending on the exact values of t12* and s2*.
In practice, there is likely to be some interaction between the failure
modes. For example, shear failure is expected to occur more easily if,
in addition to the shear stress, there is also a normal tensile stress
acting on the shear plane. The most commonly used model taking
account of this effect is the Tsai-Hill criterion. This can be expressed
mathematically as
(26)
This defines an envelope in stress space: if the stress state (s1, s2
and t12) lies outside of this envelope, i.e. if the sum of the terms on
the left hand side is equal to or greater than unity, then failure is
predicted. The failure mechanism is not specifically identified,
although inspection of the relative magnitudes of the terms in Eq.(26)
gives an indication of the likely contribution of the three modes. Under
uniaxial loading, the Tsai-Hill criterion tends to give rather similar
predictions to the Maximum Stress criterion for the strength as a
function of loading angle. The predicted values tend to be somewhat
lower with the Tsai-Hill criterion, particularly in the mixed mode
regimes where both normal and shear stresses are significant. This
can be explored on page 6.
What is the Failure Strength of a Laminate?
The strength of laminates can be predicted by an extension of the
above treatment, taking account of the stress distributions in
laminates, which were covered in the preceding section. Once these
stresses are known (in terms of the applied load), an appropriate
failure criterion can be applied and the onset and nature of the failure
predicted.
Figure 10
However, failure of an individual ply within a laminate does not
necessarily mean that the component is no longer usable, as other
plies may be capable of withstanding considerably greater loads
without catastrophic failure. Analysis of the behaviour beyond the
initial, fully elastic stage is complicated by uncertainties as to the
degree to which the damaged plies continue to bear some load.
Nevertheless, useful calculations can be made in this regime
(although the major interest may be in the avoidance of any damage
to the component).In page 7, a crossply (0/90) laminate is loaded in
tension along one of the fibre directions. The stresses acting in each
ply, relative to the fibre directions, are monitored as the applied stress
is increased. Only transverse or axial tensile failure is possible in
either ply, since no shear stresses act on the planes parallel to the
fibre directions. The software allows the onset of failure to be
predicted for any given composite with specified strength values.
Although the parallel ply takes most of the load, it is commonly the
transverse ply which fails first, since its strength is usually very low.
In page 8, any specified laminate can be subjected to an imposed
stress state and the onset of failure predicted. An example of such a
calculation is shown in Fig. 10.
What is the Toughness (Fracture Energy) of a Composite?
The fracture energy, Gc, of a material is the energy absorbed within it
when a crack advances through the section of a specimen by unit
area. Potentially the most significant source of fracture work for most
fibre composites is interfacial frictional sliding. Depending on the
interfacial roughness, contact pressure and sliding distance, this
process can absorb large quantities of energy. The case of most
interest is pull-out of fibres from their sockets in the matrix. This
process is illustrated schematically in page 9.
The work done as a crack opens up and fibres are pulled out of their
sockets can be calculated in the following way. A simple shear lag
approach is used. Provided the fibre aspect ratio, s (=L/r), is less than
the critical value, s* (=sf*/2ti*), see page 10 of the Load Transfer
section, all of the fibres intersected by the crack debond and are
subsequently pulled out of their sockets in the matrix (rather than
fracturing). Consider a fibre with a remaining embedded length of x
being pulled out an increment of distance dx. The associated work is
given by the product of the force acting on the fibre and the distance
it moves
dU = (2prxti*) dx(27)
where ti* is the interfacial shear stress, taken here as constant along the length of the
fibre. The work done in pulling this fibre out completely is therefore given by
(28)
where x0 is the embedded length of the fibre concerned on the side of
the crack where debonding occurs (x0 = L). The next step is an
integration over all of the fibres. If there are N fibres per m2, then
there will be (N dx0 / L) per m2 with an embedded length between x0
and (x0 + dx0). This allows an expression to be derived for the pull-out
work of fracture, Gc
(29)
The value of N is related to the fibre volume fraction, f, and the fibre
radius, r
N =
(30)
Eq.(29) therefore simplifies to
(31)
This contribution to the overall fracture energy can be large. For
example, taking f=0.5, s=50, r=10 µm and ti*=20 MPa gives a value of
about 80 kJ m-2. This is greater than the fracture energy of many
metals. Since sf* would typically be about 3 GPa, the critical aspect
ratio, s* (=sf*/2ti*), for this value of ti*, would be about 75. Since this is
greater than the actual aspect ratio, pull-out is expected to occur
(rather than fibre fracture), so the calculation should be valid. The
pull-out energy is greater when the fibres have a larger diameter,
assuming that the fibre aspect ratio is the same. In page 10, the
cumulative fracture energy is plotted as the crack opens up and fibres
are pulled out of their sockets. The end result for a particular case is
shown in Fig. 11.
Figure 11
CHAPTER-III
PRO-E & ANSYS
PRO-ENGINEER
Pro/ENGINEER, PTC's parametric, integrated 3D
CAD/CAM/CAE solution, is used by discrete manufacturers for
mechanical engineering, design and manufacturing. Created by Dr.
Samuel P. Geisberg in the mid-1980s, Pro/ENGINEER was the
industry's first successful parametric, 3D CAD modeling system. The
parametric modeling approach uses parameters, dimensions,
features, and relationships to capture intended product behavior and
create a recipe which enables design automation and the
optimization of design and product development processes. This
powerful and rich design approach is used by companies whose
product strategy is family-based or platform-driven, where a
prescriptive design strategy is critical to the success of the design
process by embedding engineering constraints and relationships to
quickly optimize the design, or where the resulting geometry may be
complex or based upon equations. Pro/ENGINEER provides a
complete set of design, analysis and manufacturing capabilities on
one, integral, scalable platform. These capabilities, include Solid
Modeling, Surfacing, Rendering, Data Interoperability, Routed
Systems Design, Simulation, Tolerance Analysis, and NC and
Tooling Design.
ANSYS
ANSYS is an engineering simulation software provider founded
by software engineer John Swanson. It develops general-purpose
finite element analysis and computational fluid dynamics software.
While ANSYS has developed a range of computer-aided engineering
(CAE) products, it is perhaps best known for its ANSYS Mechanical
and ANSYS Multiphysics products.
ANSYS Mechanical and ANSYS Multiphysics software are non
exportable analysis tools incorporating pre-processing (geometry
creation, meshing), solver and post-processing modules in a
graphical user interface. These are general-purpose finite element
modeling packages for numerically solving mechanical problems,
including static/dynamic structural analysis (both linear and non-
linear), heat transfer and fluid problems, as well as acoustic and
electro-magnetic problems.
ANSYS Mechanical technology incorporates both structural and
material non-linearities. ANSYS Multiphysics software includes
solvers for thermal, structural, CFD, electromagnetics, and acoustics
and can sometimes couple these separate physics together in order
to address multidisciplinary applications. ANSYS software can also
be used in civil engineering, electrical engineering, physics and
chemistry.
ANSYS, Inc. acquired the CFX computational fluid dynamics
code in 2003 and Fluent, Inc. in 2006. The CFD packages from
ANSYS are used for engineering simulations. In 2008, ANSYS
acquired Ansoft Corporation, a leading developer of high-
performance electronic design automation (EDA) software, and
added a suite of products designed to simulate high-performance
electronics designs found in mobile communication and Internet
devices, broadband networking components and systems, integrated
circuits, printed circuit boards, and electromechanical systems. The
acquisition allowed ANSYS to address the continuing convergence of
the mechanical and electrical worlds across a whole range of industry
sectors.
UNDERSTANDING THE NODES AND ELEMENTS
Red dots represent the element's nodes.
Elements can have straight or curved edges.
Each node has three unknowns, namely, the translations in the
three global directions.
The process of subdividing the part into small pieces (elements)
is called meshing. In general, smaller elements give more
accurate results but require more computer resources and time.
Ansys suggests a global element size and tolerance for
meshing. The size is only an average value, actual element
sizes may vary from one location to another depending on
geometry.
It is recommended to use the default settings of meshing for the
initial run. For a more accurate solution, use a smaller element
size.
LOADS & SUPPPORT APPLIED ON FLYWHEEL
CHAPTER-IV
MODELLING COMMANDS USED IN PRO-E
CREATE THE WORKING DIRECTORY-First create the working
directory to save the all model in one folder
File – set working directory – select the required folder – ok.
SKETCH- This command is used to create the new sketch like circle,
line, rectangle, ellipse, etc,..
The pro-e window select the sketch icon and select the plane or
surface want to sketch.
CIRCLE- This command is used to create the circle. Create circle by
picking the center point and a point on the circle from Right
Toolchest.
Pick the origin for the circle’s center - pick a point on the circle’s
edge- click the middle mouse button – ok
ELLIPSE- This command is used to create the ellipse. Create ellipse
by picking the center point and a minor radius point and major radius
point, the minor and major radius of the ellipse is vertical and
horizontal direction depend upon the shape of ellipse we want.
Select the ellipse icon from right toolchest- Pick the center for
the ellipse – pick the minor radius of ellipse point and pick the major
radius of the ellipse- click the middle mouse button – ok
LINE- This command is used to create the line. Create the line by
start point and end point.
Select the line icon from the right Toolchest – click the start point of
the line – click the end point of the circle -enter
ARC- This command is used to create the arc. Create the arc by
using three points. The three points are start point, end point and
center point of the arc.
Select the arc icon from the right Toolchest – click the start point of
the arc – click the end point of the arc and click the middle point of
the arc –enter.
The dimension of the arc is modified by double click on the arc
then the dimension will appear in the pop up box, then provide the
value of the arc.
CREATE THE HEXAGON – The hexagon is created by insert foreign
data icon in the Right Toolchest.
Insert foreign data from Palette into active object - scroll down to see
the hexagon - double-click hexagon- Place the hexagon on the
sketch by picking a position - with the left mouse button, drag and
drop the center of the hexagon at the origin - modify Scale value to
the required size – click enter
RECTANGLE- This command is used to create the rectangle and
square.
Click the rectangle icon in the right Toolchest – click the lower
left point of the rectangle and higher right corner of the rectangle we
want to draw.
After drawing the rectangle the dimension of the rectangle is
provided by the pick the dimension command from the dimension
icon in the right toolchest of the pro-e software.
DIMENSION- This command is used to provide the dimension of the
sketched entities the entities may be circle, line, rectangle, ellipse,
etc,..
The dimension is provide to the sketch by select the dimension
icon from the right tool chest then select the sketched entities and
press the middle mouse button to finish the dimensioning.
To change the dimension of the sketched entities by just double
click the dimension line of created sketch.
EXTRUDE – This command is used to create the material (to make
3D object from 2D sketch) from the sketched entities. The entities
may be circle, line or rectangle, etc,...
Select the extrude icon from the right toolchest then select the
sketched part in the window, enter the extrude length and press the
middle mouse button to finish the extrude command.
REVOLVE- This command is used to create the material from taking
the one axis and sketched entities. The axis is the center of the
revolved part. The revolve angle should between 0 degree to 360
degree.
Select the revolve icon from the right toolchest then select the
sketched part and axis of the object in the graphical window, enter
the revolve angle and press the middle mouse button to finish the
extrude command.
SWEEP FEATURES
The Sweep option extrudes a section along a defined trajectory.
The order of operation is to first create a trajectory and then a
section. A trajectory is a path along which a section is swept. The
trajectory for a sweep feature can be sketched or selected. The
Sweep option of protrusion is similar to the Extrude option. The only
difference is that in the case of the Extrude option, the feature is
extruded in a direction normal to the sketching plane, but in the case
of the Sweep option, the section is swept along the sketched or
selected trajectory. The trajectory can be open or closed. Normal
sketching tools are used for sketching the trajectory. The cross-
section of the swept feature remains constant throughout the sweep.
SWEEP CUT
To create a Sweep Cut feature, the procedure to be followed is
the same as that in Sweep Protrusion. The only difference is that in
case of cut features, the material is removed from an existing feature.
The Cut option can be invoked by choosing Insert > Sweep >
Cut from the menu bar. A cut can be a solid swept cut or a thin swept
cut.
CHAPTER-V
ANALYSIS PROCEDURE
FLEXIBLE DYNAMIC
Flexible dynamic analysis (also called time-history analysis) is a
technique used to determine the dynamic response of a structure
under the action of any general time-dependent loads. You can use
this type of analysis to determine the time-varying displacements,
strains, stresses, and forces in a structure as it responds to any
combination of static, transient, and harmonic loads. The time scale
of the loading is such that the inertia or damping effects are
considered to be important. If the inertia and damping effects are not
important, you might be able to use a static analysis instead.
ANALYZING THE FLYWHEEL – STEP BY STEP PROCEDURE
The 3D model of the flywheel is designed by using pro-e
software and it is converted as IGES format.
The IGES (International Graphic Exchange System) format is
suitable to import in the ANSYS Workbench for analyzing
Open the ANSYS workbench
Create new geometry
File – import external geometry file – generate
Project – new mesh
Defaults – physical preference – mechanical
Advanced – relevance center – fine
Advanced – element size – 100 mm
Right click the mesh in tree view – generate mesh
Project – convert to simulation – yes
Select the all solid in geometry tree
Definition – material – new material
New material – right click – rename – CAST IRON
Enter the value of the young’s modulus, poisons ratio, density
and etc,…
Define the another material – right click the materials – insert
new material – name it to EPOXY CARBON
Enter the value of the young’s modulus, poisons ratio, density
and etc,…
New analysis – flexible dynamic
Flexible dynamic – right click – insert – fixed support
Select the inner circular face of the flywheel
Geometry – apply
Flexible dynamic – right click - insert – rotational velocity –
select the face to define the velocity direction
Geometry – apply
Provide the value of the rotational velocity to 2600RPM
Flexible dynamic – right click - insert – moment – select the
face to define the moment direction and select the all surfaces
to the moment load
Provide the value of the moment 461N.m
Then define the solution
Solution – right click - insert the total deformation, equivalent
elastic strain, equivalent stress, shear elastic strain, shear
stress and total acceleration.
Right click the solution icon in the tree – solve
After solve the analysis – take the reading of above mentioned
items (i.e. total deformation, directional deformation, etc,…)
The all results are taken in a picture – and save it to the
required folder in the system
The material is changed to cast iron – in the previous steps –
the loads are to be same as the epoxy carbon
Solve again this analysis in the cast iron material
Now take again the six results – save the picture to the required
folder in the system
The all readings are tabulated
The results are compared to the two design of the flywheel
Finally we get the result which design withstands the load in
same load condition.
CHAPTER-VI
MATERIAL PROPERTIES
CAST IRON
Cast iron usually refers to grey iron, but also identifies a large
group of ferrous alloys, which solidify with a eutectic. The colour of a
fractured surface can be used to identify an alloy. White cast iron is
named after its white surface when fractured, due to its carbide
impurities which allow cracks to pass straight through. Grey cast iron
is named after its grey fractured surface, which occurs because the
graphitic flakes deflect a passing crack and initiate countless new
cracks as the material breaks.
Iron (Fe) accounts for more than 95% by weight (wt%) of the
alloy material, while the main alloying elements are carbon (C) and
silicon (Si). The amount of carbon in cast irons is 2.1 to 4 wt%. Cast
irons contain appreciable amounts of silicon, normally 1 to 3 wt%,
and consequently these alloys should be considered ternary Fe-C-Si
alloys. Despite this, the principles of cast iron solidification are
understood from the binary iron-carbon phase diagram, where the
eutectic point lies at 1,154 °C (2,109 °F) and 4.3 wt% carbon. Since
cast iron has nearly this composition, its melting temperature of 1,150
to 1,200 °C (2,102 to 2,192 °F) is about 300 °C (572 °F) lower than
the melting point of pure iron.
Cast iron tends to be brittle, except for malleable cast irons.
With its low melting point, good fluidity, castability, excellent
machinability, resistance to deformation, and wear resistance, cast
irons have become an engineering material with a wide range of
applications, including pipes, machine and automotive industry parts,
such as cylinder heads (declining usage), cylinder blocks, and
gearbox cases (declining usage). It is resistant to destruction and
weakening by oxidisation (rust).
DURALUMIN
Duralumin (also called duraluminum, duraluminium or dural) is
an alloy of aluminium (about 95%), copper (about 4%), and small
amounts of magnesium (0.5%–1%) and manganese (less than 1%). It
is far better in tensile strength than elemental aluminium, though less
resistant to corrosion. Its heat and electrical conductivity are less than
that of pure aluminium but much more than that of steel.
Duralumin was invented in 1908 by Alfred Wilm during research
for the German army. Its first use was rigid airship frames. Its
composition and heat-treatment were a wartime secret. With this new
rip-resistant mixture, duralumin quickly spread throughout the aircraft
industry in the early 1930s, where it was well suited to the new
monocoque construction techniques that were being introduced at the
same time. Duralumin also is popular for use in precision tools such
as levels because of its light weight and strength.
To prevent corrosion, alloy sheet can be covered with a thin
layer of pure aluminium. Alclad is a common trade name for this
material. Another unusually effective way of protecting the surface is
Anodising. Both methods can be used at once.
Its use in ground vehicle components has been limited by cost
of material and fabrication, relative to mild steel and cast iron, but it
has become fairly common, especially in cases where requirements
for acceleration, fuel efficiency, etc. demand light weight. Duralumin
components include wheels, cylinder heads, blocks, crank cases, oil
sumps, manifolds, bodies or body parts (Land Rover, Honda Insight,
Lotus Seven, Austin-Healey), frames (M2 Bradley fighting vehicle, a
very high performance Chevrolet Corvette version, Messerschmitt
KR200), bumpers and fuel tank (Panhard), differential case
(Peugeot), bonnet (hood) and boot cover (trunk lid) (MG A).
Today almost all material that claims to be aluminium is actually
an alloy thereof. Pure aluminium is encountered only when corrosion
resistance is more important than strength or hardness. Copper-free
aluminium is specified for such uses. Conversely, the term "alloy"
usually means aluminium alloy. In modern aircraft Duralumin has
evolved into the alloys known as 2017 2117 and 2024.
HIGH STRENGTH EPOXY CARBON
This material is known for its high specific stiffness and
strength, given by epoxy carbon. The material has an advantageous
combination of good mechanical properties and low weight.
The properties of the material vary depending on the content
and orientation of the fibres.
It is used for very stiff and light structures within sport
equipment, aerospace, medical equipment (protheses) and
prototyping.
Epoxy is a strong and very resistant thermoset plastic. It is used
as an adhesive agent, as filling material, for moulding dies, and as a
protective coating on steel and concrete. Many composite materials
are reinforced epoxy.
Epoxy is resistant to almost all acids and solvents, but not to
strong bases or solvents with chlorine content.
By adding a hardening agent curing takes place. The type of
hardener has a major influence on properties and applications of
epoxies.
CHAPTER-VII
RESULTS
DESIGN OF CAST IRON
Total Deformation
Equivalent Elastic Strain
Equivalent Stress
DESIGN OF DURALUMIN
Total Deformation
Equivalent Elastic Strain
Equivalent Stress
DESIGN OF EPOXY CARBON
Total Deformation
Equivalent Elastic Strain
Equivalent Stress
RESULT COMPARISION FOR CAST IRON
CAST IRON OLD DESIGN MODIFIED
Total deformation (mm) 1.9466e-002 1.4553e-002
Equivalent elastic strain 3.0523e-004 3.1043e-004
Equivalent stress (N/mm2) 33.576 34.147
RESULT COMPARISION OF DURALUMIN
DURALUMIN OLD DESIGN MODIFIED
Total deformation (mm) 1.5307e-008 1.1208e-008
Equivalent elastic strain 2.3114e-010 2.147e-010
Equivalent stress (N/mm2) 18.491 17.176
RESULT COMPARISION OF EPOXY CARBON
EPOXY CARBON OLD DESIGN MODIFIED
Total deformation (mm) 0.13184 9.585e-002
Equivalent elastic strain 1.9536e-003 1.6809e-003
Equivalent stress (N/mm2) 1.9536e-003 18.551
CHAPTER-VIII
CONCLUSION
The analysis of flywheel we found that the duralumin material
have a good physical properties and it have a less deformation under
the moment and velocity, then the epoxy carbon material have just
more deformation compared to the duralumin and finally the
deformation, stress, strain of the duralumin is low compared to the
three materials. From the analysis the shear stress produced by the
epoxy carbon is less compared to the cast iron and the shear stress
produced by the epoxy carbon is just high compared to the
duralumin. So the material chosen to manufacturing the flywheel is
duralumin and epoxy carbon to replacing the present material of the
cast iron.
The project carried out by us will make an impressing mark in
the field of automobile. This project we are design and analyze the
flywheel used in an IC engine.
Doing this project we are study about the 3Dmodelling software
(PRO-E) and Study about the analyzing software (ansys) to develop
our basic knowledge to know about the industrial design.
REFERENCE
1. Machine design, R S Khurmi, 2003 edition, Pg No’s:701-741
2. Theory and Design of Automotive Engines - B Dinesh Prabhu,
Assistant Professor, P E S College of Engineering, Mandya,
Karnataka
3. Design Data Book – PSG Tech
4. http://www.carfolio.com/ - For Ambassador Car specifications
5. COMPOSITE MATERIALS DESIGN AND APPLICATIONS, Daniel
Gay, Suong V. Hoa, Stephen W. Tsai.