Corrosion Fatigue Crack Growth in Aircraft Structural Materials

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Report Number: AFML TR 73-204
Author(s): Hall, L. R., Finger; R. W., Spurr, W. F.
Corporate Author(s): Boeing Aerospace Company
Laboratory: Air Force Materials Laboratory
Date of Publication: 1973-09
Pages: 178
Contract: AF 33615-71-C-1687
DoD Task:
Identifier: AD0916695

This experimental program was undertaken to obtain information on stress corrosion cracking and corrosion fatigue crack growth in high strength metal alloys suitable for airframe components. In addition, tests were conducted to evaluate the effects of overloads and metallurgical factors on corrosion fatigue crack growth. The test program involved five alloys and seven test media. The four principal alloys were: 7075-T651 Aluminum, 6Al-4V(ELI) Beta annealed (Beta A) Titanium, 6Al-4V recrystallize Annealed (RA) titanium, and 9Ni-4Co-0.3C Steel (220-240 ksi); in addition the 7475-T651 alloy was subjected to a limited number of tests. All alloys were tested in the form of hot rolled plate. Test media included: desiccated air, water saturated JP-4 fuel, distilled water, 3.5% NaCl solution, sump tank water, alternating JP-4 fuel and distilled water, and dye penetrant (type ZL-2A). Most tests were conducted at 72F with a few tests being performed at +175F and -65F. Double cantilever beam specimens were used for all tests with the exception of a limited number of surface-flawed specimen tests. Corrosion fatigue tests were conducted using two cyclic frequencies (6 and 60 cpm) and three ratios of minimum to maximum stress (0.1, 0.5 and 0.8). Overload effects were investigated by testing 7075-T651 Aluminum, Ti-6Al-4V and Ti-6Al-4V RA tapered double cantilever beam specimens in both desiccated air and 3.5% NaCl solution. Finally, a series of tests was undertaken to evaluate the effects on SCC and corrosion fatigue cracking of variations in metallurgical characteristics imparted to Ti-6Al-4V RA alloy plate by various thermal cycles.

Provenance: Bombardier/Aero

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