A Complete analysis of Leaf Spring Used in TATA Ace Vehicle

1. 1
PROJECT REPORT
ON
Stress analysis in the Leaf Spring used in Goods
Carrying Vehicle (TATA Ace)
By
NAME Roll No
Chinmay Nair 64
Nandu Vijayraj 65
Vishnu RC Vijayan 74
Jeetson Gonsalves 76
Under the guidance
Of
Prof. Mandar Damle
DON BOSCO INSTITUTE OF TECHNOLOGY
PREMIER AUTOMOBILES ROAD
KURLA(W)
MUMBAI – 400070

2. 2
ACKNOWLEDGEMENT
We are grateful to Don Bosco Institute of Technology, the Principal Dr.Prasanna
Nambiar and our HOD, Dr. Sarangi for providing the necessary resources for the
completion of the project.
We would like to express our gratitude to Prof. Mandar Damle for his constant
encouragement, support and guidance during the entire course of the project.
We express our sincere thanks to all those who have directly and indirectly helped
us in the completion of this project.

3. 3
CERTIFICATE
This is to certify that the project entitled
“Stress analysis in the Leaf Spring used in Goods Carrying Vehicle (TATA Ace)”
is a bonafide work of
Chinmay Nair (Roll No- 64)
Nandu Vijayraj (Roll No- 65)
Vishnu RC Vijayan (Roll No- 74)
Jeetson Gonsalves (Roll No -76)
Submitted to the University of Mumbai in partial fulfilment of the requirement for the term work of
the subject “Finite Element Analysis” [Course Code: MEC606] studied in Semester VI of
Third Year of Mechanical Engineering.
Mandar Damle
Date: Subject In charge

4. 4
INDEX
SR. NO CONTENTS PAGE NO
1 Introduction 6
2 Problem description 7
3 Objective 7
4 Scope 7
5 Material Selection 8
6 Design Parameters 9
7 Design Calculation 10
8 Results and Discussions 11
9 Conclusion &Reference 13

5. 5
List of Figures
Dia. No Representation Pg. No
Dia. 1 General Representation of Leaf Spring 9
Dia. 2 Load Point Figure 10
Dia. 3 Deflection Analysis 11
Dia. 4 Stress Analysis 12

6. 6
INTRODUCTION
Ever increasing demands of high performance together with long life and light weight necessitate
consistent development of almost every part of automobile. Increasing competition and
innovations in automobile sector tends to modify the existing products or replacing old
products by new and advanced material products.
A suspension system of vehicle is also an area where these innovations are carried out
regularly. 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. The
suspension leaf spring is one of the potential items for weight reduction in automobiles
un-sprung weight. This achieves the vehicle with more fuel efficiency and improved
riding qualities. Weight reduction can be achieved primarily by the introduction of better
material, design optimization and better manufacturing processes.
The study demonstrated that composites can be used for leaf springs for light weight
vehicles and meet the requirements, together with substantial weight savings.
Leaf springs are one of the oldest suspension components they are still frequently used,
especially in commercial vehicles. This work is carried out on multi leaf spring consist
three full length leaves in which one is with eyed ends used by a light commercial
vehicle.

7. 7
PROBLEM DESCRIPTION
The suspension leaf spring is one of the potential items for weight reduction in
automobile as it accounts for ten to twenty percent of the un-sprung weight. The steel leaf
spring has some problems which are listed as follow:
 Due to continuous running of the mini loader vehicle there is a decrease in the
level of comfort provided by the spring
 It is observed that the leaf springs tend to break and weaken at the eye end portion
which is very close to the shackle and at the centre.
 Hence the stress analysis will be done to analyse the failure stress
OBJECTIVE
The objective of this project is as follows:
 Comparing the stresses (Tensile) of steel leaf spring using FEA with the analytical
method in order to avoid failure
 The focused on the implementation of safer steel leaf spring for the suspension
system to reduce product weight, improving the safety, comfort and durability
SCOPE
 The Similar FEA Model Analysis can be used for the design considerations of any
Leaf Spring.
 The resulting Analysis will provide failure stress i.e. well above the permissible
stresses for the long lasting life.

8. 8
WORK/ANALYSIS CARRIED OUT
Material for conventional steel leaf spring
Conventional steel leaf springs are manufactured by EN45, EN45A, 60Si7, EN47,
50Cr4V2, 55SiCr7 and 50CrMoCV4 etc. These materials are widely used for production
of the parabolic leaf springs and conventional multi leaf springs.
In general terms higher alloy content is mandatory to ensure adequate harden ability
when the thick leaf sections are used. Plain carbon steel, Chromium vanadium steel,
Chromium- Nickel- Molybdenum steel, Silicon-manganese steel, are the typical materials
that are used in the design of leaf springs. The material used for this work is 65Si7.
Material 65Si7 Properties
Parameters Parameters Value
Material of Spring 65Si7
Young’s Modulus, E 2.1×105 MPa
Poisson’s Ratio, r 0.266
Tensile Strength Ultimate 1272 MPa
Tensile Yield Strength 1158 MPa
Density 7.86×10-6 Kg/mm3
65Si7 has high ultimate tensile strength and high yield strength and hence has good
modulus of elasticity. Hence this material can be used as a spring. The chemical
composition of material is Mn-0.72%, C-0.53%, S-0.007%, Si 0.20%, P-0.019% and Cr –
0.73%. For the fabrication of high strength Leaf Springs, the process comprises various
operations. Hence the selected material will able to satisfy the load.

9. 9
Design Parameters of Leaf Spring
Parameters Value
Leaf Span 860 mm
Width of all leaves 60 mm
Thickness of the leaves 8 mm
Total no of leaves 3
Maximum Load given on Leafs 4169N
Figure 1- A general representation of Leaf Spring
Assumptions for Analysis
 Automobile is assumed to be stationary
 There are four Semi-elliptic leaf spring, two at front and two at rear axle
 Static analysis is carried out for rear single semi-elliptic leaf spring
 Material of leaf spring 65Si7

10. 10
Design Calculation
Here Weight and initial measurements of four wheeler “TATA ACE” Light commercial
vehicle is taken
Weight of vehicle= 700 kg
Maximum load carrying capacity= 1000 kg
Total weight= 700 + 1000 = 1700 kg
Acceleration due to gravity (g) = 9.81 m/s2
Therefore; Total Weight = 1700 X 9.81 = 16677 N
Since the vehicle is 4-wheeler, a single leaf spring corresponding to one of the wheels
takes up one 4th of the total weight.
16677/4 = 4169 N
But 2F = 4169 N. F = 2084 N (Considering on both Eye ends)
Span length, L = 860 mm
Now the Maximum Bending stress of a leaf spring is given by the formula [14]
Bending Stress,
σb = 6FL / nbt2 (From PSG 7.104)
= (6*2084*430) / (3*60*82) = 466.84 MPa
Taking FOS 1.5, So 466.84 X 1.5 =700.26 Mpa
This is for 3 leaf springs attached parallel.
So 700.26/3 = 233.42/mm2
Figure 2- Shows the point where 2084 N is placed.

11. 11
RESULTS AND DISCUSSION
From the results of static analysis of steel leaf spring, it is seen the stress of leaf spring is
185.651N/mm2which is well below the ultimate stress of leaf spring shown in. It is seen
that the maximum bending stress is about 233.42MPa, which is less than the tensile
strength of the material. The FEA results are compared with the theoretical results and
found that the theoretical result and FEA result are nearer to each other.
Parameter Theoretical Results
for steel leaf spring
FEA Results for
steel leaf spring
Variation
Load N 4169 N 4169N Nil
Bending Stress 233.42 MPa 185.651 MPa 20.46%
Thus the FEA analysis shows the stress is below analytical method, hence the selected
material will able to sustain the applied load.
Figure 3- Normal Deflection Analysis

12. 12
Figure 4- Stress Analysis
185.651

13. 13
Conclusion
In the present work, a steel leaf spring was analysed due to high strength to weight ratio
for the same load carrying capacity dimension.
 A semi-elliptical multi leaf spring is designed for a four wheel automobile
 Under the same static load conditions the stresses in leaf springs are found with
less difference in the analytical and FEA Solutions
 All the FEA results are compared with the theoretical results and it is found that
they are within the allowable limits and nearly equal to the theoretical results.
 The steel leaf spring can be suggested for both from stiffness and stress point of
view
Therefore, it is concluded that leaf spring is within the permissible limits; hence it can be
used for the said vehicle.
References
V.B. Bhandari,”Design of Machine Element”- Third Edition –Tata McGraw Hill
Education Privet
Limited-2010
PSG Data book, Coimbatore
Website
Ace.tatamotors.com
Suspensionspecialist.com
Sonicoleafspring.com
Metalravne.com
Hindawi.com