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National Advisory Committee for Aeronautics, Technical Notes - Endurance and Other Properties at Low Temperatures

The low temperature endurance properties of materials for
aircraft construction are not well known. In order to deter—
mine them, apparatus for testing endurance at -éO°C has been
devised.

The endurance prOperties of monel metal, low—carbon stain-
less steel, "18 and 8, 3--% Hi steel, and ;chromium—molybdenum
steel have been determined- at -40°C and at room temperature
(about 20°C). "Tensile, impact and hardness tests of these ma-
terials have also been made at various temperatures.

The results show an increase in-endurance limit, tensile
strength, and hardness with decreased-temperature. Impact
lstrength is, in_ general, decreased, but of all the alloys
tested, only one, low-carbon stainless steel, gives less-than
'15 ft. lb. Gharpy impact test at —40C 0.
The metals subcommittee of the National Advisory Committee for
Aeronautics has observed various failures in airplane streamline
wire which were obviously due to corrosion fatigue.

The fractures started at corroded spots as nuclei,
these spots sometimes developing beneath the paint and giving no
visible sign of existence. An obvious_way of combating'corro-
Lsion—fatigue is the use of corroSion-resistant alloys. Several
corrosion—resistant alloys can be had with mechanical preperties
similar, as shown by the usual tests, to those of the'carbon
steel streamline wire, but a question arose as to whether their
low—temperature properties were such that they would withstand
the temperature likely to be met in aircraft service. As very
little information was found in the literature, it appeared
desirable to make direct tests of low temperature endurance
properties, and to supplement these with low temperature tests
of tensile strength, impact resistance, and hardness.