Affiliation:
1. University of Toyama
2. AISIN Corporation
3. Nachi-Fujikoshi Corporation
4. Ritsumeikan University
Abstract
The fatigue life forming fine granular area (FGA) is expected to occupy a large fraction of the total fatigue life. In order to examine the commencing time of the FGA forming and estimate the fatigue limit in the interior inclusion induced fracture mode, rotating bending fatigue tests were carried out by using SUJ2 specimens with and without the hydrogen charge. Especially, the hydrogen charge time was set in the wide variety of the cyclic loadings to confirm the FGA forming process supposing the effect of the hydrogen charge on the fatigue crack propagation behavior. From experimental and analytical results, it is concluded that the FGA formation is already started at early stage as 5 % of the fatigue life. Another finding is that we have a clear correlation between the stress intensity factor range and the FGA growth ratio. Based on this aspect, the critical value of the stress intensity factor range in which the FGA is not formed around the inclusion was given as 2.65 MPa.
Publisher
Trans Tech Publications, Ltd.
Subject
Mechanical Engineering,Mechanics of Materials,General Materials Science
Reference23 articles.
1. T. Sakai, M. Takeda, K. Shiozawa, Y. Ochi, M. Nakajima, T. Nakamura and N. Oguma, Experimental evidence of duplex S-N characteristics in wide life region for high strength steels, Proceedings of the 7th international fatigue congress, 1 (1999).
2. K. Shiozawa, L. Lu and S. Ishihara, Subsurface fatigue crack initiation behavior and S-N curve characteristics in high carbon chromium bearing steel, Journal of the Society of Materials and Science, Japan, 48 (1999) 1095-1100.
3. H. Mughrabi, Zur dauerschwingfestigkeit im bereich extrem hoher bruchlastspielzahlen: mehrstufige lebensdauerkurven, Harterei-Technische Mitteilungen, 56 (2001) 300-303.
4. T. Sakai, Y. Sato and N. Oguma, Characteristic S-N properties of high-carbon-chromium-bearing steel under axial loading in long-life fatigue, Fatigue & Fracture of Engineering Materials & Structures, 25 (2002) 765-773.
5. Q. Y. Wang, C. Bathias, N. Kawagoishi and Q. Chen, Effect of inclusion on subsurface crack initiation and gigacycle fatigue strength, International Journal of Fatigue, 24 (2002) 1269-1274.