Design of leaf spring

1. Presentation on
Design of composite leaf spring
Under the guidance of: Dr. H.K Govindaraju
Submitted by: Ananda

2. Contents
• Introduction
• Spring of simply supported beam type
• Nipping
• Material selection
• FEA
• Results and discussion
• Advantages and disadvantages
• Conclusion
• References

3. Introduction
• A spring is an elastic body, whose expand in size
when load applied and regain its original shape when
removed. Leaf spring is the simplest form of spring
used in the suspension system of vehicle.
• It absorbs automobile vibrations, shocks and loads by
springing action and to extend by some damping
functions.
• Most widely used leaf spring type is semi-elliptic in
heavy and light automobile vehicles.
• The introduction of composite materials was made it
possible to reduce the weight of leaf spring without
any reduction on load carrying capacity and stiffness.

4. Continued...
• A leaf spring can either be attached directly to the frame at both
ends or attached directly at one end, usually the front, with the
other end attached through a shackle.
• Tension spring is designed to operate with a tension load, so
the spring stretches as the load is applied to it. Torsion spring,
as the load applied to a torsion spring is a torque or twisting
force, end of the spring rotates through an angle as the load is
applied.
• Dimensions of the composite leaf spring are to be taken as
same dimensions of the conventional leaf spring.
• The finite element modeling and analysis of a multi leaf
spring has been carried out.
• Automobile industry has shown increased interest in the
replacement of steel spring with composite leaf spring due to
high strength to weight ratio.

5. Spring of simply supported beam type
• Central location of the spring is fixed
to the wheel axel. The wheel exerts
the force F on the spring and support
reactions at the two ends of the
spring come from the carriage.
• The front eye of the leaf spring is
coupled directly with a pin to the
frame so that the eye can rotate
freely about the pin but no
translation is occurred.
• The rear eye of the spring is
connected to the shackle which is a
flexible link the other end of the
shackle is connected to the frame of
the vehicle.

6. Nipping of leaf spring
• The stress in the full length
leaves is 50% greater than the
stress in the graduated leaves.
• To distribute this additional
stress from the full length
leaves, pre-stressing is done.
This is achieved by bending
the leaves to different radii of
curvature, before they are
assembled with the centre bolt.
• Full length leaves are greater
radii of curvature and staked with
the graduated leaves, without
bolting.

7. Material selection
• The ability to absorb and store more amount of energy
ensures the comfortable operation of a suspension system.
• Introducing composite material, in place of steel in the
conventional leaf spring. From several studies it is found
that the e-glass/epoxy is better material for replacing the
conventional steel as per strength and cost factor.
• The E-glass fiber is a high quality glass, which is used as
standard reinforcement fiber for all the present systems
well complying with mechanical property requirements.
The material select is E-Glass/Epoxy material.
• strength to weight-proportion and modulus to weight-
proportions of these composite materials are better than
those of metallic materials.

8. Sr.No. Parameter Value
1 Tensile Strength (Mpa) 900
2 Compressive Strength(Mpa) 450
3 Poissons Ratio 0.217
4 Density (kg/mm3) 2.6*10^-6
5 Flexural modulus (E) (Mpa) 40000
Properties of E-Glass/ Epoxy composite

9. Theoretical calculation
• Design parameters leaf spring:
leaf span=860mm
Free camber=90mm
Width of all leaves=60mm
Thickness of the spring=8mm
Weight of leaf spring=10.26Kg
Total number of full leaves=3
Maximum load given on spring=4169N

10. continued....
Weight and measurements of 4 wheeler “TATA ACE’ vehicle is taken
Weight of vehicle= 700 kg
• Maximum load carrying capacity= 1000 kg
• Total weight= 700 + 1000 = 1700 kg
• (FS) = 2
g = 9.81 m/s2
Total Weight = 1700*9.81 = 16677
• weight.
16677/4 = 4169 N,
• But 2F = 4169 N. F = 2084 N.
• Span length, 2L = 860 mm, L= 430mm.
• σb = 6FL / nbt2
= (6*2084*430) / (3*60*8^2) = 466.84 MPa
• δmax = 6FL^3/ Enbt3
= (6*2084*4303) / (2.1*105*3*60*8^3) = 51.38 mm

11. Finite element analysis
1.Solid modeling:
Solid modeling is the first step for doing any 3D analysis and
testing and it gives 3D physical picture for new products. Modeling
has been carried out in ProE-5.0 and the analysis is carried out in
ANSYS-12. For modeling the steel spring, the dimensions of a
conventional leaf spring of a light weight commercial vehicle are
chosen.
2.Element type: SOLID45- 3-D Structural Solid.
CONTA174 - 3-D 8-Node Surface-to-Surface Contact.
3.Meshing:
• Meshing involves division of the entire model into small pieces
called elements. It is convenient to select the free mesh because the
leaf spring has sharp curves
• Shape of the object will not alter. To mesh the leaf spring the
element type must be decided first.
4.Boundary conditions:

12. FEA results
Bending stress of steel leaf
spring
Total deformation of steel
leaf spring

13. Continued....
Bending stress of composite leaf
spring
Total deformation of composite
leaf spring

14. Results and discussion
Compaison between theoretical and
ANSYS results of steel leaf spring
parame
ter
Theoretic
al results
FEA
results
variation
Load, N 4169 4169 NIL
Bending
stress,
Mpa
466.84 450.73 3.04 %
Total
deflecti
on,mm
51.38 53.159 3.06 %
FEA results comparison between
steel and composite leaf spring
paramet
er
FEA
FEA
results
for steel
leaf
spring
FEA
results
For
compos
ite leaf
spring
variatio
n
Load, N 4169 4169 NIL
Bending
stress,
Mpa
450.73 338.03 -25.05 %
Total
deflectio
n,mm
53.159 34.676 -34.76 %

15. Continued....
materials weights % weight saving
Conventional steel 10.27 kg -----
E-glass/epoxy 3.26 kg 67.88 %
Percent saving of weight by composites
•By the comparison of results between steel leaf spring and the
composite leaf spring from ANSYS-12 the deflection is decreased
by 34.76 % in composite leaf spring that is within the camber range.
•less stress induced with same load carrying conditions.
•The conventional multi leaf spring weights about 10.27kg whereas
the E-glass/Epoxy multi leaf spring weighs only 3.26 kg. Thus the
weight reduction of 67.88% is achieved.
• By the reduction of weight and the less stresses, the fatigue life of
composite leaf spring is to be higher than that of steel leaf spring.

16. Advantages
1.Supports the chassis weight
2. Controls axel damping
3. Controls braking forces
4. Regulates wheel base lengths (rear steer) under acceleration
and braking.
Disadvantages
1. Nipping
2. Heavy wear on the joints and connections.
3. The rear axel will simply bounce around high speed
corners as the suspension and axel are forced to move
around together.

17. CONCLUSION
• In the present work, a steel leaf spring was replaced by a
composite leaf spring due to high strength to weight ratio for
the same load carrying capacity and stiffness with same
dimension as that of steel leaf spring.
• Stresses and deflection in composite leaf springs is found out to
be less as compared to the conventional steel leaf springs.
• A comparative study has been made between steel and
composite leaf spring with respect to strength and weight.
Composite leaf spring reduces the weight by 67.88% for E-
Glass/Epoxy.
• Totally it is found that the composite leaf spring is the better
that of steel leaf spring. Therefore, it is concluded that
composite multi leaf spring is an effective replacement for the
existing steel leaf spring in vehicles.

18. REFERENCES
• Ashish V Amrute, Edward Nikhil Karlus, R.K.Rathore ‘design and
assessment of multi leaf spring’ published in ijrame on Nov.
2013 , vol.1.
• Baviskar A C, Bhamre V G, Sarode S S, ‘design and analysis of a
leaf spring for automobile suspension system’ published in ijetae on
June.2013 ,vol.3.
• Rupesh N. Kalwaghe1, Prof. K. R. Sontakke ‘design and analysis of
composite leaf spring by using fea and ansys’ published in ijser on
2014 ,vol.3.
• Rajendran S Vijayarangan ‘optimal design of composite leaf spring
using genetic algorithm’ published in elsevier on July.2000
• Dev Dutt Dwivedi1, V. K. Jain ‘design and analysis of automobile
leaf spring using ansys’ published in ijcesr on 2016 ,vol.3.