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In situ near‐tip normal strain evolution of a growing fatigue crack
Author(s) -
Zhu M.L.,
Lu Y.W.,
Lupton C.,
Tong J.
Publication year - 2016
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/ffe.12391
Subject(s) - materials science , perpendicular , crack closure , crack tip opening displacement , digital image correlation , tension (geology) , crack growth resistance curve , strain (injury) , compact tension specimen , composite material , in situ , structural engineering , plane stress , paris' law , plane (geometry) , fracture mechanics , geometry , finite element method , mathematics , ultimate tensile strength , engineering , chemistry , anatomy , medicine , organic chemistry
Normal strains near a growing fatigue crack have been studied in situ using the Digital Image Correlation technique in a compact tension specimen of stainless steel 316L under tension–tension cyclic loading. An error analysis of the measured displacements and strains has been carried out, and the results show that the precisions of displacements and strains in the direction perpendicular to the crack plane and ahead of the crack are better than those parallel to the crack plane and in the wake of the crack. The errors in the measured displacements are in the range of 0.06 to 0.1 µm and between 0.2% and 0.4% for the measured strains, the latter are well below the critical strain at the onset of crack growth about 8%. Strain ratchetting was found ahead of the growing fatigue crack tip, albeit very close to the crack tip.