Static and free vibration analysis of leaf springs by finite element method

Abstract

Leaf springs are essential components in some of the suspension systems. They are mainly used in heavy-duty vehicles, railroad carriages, trucks, and many SUVs nowadays. The function of the leaf spring is to absorb and store energy to then release it just like all other springs. When leaf spring undergoes loading conditions, the spring experiences stress and deflection. To prevent failure, the maximum stress experienced by the spring must be lower than the yield stress of the material and the maximum deflection must also be less than a certain maximum permissible deflection.

In this Final Year Project (FYP), leaf springs are analysed using the finite element method for stress, deflection, and natural frequencies. The finite element software ANSYS-Mechanical APDL (ANSYS 2021 R1Student Version) is used for this project. For stress and deflection analysis, the stress distribution and force-deflection response are studied with different numbers of leaves in the leaf spring assembly as well as by changing the length of the 2nd to 5th leaf. The effect of friction on the force-deflection response is also studied by introducing friction at the interface between the leaves. The effect of adding pins to the leaf spring model on the force-deflection response and stress distribution is compared with the model without pins. Free vibration analysis is also carried out to determine the natural frequencies and mode shapes of the leaf spring.

The deflection analysis shows that the slope of the force-deflection response is steeper for small deflections and becomes shallower progressively as the deflection increases. The friction between the leaves increases the force required to cause a given deflection. The stress analysis reveals that the maximum value of von Mises stress occurs at the midsection of the leaf spring when only one leaf is used and it occurs at the eyes if multiple leaves are used in the design. By adding the pins in the model, it is observed that the force required to cause a given displacement decreases.