Spectrum Fatigue Behaviour of Powder Metallurgy Aluminum Alloys.

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Abstract:

The fatigue crack growth behavior of three aluminum alloys was examined under constant amplitude and spectrum loading. The fatigue behavior of extrusions and hand forgings of second-generation powder metallurgy PM alloy CW67 X7093 was compared to the fatigue behavior of extrusions of 7091 a first-generation PM alloy and 7075 an ingot metallurgy alloy. Spectrum fatigue crack growth tests were performed using the FALSTAFF fighter spectrum as well as an actual fighter aircraft spectrum. Additionally, overloadunderload fatigue crack growth tests were performed to correlate the constant amplitude and spectrum fatigue behaviors. For these tests, overload-induced crack jumps and crack growth retardation were measured. Tensile properties, fracture toughness, stress-life fatigue, and stress corrosion cracking were also evaluated. For the spectrum fatigue tests in particular, the crack growth behavior was correlated to the microstructure and fractography. In summary, the fine-grained PM alloys exhibited significantly higher strengths, toughness, and stress -life fatigue resistance than 7075, but markedly lower constant amplitude fatigue crack growth resistance. Under a tension-dominated FALSTAFF spectrum, PM alloys were generally inferior in crack growth resistance compared to IM alloys, which is consistent with constant amplitude fatigue behavior. However, in spectrums having more compressive loads, Fatigue, Fatigue Crack Growth, Spectrum Fatigue, Overload, FALSTAFF, Powder Metallurgy, Aluminum Alloys, CW67, X7093, 7091, 7075, Stress Corrosion, Fractography.

Author(s):
Searich, G. V. ; Hahn, M. T.
Author Organization(s):
NORTHROP CORP HAWTHORNE CA AIRCRAFT DIV
Descriptive Note:
Final rept. Sept 85-Mar 91,
Pagination:
0275

Security Markings

DOCUMENT & CONTEXTUAL SUMMARY

Distribution:
Approved For Public Release

RECORD

Collection: TR
Identifying Numbers
Report Number(s):
NOR-91-49, WL*-TR-91-4064
Contract/Grant Number(s):
F33615-C-5041
Task Number(s):
01
Project Number(s):
2418
Monitor Series:
TR-91-4064, WL*
 Subject Terms
Joint Capability Areas:
JCA_6.3.3_Spectrum Management; JCA_6.3_Net Management; JCA_6_Net Centric
Communities of Interest:
Air Platforms
Descriptor(s):
*ALUMINUM ALLOYS, *POWDER METALLURGY, *FATIGUE(MECHANICS), AIRCRAFT, ALLOYS, ALUMINUM, AMPLITUDE, BEHAVIOR, CONSTANTS, CORROSION, CRACKS, EXTRUSION, FIGHTER AIRCRAFT, FINES, FORGING, FRACTOGRAPHY, METALLURGY, MICROSTRUCTURE, OVERLOAD, POWDERS, RESISTANCE, RETARDATION, STRESS CORROSION, TENSILE PROPERTIES, TENSION, TEST AND EVALUATION, TOUGHNESS, CRACK PROPAGATION, STRENGTH(MECHANICS), SPECTRA
Field(s)/Group(s):
Properties of Metals and Alloys, Fabrication Metallurgy, Aircraft
Keyword(s):
Compressive loads, Compressive strength, PE62102F, WUWL24180140
Report Date:
1991 Oct 01