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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.

Parabolic leaf springs are used as safety parts in heavy/ light commercial vehicles. When designing leaf springs, one must complete the evaluation from the perspectives of fatigue life and durability in order to ensure optimization of the design. After the initial design, rather than trying to establish optimization by producing prototypes by trial and error method, using the virtual prototype process to achieve design optimization, thereby reducing the costs will offer competitive advantage for both suppliers and original equipment manufacturers in the global market. In a reference study carried out in a partnership with Ford Otosan, the finite element methodology was used to verify the design of a 4- layered parabolic leaf spring and a multi-parabolic spring designed as its alternative. The stress distribution on layers during vertical, loaded and windup moment was examined.

Besides the innovative work in the commercial vehicles sector, where there is an ever growing competition, lighter, more comfortable, safer, and more robust products are also being developed through optimization of design parameters of currently available systems. This study explains the possible effects of changing the design parameters of leaf springs on a vehicle's driving dynamics, which has a significant effect on the total weight of the vehicle. These effects include the vehicle's suspension specifications and the suspension system's interaction with the steering system. A virtual vehicle model is analyzed under the loads gathered in road tests, to measure the stress levels on the spring layers and the movement of the leaf spring depending on the limits determined by the vehicle manufacturer. Furthermore, the conformity of the movement of the front axles in connection with the leaf spring with the steering system is also analyzed.

Leaf springs are used as the suspension elements for the front and rear axles of light and heavy commercial vehicles in the automotive key industry. While the vehicle is running empty or with a load under on-road or off-road conditions, it catches the loads transmitted from the wheels i.e., the loads from the ground to the hub axle, and working together with the damper it helps absorption of such loads and prevents them from being transmitted to the chassis. As a result, vehicle comfort is achieved. In addition to this function, leaf springs act as a safety part that continuously hold the chassis and axle together under static and dynamic loads. While the vehicle is runs under rough road conditions, the impact loads from the road not only cause negative impacts on the vehicle but also damage the drivetrain. Such impact loads substantially disturb both the vehicle and the passengers.