Axial fatigue tests were carried out on tufftrided and non-tufftrided S15CK steel specimens. The main results obtained are summarized as follows.
(1) Tufftriding of steel specimens had obviously an effect of improving their fatigue strength under axial load, but the effect was not so pronounced as in the case of rotating bending fatigue tests which had been reported by many researchers.
(2) Large notch effect was observed on the tufftrided small size specimens having a diameter of 5mm, but for the large size specimens with a diameter of 25mm, notch effect was rather moderate.
(3) Among the tufftrided specimens, the plain specimens showed larger size effect than the notched specimens. And, among the notched specimens, the non-tufftrided specimens showed larger size effect than the tufftrided ones.
