Open Access
ARTICLE
Correlation of Crack Initiation Parameters with Life Estimation for Very-High-Cycle Fatigue of High Strength Steels
Chengqi Sun1, Aiguo Zhao1, Youshi Hong1,2
1 LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China
2 Correspondence author. E-mail: hongys@imech.ac.cn
Structural Longevity 2009, 2(3), 157-168. https://doi.org/10.3970/sl.2009.002.157
Abstract
The researches on the behavior of very-high-cycle fatigue (VHCF) for
high strength steels have become a new branch in the field of metal fatigue since
1980s. The characteristics of crack initiation and propagation for high strength
steels in VHCF regime differ from those in low cycle regime. One of the most
distinct phenomena for VHCF regime is the interior or subsurface crack initiation
at inclusions or at other inhomogeneities. This paper attempts to further investigate
the crack initiation with the morphology of so-called fish-eye and fine granular
area (FGA) or optical dark area (ODA) for high strength steels. Fatigue tests were
carried out on a high carbon low alloy steel by using rotating bending (52.5 Hz)
and ultrasonic push-pull (20 kHz) machines and the fatigue fracture surfaces were
examined by scanning electron microscopy. The present results showed the data
of the stress intensity factor range (SIF) as a function of the dimension for FGA.
Based on the present results and the ones from literature, two models are developed.
One is to estimate the threshold value for FGA by taking into account the size of
plastic zone at crack tip in relation with the value of SIF at FGA, and the other is
to estimate the fatigue life by considering the fatigue damage cumulative process
in relation with the microscopic parameters (inclusion size and FGA size) at the
fracture region along with macroscopic quantities (tensile strength and stress level).
The estimations are in good agreement with experimental results.
Keywords
Cite This Article
Sun, C., Zhao, A., Hong, Y. (2009). Correlation of Crack Initiation Parameters with Life Estimation for Very-High-Cycle Fatigue of High Strength Steels.
Structural Longevity, 2(3), 157–168. https://doi.org/10.3970/sl.2009.002.157