Is fatigue surface roughness a sufficient condition for the generation of crack closure?

Journal Article · Sun Dec 01 04:00:00 EST 1996 · Scripta Materialia

DOI:https://doi.org/10.1016/1359-6462(96)00299-0· OSTI ID:413269

Fitzpatrick, M E; Bhattacharjee, D; Daykin, C R.S. ^[1]; Cree, A M ^[2]

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1. Univ. of Cambridge (United Kingdom). Dept. of Materials Science and Metallurgy
2. Open Univ., Milton Keynes (United Kingdom)

In metallic materials, it is well-established that a fatigue crack can be closed at a point behind the crack tip even when an opening load is applied at low stress ratios where the sample is almost unloaded at K{sub min} during the fatigue cycle. It is the authors contention that roughness-induced closure, particularly during stage 2, Paris-regime, fatigue crack growth, cannot arise simply from elastic displacements of the crack faces, and that an additional condition is needed in order for crack face contact to occur. This condition is essentially that there must be a residual displacement of material in the crack wake: this may be due to plasticity, formation of an oxide layer, or relaxation of residual stress. Surface roughness will not itself lead to crack face contact above zero load. This is supported by results obtained from aluminium alloy samples, where an increase in crack path tortuosity (which would be expected, from simple considerations, to produce higher levels of roughness-induced closure) is seen to correspond with a decrease in the levels of crack closure.

• OSTI ID: 413269
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 11 Vol. 35; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CRACK PROPAGATION
CRACKS
FATIGUE
FRACTURE MECHANICS
FRACTURE PROPERTIES
OXIDES
PLASTICITY
STRESS RELAXATION
STRESSES