Scaling and universality in real cracks

Book · Sun Dec 01 04:00:00 EST 1996

OSTI ID:400639

Daguier, P; Bouchaud, E ^[1]

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1. O.N.E.R.A., Chatillon (France)

The morphology of fracture surfaces in complex metallic alloys is analyzed. The simultaneous use of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) allows the measurement of the universal roughness exponent {zeta}{sub {perpendicular}} = 0.78 over five decades of lengthscales (0.5 nm--0.5 mm). Furthermore, a small lengthscales regime (1 nm--11 {micro}m) is shown to be characterized by a roughness index {zeta}{sub {perpendicular}Qs} {approx_equal} 0.5. On the other hand, cracks fronts stopped during their propagation at pinning microstructural obstacles in two different metallic alloys is analyzed, and their in-plane roughness index is determined for the first time. In the case of the 8090 Al-Li alloy, which has a very anisotropic microstructure, the roughness of the tensile crack front propagating along the grains length is equal to {zeta} {approx_equal} 0.60. On the other hand, the roughness of the purely three-dimensional fatigue crack front in the Super{alpha}{sub 2} Ti{sub 3}Al-based alloy is equal to {zeta} {approx_equal} 0.54.

• OSTI ID: 400639
• Report Number(s): CONF-951155--; ISBN 1-55899-312-6
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CRACK PROPAGATION
EXPERIMENTAL DATA
FRACTURE MECHANICS
FRACTURE PROPERTIES
INTERMETALLIC COMPOUNDS
LITHIUM ALLOYS
MORPHOLOGY
NOTCHES
ROUGHNESS
SCANNING ELECTRON MICROSCOPY
STRESS INTENSITY FACTORS
SURFACES
TITANIUM ALLOYS