Improve the Design of Leaf Spring by Reducing the Frictional Stress

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 08 | Aug -2017 www.irjet.net p-ISSN: 2395-0072
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Improve The Design Of Leaf Spring By Reducing The Frictional Stress
Basavaraj Kabanur1, Prof.P.S.Patil2
1M.Tech (Machine Design), B.L.D.E.A’s V. P. Dr.P.G.H College of Engineering and Technology, Vijayapur, Karnataka,
India
2 Asst. Professor, Dept. of Mechanical Engineering, B.L.D.E.A’s V. P. Dr.P.G.H College of Engineering and Technology,
Vijayapur, Karnataka, India
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Abstract - The automotive suspension system is the one of the
important unit in automotive design, especially leaf spring
design. It absorbs payload and road load to give the comfort
ride to a passengers in the vehicle. In the presenttrendpeoples
are interested to buy a vehicle with good mileage for this
reason the automobile industry show an interest toreducethe
weight of an vehicle components. The weight of vehicle and
mileage are inversely proportional as the weightincreasesthe
mileage decreases .In the leaf spring the friction between the
leaves of spring is one of the problem the friction between the
leaves causes the wearing of the leaves and this leads to a
breakdown of leaves. The objective of this project is to
compare the deformation, strain energy, weight of the new
model of leaf spring with conventional elliptical leaf spring
and also the study of static and dynamic analysis of three
models. Design modeling is done using CATIA V5R20 and
analysis is carried out by using ANSYS 17.0 software.
Key Words: Leaf spring, Frictional stress, Strain energy,
mode shape & Natural frequency, CATIA V5R20, ANSYS17.0
1. INTRODUCTION
Leaf spring was invented by Obadiah Elliot of London in
18thccentury. He simply pilled one steel plate on top of
another pinned them together and shackled each end to a
carriage it was the first ever leaf spring used on vehicle. Leaf
spring as the name indicates it is made of leaf like structure
with rectangular cross section placed one over the above.
Leaf springs are used in vehicles such as heavy commercial
vehicle like truck, dumpers, rails etc. When compare theleaf
spring over the helical spring the advantage of leaf spring
over the helical spring is that ends of spring may be guided
along a definite path so as to act as a structural member in
addition to shock absorbing device. The springs are used to
absorb energy during the loading conditionandthenrelease
it, then strain energy of material becomesa majorparameter
in designing the spring where as in the coil spring load
transfer to single point. A leaf spring is directly attached to
the frame or chassis of the vehicle. The leafspringhavingthe
eyes at both the ends one end is directly attached to the
frame of the vehicle while other end attached to shackle
(Swinging arm). Due to bounces on the road surfaces the
spring get compress at that time shackle makes the leaf
spring to expand and thus makes for smoother springiness.
The design of leaf spring involves it is flat thin and adaptable
bit of spring steel or composite material that oppose
bending. The basic principle of leaf spring design and
assembly are moderately simple the number of leaves in an
spring is relies on the weight conveying limit of a vehicle
most heavy duty vehicle today use two pairs of leaf spring
per axle. The leaf spring placed perpendicularly to support
the weight of vehicle. The spring comprises of a number of
plates with a rectangular cross section called as leaves. The
leaves are in increasing length. The leaf having maximum
length called as master leaf, the other leaves are known
graduated leaves.. The leaf spring is fitted on the axle of the
vehicle. The front end of the spring is connected to the
chassis with a simple pin joint, while the rear end is
connected with a shackle (flexible link).
2. SCOPE OF PROJECT
The scope of our project is to improve the design of leaf
spring suspension by modifying the existing design. In
automobile, suspension system is important consideration.
Our scope is to improve riding comfort of a vehicle by
modifying the existing designandalsoreducingthefrictional
stress, stress developed by friction between to mating
surface which leads to a failure of the component. To create
three models of leaf spring one is standard design and other
two models are different. To determine the deformation,
strain energy and stress developed and also compare the
result of all three models of leaf spring. Analysis of mode
shapes for different natural frequencies .our projectscopeis
to reduce the weight of leaf spring suspension system.

3. METHODOLOGY
Fig3.1 Methodology of Project
3.1 DESIGN OF LEAF SPRING
Fig 3.1.1 Design of leaf spring
W – Weight of leaf spring
2L – Span length of leaf spring
F – Maximum load on the spring
b – Width of all leaves
t – Thickness of the spring
n – Number of springs
E – Young’s modulus of the material
C – Camber length
Maximum bending stress of leaf spring
Total deflection of leaf spring
3.2 GEOMETRY IN CATIA
The below all three models are designed in CATIA V5R20 ,it
consist of number of leaves, U shape boltforholdingtheaxle,
nut and coil spring for improving the riding comfort,
rectangular plates for holding the leaves.
The models are created in CATIA software, starting with
mechanical design and then goes to part design and the
select the desire plane for 2D sketching, then created 2D
sketch is converted to 3D model like this all the leaves are
created
Fig 3.2.1 Model 1 Standard leaf spring
Fig 3.2.2 Model 2 leaf spring with variable radius
curvature
Fig 3.2.3 Model-3 Leaf spring with U shape bend at the
center

3.3 MATERIAL PROPERTIES
Then assign the material of structural steel to all three
models and compare the results. Structural steel differsfrom
other material from its properties like compressivestrength
as well as tensile strength. For all three model namely
Model-1 standard leaf spring, Model-2 leaf spring with
variable radius of curvature, Model-3 Leaf spring with U
shape bend at the center, The properties of structural steel
are as follows.
Table 3.3.1 Material property structural steel
3.4 MESHING
For meshing purpose CAD models are imported to ANSYS
software. In the ANSYS design modeler cleaning of CAD
models takes place because of some defects in CAD models
like sharp edges, holes, small fillets etc these are cleaned by
using clean up tools.. Meshing involves the discretization of
given quantinum in to number of parts, each part is called as
element.
Fig 3.4.1 Meshing of Model 1 (Standard leaf spring)
Fig 3.4.2 Meshing of Model 2 (leaf spring with variable
radius of curvature)
Fig 3.4.3 Meshing of Model-3 (Leaf spring with U shape
bend at the center)
3.5 LOAD AND BOUNDARY CONDITION
In load and boundary condition, creating the symmetry
plane at the middle of model for easy, accurate and time
saving purpose. The front side eye of the leaf spring is
connected to chassis by a pin. The pin provides a rotational
motion but prevent a translation motion. The back side eye
of the leaf spring is connected to the shackle (flexible link)
other end of shackle is connected to chassis of automobile.
The bottom plate of leaf spring is mounted on wheel axle
which is fixed.
The force of 500N is applied on the two eyes of the leaf
spring the leaf spring have the flexibility to slide along Y-
direction, eye of the leaf spring to rotate about an pin in X-
direction when the load applied on the spring so that
displacement of eye is constrained in the X and Z direction.
Fig 3.5.1 Load and boundary condition of Model 1
(Standard leaf spring)

Fig 3.5.2 Load and boundary condition of Model 2 (leaf
spring with variable radius of curvature)
Fig 3.5.3 Load and boundary condition of Model-3 (Leaf
spring with U shape bend at the center)
4. RESULT AND DISCUSSIONS
4.1 NATURAL FREQUENCIES AND MODE SHAPES
MODEL 1
The modal analysis technique is used to determine the
vibration characteristics (i.e. natural frequencies and mode
shapes)of linear elastic structures.
Fig 4.1.1 Mode 1
Fig 4.1.2 Mode 2
The Fig 4.1.1 shows that the natural frequency of 99.806 Hz,
and the mode shape for this frequency is in longitudinal
direction. The Fig 4.1.2 shows that the natural frequency of
159.2 Hz, and the mode shape for this frequency is in lateral
direction.
MODEL 2
Fig 4.2.1 Mode 1
Fig 4.2.2 Mode 2
The Fig 4.2.1 shows that the natural frequency of 33.478 Hz,
102.93 Hz, and the mode shape for this frequency is in
lateral direction.

MODEL 3
Fig 4.3.1 Mode 1
Fig 4.3.2 Mode 2
The Fig 4.3.1shows that the natural frequency of 73.919 Hz,
68.681 Hz, and the mode shape for this frequency is in
lateral direction.
4.4 DEFORMATION
Fig 4.4.1 Deformation result of model 1(Standard leaf
spring)
Fig 4.4.2 Deformation result of model 2 (leaf spring with
variable radius of curvature)
Fig 4.4.3 Deformation result of model 3 (Leaf spring with U
shape bend at the center)
In the model 1 (Fig 4.4.1) the maximum deformation is
37.048 mm at eyes and minimumdeformationof4.1165 mm
at the center of leaf spring. In the model 2 (Fig 4.4.2) the
maximum deformation is 38.579 mm at eyes and minimum
deformation of 4.2866 mm at the center of leaf spring. In the
model 3 (Fig 4.4.3) the maximum deformation is 66.665mm
at eyes and minimum deformation of 7.4072 mm at the
center of leaf spring.
4.5 STRAIN ENERGY
Fig 4.5.1 Strain energy result of model 1(Standard leaf
spring)

Fig 4.5.2 Strain energy result of model 2(leaf spring with
variable radius of curvature)
Fig 4.5.3 Strain energy result of model 3 (Leaf spring with
U shape bend at the center)
In the model 1 (Fig 4.5.1) the maximum strain energy is
3.9281 mJ at the center and minimum strain energy of
7.5595e-26 mJ at the eyes of leaf spring. In the model 2 (Fig
4.5.2) the maximum strain energy is 8.0229 mJ at the center
and minimum strain energy of 2.2328e-19 mJ at the eyes of
leaf spring. In the model 3 (Fig 4.5.3) the maximum strain
energy is 21.246 mJ at the center and minimum strain
energy of 2.4142e-8 mJ at the eyes of leaf spring.
5. RESULT SUMMARY
Table 5.1 Result table
The above table shows the Deformation and strain energy
result of three models of leaf spring suspension. By applying
the load at the eyes and fix the plate which ismountedonthe
axle. By comparing the deformation result of all three
models, the model 1 having the lowest deformation of
37.048mm compare to other two models becausethereis no
gap between the leaves and leaves are bounded by the
bounded contact. The model 2 having the deformation of
38.579 mm which is slightly larger than model 2andsmaller
than model 3 this due to leaves in the model 2 having the
different radius of curvature there is no complete contact
between leaves, there will be small gap between the leaves.
The model 3 having the deformation 66.66mm which is
larger than all three models this due to an installed spring
between leaves of model 3. The strain energy of model 1 is
3.928mJ which is smaller comparing to all three models
because there is no gap between in the leaves and leaves are
properly bounded. The strain energy of model 2is8.0229 mJ
which slightly larger than the model 1 and smaller than
model 3 this is due to a variable radius of curvatureofmodel
2 and there is gap between the leaves of model 2. The strain
energy of model 3 is 21.246mJ whichislargerthanother two
models this is due to installing the spring between the
leaves. From all three models, model 3 having larger strain
energy which improves the riding comfort of vehicle.
6. VALIDATION
Dimensions of “TATA ACE” commercial goods vehicle is
taken for validation and dimensions are as follows.
6.1 ANALYTICAL CALCULATION
Total Weight of the vehicle= 700 kg
Maximum load carrying capacity= 1000 kg
Total weight= 700 + 1000 = 1700 kg
Taking factor of safety (FS) = 2
Acceleration due to gravity (g) = 9.81 m/s2
Total Weight =1700 ×09.81 = 16677 N
TATA ACE vehicle has four wheels, each leaf spring per
wheel ( th of total vehicle weight )
= 4169 But 2F = 4169 N. F = = 2084 N.
Span length, 2L =860 mm, L = = 430 mm.

Maximum Bending stress of a leaf spring is given by
Bending Stress,
= = 466.84 Mpa
Total Deflection of the leaf spring is given by
Total Deflection
= = 51.38 mm
6.1 ANSYS RESULT
Fig 6.1.1 Load and boundary condition of steel leaf spring
Fig 6.1.2 Bending stress of steel leaf spring
Fig 6.1.3 Total deformation of steel leaf spring
6.2 VALIDATION TABLE
Table 6.2.1 Validation Table
7. CONCLUSION AND FUTURE SCOPE
7.1 CONCLUSION
The project was mainly aimed to minimize the frictional
stress developed between the leaves. thereforechangingthe
design of leaf spring by modifying the traditional leaf spring.
three modified design of leaf spring was created including
traditional leaf spring, Model 1 Standard leafspring,Model 2
leaf spring with variable radius of curvature, Model 3 Leaf
spring with U shape bend at the center. In model 2 and
Model 3 the area of contact between the leaves are reduced.
 Due to reduction in the area of contact between
leaves in Model 2 and Model 3 compare to Model 1,
the frictional stress developed will be minimum in
Model 2 and Model 3.
 The riding comfort of vehicle was improved due to
increase in a strain energy in model 2 and model 3
compare to model 1.
 The natural frequency and mode shapes show the
modal behavior of the leaf spring suspension
system under excitation.
 There is substantial reduction in weight, the
modified leaf spring having the less number of
leaves.
7.2 FUTURE SCOPE
 From the obtained results, carry out the fatigue
analysis for the vibration of a leaf springsuspension
system to predict the life.
 Carry out the random analysis with PSD data
 Carry out the fatigue analysis to determine the life
 To minimize the deformation of leaf spring.
 Use alternate materials for the leafspringandstudy
the result.
8. REFERENCES
1. Zheng Yinhuan, Xue Ka, Huang Zhigao. Finite Element
Analysis of Composite Leaf Spring, The 6th International

Conference on Computer Science & Education (ICCSE
2011) August 3-5, 2011. Superstar Virgo, Singapore.
2. Mahmood M. Shokrieh, Davood Rezaei. Analysis and
optimization of a composite leaf spring, Composite
Structures 60 (2003) 317–325, in 2003.
3. H.A. Al-Qureshi. Automobile leaf spring from composite
material, Journal of Material Processing Technologies
118 (2001) 58-61.
4. D.Younesian, M.S. Fallahzadeh. Numerical and
Experimental Analysis of Nonlinear Parabolic Springs
Employed in Suspension System of freight cars,
International Journal of Automotive Engineering Vol. 4,
Number 3, Sept 2014.
5. Prof. R.M.Bhoraniya, Trivedi Achyut V. Static and
Dynamic AnalysisofAutomobileLeafSpring (TATAACE),
IJSTE - International Journal of Science Technology &
Engineering , Volume 1 , Issue 11 ,May 2015.
6. K.K.Jadhao, Dr. R.S.Dalu, Experimental Investigation and
Numerical Analysis of Composite Leaf Spring,
International Journal of Engineering Science and
Technology (IJEST), ISSN : 0975-5462 Vol. 3 No. 6 June
2011.
7. Ashish V. Amrute, Edward Nikhil karlus, R.K.Rathore.
International journal of research in aeronautical and
mechanical engineering, ISSN : 2321-3051,vol 1,issue 7,
November 2013.
8. B.Vijaya Lakshmi, I. Satyanarayana. Static and dynamic
analysis on composite leaf spring in heavy vehicle,
International Journal of Advanced Engineering Research
and Studies E-ISSN2249–8974, IJAERS/Vol. II/ Issue
I/Oct.-Dec.,2012/80-84.

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Improve the Design of Leaf Spring by Reducing the Frictional Stress