Abstract
in succession to the preceding optical microscope study, electron microscope and x-ray diffraction studies are carried out on the ultrasonic-fatigue of metals. In iron fatigued at an ultrasonic frequency, slip markings could not be observed on the whole even at high magnification (×3500), except rare occasions. This is in contrast with the feature of the specimen-surface formed by the conventional fatigue, in which ample slip bands with many microcracks appear. The mode of crack propagation in both cases, however, was not distinguishable by electron fractography. On the other hand, this observation ascertained that the surface appearance of copper-specimens fatigued by a stress cycle of the ultrasonic frequency was similar to that of the conventional fatigue. X-ray diffraction study showed that fragmentation of grains scarcely occurred in such a high frequency fatigue tests on iron.
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