Fatigue Lifetime of Bearing Steel in Ultra-High-Cycle Region

Fatigue initiation mechanism in high-cycle and ultra-high-cycle region is a topic of increasing importance due to rising demands on lifetime of engineering components. Car engines, high-speed trains and turbines are typical examples of engineering systems loaded up to gigacycle region [Bathias, C., Paris, P.C., Gigacycle fatigue in mechanical practice, M. Dekker, New York, USA, 2005.]. According to the valid standards, e.g. [ISO Standard 12107:2003(E) Metallic materials — Fatigue testing — Statistical planning and analysis of data.], S-N curves are generally limited to 107 cycles. It is assumed, that the fatigue limit can be determined as a horizontal line below which no failure takes place. Stair case method is frequently applied to the experimental determination of fatigue limit on the basis of 107 cycles. In contrast to low-cycle and conventional high-cycle fatigue, where the mechanisms of fatigue damage, crack initiation and propagation are more explored, progress in ultra-high-cycle fatigue is highly desirable.