13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- 200 400 600 800 1000 1200 1400 1600 1 10 100 1000 10000 Cycles to fracture N (x10 3 ) Rupture Stress σa (MPa) PH-42 Supra steel plasma nitrided no rupture (nitrided) PH-42 Supra steel non-nitrided no rupture (non-nitrided) Figure 5. Stress versus number of cylces N to fracture curves for rotating bending fatigue test for PH-42 Supra steel non-nitrided and plasma nitrided with layer of 0.3mm. Fatigue limit is for N=106 cycles. In Fig. 6, some fractured non-nitrided specimens after the rotating bending fatigue tests can be observed which fracture site is similar to the plasma nitrided specimens. Figure 6. Photo of three non-nitrided specimens after the fatigue test. 3.3. Tensile Tests Tensile tests were also performed, using the same fatigue test specimens of PH-42 Supra steel plasma nitrided with nitriding layer of 0.3mm and non-nitrided as seen in Fig. 2. The ultimate tensile strength values are shown in Table 6.
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