Significance of the small crack growth law and its practical application |
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Authors: | N Kawagoishi Q Chen H Nisitani |
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Affiliation: | (1) the Faculty of Engineering, Kagoshima University, 890-0065 Kagoshima, Japan;(2) the Faculty of Engineering, Kyushu Sangyo University, 813-8503 Fukuoka, Japan |
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Abstract: | The effects of microstructure and specimen size on the fatigue crack growth rate of an annealed 0.42 C steel were investigated
under uniaxial fatigue loading in air. Although a dramatic fluctuation of crack growth rate was found in the propagation process
of microstructurally small cracks, the mean value of crack growth rate can be evaluated by a simple mechanical parameter,
σ
a
n
l (l, crack length; n, constant), under high stress levels where small-scale yielding conditions are exceeded. This parameter is also effective
for cracks larger than 1 to 2 mm under high stress levels, as long as the finite boundary effect of a specimen on the driving
force of crack propagation is considered. The crack growth rate of the alloy was described as a function of stress amplitude
and crack length in terms of two mechanical parameters, σ
a
n
l and ΔK. The applicable conditions of the two parameters were discussed and manifested. |
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Keywords: | |
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