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THE EFFECT OF ARTIFICIAL FATIGUE‐CRACK CLOSURE ON FATIGUE‐CRACK GROWTH
Author(s) -
UrRehman A.,
Thomason P. F.
Publication year - 1993
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.1460-2695.1993.tb00079.x
Subject(s) - crack closure , materials science , wedge (geometry) , paris' law , composite material , crack growth resistance curve , crack tip opening displacement , stress intensity factor , stress concentration , fracture mechanics , mathematics , geometry
Abstract An investigation of the effects of artificial fatigue‐crack closure on the subsequent growth of fatigue cracks, at constant range of stress‐intensity factor, was carried out for the following closure materials: (i) electroplated nickel; (ii) electroless nickel; (iii) ethylcyanoacrylate (ECA) adhesive; (iv) low‐melting point (LMP) solder. It was observed that (a) the wedge thickness and area of crack surface covered by the artificial‐closure material and (b) the distance of the tip of the closure wedge from the crack tip (i.e. the penetration of the closure material towards the crack tip) were the main parameters controlling the reduction in the subsequent growth rate of the fatigue crack. The results suggest that if the crack thickness (opening) is completely filled with a dense wedge of artificial‐closure material, the wedge becomes effectively rigid and the precise mechanical properties of the closure material will have only a secondary influence on subsequent fatigue‐crack growth in comparison to (a) and (b) above. This follows from the fact that the closure material is effectively a very thin strip compressed between the rough (high friction) sides of a crack. A rigid‐wedge and elastic‐crack model was found to successfully predict the changes in fatigue‐crack growth rate following artificial crack‐closure and gave a lower bound to the measured growth rates.