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DETERMINATION OF FATIGUE CRACK INITIATION LIFE
Author(s) -
IBRAHIM M. F. E.,
MILLER K. J.
Publication year - 1979
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.1979.tb01093.x
Subject(s) - materials science , crack closure , crack growth resistance curve , fracture mechanics , composite material , structural engineering , strain (injury) , stress concentration , shear (geology) , grain size , plasticity , engineering , medicine
— A reanalysis has been carried out on the results of Zachariah. An elastic‐plastic analysis based on S‐N data indicates that the mechanism of growth of very small cracks is similar to that expressed by linear elastic fracture mechanics, i.e. crack growth in mild steel is given bywhere Δγ p is the plastic shear strain range and a is the crack length. Crack initiation occurs within a single grain and crack propagation is given by the above equation for cracks which can be smaller than a few microns. The size of an initiated crack is a function of stress level varying from 0·1–1·0 μm in the high strain fatigue regime to 2·3 μm close to the fatigue limit. The period of crack initiation is negligible in the HSF regime whilst the initiation period can dominate lifetime at low stress levels.