The double-repeated rotating bending fatigue tests of 18-8 austenitic steel were carried out at room temperature, 400°C, 500°C and 600°C.
The main conclusions arrived at are as follows.
(1) Remarkable surface temperature rise is measured during the fatigue tests of solution-treated 18-8 austenitic steel. Its behavior has the same tendency as that of the deflection of the specimens during the fatigue tests.
(2) Generally, cumulative cycle ratio Σ(
n/N) is larger than one when the secondary stress level σ
2 is higher than the primary stress level σ
1. However, the effect of stress sequence on Σ(
n/N) is not observed at 600°C, nor is it observed at any temperature when the cycle ratio of the primary stress level
n1/
N1 is 0.25.
(3) The relation between Σ(
n/N) and the surface temperature and deflection during the double-repeated fatigue tests are as follows. When σ
1<σ
2, the surface temperature and deflection under the secondary stress level σ
2 are smaller than those under the constant stress σ
2 of the same level. When σ
1>σ
2, the former is larger than the latter. When the stress sequence have not an effect on Σ(
n/N), the former is much the same as the latter.
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