Open Access
ARTICLE
N. Yan1, N. Kawagoishi2, Y. Maeda3, Q. Chen4
Structural Longevity, Vol.2, No.3, pp. 139-146, 2009, DOI:10.3970/sl.2009.002.139
Abstract Fatigue tests under rotating bending and ultrasonic loading were carried out using plain specimens with different grain sizes of Ni-base super alloy, Inconel 718, in order to investigate the effects of grain size and loading frequency on
fatigue properties. Fatigue strength was increased with decreasing in grain size under both tests. Moreover, the fatigue strength under ultrasonic loading was higher
than that under rotating bending. The resistance to crack initiation was larger in
smaller grain sized alloy under both tests, and larger under ultrasonic loading than
under rotating bending. Effects of loading frequency and grain size on crack initiation were… More >
Open Access
ARTICLE
Y. Furuya1
Structural Longevity, Vol.2, No.3, pp. 147-156, 2009, DOI:10.3970/sl.2009.002.147
Abstract This paper introduces results of researches on gigacycle fatigue using ultrasonic fatigue testing in NIMS. The first step was investigations of validity of the ultrasonic fatigue testing. As the result, the validity was conformed on
conditions where fish-eye fracture occurred. The second step was additional developments on the ultrasonic fatigue testing, such as superimposing mean stress,
enlargement of specimens and so on. This step elucidated the mean stress effects
and size effects on the fish-eye fracture properties. More >
Open Access
ARTICLE
Chengqi Sun1, Aiguo Zhao1, Youshi Hong1,2
Structural Longevity, Vol.2, No.3, pp. 157-168, 2009, DOI: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… More >
Open Access
ARTICLE
Y.J. Liu1, Q.L. Ouyang2, R.H. Tian3, Q.Y. Wang4
Structural Longevity, Vol.2, No.3, pp. 169-175, 2009, DOI:10.3970/sl.2009.002.169
Abstract Fatigue properties of Ti-6Al-4V subjected to simulated body fluid (SBF)
environment were presented in this paper. Using the ultrasonic fatigue testing technique, the ultra-high cycle fatigue properties of Ti-6Al-4V alloy subjection to SBF
in two groups for two days and six days respectively in body temperature were
studied and the initiation mechanisms of fatigue cracks were investigated and analyzed with scanning electron microscopy (SEM) and energy dispersive atomic
X-ray (EDX). Then, a comparison with corresponding behaviors of the Ti-6Al-4V
alloy with no treatment was made. The results show that, the S-N curves of the Ti-
6Al-4V alloy after subjection have… More >
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