Abstract
Rotational bending fatigue tests for KSFA80,KSFA110 were carried out to clarify the property of fatigue strength of high tensile forged materials. Fatigue fracture occurred even though the repeated stress exceeded (10)^8 cycles, which started at interior non-metallic inclusion. Fatigue strength of the forged material shows anisotropy depending on the relative direction of specimen to forged grain flow, and it is shown that this anisotropy of fatigue strength is due to the projective size/shape of non-metallic inclusions at crack origin to a plain perpendicular to the maximum stress direction. Fatigue tests of shot peened specimens for KSFA110 were also carried out. The effect of shot peening process on improvement of fatigue strength are clarified.
