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CRACK FACE INTERACTIONS AND NEAR‐THRESHOLD FATIGUE CRACK GROWTH
Author(s) -
Tschegg E. K.,
Stanzl S. E.,
Mayer H. R.,
Czegley M.
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.tb00071.x
Subject(s) - materials science , crack closure , paris' law , composite material , fretting , crack growth resistance curve , cyclic stress , fracture (geology) , structural engineering , mode (computer interface) , fracture mechanics , computer science , engineering , operating system
Rough fracture surfaces usually influence substantially the fatigue growth properties of materials in the regime of low growth rates. Friction, abrasion, interlocking of fracture surface asperites and fretting debris reduce the applied load amplitude to a smaller effective value at the crack tip (“sliding crack closure”, or “crack surface interaction” or “crack surface interference”). The influence of these phenomena on the fatigue crack growth properties of structural steel is discussed and compared for the two kinds of mixed mode loading employed in this work. Mixed mode loading was performed by (A): cyclic mode III + superimposed static mode I and (B): cyclic mode I + superimposed static mode III loading. Such loading cases frequently occur in rotating load‐transmission devices. Several differences are typical for these two mixed‐mode loading cases. A superimposed static mode I load increases the crack propagation rate under cyclic mode III loading whereas cyclic mode I fatigue crack propagation is retarded when a static mode III load is superimposed. Increase of the R ‐ratio (of the cyclic mode III load) leads to an insignificant increase of fracture surface interaction and subsequently to a small decrease of the crack growth rate for cyclic mode III loading, whereas higher R ‐values during cyclic mode I+ superimposed static mode III loading lead to a significant reduction of the crack growth rates.