Investigation of Small Crack Fatigue Propagation in 16 MnR Steel

The process of small crack low cycle fatigue propagation was investigated with 16 MnR low carbon manganese steel. Experiments were carried out with bar specimens which contain small surface holes of different diameter. The effect of original defect size on the fatigue life can be described with the fourth root of the defect area perpendicular to the loading direction. The relation between the formula of crack propagating rates and Manson-Coffin equation has been discussed.