Abstract
In the present study the torsion fatigue behavior of SUS 630 steel has been investigated by conducting torsion fatigue test using servo hydraulic torsion fatigue testing machine at 20 Hz frequency. The shape of surface crack under torsion loading conditions has been studied by using replica technique and crack nucleation mechanisms were studied by examining fracture surface using scanning electron microscope. The results showed that the crack nucleation mechanism changes as the number of cycles to failure moved from low cycle to high cycle regime.
