2009 | OriginalPaper | Chapter
Assessing the Development of Fatigue Cracks: From Griffith Fundamentals to the Latest Applications in Fracture Mechanics
Author : Donka Angelova
Published in: Security and Reliability of Damaged Structures and Defective Materials
Publisher: Springer Netherlands
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Engineering analysis of fatigue crack growth depend on different loading conditions, wherever those conditions have been studied, in laboratory or real-world practice. Such analyses can be done on basis of different parameters: the stress intensity factor range, ֵ
K
, introduced in linear elastic fracture mechanics; the
J
-integral range, ֵ
J
, employed in elastic-plastic material characterization; the square-root area parameter of Murakami, effective in the presence of small defects and non-metallic inclusions. An alternative presentation of fatigue data has been proposed that uses the crack growth rate against a newly introduced parameter, namely an energy fatigue-function ֵ
W
based at different conditions on different parameters, ֵ
K
or ֵ
J
or the square-root area parameter of Murakami. This alternative presentation shows fatigue data as forming an almost straight line, which may be termed the “natural fatigue tendency” of a material, and specified more precisely at a given stress range. Also the present study introduces a physical interpretation of the line presentation of fatigue data and some illustrations of the “natural fatigue tendency” for different materials under different conditions.