Fatigue Strength of Low Carbon Steel Plate with a Sharp Notch and a Precrack under Plane Bending at Elevated Temperatures

Abstract

The effect of the rapid strain aging during fatigues stressing at 350 ∼400 °C on the fatigue strength of a low carbon steel plate was examined. The fatigue tests were made in plane bending at room temperature, 200°C, 375°C and 450°C. Both of the endurance limits of the sharp notched specimen, that is, the critical stress required for crack initiation and that required for crack propagation reached a maximum at 375°C and a minimum at 200°C. The threshold stress intensity factor range of a precracked specimen also reached a maximum at 375°C. The number of cycles to crack initiation and that to fracture at higher stress than the endurance limit showed the same temperature dependence as described above. The rapid strain aging at the peaking temperature is more effective inhibiting the crack propagation than the crack initiation.