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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.

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.

Decarburization occurs on heat treated components. At leaf spring manufacturers, the occurrence of decarburization, which has a negative impact on fatigue, starts at hot rolled leaf spring steel raw materials' production process. The decarburization rate of the raw material, which is taken through a heat treatment, increases during the leaf spring manufacturing process. Through metallographic analyses and experimental tests, this study manifests how leaf spring's resistance to fatigue is affected by the correlation of ferrite structure occurred by decarburization on heat treated leaf springs, the surface hardness, and the permanent surface tension to be occurred during the shot peening process. This study conveys the techniques that can be applied to obtain low decarburization in leaf spring manufacturing, and the improvements achieved through optimization of high temperature treatment times of materials through use of thermographic survey at heat treatment furnaces.