Fatigue Life Analysis of Parabolic Leaf Spring

A parabolic leaf spring which can last longer without failure in rough road is proposed here. A parabolic leaf spring has two or more leaves. The leaves touch each other at the centre where they are fixed to the axel and at the outer ends where they are fixed to the vehicle. In between these points the leaves don’t touch each other as in conventional leaf springs. Each leaf represents a complete spring in itself and will act as such. To enable this the leaf is tapered, from the centre (thick) to the outer ends (thin). This tapering is parabolic, it means that every centimetre (or inch) the thickness of the leaf decreases with its length.. Every single leaf will have, more or less, the shape of a complete multi leaf spring and thus it's capable to cope with the same forces. This means that the ideal parabolic spring could have only one leaf, however, this type of "mono leaf" spring will have very limited articulation/weight ratio due to high internal stresses so a 2 or 3 leaf parabolic spring can divide the stresses more evenly across the other leaves and thus more axle movement is possible. Another reason to increase the number of leaves on a parabolic spring is to increase the rate (load capacity). Because every leaf is one spring we can add or take out leaves without compromising the strength of the leaf itself. So for example we have a 3 leaf rear spring and we add one similar leaf the rate will go up for about 30% which means that the load capacity increases by +/- 30%. The objectives of this thesis is to use different composite materials for the leaf spring and to obtain a material that can be used as a material for parabolic leaf spring giving improved fatigue life. In this thesis  continuous fibre composite Kevlar/Epoxy and S2-Glass/Epoxy are chosen and FEM analysis is performed on Ansys 15 and fatigue life of each material is predicted. Then the modal analysis is done to see whether the natural frequency of vibration of the leaf spring is greater than the frequency imparted by the road and also the points of maximum stress and deformation gives the points where stiffness has to be increased so that fatigue life and overall performance of the leaf spring can be improved.