The growth of small corrosion fatigue cracks in alloy 2024

Technical Report · Thu Apr 01 04:00:00 EST 1993

OSTI ID:5995268

Piascik, R S; Willard, S A

The corrosion fatigue crack growth characteristics of small surface and corner cracks in aluminum alloy 2024 is established. The damaging effect of salt water on the early stages of small crack growth is characterized by crack initiation at constituent particle pits, intergranular microcracking for a less than 100 micrometers, and transgranular small crack growth for a micrometer. In aqueous 1 percent NaCl and at a constant anodic potential of -700 mV(sub SCE), small cracks exhibit a factor of three increase in fatigue crack growth rates compared to laboratory air. Small cracks exhibit accelerated corrosion fatigue crack growth rates at low levels of delta-K (less than 1 MPa square root of m) below long crack delta-K (sub th). When exposed to Paris regime levels of crack tip stress intensity, small corrosion fatigue cracks exhibit growth rates similar to that observed for long cracks. Results suggest that crack closure effects influence the corrosion fatigue crack growth rates of small cracks (a less than or equal to 100 micrometers). This is evidenced by similar small and long crack growth behavior at various levels of R. Contrary to the corrosion fatigue characteristics of small cracks in high strength steels, no pronounced chemical crack length effect is observed for Al by 2024 exposed to salt water.

• Research Organization: National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center
• OSTI ID: 5995268
• Report Number(s): N-93-29069; NASA-TM--107755; NAS--1.15:107755; CNN: RTOP 538-02-10-01
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALKALI METAL COMPOUNDS
ALLOYS
ALUMINIUM ALLOYS
AQUEOUS SOLUTIONS
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
CORROSION
CORROSION FATIGUE
CRACK PROPAGATION
DISPERSIONS
ELECTROCHEMICAL CORROSION
FATIGUE
FRACTURE MECHANICS
HALIDES
HALOGEN COMPOUNDS
MECHANICAL PROPERTIES
MECHANICS
MIXTURES
SODIUM CHLORIDES
SODIUM COMPOUNDS
SOLUTIONS
STRESS INTENSITY FACTORS