Crack closure and residual stress effects in fatigue of a particle-reinforced metal matrix composite

Journal Article · Thu Apr 01 04:00:00 EST 1993 · Acta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-7151(93)90167-Q· OSTI ID:6237679

Knowles, D M; Downes, T J; King, J E ^[1]

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1. Dept. of Materials Science and Metallurgy, Cambridge (United Kingdom)

A study of the influence of macroscopic quenching stresses on long fatigue crack growth in a aluminum alloy--SiC composite has been made. Direct comparison between quenched plate, where high residual stresses are present, and quenched and stretched plate, where they have been eliminated, has highlighted their role in crack closure. Despite similar strength levels and identical crack growth mechanisms, the stretched composite displays faster crack growth rates over the complete range of [Delta]K, measured at R = 0.1, with threshold being displaced to a lower nominal [Delta]K value. Closure levels are dependent upon crack length, but are greater in the unstretched composite, due to the effect of surface compressive stresses acting to close the crack tip. These result in lower values of [Delta]K[sub eff] in the unstretched material, explaining the slower crack growth rates. Effective [Delta]K[sub th] values are measured at 1.7 MPa[radical]m, confirmed by constant K[sub max] testing. In the absence of residual stress, closure levels of approximately 2.5 MPa[radical]m are measured and this is attributed to a roughness mechanism.

• OSTI ID: 6237679
• Journal Information: Acta Metallurgica et Materialia; (United States), Journal Name: Acta Metallurgica et Materialia; (United States) Vol. 41:4; ISSN 0956-7151; ISSN AMATEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
ALLOYS
ALUMINIUM ALLOYS
CARBIDES
CARBON COMPOUNDS
COMPOSITE MATERIALS
CRACK PROPAGATION
FATIGUE
MATERIALS
MECHANICAL PROPERTIES
REINFORCED MATERIALS
SILICON CARBIDES
SILICON COMPOUNDS
STRESSES