Abstract
Rotating bending fatigue tests were performed for SUS 304 stainless steel, which had various grain sizes. The fatigue limit of a plain specimen is much higher than the 0.2% proof stress, and the increase in the fatigue limit caused by the coaxing effect amounts to about 40% of that in the test under the condition of constant stress amplitude. The strain measured by using a slip ring shows that these results are due to a marked hardening produced during cyclic stressing. A non-propagating fatigue crack forms only at the elevated temperature in a notched specimen. The maximum depth of that crack is about 600μm independently of grain size. According to a detailed examination by the scanning electron microscope, a great number of carbide precipitates get together preferentially around the non-propagating fatigue crack. From this it is suggested that the formation of the non-propagating fatigue crack might be greatly controlled by such a metallurgical factor as well as a mechanical one.
