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Parabolic leaf springs are safety components on the suspension system. They provide ride comfort due to calculated stiffness characteristics and they absorb and release energy associated with the road outputs of a fully loaded vehicle. Leaf springs determine the desired vehicle ride height from the ground. As a critical safety part, leaf spring endurance must be ensured. Conventional leaf springs, multi-parabolic leaf springs and parabolic leaf springs are the general types in use. The most commonly used type of leaf spring is the parabolic leaf spring. The main advantages of parabolic leaf springs are that they are lighter, cheaper, with fatigue advantages, and they isolate more noise. Classical leaf spring design and prototype process methodology consists of fatigue tests repeated for each case considering different geometry alternatives, leaf layer additions, material and suspension hard points improvements. This methodology takes a long time and requires a significant budget.

The parabolic leaf spring plays a vital role in suspension systems, since it has an effect on ride comfort and vehicle dynamics. Primarily, leaf spring endurance must be ensured. Presently, there are two approaches to designing a leaf spring. In the traditional method, fatigue tests should be repeated for each case, considering different material, geometry and suspension hard points. However, it takes a long time and requires a heavy budget to get the optimized solution. In the contemporary method, a numerical approach is used to obtain the fatigue life and the leaf geometry against the environmental condition on the basis of material properties. This paper presents a more precise method based on non-linear finite element solutions by evaluating the effects of the production parameters, the geometrical tolerances and the variations in the characteristics of the material.

In pursuit of offering the best driving comfort, heavy/ light commercial vehicle producers usually need to make serious optimizations on the design of leaf springs and natural frequency calculations in order to decrease the vibration and noise that have negative effects on the human body - especially severe on long road trips. Leaf spring design parameters and natural frequency calculations provide a different approach to minimizing such negative effects on the driver. In this study, design of the leaf spring, boundary conditions of which depend on vehicle, is examined virtually within the triangle of driving comfort by natural frequency, durability and stiffness. Besides the driving comfort, optimization work aimed at decreasing the vibration and noise factors are also determined through finite element methods. Prototypes of leaf springs are produced and their natural frequency measurements, stress levels under maximum load through strain gauges as well as life tests are completed.