Fatigue assessment of high strength leaf springs based on the FKM guideline

Analytical fatigue strength calculations based on the FKM guideline have been performed for hot tapered and stress-shot-peened high-strength leaf spring specimens subjected to three-point fatigue bending. The ultimate tensile strength of the decarburized specimens' surface has been approached by means of Rockwell-C hardness measurements, and used as input for the approximation of its fatigue limit and mean stress sensitivity. Surface roughness and residual stress measurements were performed to take account for the technological life influencing factors. Fatigue tests at a constant mean stress and various stress amplitude levels were performed to determine the specimens' S-N curve and validate the calculation's accuracy. Comparison of calculated with experimentally determined fatigue lives, though satisfactorily, pinpoints the necessity for more accurate implementation of the stress-shot-peening process within the FKM guideline.