SEDL / STP / STP1298-EB / STP19954S

Corrosion-Fatigue Crack Nucleation in Alclad 2024-T3 Commercial Aircraft Skin

Schmidt, CG
Senior materials scientist, program manager, materials scientist, and associate laboratory director, SRI International, Menlo Park, CA

Crocker, JE
graduate student, University of Connecticut, Storrs, CT

Giovanola, JH
Senior materials scientist, program manager, materials scientist, and associate laboratory director, SRI International, Menlo Park, CA

Kanazawa, CH
Senior materials scientist, program manager, materials scientist, and associate laboratory director, SRI International, Menlo Park, CA

Shockey, DA
Senior materials scientist, program manager, materials scientist, and associate laboratory director, SRI International, Menlo Park, CA

Flournoy, TH
Program monitor, FAA Technical Center, Atlantic City, NJ

Pages: 15    Published: Jan 1997

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Abstract

The processes that influence the transition from corrosion pit to crack formation in Alclad 2024-T3 under cyclic loads in aqueous environments were examined in laboratory experiments in salt water. Results suggest that the nucleation of corrosion-fatigue cracks involves two competing mechanisms: hydrogen effects in the cladding and electrochemical dissolution at constituent particles in the core alloy. Cracks in the clad did not necessarily nucleate at the largest corrosion pit, suggesting that a contributing factor to crack nucleation from a pit may be the creation of a local region of weakness. This paper presents results from experiments to assess the effects of pH and cladding on the nucleation and propagation of corrosion-fatigue cracks.