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CRACK CLOSURE IN SMALL FATIGUE CRACKS—A COMPARISON OF FINITE ELEMENT PREDICTIONS WITH IN‐SITU SCANNING ELECTRON MICROSCOPE MEASUREMENTS
Author(s) -
Zhang J. Z.,
Halliday M. D.,
Poole P.,
Bowen P.
Publication year - 1997
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.1460-2695.1997.tb01487.x
Subject(s) - materials science , crack closure , finite element method , scanning electron microscope , composite material , paris' law , crack growth resistance curve , plasticity , crack tip opening displacement , stress concentration , aluminium , structural engineering , fracture mechanics , engineering
— A three dimensional, elastic‐plastic, finite element analysis of fatigue crack growth and plasticity‐induced crack closure has been performed for a range of small, semi‐circular cracks. Predicted crack opening displacements have been compared with data obtained from in‐situ SEM measurements for a coarse‐grained aluminium alloy 2024‐T351. The magnitude of fatigue crack closure measured from in‐situ SEM measurements was consistently higher than that predicted from the finite element analysis. It is deduced that the higher closure stresses obtained from in‐situ SEM measurements are due to the contact of asperities on the fatigue crack surfaces. A simple mathematical model is suggested to describe the fatigue crack closure stress caused by the combination of both a plastic wake and asperities on the fatigue crack surfaces. The predicted fatigue crack closure stresses and their dependence on crack size are consistent with experimental measurement.