20120140505002 2

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print),
ISSN 0976 – 6499(Online) Volume 5, Issue 5, May (2014), pp. 09-16 © IAEME
9
ANALYSIS OF COMPOSITE MONO LEAF SPRING
Prof. N.V. Hargude1
, Mr. J.G. Herekar2
, Prof. P.P. Awate3
1
Associate Professor, 2
M. E. MECH- Design Student, 3
Assistant Professor
P.V.P.I.T. Budhgaon
ABSTRACT
A leaf spring is a simple form of spring commonly used for the suspension in wheeled
vehicles. Originally called a laminated or carriage spring, and sometimes referred to as a semi-
elliptical spring or cart spring, it is one of the oldest forms of springing, dating back to medieval
times. A leaf spring takes the form of a slender arc-shaped length of spring steel of rectangular cross-
section. The center of the arc provides location for the axle, while tie holes are provided at either end
for attaching to the vehicle body. For very heavy vehicles, a leaf spring can be made from several
leaves stacked on top of each other in several layers, often with progressively shorter leaves. Leaf
springs can serve locating and to some extent damping as well as springing functions. While the
interleaf friction provides a damping action, it is not well controlled and results in friction in the
motion of the suspension. For this reason manufacturers have experimented with mono-leaf springs.
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, a short swinging arm. The shackle
takes up the tendency of the leaf spring to elongate when compressed and thus makes for softer
springiness. Some springs terminated in a concave end, called a spoon end (seldom used now), to
carry a swiveling member. The objective of this paper is to review various techniques used to
analyses of composite mono leaf spring for the load carrying capacity, stiffness and weight savings
of composite leaf spring. The dimensions of an existing conventional steel leaf spring of a Heavy
commercial vehicle are taken Same dimensions of conventional leaf spring are used to fabricate a
composite multi leaf spring using E-GLASS/EPOXY, C- GLASS/EPOXY, S- LASS/EPOXY
unidirectional laminates.
Keywords: Leaf Spring, Vehicles Suspension, Composite Laminates, Analyses Techniques.
INTERNATIONAL JOURNAL OF ADVANCED RESEARCH
IN ENGINEERING AND TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 5, Issue 5, May (2014), pp. 09-16
© IAEME: www.iaeme.com/ijaret.asp
Journal Impact Factor (2014): 7.8273 (Calculated by GISI)
www.jifactor.com
IJARET
© I A E M E

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1. INTRODUCTION
Various models such as MCD model, model estimation by MLE, and estimated strength
distribution for carbon micro-composites are developed for tensile strength of carbon composites,
which is based on a multiplicative cumulative-damage approach. Analysis of composite leaf spring is
carried out by using analytical & finite element analysis method. SMA Wires are used in FE
Simulation and Optimal Control of Adaptive Beams and static and dynamic analysis of composite
leaf spring for heavy vehicle is done. Also CAE tools are used for eye design analysis of single leaf
spring in automotive vehicles.
2. DESCRIPTION OF ANALYSES
The MCD model, model estimation by MLE, and estimated STRENGTH DISTRJBUTION
for carbon micro-composites are developed for tensile strength of carbon composites requires
Knowledge of the tensile strength properties of a fibrous composite material is essential in the design
of reliable structures from that material. Determination of statistical models for the tensile strength of
a composite material which provide good fits to experimental data from tensile tests on material
specimens is therefore important for engineering design. Perhaps the most commonly used statistical
model is the Weibull distribution, based on ‘weakest link of a chain’ arguments. However, in many
cases the usual Weibull distribution does not adequately fit experimental data on tensile strength for
composite materials made from brittle fibers such as carbon. Here, an alternative model is developed
for tensile strength of carbon composites, which is based on a multiplicative cumulative-damage
approach. This approach results in a 3-parameter extension of the Birnbaum-Saunders fatigue model
and incorporates the material specimen size (size effect) a5 a known variable. This new distribution
can also be written as an inverse Gaussian-type distribution, which can be interpreted as the first
passage of the accumulated damage past a damage threshold, resulting in material failure. The new
model fits experimental tensile-strength data for carbon micro-composites better than existing
models, providing more accurate estimates of material strength. The importance in materials
engineering is the determination of tensile strength properties of complex materials such as
composites. Even in the most carefully controlled laboratory testing, tensile strength measurements
of material specimens under study have a relatively large amount of scatter. Thus, statistical models
must be used to describe tensile strength of a specific type of material. Modern materials, such as
carbon fibrous composites, present a challenge in the development of good statistical models for
their strength. In many cases, common statistical distributions such as Gaussian, lognormal, or
Weibull do not adequately fit experimental strength data from fibrous composite specimens -
indicating that new models are needed to describe the failure or strength of these materials
The behavior of concrete beams actuated by embedded shape memory alloy (SMA for short)
wires through an extensive experimental program. Ti-50wt.% NiTi SMA wires were used. Electrical
power was used to heat the SMA wires. Some of the factors affecting the deflection of the beam
were examined experimentally. These factors include the cross-sectional areas of the beam and the
number of SMA wires, the pre-strain of the SMA wire, the curing condition (in a water tank or in a
standard fog-curing box), the curing time of the specimen, the actuation mode for the SMA wire, the
volume fraction of the embedded SMA wires, and the diameter of the SMA wire, etc. The
experimental results indicate that a large recovery force in the concrete beam could be obtained when
the SMA wires were heated and, accordingly, the SMA wires could be used as actuators to change
the deflection of a concrete beam. Improvements in materials and advances in computing and control
technology make it possible to apply sophisticated active control technology to civil engineering
structures. Shape memory alloys (SMAs) are one of the so-called “smart materials”. From a
macroscopic point of view, the observable mechanical behavior of shape memory alloys can be

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separated into two major categories: one is the shape memory effect (SME), in which a specimen
exhibits a larger residual strain after loading and unloading that can be fully recovered upon raising
the temperature of the material; the other is the pseudo-elasticity, in which a specimen achieves a
very large strain upon loading that is then fully recovered in a hysteresis loop upon unloading.
Regarding the shape memory effect of SMA, the amount of recovery depends on the activation
temperature, the initial deformation, and the percentage of marstensite phase that is present in the
material. The recovery properties have led to many applications of SMAs as activated actuators.
One-way shape memory occurs when a SMA is deformed at its martensitic temperature and, upon
heating to an austenitic temperature, changes back to its original shape, recovering the original
deformation. A two-way shape memory effect is induced by cyclic thermo-mechanical
transformation training to create a favorable residual stress field in the SMA. Stress-free cooling of
the austenite produces a transformation strain that is recovered hysterically during stress-free heating
of the marstensite. SMA has been proposed for large strain actuators for use in smart structures. Such
applications include shape and active vibration control and acoustic control with a shape memory
alloy wire or layer, the active control of electrometric rods with embedded two-way shape memory
alloy actuators, a base isolation system with a shape memory alloy device that is based on the
pseudoelastic effect for elevated highway bridges, a structure’s seismic isolation and a shape
memory alloy damper for the control of structures. Numerical simulation such as the element free
Galerkin method can be used to calculate some large deformations of the pseudo-elastic behavior of
SMA beams effectively. Here finite element formulation for a shape memory wire introduced. The
element has subsequently been used to model the response of an adaptive elastic beam, changing its
shape according to prescribed wire heating. The application is not confined to simple beam cases;
rather does the general nature of the FE formulation offer the possibility of simulating arbitrary smart
structures using SMA wires. The second part of the paper has shown the potential of the SMA model
with respect to Control applications. Modeling temperature dependence and hysteretic behavior in a
natural way, it permits the calculation of an optimal control for the adjustment of beam shapes. This
can be used either for the planning of optimal trajectories or as basic input for realtimecontrol
applications.
In order to conserve natural resources and economize energy, weight reduction has been the
main focus of automobile manufacturers in the present scenario. Weight reduction can be achieved
primarily by the introduction of better material, design optimization and better manufacturing
processes. The suspension leaf spring is one of the potential items for weight reduction in
automobiles as it accounts for 10% - 20% of the unstrung weight. This achieves the vehicle with
more fuel efficiency and improved riding qualities. 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. Since, the composite materials have more elastic strain energy storage capacity and
high strength to weight ratio as compared with those of steel, multi-leaf steel springs are being
replaced by mono-leaf composite springs. The composite material offer opportunities for substantial
weight saving but not always are cost-effective over their steel counter parts. The leaf spring should
absorb the vertical vibrations and impacts due to road irregularities by means of variations in the
spring deflection so that the potential Energy is stored in spring as strain energy and then released
slowly. So, increasing the energy storage capability of a leaf spring ensures a more compliant
suspension system. According to the studies made a material with maximum strength and minimum
modulus of elasticity in the longitudinal direction is the most suitable material for a leaf spring.
Fortunately, composites have these characteristics. In the present work, a seven-leaf steel spring used
in passenger cars is replaced with a composite multi leaf spring made of glass/epoxy composites. The
dimensions and the number of leaves for both steel leaf spring and composite leaf springs are
considered to be the same. The primary objective is to compare their load carrying capacity, stiffness
and weight savings of composite leaf spring. Finally, fatigue life of steel and composite leaf spring is

12
also predicted using life data. The objective of this paper is to calculate stresses, strength to weight
ratio, dynamic loading condition, and stiffness & compare those with conventional steel leaf spring.
For the accurate evaluation of above factor we use Finite Element Method. In Static analysis, there is
no variation of force with respect to time. Output in the form of stress, displacement, etc. with
respect to time is not taken into account. Modal analysis of leaf spring is conducted to study the
natural frequencies.
Fig 1: Mono leaf spring
Fig 2: Meshing of Mono leaf spring Fig 3: Stress Analysis of Mono leaf spring
Fig 4: Steel Mono leaf spring Fig 5: Composite Mono leaf spring

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4.1 Results for standard eye
Figure 6: Total deformation Figure 7: Normal Stress
Figure 8: Von-Mises Stress Figure 9: Factory of Safety
Actuators from shape memory wires have a number of attractive properties: they are able to
produce large strains with a very high work output per volume; they are lightweight and perform
silently without any additional gear. This makes them very suitable as devices for the control of
flexible structures, like lightweight robot arms, parts of airfoils etc. For the design and subsequent
control of these structures, a simulation by a finite element procedure is very useful in order to avoid
immense testing. A prerequisite for such an analysis, however, is a finite element formulation of a
shape memory alloy constitutive model. A number of one-dimensional shape memory models have
been proposed in the last years, for a comparison of some of the models. To date, at least to the
knowledge of the authors, the only FE implementations have been done by Brinson and Lammering
and Lagoudas et al. In this paper, we will present a finite element formulation for an improved
version of the model originally developed by Müller and Achenbach. It is very attractive for the
simulation of SMA actuators for at least two reasons. It reproduces the time-dependent, hysteretic
behavior of such materials for a continuous spectrum of temperatures, and it is based on purely
thermo mechanical arguments without requiring any additional external criteria like
loading/unloading conditions etc. For this reason, we have used the model for the simulation and
optimal control of simple smart structures using shape memory wires. In a variant of the model is
introduced, which is based on an approximate evaluation of its integral expressions, thus being
suitable for fast and efficient computation. Recently, we have introduced some modifications in
order to improve the behavior for the case of deformation control, which is crucial in the context of
displacement, based finite element methods. In the following section, we give a short review of the

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basic model equations. We then discuss its implementation into the framework of the finite element
method in section 3, and present some results about the simulation of the adaptive. This beam is used
as a prototype smart structure in our laboratory at TU Berlin to evaluate different control strategies,
for details. In the last part, we discuss an optimal control method which determines the heating
function for a shape memory wire necessary to produce a desired beam shape. For simplicity, we
resort to elementary beam theory, which can be treated without requiring FE methods. The problem
leads to a system of nonlinear ODEs, which is implemented into NUDOCCCS, a direct optimal
control code developed by Büskens. The incorporation of a new integration algorithm considerably
accelerates the computations, thus making the method attractive for future real-time control
applications.
Semi-elliptic leaf springs are almost universally used for suspension in light and heavy
commercial vehicles. For cars also, these are widely used in rear suspension the spring consists of a
number of leaves called blades. The blades are varying in length. The blades are us usually given an
initial curvature or cambered so that they will tend to straighten under the load. The leaf spring is
based upon the theory of a beam of uniform strength. The lengthiest blade has eyes on its ends. This
blade is called main or master leaf, the remaining blades are called graduated leaves. All the blades
are bound together by means of steel straps. The spring is mounted on the axle of the vehicle. The
entire vehicle load is rests on the leaf spring. The front end of the spring is connected to the frame
with a simple pin joint, while the rear end of the spring is connected with a shackle. Shackle is the
flexible link which connects between leaf spring rear eye and frame. When the vehicle comes across
a projection on the road surface, the wheel moves up, this leads to deflecting the spring. This changes
the length between the spring eyes.
Suspension System The automobile chassis is mounted on the axles, not direct but some form
of springs. This is done to isolate the vehicle body from the road shocks, which may be in the form
of bounce, pitch, roll or sway. These tendencies give rise to an uncomfortable ride and also cause
additional stress in the automobile frame anybody. All the part, which performs the function of
isolating the automobile from the road shocks, is collectively called a suspension system. It includes
the springing device used and various mountings for the same. Broadly speaking, suspension system
consists of a spring and a damper. The energy of road shock causes the spring to oscillate. These
oscillations are restricted to a reasonable level by the damper which is more commonly called a
shock absorber. Objective of Suspension are to prevent the road shocks from being transmitted to the
vehicle components, to safeguard the occupants from road shocks and to preserve the stability of the
vehicle in pitting or rolling, while in motion
There are Basic Considerations for vertical loading. When the rear wheel comes across a
bump or pit on the road, it is subjected to vertical forces, tensile or compressive depending upon the
nature of the road irregularity. These are absorbed by the elastic compression, shear, bending or
twisting of the spring. The mode of spring resistance depends upon the type and material of the
spring used. Further when the front wheel strikes a bump it starts vibrating. These vibrations die
down exponentially due to damping present in the system. The rear wheel however, reaches the same
bump after certain time depending on the wheel base and the speed of the vehicle. Of course, when
the tear wheel reaches the bump, it experiences similar vibrations as experienced by the front wheel
some time ago. It is seen that to reduce pitching tendency of the vehicle, the frequency of the front
springing system be less than that of the rear springing system. From human comfort point also it is
seen that it is desirable to have low vibration frequencies. The
Results of the studies of human beings have shown that the maximum amplitude which may
be allowed for a certain level of discomfort decreases with the increase of vibration frequency.

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Fig. Mode of Leaf Spring
In this work single leaf spring is modeled using dedicated modeling software CATIA and
considering various eye design the stresses induced in the leaf spring are computed. As eye end plays
a vital role during application of leaf spring like, eyes have the critical areas where the most stresses
induced in a leaf spring. Thus by changing the design of eye, stresses can be reduced. For this
purpose two different types of eye designs for leaf spring analysis were considered. These two eye
design are 1) Standard eye and 2) Casted eye. The eye end and spring are manufactured
simultaneously from the same material. There is no stress concentration in this type. Reinforcement
of composites at the junction of the eye and spring is necessary to avoid the delamination of
unidirectional fibers. This joint configuration has the disadvantages of high cost and manufacturing
complexity.
3. CONCLUSIONS
1) When the SMA wire is actuated, the SMA wires can also transfer recovery force to the
concrete beam. During actuation, the higher the temperature of SMA wire, the larger the
deflection of beam that was obtained. The actuation mode for the embedded SMA wires has a
significant effect on the deflection behavior of a concrete beam and on the performing speed
of reverse transformation of SMA wires. The performing speed of reverse transformation
depends not only on the electric current intensity, but also on the actuation performing time.
The effective actuation mode for reverse transformation is that the electric current intensity is
increased step by step. The deflection of a concrete beam induced by embedded in SMA
wires is larger than that induced by larger diameter wires, even with equal total cross-
sectional area of wires
2) Under the dynamic load conditions natural frequency and stresses of steel leaf spring and
composite leaf spring are found with the great difference. The natural frequency of composite
material is high than the steel leaf spring. Reductions in weight about 85 to 90% in composite
leaf spring are observed than conventional with same level of performance. Conventional
Leaf spring shows failure at eye end only. Composite leaf spring can be used on smooth
roads with very high performance expectations. However on rough road conditions due to
lower chipping resistance failure from chipping of composite leaf spring is highly probable.
That is the composite leaf spring is having greater vibration absorbing capacity than
conventional steel leaf spring. Also the stress of composite leaf spring is higher than
conventional steel leaf spring. Because of using only mono leaf spring space also reduced.

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The corrosion resistance of composite leaf spring is higher i.e. it will work in environmental
condition than conventional steel leaf spring.
3) E-glass epoxy is better than using Mild-steel as though stresses are little bit higher than mild
steel, E-glass epoxy is having good yield strength value and also epoxy material components
are easy to manufacture and this having very low weight while comparing with traditional
materials. S-glass is having better results while comparing with E-glass and mild steel. So
better to use S-glass epoxy (Carbon reinforced fiber) and also we have increased the number
of leafs to reduce the stress for structural stability. While comparing with the weight it is
having less weight than traditional leaf spring (Mild steel).After static analysis we have
analyzed frequency analysis. Model analysis is mainly used to match the frequency of
previous leaf spring model. Hence S-glass epoxy is the best material to manufacture leaf
spring because of good structural stability low production cost and good efficiency.
4) CAE tools provides a cost effective and less time consuming solution in comparison with the
experimental testing but the results may vary in the specified range.
4. REFERENCES
[1] W. J. Padgett, a Multiplicative Damage Model of Strength of Fibrous Composite Materials,
IEEE TRANSACTIONS ON RELIABILITY, VOL. 47, NO. 1, 1998 MARCH
[2] Zongcai Denga, Qingbin Lib, Hongjun Suna, Behavior of concrete beam with embedded
shape memory alloy wires, Engineering Structures 28 (2006) 1691–1697
[3] ANALYSIS OF COMPOSITE LEAF SPRING BY USING ANALYTICAL & FEA,
*Ranjeet Mithari, *Amar Patil, **Prof. E. N. Aitavade, Ranjeet Mithari et al. / International
Journal of Engineering Science and Technology (IJEST).
[4] FE Simulation and Optimal Control of Adaptive Beams Using SMA Wires, Stefan Seelecke,
Institut für Verfahrenstechnik, Technical University Berlin, Sekr. HF2 Straße des 17. Juni
135 D-10623 Berlin.
[5] STATIC AND DYNAMIC ANALYSIS ON COMPOSITE LEAF SPRING IN HEAVY
VEHICLE, B.Vijaya Lakshmi1 I. Satyanarayana2, Lakshmi et al, International Journal of
Advanced Engineering Research and Studies E-ISSN2249–8974.
[6] Vinkel Arora1, Gian Bhushan2 and M.L. Aggarwal3, International Journal of Applied
Engineering and Technology ISSN: 2277-212X (Online) An Online International
Journal Available at http://www.cibtech.org/jet.htm, 2011 Vol. 1 (1) October-December,
pp.88-97/Arora et al.
[7] Anurag bajpai, Sandeep Agarwal and Suruchi, “Mechanical Properties of Epoxy Resin Based
Polymer Concrete”, International Journal of Mechanical Engineering & Technology
(IJMET), Volume 3, Issue 1, 2012, pp. 267 - 276, ISSN Print: 0976 – 6340, ISSN Online:
0976 – 6359.
[8] Rakesh Hota, Kshitij Kumar, Ganni Gowtham and Avinash Kumar Kotni, “Experimental
Investigation of Fiberglass Reinforced Mono-Composite Leaf Spring”, International Journal
of Design and Manufacturing Technology (IJDMT), Volume 4, Issue 1, 2013, pp. 30 - 42,
ISSN Print: 0976 – 6995, ISSN Online: 0976 – 7002.
[9] Hargude N.V and Ghatage k.D, “An Overview of Genetic Algorithm Based Optimum Design
of an Automotive Composite (E-Glass / Epoxy and Hm-Carbon / Epoxy) Drive Shaft”,
International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 1,
2012, pp. 110 - 119, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.

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