Crack growth process in GBF area of SUJ2 bearing steel in very high cycle fatigue regime

Author： Li Y D Guo W M Xu N Wu X F Shi J B Ma H

ISSN： 1743-2847

Source： Materials Science and Technology, Vol.29, Iss.12, 2013-12, pp. : 1463-1469

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Abstract

The crack growth process in GBF of high strength bearing steel JIS SUJ2 is qualitatively investigated by low-high two-step variable amplitude loading (TSAL) tests. It is demonstrated that the GBF size reduces with the increase in applied stress amplitude, and that the GBF size at a given stress amplitude is a constant which is independent of inclusion size at the crack origin. The fatigue life at a given stress amplitude, which is proportional to −8 power of the inclusion size, reduces with increasing inclusion size. It was shown by TSAL tests that GBF was formed at the earlier stage (approximate 10⁵ cycles corresponding to less than 1% total fatigue life in the regime N_f≧10⁷ cycles) and propagated hardly until near to the final life (more than 90% total fatigue life). After that the GBF crack will propagate rapidly to the ultimate size in a short time.