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Manisa, Turkey

Karaagac M.,Olgun Celik | Soner M.,Olgun Celik | Keskin A.,Olguncelik | Yildiz S.,Olguncelik | And 2 more authors.
SAE Technical Papers | Year: 2013

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. Copyright © 2013 SAE International. Source

Soner M.,Olguncelik | Guven M.,Daimler AG | Tokgonul S.G.,Olguncelik | Erdogus T.,Olguncelik | And 2 more authors.
SAE Technical Papers | Year: 2013

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. In these analyses, vertical loading, braking forward and braking backward load cases are taken into consideration. Copyright © 2013 SAE International. Source

Kanbolat A.,Olguncelik | Soner M.,Olguncelik | Erdogus T.,Olguncelik | Karaagac M.,Olguncelik
SAE Technical Papers | Year: 2011

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 other words, it is a hybrid method, a blend of the traditional and the recent ones, which correlates the real life conditions and the results of computer aided engineering. Leaf springs of different characteristics were produced and tested in the plant of OlgunCelik plant. The design methodology of this paper also offers a practical approach to industry professionals. The aim was to create a design tool with 2D FEA which is well correlated with 3D.The correlation of 3D and simple 2D methods with experiments are validated through a design of experiment (DOE) study. Copyright © 2011 SAE International. Source

Karaagac M.,Olguncelik | Soner M.,Olguncelik | Togay A.,Olguncelik | Sevimli K.,Olguncelik | Kanbolat A.,Olguncelik
SAE International Journal of Materials and Manufacturing | Year: 2012

The leaf spring manufacturer must supply high quality raw material at required strength for ensuring endurance rig tests. It's very important to maintain both inside and surface cleanliness of raw material. This study presents micro crack effects on material surface by evaluating residual stress values. Residual stress values on leaf springs are measured with X-ray diffractometer and different residual stress values are classified on the same raw material batch which have also the same material failures. Finally, micro cracks are measured in metrics. Micro crack standardization is performed considering the residual stress values and rig tests. The outputs in metrics which correlated with endurance rig tests can be taken as reference by the manufacturers of leaf spring and original equipment manufacturers. © 2012 SAE International. Source

Soner M.,Olguncelik | Guven N.,Olguncelik | Kanbolat A.,Olguncelik | Erdogus T.,Olguncelik | Karaagac M.,Olguncelik
SAE Technical Papers | Year: 2011

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. In this study, five-layer parabolic leaf springs have been optimised to four layers based on material, geometric design improvement, non linear finite element analyse calculations regarding boundary conditions of leaf spring. The rig test validation of 5 layer parabolic leaf springs which is well correlated with finite element results have been summarized. Later, the finite element model of the new design has been generated by decreasing weight through removing layers at the same boundry conditions and evaluations have been made in comparison with the first design. Performance requirement considering load and deflection, packaging requirements considering parabolic leaf spring length, width, service requirement, risk assessments, business considerations, and all other requirements regarding optimised parabolic leaf spring design have been detailed. This paper presents a precise method called the OlgunÇelik virtual prototype process and will remain as a reference for leaf spring producers and designers. Copyright © 2011 SAE International. Source

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