ARC-CP-460
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- July 15, 2016 Create Date
- July 15, 2016 Last Updated
Fatigue Tests on Notched Extruded Aluminum Alloy (DTD 364B) having a Theoretical Stress Concentration Factor of 3.65
In aircraft structures the effective stress concentration factor often
exceeds a value of 3.0. Insufficient information has existed for making
design fatigue estimates for stress concentration factors of this order,
particularly for various mean stresses such as may occur in wing spars. The
present limited progranne of tests was arranged with a view to providing a
basis for such calculations.
Fatigue tests in axial tension were made on flat bars in material to 2
DTD 3648 (see Appendix) for a range of mean stress from 8000 to 18,000 Ib/in. .
The bars had notches machined on each side at the central cross section, giving
a theoretical stress concentration factor of 3.65. For practical testing
reaSOns, the mean stress always exceeded the alternating stress; thus the case
of zero mean stress was not covered.
For estimating the appropriate notch sensitivity index, a 'machined
finish’ datum for similar material was taken from tests1 on machined bars for
various mean stresses and an isolated value for a highly polished bar test2
made by Vickers Armstrong (Weybridge). From the present tests a value for the
notch sensitivity index, Kf———T , was found which is compared with that deduced
from tests1 (also by Vickers Armstrong) on round bars with unloaded holes
(Kt = 2.65) having a somewhat greater notch radius.
| File | Action |
|---|---|
| ARC-CP-460 Fatigue Tests on Notched Extruded Aluminum Alloy (DTD 364B) having a Theoretical Stress Concentration Factor of 3.65.pdf | Download |
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