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A FATIGUE CRACK CLOSURE MECHANISM IN TITANIUM
Author(s) -
WALKER N.,
BEEVERS C. 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.tb00372.x
Subject(s) - crack closure , materials science , crack tip opening displacement , stress intensity factor , crack growth resistance curve , wedge (geometry) , structural engineering , closure (psychology) , displacement (psychology) , composite material , mechanics , paris' law , stress concentration , intensity (physics) , fracture mechanics , mathematics , geometry , engineering , physics , optics , market economy , psychology , economics , psychotherapist
— Fatigue crack closure in commercial titanium has been investigated by examining the crack profile using a two‐stage replica technique and by monitoring the crack raouth opening displacement. The replicas show that when closure occurs the crack does not close back from the crack tip but at discrete contact points along the crack faces. The observed closure mechanism is therefore quite different from the generally accepted model. Assuming that the contact points wedge the crack open, the stress intensity at the minimum load is greater than expected and the range of the stress intensity is effectively reduced. Also, it was found that the crack growth rates measured in the range 0·05 ≦ R ≦ 0·7 showed a singular dependence on the parameter Δθ which for SEN specimens approximates to the change in angle subtended by the crack faces. It is therefore suggested that there is a direct link between Δθ and the effective stress intensity amplitude.