Introduction
Introduction Statistics Contact Development Disclaimer Help
NASA Technical Reports Server (NTRS) 20140001402: Crack Growth Beha...
by NASA Technical Reports Server (NTRS)
Thumbnail
Download
Web page
The research results described in this paper presents a
new understanding of the behavior of fatigue crack growth
in the threshold region. It is believed by some crack
growth experts that the ASTM load shedding test method
does not produce true or valid threshold properties. The
concern involves the observed fanning of threshold region
da/dN data plots for some materials in which the low R-
ratio data fans out or away from the high R-ratio data.
This data fanning or elevation of threshold values is
obviously caused by an increase in crack closure in the
low R-ratio tested specimens. This increase in crack
closure is assumed by some investigators to be caused by
a plastic wake on the crack surfaces that was created
during the load shedding test phase. This study shows
that the increase in crack closure is the result of an
extensive occurrence of crack bifurcation behavior in
some materials, particularly in aluminum alloys, when the
crack tip cyclic yield zone size becomes less than the
grain size of the alloy. This behavior is related to the
high stacking fault energy (SFE) property of aluminum
alloys which results in easier slip characteristics.
Therefore, the particular fanning behavior in aluminum
alloys is a function of intrinsic dislocation property of
the materials and that the fanned data represents valid
material properties. However, for corrosion sensitive
steel alloys used in this study the fanning was caused by
a build-up of iron oxide at the crack tip from fretting
corrosion.
Date Published: 2016-11-16 05:30:31
Identifier: NASA_NTRS_Archive_20140001402
Item Size: 367559
Language: english
Media Type: texts
# Topics
NASA Technical Reports Server (NTRS);...
# Collections
NASA_NTRS_Archive
additional_collections
# Uploaded by
@chris85
# Similar Items
View similar items
PHAROS
You are viewing proxied material from tilde.pink. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.