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Optical methods for measurement of fatigue crack closure: moiré interferometry and digital image correlation
Author(s) -
NOWELL D.,
PAYNTER R. J. H.,
DE MATOS P. F. P
Publication year - 2010
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.1460-2695.2010.01447.x
Subject(s) - digital image correlation , moiré pattern , interferometry , optics , materials science , closure (psychology) , phase (matter) , plane (geometry) , acoustics , structural engineering , physics , engineering , mathematics , geometry , economics , market economy , quantum mechanics
This paper describes three different optical techniques for the measurement of in‐plane displacements close to the crack tip which can then be used to determine the presence of crack closure in propagating fatigue cracks. Conventional temporal phase shifting moiré interferometry is described first, followed by an improvement to this technique, load sequence phase stepping, which allows data to be collected much more frequently during a load cycle. Finally, more recent measurements using digital image correlation are reported. Results from all three techniques are compared and the advantages and disadvantages of each approach are discussed.