Comprehensive Durability Assessment of Leaf Springs with CAE Methods 2014-01-2297

In today's world, there are a prominent number of weight and cost reduction projects within the vehicle engineering development activities. Regarding this phenomenon, a complete optimization study is applied to a leaf spring assembly, which has 4 leaves and which is used in heavy duty trucks, by reducing the number of leaves down to 3 together with weight and cost reductions.

At the first step of the project, the stiffness of the leaf spring is calculated with in-house software based on mathematical calculations using the thickness profile of the leaves. Then the results of these calculations are compared with non-linear elastic leaf spring calculations which are conducted with FEA. This elastic leaf spring finite element model is transferred into Multi-Body-Simulation (MBS) model in order to determine the forces acting on the leaf spring. Using the results of the MBS calculations, which are time histories of the internal forces and moments on the leaf spring, the FE simulations are performed. Stress results are not always enough to conclude that the leaf spring will preserve its integrity until the desired lifetime although they may give a rough estimation. Concurrently, without multi-channel fatigue life analysis it is not correct to make a final decision. Therefore, as the final step of the project, a multi-channel fatigue life calculation process is performed to assess the durability characteristics of the new design, showing that the weight and cost reduction is achievable without worsening the fatigue life of the leaf spring.