ENGINEERING DESIGN LABORATORY

(09PD52)

PRESENTATION-I

Project Title: Design And Analysis Of Composite Parabolic Leaf Spring

WHAT IS PARABOLIC LEAF SPRING? A more modern implementation is the parabolic leaf spring.

This design is characterized by fewer leaves whose thickness varies from centre to ends following a parabolic curve.

In this design, inter-leaf friction is reduced by spacers, and therefore there is only contact between the springs at the ends and at the centre where the axle is connected.

Not as "stiff" as conventional "multi-leaf springs".

Fig.1 Semi-Elliptical Leaf Spring Fig.2 Parabolic Leaf Spring

PROBLEM DESCRIPTION: When a leaf spring is compressed, the length of the leaves changes and the

leaves slide on each other.

This sliding action could be a source of noise and can also produce friction.

Weight of single steel leaf spring is around 9.2kg.

NEED FOR CURRENT STUDY: The automobile industry has shown increased interest in the replacement of steel

leaf spring with fibre glass reinforced polymers.

To match Reduce the weight of the steel leaf spring by introducing composite material.

With increase in the fatigue life of the spring.

Increase the Stiffness of the leaf spring.

LITERATURE REVIEW:

ANALYSIS AND OPTIMIZATION OF A COMPOSITE LEAF SPRING

Mahmood M. Shokrieh , Davood Rezaei

A four-leaf steel spring used in the rear suspension system of light vehicles is analyzed using ANSYS V5.4 software.

The finite element results showing stresses and deflections verified the existing analytical and experimental solutions.

Using the results, a composite one made from fiberglass with epoxy resin is designed and optimized using ANSYS.

Main consideration is given to the optimization of the spring geometry. The objective was to obtain a spring with minimum weight that is capable of carrying given static external forces without failure.

AUTOMOBILE LEAF SPRINGS BY COMPOSITE MATERIALS

H.A. Al-Qureshi

The suspension spring of a Jeep is selected.

A single leaf, variable thickness spring of glassfiber reinforced plastic (GFRP) with similar mechanical and geometrical properties to the multileaf steel spring, was designed, fabricated and tested.

The testing was performed in laboratory and was followed by the road test. Comparison between the performance of the GFRP and the multileaf steel springs is presented.

Weight reduced from 18.7kg to 3.5kg.

COMPOSITE MATERIALS CHOOSEN:Matrix-Epoxy Resin:

Cost is low, exhibits moderate shrinkage.

Fiber-E Glass:

Lighter, stiffer and stronger Less fatigue Water resistance.

PROPOSED METHODOLOGY: To carry out static analysis on parabolic spring using FEM to

Find the stiffness of the Leaf spring.Find the max stress and location corresponding to Rated load and Over

condition.

To design a Composite leaf spring made of Fiber Glass/ epoxy resin.

Comparative FEM study of composite leaf spring with Steel leaf spring.

The CAD models of the parabolic leaf spring will be meshed by 3D 8-node structural solid elements.

3D contact elements (CONTACT 49) represent contact and sliding between adjacent surfaces of leaves.

An average coefficient of friction 0.03 was taken between surfaces.

Software to be used: Hypermesh, Ansys

Units: Load in Kg, Displacement in mm

PARAMETERS OF STEEL LEAF SPRING: Total length 1245 mm

Front half (the arc length between the axle seat and the front eye) 559 mm

Normal static loading 2500 N(Rated)

Full bump loading 4660 N(Over)

Spring Width 50-60mm.

Spring Thickness 7mm.