ISSN: 1945-7553
CODEN: JTEVAB
Published Online: 22 January 2013
Page Count: 6

Method for Assessing Applicability of an Artificial Flaw as a Small Initial Crack for Fatigue Limit Evaluation and Its Application to a Drill Hole and an FIB Processed Sharp Notch in Annealed 0.45% Carbon Steel

Sakamoto, Junji
Dept. of Mechanical Engineering Science, Graduate School of Engineering, Kyushu Univ., Nishi-ku, Fukuoka

Takahashi, Yoshimasa
Dept. of Mechanical Engineering, Kansai Univ., Suita-shi, Osaka

Aono, Yuuta
Dept. of Mechanical Engineering, Faculty of Engineering, Kyushu Univ., Nishi-ku, Fukuoka

Noguchi, Hiroshi
Dept. of Mechanical Engineering, Faculty of Engineering, Kyushu Univ., Nishi-ku, Fukuoka

(Received 19 May 2012; accepted 22 August 2012)

Abstract

In this study, we propose a method for assessing the applicability of an artificial flaw as a small initial crack for fatigue limit evaluation. The proposed method is applied to drill holes and sharp notches introduced using a focused ion beam (FIB) technique in annealed 0.45% carbon steel. It is found that under rotating bending fatigue, an FIB notch can be used as a small initial crack for fatigue limit evaluation, whereas a drill hole cannot, for √area of ∼50 μm. Here, √area is the square root of the area obtained by projecting the defect onto a plane perpendicular to the load axial direction. The results indicate that an FIB notch can be used as a small initial crack for fatigue limit evaluation in a greater number of materials than those in which a drill hole can be used.

Keywords:
metal fatigue, fatigue limit, fatigue crack growth, focused ion beam, small initial crack, non-propagating crack

Paper ID: JTE20120176
DOI: 10.1520/JTE20120176
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