Fatigue Life of Normalized and Quenching & Tempered Stabilizer Bars

The current study has the proposal to investigate the differences in fatigue behavior between stabilizer bar manufactured in quenched & tempered and normalized SAE5160 steels. As it known, quenched & tempered stabilizer bars have higher mechanical and fatigue strengths, on the other hand, they are more expensive. Besides that, this type of part still receives a shot peening surface treatment to improve the fatigue strength due to creation of compressive surface residual stresses and by surface plastic strain. The previous subjects have affected directly the fatigue crack nucleation, then, in order to reduce the nucleation stage and study mainly the growth stage, a micro-notch (short crack) was introduced by EDM (Electric Discharge Machine) process on samples and stabilizer bars.

The proposed experimental study consists of comparative analysis of da/dN-ΔK curves, fractographic and metallographic analyses, bench tests, and after that, it is intended to show the relevant aspects between the two microstructural classes specified for stabilizer bars and the beneficial effects obtained by shot peening process. The main objective of this paper is to show that the better performance of martensitic stabilizer bar in fatigue life could be reduced or lost when a micro-notch is present.