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IJSTE - International Journal of Science Technology &
Engineering | Volume 1 | Issue 11 | May 2015 ISSN (online):
2349-784X
All rights reserved by www.ijste.org
151
Static and Dynamic Analysis of Automobile Leaf
Spring (TATA ACE)
Trivedi Achyut V. Prof. R.M. Bhoraniya
M. Tech CAD/CAM Professor
Department of Mechanical Engineering Department of Mechanical
Engineering
Marwadi Education Foundations Group of Institution
Rajkot-360007,India
Marwadi Education Foundations Group of Institution
Rajkot-360007,India
Abstract
The Automobile firm has shown greater interest for replacement
of conventional steel leaf spring with that of composite leaf
spring, as the composite material has high strength to weight
ratio, good corrosion resistance. The objective of this work is
to
compare the load enhancing capacity, and weight savings of
composite leaf spring with respect to conventional steel leaf
spring.
The dimensions of an existing conventional steel leaf spring of
a Light design calculations. Static Analysis of 3-D model of
conventional leaf spring is performed using analysis commercial
software. And that dimensions are used for composite multi
leaf spring as well by taking composites as carbon/Epoxy and
Graphite/Epoxy . The constraints are stress and deformation and
weight of composite leaf spring with respect to conventional
steel leaf spring. For static condition static analysis done and
for
real time problem dynamic analysis work present here.
Keywords: Leaf Spring, Dynamic Analysis
________________________________________________________________________________________________________
I. INTRODUCTION
Insight to take maximum advantages of natural resources and also
to economize the energy, weight reduction has been the main
area of focus for an automobile manufacturer in the today
scenario. Initially Weight can be reducing by the introduction of
better
material, doing design optimization and by applying better
manufacturing processes. The suspension system element termed
as
leaf spring is one of the critical part for weight reduction in
automobile as it takes ten to twenty percent of the unstrung
weight.
That can been helpful to achieve the vehicle been improved
riding qualities. As we know that springs, are mainly designed
to
absorb (catch-up) and store energy and then when it need it can
release that energy. In that, the strain energy (for spring) of
the
material can become a major part in designing the springs.
Main proposes for the introduction of composite materials mainly
was made it possible for reduction into the weight of the
leaf spring, without any reduction on load carrying capacity and
stiffness. As we all know that the composite materials having
more elastic (strain) energy storage capacity and high
strength-to-weight ratio with respect to those of steel.
Multi-leaf springs are more used for automobile and sometime for
rail road suspensions. It has a geometry which consist a
series of flat plates, usually having a semi- elliptical shape
as shown in fig. 1.1. As shown in figure the leaves are held
together
with the help of two U-bolts and also centre clip. Also in that
Rebound clips are provided to keep the leaves in alignment and
save from lateral shifting of the plates during the working
condition. The leaf having maximum length, called the master
leaf,
master leaf is bent at both ends to form the spring eye
part.
Fig. 1: Leaf Spring
At the center position, the spring is fixed to the main axle
(front or rear) of the car. Mainly Multi- leaf springs are
provided
with one or mostly with two extra full length leaves in addition
to the master leaf. These extra full-length leaves can be
stacked
between the master leaf having maximum length and the
graduated-length leaves. The extra full-length are provided to
support
the transverse shear force acting on the component.
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Static and Dynamic Analysis of Automobile Leaf Spring (TATA ACE)
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II. WORKING PRINCIPLE OF LEAF SPRING
The suspension system having main element termed as leaf spring
is one of the potential and very critical term for weight
reduction in automobile industries as its having a ten to twenty
percent of the unsprung weight. By introducing composites, it
can
helpful for design a better suspension system having a better
ride quality but the condition is it must be achieved without
much
increase cost and also decrease quality and reliability. In the
design of springs, strain energy becomes the major factor. The
relationship of the specific strain energy can be expressed
as
U=2/Eeq. (1.1) Where = strength, =density E =Youngs Modulus of
the spring material
It can be noted that material which is having a lower modulus
and also having a lower density will have a greater specific
strain energy capacity. So the introduction of composite
materials can made it possible to reduce the weight of the leaf
spring
without any reduction into the load carrying capacity and
stiffness. A Composite mainly is any materials that have been
physically assembled to form one single bulk without physical
blending to foam a homogeneous material. The resulting
material would still have components identifiable as the
constituent of the different materials. One of the advantages
of
composite is that two or more materials could be combined to
take advantage of the good characteristics of each.
Fig. 1.2 shows an Arrangement of leaf spring into a car Model a
spring eye section is used to attach the front end of semi-
elliptic shape leaf spring to the chassis frame, and a free end
having a bracket constraining vertical motion to attach the back
end
of semi-elliptic leaf spring to the chassis frame.
Fig. 2: Arrangement of Leaf Spring in Car Model
III. SPECIFICATION OF LEAF SPRING
Forces acting on leaf spring are as shown in fig. Main forces
acting on leaf spring are as follow but in this analysis only
vertical
loading condition is considered. Forces acting on leaf
spring:
Vertical loading (Fv)
Side load (Fs)
Longitudinal load (Ft)
Twisting torque (Tt)
Windup torque (Tw)
Fig. 3: Load Acting on Leaf Spring
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Static and Dynamic Analysis of Automobile Leaf Spring (TATA ACE)
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Assumptions for Analysis: A.
Automobile is assumed to be stationary.
There are 2Semi-elliptic leaf spring, one at front and one at
rear axle. And for Only vertical loading.
Static analysis is carried out for rear single semi-elliptic
leaf spring.
IV. ANALYSIS OF LEAF SPRING
The leaf spring having specification as shown in table 1
initially static analysis done on leaf spring by considering leaf
spring as
a simple supported beam and design constraints are stress and
deformation. The result as show in figure . analysis done on
ansys
and for validation mathematical calculation done. For real time
problem the dynamic (Modal analysis ) considered for time
period of 5s. the purpose of this work is to avoid the resonance
occur with new leaf spring. Table 1
Specification of TATA ACE Leaf Spring
Sr.no Design parameter Value
1 Total length of spring(L) 930mm
2 Length of spring from eye to eye 754mmm
3 Thickness(t) 8mm
4 Width of leaf spring(b) 60mm 1) Specification of TATA ACE
[15]
Weight of vehicle = 500 Kg
Maximum load carrying capacity = 325 Kg
Total weight = 500+325
So , total weight = 825 Kg
Static load apply on vehicle = 825*9.81 N
So , static load apply on vehicle 8000 N (approx.)
At every wheel load = 2000 N and same as reaction force = 4000 N
at downward point. Table 2
Material Properties of Conventional Material
Material selected[10] 65si7
Youngs Modulus,(E) 2.1*105 N/mm2
Poissons Ratio 0.266
Tensile Yield strength 250 MPa
Density 7850 Kg/m3
Behavior Isotropic
Fig. 4: Model of Leaf Spring (TATA ACE)
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Static and Dynamic Analysis of Automobile Leaf Spring (TATA ACE)
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Fig. 5: Stress in Conventional Material
Fig. 6: Deflection in Conventional Material
Table 3 Composites Material Properties
Material selected[15] E-Poxy
Exx 34000 MPa
Eyy 6530 MPa
Ezz 6530 MPa
Poisons ratio along XY 0.217
Poisons ratio along YZ 0.366
Poisons ratio along XZ 0.217
Gxy 2433 MPa
Gyz 1698 MPa
Gxz 2433 MPa
Density of material 2.6*1000 kg/mm3
Behavior orthotropic
Fig. 7: Stress in Composites Material
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Static and Dynamic Analysis of Automobile Leaf Spring (TATA ACE)
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Fig. 8: Deflection in Composites Material
1) Mathematically Validation:
By considering beam equation[16]:
As Maximum deflection can be given by: (X=L)
Max. deflection =
Max. deflection = 0.06459 m
Table 4 Analytical and Ansys Result Comparison
Material Deformation (m) Error (%)
Conventional steel Analytical Simulation
0.06459 0.05616 2.1
Table 5 Analytical and Ansys Result Comparison
Material Stress (Pa) Deformation (m) Mass (Kg)
65si7 5.8739e8 .006 5.45
E-Poxy 4.74e8 0.05616 1.8
Fig. 7: Frequency and Deformation at Mode 5
Fig. 8: Modal Analysis at 5s for Forced Vibration
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Static and Dynamic Analysis of Automobile Leaf Spring (TATA ACE)
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156
Table 6 Comparing Frequencies for Resonance Effect
Sr. no
For max modal shape at 5s time
Frequency(Hz) Natural frequency(Hz)
655 598
V. CONCLUSION
In this research we can conclude that with respect to
conventional steel leaf spring composites having high strength to
weight
ration. Also composites having nearly 400% less weight than
conventional steel leaf spring. And also from Modal analysis we
can conclude that composite leaf spring is safe as its not
showing resonance effect so its safe in that manner.
REFERENCES
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[3] I.Rajendran ,& S.Vijayarangan , optimal design of a
composite leaf spring using genetic algorithms, computers &
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[4] M. Raghavedra,& Syed Altaf Hussain, Modeling and
Analysis of Laminated Composite Leaf Spring under the Static Load
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Research (IJMER) www.ijmer.com Vol.2, Issue.4, July-Aug. 2012,
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[5] H.A.Al-Quereshi Automobile leaf spring from composite
materials, journal of material processing technology, 118(2001),
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