Study on the Influence of Inclusion and Void on Fatigue Life of Bearing Steel Using Statistics of Extreme Values
The maximum nonmetallic inclusion size and void of bearing steel has been analyzed using statistics of extreme values (SEV) in this study, and the influence of the maximum nonmetallic inclusion and void size on fatigue life of bearing steel has been discussed as well. Scanning electron microscopy (SEM) was used to measure the inclusion and void size, and the identification of inclusion type has been carried out by energy dispersive spectrometer (EDS). The results show that there are small hard round oxides or sharp TiN inside or beside the soft MnS strip in steels, single MnS strips and small clustered Al2O3 are also present. Most of voids in steels are branched rod-like or feathery, and the size of void is much smaller than inclusion for all steels. Therefore, the void is not the fatigue orgin for bearing steels. By adopting the criterion of return period (T) at 200, a serial analysis shows that the relation between inclusion/void size and fatigue life for steels is inverse proportion except B steel. This results from that larger inclusion could not only initialize crack, but also increase the propagation path of crack and accelerate fracture.
Xiaoming Sang, Pengcheng Wang, Liqun Ai, Yungang Li and Jinglong Bu
C. C. Hsu and H. H. Chung, "Study on the Influence of Inclusion and Void on Fatigue Life of Bearing Steel Using Statistics of Extreme Values", Advanced Materials Research, Vols. 284-286, pp. 1258-1261, 2011