EFFECT OF VACUUM ON THE MECHANICAL BEHAVIOR OF METALS.
Final rept., 1 Oct 64-1 Oct 65,
MARTIN CO BALTIMORE MD
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The fatigue life of Aluminum 1100 has been studied as a function of pressure, stress, frequency, and temperature. The data indicate that the amount of fatigue improvement and the frequency effect observed in vacuum decrease with increasing stress amplitude. The results of resonant frequency measurements, showing the correlation of the fatigue improvement and the frequency effect with the rate of change in the resonant frequency, suggest a possible new method to detect the rate of damage formation for fatigue studies. Iron has been used for studying the various effects of vacuum on BCC metals. Results reveal that vacuum has greater effect on the fatigue life of iron than on the fatigue life of aliminum. As for the tensile studies, the stress-strain curves of iron and recrystallized molybdenum wire specimens have been studied in vacuum. It is found that in the case of iron, only the stress at the Luders band region is subject to the effect of vacuum. However, the amount of change is dependent on the strain rate. When a very slow strain rate, 9 x 10 to the minus 7th powersec, is used, the decrease may amount to as much as 1200 psi. The effects of vacuum on the ultimate tensile stress and the total elongation of molybdenum at high temperatures are attributed to a decrease in the rate of oxidation. Author
- Metallurgy and Metallography