The conventional semi elliptical leaf spring assembly has higher frictional losses due to the material properties and mode of assembly. The leaves in the assembly have sliding contact between each other, which increases the losses due to friction. When the springs are used for longer period of time due to wear, the frictional losses increases considerably. Also to increase the load carrying capacity of the leaf springs and to obtain good suspension effect balls are introduced in between two leaves of SUP9 grade. Modeling is done by using ProE and Analysis is carried out by using Ansys 13.0 for better understanding. Analytical results compared with the FEA results. After analyzing the existing geometry a new concept design is proposed to increase the load carrying capacity of the leaf springs and also for good suspension effects.
Current trends involving improvement:
A more modern implementation of old leaf springs is the parabolic leaf spring for automobiles. The new innovative design is characterized by the use of the less leaves whose thick varies from the centre to the outer side following a parabolic pattern.
This results in inter leaf friction, because of which the only contact point between the springs in vehicle is at the end and the centre where the axle is connected. Spacers used in the new design prevent the other parts collisions.
Besides being less in weight the main benefit of parabolic springs is their greater flexibility, which is translated as a high ride quality of the vehicle. It gives us the high ride quality which refers to the high degree of safety to the riders from the uneven road surfaces and gives high level of comfort.
Since there is no contact between the leaves the coefficient of friction is nearly equals to zero.
Higher span requirement when compared with semi elliptical leaf spring, due to decreased rigidity.
Higher winding up effect when compared with semi elliptical leaf spring.
Due to decreased rigidity the roll stiffness of the vehicle needs to be compromised with additional factors like anti roll bars.
Mono composite leaf springs:
Mono-leaf springs consist of one plate of spring steel that is thick in the centre and tapers out to the ends. Being only one leaf there are no supporting leaves. The material used is of a higher grade material.
Sudden shifting of the axle causes a change in the control of the vehicle. This change of control can vary from slight loss to a complete loss of control.
Widely used only in light duty vehicle due to reduced load carrying capacity.
Usage of higher grade composite material increases the material and manufacturing cost.
In this project, an attempt was made to develop an semi elliptical leaf spring assembly which reduces the inter leaf friction considerably when compared with the existing semi elliptical leaf spring assemblies.
Existing Tata LPT 912R front semi elliptical leaf spring assembly is taken as the base model for working out a new design. The major advantages of semi elliptical leaf spring assembly with balls are,
Interleaf friction can be considerably decreased when compared with existing semi elliptical leaf spring assembly.
The rigidity is not as like the semi elliptical leaf spring assembly since the contacts between the leaves are not lost.
Since the rigidity is not lost, the windup of springs will be less compared to the parabolic leaf springs.
The fatigue life will increase considerably when compared to the existing semi elliptical leaf spring.
The weight of the spring assembly can be reduced considerably due to usage of lesser no of leaves.
The vehicle handling parameters are improved considerably, because the vehicle using parabolic springs may require Anti Roll bar as an additional factor to increase the roll stiffness of the vehicle.