PROJECT REPORTON

Stress analysis in the Leaf Spring used in Goods Carrying Vehicle (TATA Ace)

By

NAME Roll NoChinmay Nair 64

Nandu Vijayraj 65Vishnu RC Vijayan 74Jeetson Gonsalves 76

Under the guidanceOf

Prof. Mandar Damle

DON BOSCO INSTITUTE OF TECHNOLOGYPREMIER AUTOMOBILES ROAD

KURLA(W)MUMBAI – 400070

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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.

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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

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INDEX

SR. NO CONTENTS PAGE NO1 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

List of Figures4

Dia. No Representation Pg. No

Dia. 1 General Representation of Leaf Spring 9Dia. 2 Load Point Figure 10

Dia. 3 Deflection Analysis 11

Dia. 4 Stress Analysis 12

INTRODUCTION

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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.

PROBLEM DESCRIPTION

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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.

WORK/ANALYSIS CARRIED OUT

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Material for conventional steel leaf springConventional 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.

Design Parameters of Leaf Spring

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Parameters ValueLeaf Span 860 mmWidth of all leaves 60 mmThickness of the leaves 8 mmTotal no of leaves 3Maximum 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

Design Calculation

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Here Weight and initial measurements of four wheeler “TATA ACE” Light commercial vehicle is taken

Weight of vehicle= 700 kgMaximum load carrying capacity= 1000 kgTotal weight= 700 + 1000 = 1700 kgAcceleration due to gravity (g) = 9.81 m/s2Therefore; Total Weight = 1700 X 9.81 = 16677 NSince 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 NBut 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 MPaTaking 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.

RESULTS AND DISCUSSION

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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 Resultsfor steel leaf spring

FEA Results forsteel leaf spring

Variation

Load N 4169 N 4169N NilBending 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

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Figure 4- Stress Analysis

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185.651

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 PrivetLimited-2010

PSG Data book, Coimbatore

WebsiteAce.tatamotors.comSuspensionspecialist.comSonicoleafspring.comMetalravne.comHindawi.com

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