The existance of an endurance limit generally correlates with the linearity of the stress-strain curves and a sharply defined yield point. (Juvinall[1], p.˙201; Grosskreutz[1], p.˙42) If this is the case, then most aluminums should not have a fatigue limit. However, Maennig[1] indicates (p.˙614) that the high-strength age-hardening aluminum alloys may have a true fatigue limit (at conventional test frequencies) at 1011 to 1013 cycles (i.e., 1400 hours to 140,000 hours at 20 kHz) for stresses of about 20 MPa (2900 lbf/in2).

Lesuer, Donald - 'Experimental Investigations of Material Models for Ti-6Al-4V Titanium and 2024-T3 Aluminum' (high strain rate tests)
	Fig 2 shows anisotropic 2D etched microstructure of 2024-T3.


Figure˙2 from Juvinall[1] (p.˙335) shows that the fatigue strength of various aluminum alloys increases as the ultimate tensile strength increases up to about 340˙MPa [50˙kpsi]. --> how many cycles?

Juvinall shows fatigue graphs for 2024 (p. 272) & 7075 (p. 273) up to 10^9 cycles.

Boyer (p. 335) notes that 2024 is better under fluctuating stress. Note: ultrasonic startup & decay - considered fluctuating?

Should include hatch_p376__grain_directionality_in_rolled_al7075t6_1c.png?

Effect of temperature on modulus -
	See my black 3-ring binder, tab M --> cubic regression equation

-------------- To do --------------
4/Dec/2017 11:48
	Include data for Culp Poisson tests on large dia spool horns
	
20/Nov/2017 18:02
	Look for Al in Ogden fatigue book.

3/22/2015
- Replace all refs to "Aerospace" aluminum.