Multi-leaf springs are widely used for automobile and rail road suspensions. It consists of a series of flat plates, usually of semi- elliptical shape.
The leaves are held together by means of two U-bolts and a centre clip. Rebound clips are provided to keep the leaves in alignment and prevent lateral shifting of the plates during the operation.
The longest leaf, called the master leaf, is bent at both ends to form the spring eye. At the center, the spring is fixed to the axle of the car. Multi- leaf springs are provided with one or two extra full length leaves in addition to the master leaf.
These extra full-length leaves are stacked between the master leaf and the graduated-length leaves.
The extra full-length are provided to support the transverse shear force.
For the purpose of analysis, the leaves are divided into two group’s namely master leaf along with graduated-length leaves forming one group and extra full-length leaves forming the other.
The following notations are used in the analysis:
nf= number of extra full-length leaves
ng=number of graduated-length leaves including master leaf
n= total number of leaves
b= width of each leaf (mm)
t= thickness of each leaf (mm)
L=length of the cantilever or half the length of semi- elliptic spring (mm)
F= force applied at the end of the spring (N)
Ff=portion of F taken by the extra full-length leaves (N)
Fg=portion of F taken by the graduated-length leaves (N)