06-05-2013, 04:02 PM
Design and Analysis of Composite Leaf Spring
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Abstract
In these paper, composite structures for conventional metallic structures has many advantages because of higher specific
stiffness and strength of composite materials is discussed. The automobile industry has shown increased interest in the replacement
of steel spring with fiberglass composite leaf spring due to high strength to weight ratio. This work deals with the replacement of
conventional steel leaf spring with a Mono Composite leaf spring using E-Glass/Epoxy. The design parameters were selected and
analyzed with the objective of minimizing weight of the composite leaf spring as compared to the steel leaf spring. The leaf spring
was modeled in Pro/E and the analysis was done using ANSYS Metaphysics software.
INTRODUCTION
Originally called laminated or carriage spring, a leaf
spring is a simple form of spring, commonly used for
the suspension in wheeled vehicles. It is also one of the
oldest forms of springing, dating back to medieval
times. Sometimes referred to as a semi-elliptical spring
or cart spring, it takes the form of a slender
arcshaped length of spring steel of rectangular crosssection.
The center of the arc provides location for the
axle, while tie holes called eyes 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. 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.
PRINCIPLE OF LEAF SPRING
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 unsprung weight. The
introduction of composites helps in designing a better
suspension system with better ride quality if it can be
achieved without much increase in cost and decrease in
quality and reliability. In the design of springs, strain
energy becomes the major factor.
DESIGN OF LEAF SPRING
Considering several types of vehicles that have leaf
springs and different loads on them, various kinds of
composite leaf spring have been developed. In the case
of multi- leaf composite leaf spring, the interleaf spring
friction plays a spoil spot in damage tolerance. It has to
be studied carefully.
In the present work, only a leaf spring with constant
thickness, constant width design is analyzed.
PROBLEM DEFINITION
Objective of present work is to consider an existing
automobile leaf spring model TATA SUMO EZRR
PARABOLIC REAR and to design and analyze a
composite leaf spring with upturned eye without
changing stiffness in order to replace the existing steel
leaf spring with a composite leaf spring.
A spring eye is essentially the end of a leaf spring
bended into a circular shape to allow rotation about the
spring eye. The main types of spring eye designs are
upturned, military wrapper, down turned, and Berlin
eyes Fig: 4. Types Upturned eyes are the most
commonly used type of spring eye because of their
simple design and high durability. Upturned eyes are
highly durable because they resist stress due to vertical
forces on a suspension system.
STATIC ANALYSIS OF LEAF SPRING
The leaf spring modeled in Pro/E was imported to
ANSYS in IGES format. Since leaf spring was modeled
as a solid, solid element named SOLID187 was used
to mesh the model. SOLID187 element is a higher order
3-D, 10-node element. SOLID187 has a quadratic
displacement behavior and is well suited to
modeling irregular meshes (such as those produced from
various CAD/CAM systems). The element is defined by
10 nodes having three degrees of freedom at each
node: translations in the nodal x, y, and z directions. The
element has plasticity, hyper elasticity, creep, stress
stiffening, large deflection, and large strain capabilities.