HIGH AND ULTRA ? HIGH CYCLE FATIGUE OF C55 HIGH GRADE CARBON STEEL

Article provides experimental results in the field of ultra-high cycle fatigue behaviour of C55 high grade carbon steel obtained at high-frequency loading (f ? 20 kHz, T = 20 ± 10 °C, R = -1). The results confirm a continuous decrease of fatigue lifetime beyond the conventional fatigue limit. Fatigue fracture surfaces were characterized by surface fatigue crack initiation in both high and ultra-high cycle region, what means that that influence of microstructure defects was not significant enough to cause the sub-surface crack initiation.