Digital Repository, ICF12, Ottawa 2009

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In-situ fatigue test of A36-steel
K. Yamagiwa, D. W. Hoeppner

Last modified: 2013-05-03


Estimating the stress and crack propagation speed from a fatigue fracture surface is an important
element of failure analysis[1,2]. In Japan, the result of failure analysis have even come to be used
in court case. For example, an illegal inspection can sometimes be revealed by examining the
relationship between the inspection date and the crack length, which is estimated according to
the relationship between the striation width and the number of cycles.
However, in such analyses, the macroscopic crack propagation speed is assumed to be equal to
the microscopic one. Although this assumption comes into effect at stage II (b,c) or stage III of
Paris' law, it doesn't do so at stages I and II (a). Therefore, the estimation of the crack
propagation speed from a fatigue fracture surface, which is made in the early stages of fatigue
crack, is difficult.

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