implementation in leaf spring suspension system for 2 wheeler
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CHAPTER 1
INTRODUCTION
Suspension
systems have been widely applied to vehicles, from the horse-drawn carriage
with flexible leaf springs fixed in the four corners, to the modern automobile
with complex control algorithms. The suspension of a road vehicle is usually
designed with two objectives; to isolate the vehicle body from road
irregularities and to maintain contact of the wheels with the roadway.
Isolation is achieved by the use of springs and dampers and by rubber mountings
at the connections of the individual suspension components. From a system
design point of view, there are two main categories of disturbances on a
vehicle, namely road and load disturbances. Road disturbances have the
characteristics of large magnitude in low frequency such as hills and small
magnitude in high frequency such as road roughness. Load disturbances include
the variation of loads induced by accelerating, braking and cornering.
Therefore,
suspension design is an art of compromise between these two goals (Wang
2001).Today, nearly all passenger cars and light trucks use independent front
suspensions, because of the better resistance to vibrations. The main functions
of a vehicle’s suspension systems are to isolate the structure and the
occupants from shocks and vibrations generated by theroad surface. The
suspension systems basically consist of all the elements that provide the
connection between the tires and the vehicle body.In a vehicle, it reduces the
effect of traveling over rough ground, leading to improved ride quality, and
increase in comfort due to substantially reduced amplitude of disturbances.
Without shock absorbers, the vehicle would have a bouncing ride, as energy is
stored in the spring and then released to the vehicle, possibly exceeding the
allowed range of suspension movement.
For
the suspension of carry-load vehicles many types of arrangements may be used
depending on the type of the vehicle and the occurring operating loads. One
advantageous type of suspension systems is the leaf-springs system, which needs
less additional components than other suspension systems, thereby leading to
lighter and lower-cost structures. Additionally, the leaf-spring’s performance
determines both the suspension and the guidance of the vehicle due to the fact
that the leaf-spring is connected with both the axle and the steering system.
The
Leaf springs are mainly used in suspension systems to absorb shock loads in
automobiles like light motor vehicles, heavy duty trucks and in rail systems.
They carry lateral loads, brake torque, driving torque in addition to shock
absorbing. Leaf springs are having an advantage that the ends of the spring may
be guided along a definite path as it deflects. The use of composite materials
for suspension leaf spring reduces the weight of conventional multi leaf steel
leaf spring by nearly 75%.This achieves the vehicle with more fuel efficiency
and improved riding qualities. For more compliant suspension system (i.e.
energy storage capability), the leaf spring should absorb the vertical
vibrations and impacts due to road irregularities by means of variations in the
spring deflection so that the potential Energy is stored in spring as strain
energy and then released slowly.
In the present work comparative study is been
carried out to understand the working principle of multi-leaf steel spring used
in passenger cars. The multi-leaf steel spring is replaced with a composite
single leaf spring made of E glass/ epoxy and Jute-Glass fiber composite. The
stresses for both steel leaf spring and composite leaf springs are considered
for the study. The primary objective is to compare their load carrying
capacity, stiffness and weight savings of composite leaf spring. Finally,
Natural frequencies and fatigue life of Natural Faber reinforced composite leaf
spring is also predicted using life data.
CHAPTER 2
LITERATURE SURVEY
1.
V.K. Aheret. al. “Fatigue Life Prediction of Multi Leaf Spring used in the
Suspension System of Light Commercial Vehicle”, International Journal on
Theoretical and Applied Research in Mechanical Engineering (IJTARME), 2012.
2.
Ravi Kumar V. et. al. “Analysis of Natural Fibre Composite Leaf Spring”,
International Journal of Latest Trends in Engineering and Technology (IJL2TET)
September 2013
The aim of present work
is to compare the Glass-Fiber-Reinforced - Composite (GFRC) leaf spring with a
Natural-Fiber-Reinforced Composite/Jute-Fiber – Reinforced – Composite
(NFRC/JFRC) leaf spring. Fabrication is carried by hand lay-up technique and
tested. The present work
3.
T.N.V. Ashok Kumar at. al. “Design and Material Optimization of Heavy Vehicle
Leaf Spring”, International Journal of Research in Mechanical Engineering &
Technology, Nov 2013 - April 2014
The paper describes
static and dynamic analysis of steel leaf spring and laminated composite Multi
leaf spring. The objective is to compare displacement, frequencies, deflections
and weight savings of composite leaf spring with that of steel leaf spring.
Static and Dynamic Analysis of 3-D model of conventional leaf spring is
performed using ANSYS 10.0. Same dimensions are used in composite multi leaf
spring using S2 Glass/Epoxy and Kevlar/Epoxy unidirectional laminates. Analysis
is done by layer stacking method for composites by changing reinforcement
angles for 3 layers, 5 layers and 11 layers. The weight of composite leaf
spring is compared with that of steel leaf spring. The design constraints are
stresses and deflection. A weight reduction of 27.5 % is achieved by using
composite leaf spring.
CHAPTER 3
SUSPENSION SYSTEM
3.1. Suspension System:
An
early form of suspension on ox-drawn carts had the
platform swing on iron chains attached to the wheeled frame of the carriage.
This system remained the basis for all suspension systems until the turn of the
19th century, although the iron chains were replaced with the use of leather
straps by the 17th century. No modern automobiles use the 'strap suspension'
system.
Automobiles were initially developed as
self-propelled versions of horse-drawn vehicles. However, horse-drawn vehicles
had been designed for relatively slow speeds, and their suspension was not well
suited to the higher speeds permitted by the internal combustion engine. The
first workable spring-suspension required advanced metallurgical knowledge and
skill, and only became possible with the advent of industrialization.
Obadiah Elliott registered the first patent for a spring-suspension vehicle; -
each wheel had two durable steel leaf springs on each side and the body of the
carriage was fixed directly to the springs which were attached to the axles. Within a decade, most British horse
carriages were equipped with springs; wooden springs in the case of light
one-horse vehicles to avoid taxation, and steel springs in larger vehicles.
These were often made of low-carbon steel and
usually took the form of multiple layer leaf springs.
Leaf springs have been around since the early Egyptians. Ancient military
engineers used leaf springs in the form of bows to power their siege engines,
with little success at first. The use of leaf springs in catapults was later
refined and made to work years later. Springs were not only made of metal, a
sturdy tree branch could be used as a spring, such as with a bow.
Horse-drawn carriages and
the Ford
Model T used this system, and it is still used
today in larger vehicles, mainly mounted in the rear suspension.This was
the first modern suspension system and, along with advances in the construction of roads, heralded
the single greatest improvement in road transport until the advent of the automobile. The British steel springs were
not well suited for use on America's rough roads of the time, so the Abbot-Downing
Company of Concord,
New Hampshire re-introduced leather strap suspension, which gave
a swinging motion instead of the jolting up and down of a spring suspension.
Figure
3.0 plunger suspension
Henri Fournier on his uniquely damped and race winning
'Mors In
1901 Mors of Paris first
fitted an automobile with shock absorbers. With the advantage of a damped
suspension system on his 'Mors Machine', Henri Fournier won the prestigious
Paris-to-Berlin race on 20 June 1901. Fournier's superior time was 11 hrs 46
min 10 sec, while the best competitor was LéonceGirardot in a Panhard with a
time of 12 hrs 15 min 40 sec.
Runabout made by the Brush Motor
Company. Today, coil springs are used in most cars. In 1920, Leyland Motors used torsion bars in a suspension system.In 1922,
independent front suspension was pioneered on the Lancia Lambda and became more common in mass market cars from 1932.
Today most cars have independent suspension on all four wheels.In 2002, a
new passive suspension component was invented by Malcolm C. Smith, the inerter. This has the ability to increase
the effective inertia of a wheel suspension using a geared flywheel, but
without adding significant mass. It was initially employed in Formula 1 in
secrecy but has since spread to other motorsport.
Figure 3.1 Shock absorber
In
addition, this suspension design uses single (mono) shock absorber bigger in
size, with a stronger spring fitted on its outside. The monoshock is usually
positioned near the center of the bike’s chassis of its ends attaches to the
chassis and the other end to the rear swing-arm of the bike which attaches to
the rear wheel. As the wheel moves up or down the monoshock absorber is either
collapsed or extended further.
Figure3.2 Leaf spring
A leaf spring takes the form of a slender
arc-shaped length of spring steel of rectangular cross-section. In the most
common configuration, the center of the arc provides location for the axle, while
loops formed at either end provide for attaching to the vehicle chassis. For
very heavy vehicles, a leaf spring can be made from several leaves stacked on
top of each other in several layers, often with progressively shorter leaves.
Leaf springs can serve locating and to some extent damping as well as springing
functions.
The stresses developed during the tests were compared with
thestresses obtained from the FE analysis performed, simulating the test-rig
configuration for two levels of developed stresses. As shown in Figure the
agreement between calculated and measured stresses is satisfactory. The stress
values are normalized by the maximum stress developed under the maximum applied
force.
3.1.1. SPECIFICATION OF SPRING:
The
helical spring is designed in this project have the following design
specifications:
1
|
Material
|
Mild steel
|
2
|
Number of coils
|
11
|
3
|
Outer diameter of spring
|
55mm
|
4
|
Inner diameter of spring
|
50mm
|
5
|
Thickness of spring
|
5 mm
|
6
|
Width of bush
|
45 mm
|
7
|
Slot width
|
50 mm
|
8
|
Length of Slot
|
160 mm
|
9
|
Shaft diameter
|
58 mm
|
Table 3.1 Specification of leaf spring
3.1.2. MANUFACTURING PROCESS:
Leaf spring:
A leaf spring takes the form of a
slender arc-shaped length of spring steel of rectangular cross-section. In the most common configuration, the
center of the arc provides location for the axle, while loops formed at either end provide for
attaching to the vehicle chassis. For very heavy vehicles, a leaf spring can be
made from several leaves stacked on top of each other in several layers, often
with progressively shorter leaves. Leaf springs can serve locating and to some
extent damping as well as springing functions. While the interleaf friction
provides a damping action, it is not well controlled and results in stilton in the motion of the suspension. For this reason, some
manufacturers have used mono-leaf springs.
Figure 3.3
manufactured leaf spring
3.2. Shock absorber:
Pneumatic and hydraulic shock absorbers are
used in conjunction with cushions and springs. An automobile shock absorber
contains spring-loaded check valves and orifices to control the flow of oil
through an internal piston.
One design
consideration, when designing or choosing a shock absorber, is where that
energy will go. In most shock absorbers, energy is converted to heat inside the
viscous fluid. In hydraulic cylinders, the hydraulic fluid heats up, while in air cylinders, the hot air is usually exhausted to
the atmosphere. In other types of shock absorbers, such as electromagnetic types, the dissipated energy can be
stored and used later. In general terms, shock absorbers help cushion vehicles
on uneven roads.Now, composite suspension system
are used mainly in 2 wheelers and also leaf spring are made up of composite
material in 4 wheelers.
Figure 3.4 mono tube and twin tube
Springs that are too
hard or too soft cause the suspension to become ineffective because they fail
to properly isolate the vehicle from the road. Vehicles that commonly
experience suspension loads heavier than normal have heavy or hard springs with
a spring rate close to the upper limit for that vehicle's weight. This allows
the vehicle to perform properly under a heavy load when control is limited by the inertia of the load. Riding in an empty truck used forcarrying
loads can be uncomfortable for passengers because of its high spring. However, even though we say
they both have heavy springs, the actual spring rates for a 2,000 lb
(910 kg) race car and a 10,000 lb (4,500 kg) truck are very
different Vehicles with worn out or damaged springs ride lower to the ground
which reduces the overall amount of compression available to the suspension and
increases the amount of body lean. Performance vehicles can
sometimes have spring rate requirements other than vehicle weight and load
sometimes have spring rate requirements other than vehicle weight and load
Figure.3.5 Shock Absorber
Figure 3.6 Shock Absorber (Side view)
Shock Absorber types:
Today's automotive
suspension systems incorporate cylinder-type shock absorbers, most of which are
of the double-acting type that generate damping forces in both the extending
and contracting strokes.
· Monotube shock absorbers
· Twin-tube shock absorber
Monotube Shock Absorbers
Body
mono-tube damper is divided into two chambers: the oil and gas. The piston and
rod moves down and creates a balancing force. In the compression process, the
oil displaced from the working stroke in the case. When working on a release,
simtec controls the fluid flow. The gas in the chamber (most often nitrogen) is
compressed and takes the whole hit and only then begins to pass the oil.
Balancing power is determined by the shape, size and number of washers on the
piston of the shock absorber piston diameter, diameter and gas pressure.
Figure.3.7Monotube shock absorber
Twin-tube Shock Absorbers:
As the name implies, shock absorbers of this type
consist of two concentric cylinders. The inner cylinder is filled with oil and
it also located a piston and rod. As in the single-tube shock absorbers inside
the cavity moves the rod with piston, on which are mounted the valves that
determine the effort, as rebound and compression. Additional bottom valve
directs oil into the outer cylinder (tank) in the compression process,
increasing the damping ratio. While working on lights out, the oil returns to
the reservoir main chamber through a control valve.
Figure.3.8.Twin-tube shock absorber
CHAPTER 4
COMPONENTS
AND DESCRIPTION
4.1. DAMPING:
Damping is the control of motion or oscillation, as seen with the use of
hydraulic gates and valves in a vehicle's shock absorber. This may also vary,
intentionally or unintentionally. Like spring rate, the optimal damping for
comfort may be less than for control.
Figure.4.1 damping in suspension system
Figure. 4.2 Block diagram of damping
4.2. LEAF SPRING:
4.2.1. Leaf spring:
Leaf
springs also known as flat spring are made out of flat plates. Leaf springs are
designed two ways: multi-leaf and mono-leaf. The leaf springs may carry loads,
brake torque, driving torque, etc...
Characteristics:
1. Weight reduction,
2. High strength,
3. Corrosiveness,
4. Low specific gravity.
Figure 4.3 leaf spring
4.2.2 Types of leaf spring:
Based on the number of plates, we have taken a brief
look at the two different types of leaf spring out there and how they work.
·
Multi Leaf Springs
·
Mono
Leaf Springs
Mono Leaf
Springs:
Mono
leaf springs are more suited to LCV’s than HGV’s as they are not designed for
heavier vehicles. They are designed with a thicker center, gradually thinning
out towards the ends, similar in structure to the multi leaf system, but
without the added plates.
Once upon a time the single leaf spring system was
popular but when they began breaking on heavier vehicles they started to go out
of fashion a bit. They can still be seen and used, although not when the
vehicle in question requires protection against a heavy load or the weight of
the vehicle itself.
Figure.4.4. mono
leaf spring
Multi Leaf Springs:
On a multi-leaf spring, the size of the plates gets
smaller as you look downwards. The plates are laid lengthwise to layer them,
with the longest piece on top manufactured with eyes or hooks to fix the
springs in place. Multi leaf springs are recognized as the most common kind of
leaf spring for light commercial vehicles and heavy good vehicles. The stacked
format means that the springs are thicker in the middle, which is known as a
semi elliptical look.
Figure4.5 Multi leaf spring
4.2.3 Different Leaf Spring Shapes:
·
Semi Elliptical – This is the normal shape for a multi-leaf
spring, similar to the bow of a bow and arrow, but without the string.
·
Elliptical – Two leaf springs can be combined facing away
from each other to create an oval shape. This is known as elliptical.
·
Quarter Elliptical – This is an older type of spring with a
similar structure to that of a normal leaf spring, only different being that it
is half.
·
Three-Quarter Elliptic – Some larger vehicles can be seen sporting an extra half of a leaf spring to support the normal leaf spring, positioned over the top of the axle.
Three-Quarter Elliptic – Some larger vehicles can be seen sporting an extra half of a leaf spring to support the normal leaf spring, positioned over the top of the axle.
Figure 4.6 shapes
4.2.4.Manufacturing process:
Multi-leaf springs are made as follows:
1.
Shearing of flat bar
2.
Center hole punching / Drilling
3.
Heating process (hot & cold process)
·
Eye Forming / Wrapper Forming
·
Diamond cutting / end trimming / width cutting
/ end tapering
·
End punching / end grooving / end bending / end
forging / eye grinding / end rolling
·
Center hole punching / Drilling / nibbing
4.
Heat Treatment
·
Heating
·
Hardening
·
Cambering
·
Quenching
·
Tempering
5.
Surface preparation
·
Shot peening / stress peening
·
Primary painting
6.
Eye bush preparation process
·
Eye reaming / eye boring
·
Bush insertion
·
Bush reaming
7.
Assemble
·
Presetting & load testing
·
Finish painting
Stress induced:
Figures show
typical stress distributions along the tension surface of leaf 1and leaf 2,
respectively, for three loading conditions. The stress values are normalized
bythe maximum allowable stress that occurs at maximum vertical loading.
Figure 4.6.1
Stress induced
4.2.5 STANDARD SIZES OF SUSPENSION LEAF SPRING
·
Standard
nominal widths are: 32,40,45,55,60,65,70,75,80,90,100 and 125 mm.
·
Standard
nominal thickness are: 3.2,4.5,5,6,6.5,7,7.5,8,9,10,11,12,14 and 16 mm.
·
At the eye,
the following bore diameter are recommended:
19,20,22,23,25,27,28,30,32,35,38,50,55 mm.
Model of the parabolic 2-leaf-spring and the additional
components
Figure4.7 Parabolic leaf spring
The shackle at the rear eye and the bushings in the two eyes
were modeled using rigid bars. All the components in the center clamped area
were modeled. In contrast to Figure 2, in the case of the 2-leaf-spring in
question only the elastomeric buffer, the so-called “S-buffer”, issued on the
vehicle, positioned at distance 325mm measured from the center of the clamped
area. Therefore only that one buffer was modeled using a non-linear spring element,
whose force-deflection characteristic was provided by the vehicle manufacturer
The silencers prevent the friction contact between the two
leaves. Their material behavior was simulated using the corresponding stress-strain
curve provided by the vehicle manufacture
4.3 .1 Parabolic mono-leaf spring for rear axles with
on-vehicle configuration
Figure.4.8 leaf spring in 4wheeler
For the design of serial leaf-springs, specific requirements
regarding the dimensions of thevehicle configuration and the allowable
developed stresses that occur under specific operating loading conditions are
taken into account. In particularthe vehicle manufacturer sets the requirement
of the fatigue life of the leaf-springs under specific operating loading conditions
referring to the corresponding vehicle. On the other hand, the leaf-spring manufacturer
having experimental
4.4 SPRING
The primary function of a spring is to deflect or distort
under load and to recover its originalshape when the load is released. During
deflection or distortion, it absorbs energy and release the same as and when
required. Springs are used in many engineering applications such as automobiles
and railway buffers in order to cushion, absorb or control energy due to shock
and vibrations. Springs will suffer a sizeable change in form without being distorted
Permanently when the loads are applied. Springs are generally
classified as leaf springs or helical springs. Leaf springs consist of a number
of thin curved plates, each of same thickness and width but of different
lengths, all bent to the same curvature.
4.4.1 CLASSIFICATION OF SPRINGS:
Based on the shape behavior
obtained by some applied force, springs are classified into the following ways:
SPIRAL SPRINGS
TORSION SPRING
TENSION HELICAL
SPRING COMPRESSION HELICAL
SPRING
I. HELICAL
SPRINGS:
DEFINITON:
It is made of wire coiled in
the form of helix.
CROSS-SECTION:
Circular, square or rectangular
CLASSIFICATION:
1. Open coil springs (or) Compression
helical springs
2.Closed coil springs (or) Tension
helical springs
4.4.2 HELICAL TENSION SPRINGS:
CHARACTERISTICS:
1. Figure shows a helical
tension spring. It has some means of transferring the load from the support to
the body by means of some arrangement.
2. It stretches apart to create
load.
3. The gap between the
successive coils is small.
4. The wire is coiled in a
sequence that the turn is at right angles to the axis of the spring.
5. The spring is loaded along
the axis.
6. By applying load the spring
elongates in action as it mainly depends upon the end hooks as shown in Figureure2.
Figure.4.9 Closed coil helical spring
Figure 4.10 open coiled helical spring
APPLICATIONS:
1.Garage door assemblies
2.Vise-grip pilers
3.Carburetor
4.3 HELICAL COMPRESSION
SPRINGS:
CHARACTERISTICS:
1. The gap between the
successive coils is larger.
2. It is made of round wire and
wrapped in cylindrical shape with a constant pitch between the coils.
3. By applying the load the
spring contracts in action.
4. There are mainly four forms
of compression springs as shown in Figure. They are as follows:
1) Plain end
2) Plain and ground end
3) Squared end
4) Squared and ground end
Among the four types, the
plain end type is less expensive to manufacture. It tends to bow sideways when
applying a compressive load.
APPLICATIONS:
1) Ball point pens
2) Pogo sticks
3) Valve assemblies in engines
1). TORSION SPRINGS:
CHARACTERISTICS:
1. It is also a form of helical
spring, but it rotates about an axis to create load.
2. It releases the load in an
arc around the axis as shown in Figure.
3. Mainly used for torque
transmission
4. The ends of the spring are
attached to other application objects, so that if the object rotates around the
center of the spring.
APPLICATIONS:
1. Mouse tracks
2. Rocker switches
3. Door hinges
4. Clipboards
2) SPIRAL SPRINGS:
CHARACTERISTICS:
1. It is made of a band of
steel wrapped around itself a number of times to create a geometric shape as
shown in Figure.
2. Its inner end is attached to
an arbor and outer end is attached to a retaining drum.
3. It has a few rotations and
also contains a thicker band of steel.
4. It releases power when it
unwinds
APPLICATIONS:
1.
Alarm timepiece
2. Watch
3.
Automotive seat recliners
II. LEAF SPRING:
DEFINITION:
A Leaf spring is a simple
form of spring commonly used in suspension
Vehicles.
CHARACTERISTICS:
1. Figureure6 shows a leaf
spring.Sometimes it is also called as a semi-elliptical spring, as it takes the
form of a slender arc shaped length of spring steel of rectangular cross
section.
2. The center of the arc
provides the location for the axle,while the tie holes are provided at either
end for attaching to the vehicle body.
3. Heavy vehicles,leaves are
stacked one upon the other to ensure rigidity and strength.
4. It provides dampness and
springing function.
5. It can be attached directly
to the frame at the both ends or attached directly to one end, usually at the
front,with the other end attached through a shackle,a short swinging arm.
6. The shackle takes up the
tendency of the leaf spring to elongate when it gets compressed and by which
the spring becomes softer.
7. Thus depending upon the load
bearing capacity of the vehicle the leaf spring is designed with graduated andungraduated
leaves
8. Because of the difference in
the leaf length, different stress will be there at each leaf.To compensate the
stress level,prestressing is to be done.Prestressing is achieved by bending the
leaves to different radius of curvature before they are assembled with the
center clip.
9. The radius of curvature
decreases with shorter leaves.
10.
The extra initial gap found between the extra full length
leaf and graduated length leaf is called as nip such prestressing achieved by a
difference in the radius of curvature.
APPLICATIONS:
Mainly in automobiles suspension systems.
ADVANTAGES:
1. It can carry lateral loads.
2. It provides braking torque.
3. It takes driving torque and
withstand the shocks provided by the vehicles.
SPRING MATERIALS:
The mainly used material for manufacturing the springs are as
follows:
1. Hard drawn high carbon
steel.
2. Oil tempered high carbon
steel.
3. Stainless steel
4. Copper or nickel based
alloys.
5. Phosphor bronze.
6. Iconel.
7. Monel
8. Titanium.
9. Chrome vanadium.
10.
4.4.5.
COIL SPRING:
A coil spring, also known as a
helical spring, is a mechanical device which is typically used to store energy
and subsequently release it, to absorb shock, or to maintain a force between
contacting surfaces. They are made of an elastic material formed into the shape
of a helix which returns to its natural length when unloaded. Under tension or
compression, the material (wire) of a coil spring undergoes torsion. The spring
characteristics therefore depend on the shear modulus, not Young’s Modulus. A
coil spring may also be used as a torsion spring: in this case the spring as a
whole is subjected to torsion about its helical axis. The material of the
spring is thereby subjected to a bending moment, either reducing or increasing
the helical radius. In this mode, it is the Young’s Modulus of the material
that determines the spring characteristics.
Figure.4.11 Helical
spring
4.5 Design of coil springs:
The design of a new spring involves the
following considerations:-Space into which the spring must fit and operate.
Values of workingforces and deflections.Accuracy and reliability needed. The primary
consideration in the design of the coil springs are that the induced stresses
are below the permissible limits
while subjected to or exerting
the external force F capable of providing the needed
deflection or maintaining the spring rate desired.
Figure.4.12 Design
of spring
4.5.1 Stress distribution
In order to determine the stress distribution along the
specimens, strain gages were used for the measurement of the occurring strains.
The corresponding stresses were calculated taking into account the standardized
Young’s modulus for steel E=2.1 GPa. The strain gages were positioned on the
side of the specimens subjected under tension at various positions along the
area between the loading-cylinders (±250 mm from the
center of the specimen), because under the 4-points bending conditions the
maximum stresses are
The stresses developed during the tests were compared with
the stresses obtained from the FE analysis performed, simulating the test-rig
configuration for two levels of developed stresses. As shown in Figure 8 the
agreement between calculated and measured stresses is satisfactory. The stress
values are normalized by the maximum stress developed under the maximum applied
force.
Figure. 4.13stress induced
:. Stress
distribution obtained from tests and FE analysis for two load level
4.6 SHAFT:
A shaft is a rotating machine
element which is used to transmit power from one place to another. This shaft form
an integral part of the machine itself. The crank shaft is an example of
machine shaft.A shaft is a rotating member, usually of circular cross section,
used to transmit power or motion. It
provides the axis of rotation, or oscillation, of elements such as gears,
pulleys, flywheels, cranks, sprockets, and the like and controls the geometry
of their motion.An axle is a non-rotating member that carries no torque and is used to support rotating
wheels, pulleys, and the like.
Figure.4.14 Design of shaft
4.7 OIL GRADES:
Figure 4.17 Oil specification
CHAPTER 5
5.1 WORKING PRINCIPLE OF LEAF SPRING
The
suspension system having main element termed as leaf spring is one of the
potential and very critical term for weight reduction in automobile industries
as its having a ten to twenty percent of the unspring weight. By introducing
composites, it can helpful for design a better suspension system having a
better ride quality but the condition is it must be achieved without much
increase cost and also decrease quality and reliability.In the design of
springs, strain energy becomes the major factor. The relationship of the
specific strain energy can be expressed as
U=σ2/ρE
Where
σ = strength,
ρ
=density
E
=Young’s Modulus of the spring material
It
can be noted that material which is having a lower modulus and also having a
lower density will have a greater specific strain energy capacity. So the
introduction of composite materials can made it possible to reduce the weight
of the leaf spring without any reduction into the load carrying capacity and
stiffness.One of the advantages of composite is that two or more materials
could be combined to take advantage of the good characteristics of each. Figure.
1.2 shows an Arrangement of leaf spring into a car Model a spring eye section
is used to attach the front end of semi-elliptic shape leaf spring to the chasesframe
and a free end having a bracket constraining vertical motion to attach the back
end of semi-elliptic leaf spring to the chassis frame
5.2
WORKING PRINCIPLES OF SHOCK ABSORBER
Figure 5.1.1 Shock absorber
Mono tube shock absorbers
These
shock absorbers are gas filled under high pressure, which consist only of a
tube and have main valve, so no matter which way it would be installed. In the
tube there are two pistons - separating piston and working piston. Working
piston design is very similar to that of twin tube shock absorbers. This type of
shock absorbers has a better prevention of aeration, allowing better
performance. The tube of these shocks is wider than that of a twin tube and
this makes difficulties of using this type of shock absorbers in cars whose OE
shocks are twin tube type. Separation valve is moving freely and divide gas
from oil at the bottom of the shock absorber. The area below the valve is
filled with gas at a pressure of about 360 psi. This gas helps to absorb some
of the weight of the car. The oil is placed over the separating piston.
CHAPTER 6
6.1 DESIGN CALCULATION FOR SHOCK ABSORBER:
The design of a new spring involves
the following considerations:-Space into which the spring must fit and operate. -Values of working forces and
deflections. -Accuracy and reliability needed. The primary
consideration in the design of the coil springs are that the induced stresses
are below the
permissible limits while
subjected to or
exerting the external
force F capable of providing the
needed deflection or maintaining the spring rate.
Figure 6.1 shock
absorber
Data of shock absorber
Spring Steel (modulus of rigidity) G = 78600 N/mm2
Mean diameter of a coil, D=55mm (wire diameter + inner
diameter)
Diameter of wire, d = 5mm
Total no of coils, n1= 12
Height, h = 150mm
Step:1
Outer diameter of spring coil, D0 = 2D +D
We know that: D = Di+d
Therefore (Di) = 55 -5 = 55mm
Di=55mm
|
D0=2D – Di =
(2x55) – 50= 60mm
|
Step: 2
No of active
turns, n= 11
Weight of bike = 144kg
Spring index, C
= D/d = 55/5=11mm
C=11mm
|
Solid length, Ls=n1×d=12×5=60mm
Ls=60mm
|
Free length of
spring,Lf = solid length + maximum compression
= 150+ 125 = 275mm
Lf=75mm
|
Step: 3
Pitch of coil, P = Lf – Ls + d/n1=
275-60+5/12=11.7 mm
P=11.7mm
|
Step: 4
Stresses in helical spring:
Maximum shear
stress induced:
τ = 0.5x σut = 0.5x 1050= 525 N/mm2.
τ =525 N/mm2
|
Result:
1. Outer diameter of
spring coil, D0 = 60mm
2. Spring index, C =11mm
3. Free length of
spring,Lf= 275mm
4. Pitch of coil, P=11.7 mm
5. Maximum
shear stress induced, τ= 525 N/mm2
CHAPTER 7
ASSEMBLE
DIAGRAM
Figure 7.1 leaf spring
suspension system
Figure.7.23D view
Figure.7.3 Side view
CHAPTER 8
COMPONENTS SPECIFICATION
8.1 MATERIAL SELECTION:
SL.NO.
|
PART
|
MATERIAL
|
NO. OF
|
1
|
Shock absorber
|
Mild steel
|
1
|
2
|
Leaf soring
|
Tempered steel
|
2
|
3
|
Steel plate
|
mild steel
|
2
|
4
|
Rubber sheet
|
Steel
|
4
|
5
|
Bush
|
Mild steel
|
1
|
6
|
Spring
|
Steel alloy
|
2
|
7
|
Shaft
|
Mild steel
|
1
|
8
|
Frame and base
|
Mild steel
|
1
|
Table 8.1 Material selection
8.2 COST
ESTIMATION:
SI.NO
|
PART AND DESCRIPTION
|
COST
|
1
|
Shock absorber
|
400
|
2
|
Steel columns
|
750
|
3
|
Shaft
|
500
|
4
|
Leaf spring material
|
600
|
5
|
Lapping plates
|
450
|
6
|
Tempered plates
|
500
|
7
|
Rubber material
|
500
|
8
|
Frame, base and other
materials
|
600
|
9
|
Labor charge
|
1200
|
10
|
TOTAL
|
5500/-
|
Table 8.2 Cost estimation
8.3 SPECIFICATION OF LEAF SPRING
Forces
acting on leaf spring are as shown in Figure. Main forces acting on leaf spring
are as follow but in this analysis only vertical loading condition is
considered. Forces acting on leaf spring:
·
Vertical loading (Fv)
·
Side load (Fs)
·
Longitudinal load (Ft)
·
Twisting torque (Tt)
·
Windup torque (Tw)
Figure. 8.3 Load Acting on Leaf Spring
Assumptions for Analysis:
·
Automobile is assumed to be stationary.
·
There are 2Semi-elliptic leaf spring, one at
front and one at rear axle. And for Only vertical loading.
CHAPTER 9
9.1 ADVANTAGES:
1.
The chassis roll can be controlled more efficiently
2.
They also controlled axle damping
3.
Leaf spring making the ideal for commercial vehicle
4.
Regains shape after bending till certain limit, useful
for spring applications.
5.
Bikes will performs in high at mountain areas
9.2 LIMITATION:
1.
Only applicable for sports bikes
2.
weighter than normal suspension
9.3 APPLICATIONS:
1.
Applicable in
dirt bike racing and requiring a high weight absorbing areas.
2.
To cushion,
absorb or control energy due to either shock or vibration as in car springs,railway
buffers, air-craft landing gears, shock absorbers and vibration dampers.
3.
To apply for
high suspension system whenever failure in occurred.
4.
To store energy and
releases in heavy vehicles like as cars,container vehicles,etc…
CHAPTER 10
CONCLUSION
From above results it is
clearly seen that the objective was to obtain a spring with minimum weight and
is capable of carrying given static external forces by constraints limiting
stresses and displacements. For this the steel leaf spring is replaced by
composite leaf spring. This is better than using steel leaf spring. After
studying all the available literature it is found that weight reduction can be
easily achieved by using composite materials instead of conventional steel, but
there occurs a problem during the operation while using the composite leaf
spring i.e. chip formation when the vehicle goes off road. Therefore there is
an immense scope for the future work regarding use of composite materials in
leaf springs to reduce the overall weight of the vehicle as well as the cost of
the vehicle.
REFERENCE
1.
M. Raghavedraet. al. “Modelling and Analysis of Laminated Composite Leaf under
the Static Load Condition by using FEA”, International Journal of Modern
Engineering Research (IJMER) Vol.2, Issue.4, July-Aug. 2012 pp-1875-1879
2.
V.K. Aheret. al. “Fatigue Life Prediction of Multi Leaf Spring used in the
Suspension System of Light Commercial Vehicle”, International Journal on
Theoretical and Applied Research in Mechanical Engineering (IJTARME), 2012.
3.
Ravi Kumar V. et. al. “Analysis of Natural Fibre Composite Leaf Spring”,
International Journal of Latest Trends in Engineering and Technology (IJL2TET)
September 2013
4.
T.N.V. Ashok Kumar at. al. “Design and Material Optimization of Heavy Vehicle
Leaf Spring”, International Journal of Research in Mechanical Engineering &
Technology, Nov 2013 - April 2014
5. PankajSainiet. al. “DESIGN AND ANALYSIS OF COMPOSITE LEAF
SPRING FOR LIGHT VEHICLES”, International Journal of Innovative Research in
Science, Engineering and Technology. Vol. 2, Issue 5, May 2013
6. Baviskar A. C. et. al. “Design and Analysis of a Leaf
Spring for automobile suspension system: A Review”, International Journal of
Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN
2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 6, June 2013)
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