Modelling and Analysis of Composite Leaf Spring under Static Load Condition using FEA

“Modelling and Analysis of Composite Leaf Spring under the Static Load Condition by using FEA”
International Journal of Mechanical & Industrial Engineering, Volume 1 Issue 1-2011
1
“Modelling and Analysis of Composite Leaf Spring under the
Static Load Condition by using FEA”
M. M. Patunkar 1
, D. R. Dolas 2
1
IInd year M.E.(Mfg. Engg.) Mech. Engg. Dept., 2 Assistant Professor, Mech. Engg. Dept.,
MGM’s Jawaharlal Nehru Engineering College, Aurangabad, Maharashtra – 431003, India.
E-mail :[e-mail], [e-mail]
Abstract - Leaf springs are one of the oldest suspension components
they are still frequently used, especially in commercial vehicles. The
past literature survey shows that leaf springs are designed as
generalized force elements where the position, velocity and orientation
of the axle mounting gives the reaction forces in the chassis attachment
positions. Another part has to be focused, is the automobile industry
has shown increased interest in the replacement of steel spring with
composite leaf spring due to high strength to weight ratio. Therefore,
analysis of the composite material becomes equally important to study
the behavior of Composite Leaf Spring. The objective of this paper is to
present modeling and analysis of composite mono leaf spring (GFRP)
and compare its results. Modelling is done using Pro-E (Wild Fire) 5.0
and Analysis is carried out by using ANSYS 10.0 software for better
understanding.
Keywords - Composite Leaf Springs, Glass Fiber Reinforced
Plastic (GFRP), Static load condition.
I. I. INTRODUCTION
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. More efforts are
taken in order to increase the comfort of user. Appropriate
balance of comfort riding qualities and economy in
manufacturing of leaf spring becomes an obvious
necessity. To improve the suspension system many
modification have taken place over the time. Inventions of
parabolic leaf spring, use of composite materials for these
springs are some of these latest modifications in
suspension systems. This paper is mainly focused on the
implementation of composite materials by replacing steel
in conventional leaf springs of a suspension system.
Automobile-sector is showing an increased interest in the
area of composite material-leaf springs due to their high
strength to weight ratio. Therefore analysis of composite
material leaf springs has become essential in showing the
comparative results with conventional leaf springs.
Advantages of leaf spring over helical spring are that
the ends of the springs are guided along a definite path so
as to act as a structural member in addition to shock
absorbing device. This is the reason why leaf springs are
still used widely in a variety of automobiles to carry axial
loads, lateral loads and brake-torque in the suspension
system.
In this analysis the conventional steel leaf spring is
tested for static load condition and results are compared
with a virtual model of composite material leaf spring.
Leaf spring is modeled in Pro-E 5.0 CAD software and it
is imported and simulated in ANSYS 10.0 for better
understanding. Results of Composite Leaf Spring are
compared on the basis of analysis reports produced by
ANSYS software. The material used for conventional steel
leaf spring is 60Si7 (BIS) and for composite leaf spring E
- Glass/Epoxy material is used.
II. LITERATURE S URVEY
Many industrial visits, past recorded data shows that
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.
Leaf springs absorb the vehicle vibrations, shocks and
bump loads (Induced due to road irregularities) by means
of spring deflections, so that the potential energy is stored
in the leaf spring and then relieved slowly [1]. Ability to
store and absorb more amount of strain energy ensures the
comfortable suspension system.
Many suspension systems work on the same principle
including conventional leaf springs. However, for the
same load and shock absorbing performance, conventional
(steel) leaf springs use excess of material making them
considerably heavy. This can be improved by introducing
composite materials in place of steel in the conventional
spring. Studies and researches were carried out on the
applications of the composite materials in leaf spring [1,2].
A composite mono leaf spring with an integral eye was
manufactured and tested for the static load conditions [2].
Fatigue life prediction was also done by authors so as to
ensure a reliable number of life cycles of a leaf spring.
Further, a leaf spring had been modeled in conventional
way and simulated for the kinematic and dynamic
comparatives [3]. Cyclic creep and cyclic deformation was
also studied [4]. Efforts were taken for Finite Element
Analysis of multi leaf springs. These springs were
simulated and analyzed by using ANSYS 7.1[5].
Premature failure in leaf springs was also studied so as to
suggest remedies on application of composite leaf springs.
[6, 7, 8]

“Modelling and Analysis of Composite Leaf Spring under the Static Load Condition by using FEA”
International Journal of Mechanical & Industrial Engineering, Volume 1 Issue 1-2011
2
III. EXPERIMENTAL P ROCEDURE
In this paper, a comparative analysis of conventional
steel leaf spring is done with a virtual model of a
composite leaf spring under static load condition only.
Conventional leaf spring is first tested under static load
condition by using Hydraulic Static Load Test Rig.
Mounting of the leaf spring is done by keeping it in
inverted manner on the test bed. Two eye ends are held in
the clamping devices and load is applied from the top, at
the center of leaf spring. The spring is loaded from zero to
maximum load (i.e. 25 Kg) and again back to zero. The
vertical deflection of the spring is recorded in the load
interval of 5 Kg and specified as per the SOP prescribed
by SAE. To measure the load dial indicator is used which
is located beside the Test Rig and deflection is measured
by strain gauges located at the clamping of the test rig.
IV. S PECIFICATION OF THE CONVENTIONAL
LEAF S PRING
The test steel leaf spring used for experiment is made
up of 60Si7. The composition of material is 0.56 C%, 1.80
SI%, 0.70 Mn%, 0.045 P%, 0.045 S%. Following are the
parameters for the 60Si7.
Table No.1 Specification of Existing Leaf Spring
The leaf spring is used in the TATA SUMO vehicle,
for Rear Suspension. Before testing of the leaf spring Shot
Peening is done on all leaves.
V. S ELECTION OF C OMPOSITE M ATERIAL
As mentioned earlier, the ability to absorb and store
more amount of energy ensures the comfortable operation
of a suspension system. However, the problem of heavy
weight of spring is still persistent. This can be remedied
by introducing composite material, in place of steel in the
conventional leaf spring. Research has indicated that the
results of E-Glass/Epoxy were found with good
characteristics for storing strain energy [1]. So, a virtual
model of leaf spring was created in Pro-E. Model is
imported in ANSYS and then material is assigned to the
model. These results can be used for comparison with the
conventional steel leaf spring.
VI. MATERIAL P ROPERTIES OF
VII. E-GLASS/ E POXY
Table No.2 Properties of E-Glass/Epoxy material
Sr.
No
Properties Value
1 Tensile modulus along X-direction
(Ex), MPa 34000
2 Tensile modulus along Y-direction
(Ey), MPa 6530
3 Tensile modulus along Z-direction
(Ez), MPa 6530
4 Tensile strength of the material,
MPa 900
5 Compressive strength of the
material, MPa 450
6 Shear modulus along XY-direction
(Gxy), MPa 2433
7 Shear modulus along YZ-direction
(Gyz), MPa 1698
8 Shear modulus along ZX-direction
(Gzx), MPa 2433
9 Poisson ratio along XY-direction
(NUxy) 0.217
10 Poisson ratio along YZ-direction
(NUyz) 0.366
11 Poisson ratio along ZX-direction
(NUzx) 0.217
12 Mass density of the material (ρ),
Kg/mm3 2.6x10 3
13 Flexural modulus of the material,
MPa 40000
14 Flexural strength of the material,
MPa 1200
VIII. C OMPARATIVE ANALYSIS OF LOAD AND
DEFELECTION OF THE S TEEL AND C OMPOSITE
LEAF S PRINGS
Table No.3 Comparative Analysis of Steel Leaf and
Virtual Model of Composite Leaf Spring
Conventional
Steel leaf spring
Virtual model of
Composite Leaf
Spring (FEA)
Sr.
No
.
Load
(Kg)
Deflectio
n (mm)
Stress
(Kgf/mm2
)
Deflectio
n (mm)
Stress
(Kgf/mm2
)
1 5 31.127 17.81
8 24.23 59.102
Parameters Value
Total Length of the spring
(Eye to Eye) 1540 mm
Free Camber (At no load condition) 136 mm
No. of full length leave
(Master Leaf) 01
Thickness of leaf 13 mm
Width of leaf spring 70 mm
Max m Load given on spring 25 Kg
Young’s Modulus of the spring 22426.09 Kgf/mm2
Weight of the leaf spring 23 Kg