13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- Between each profile, 400 cycles are performed. The red line on the figure 3 is the location where the temperature is maximum along the profile. Before 3.2086x107 cycles, it was not possible to determine a location where the temperature was maximum along the profile. For this test, the crack initiation site appeared on the left side of the specimen (on the left side of the figure 3). The locations of the points 1/2,3,4,5,6 where the maximum temperature rapidly increases were determined. From the specimen corner, the locations of the different points are : points 1 et 2 at 267 μm, point 3 at 933 μm, point 4 at 1200 μm, point 5 at 1600 μm, point 6 at 2000μm. The corresponding numbers of cycles are : N1 (point 1) at 3.2086 x10 7 cycles, N2 (point 2) at 3.2148x10 7 cycles, N3 (point 3) at 3.2149x10 7 cycles, N4 (point 4) at 3.2151x10 7 cycles, N5 (point 5) at 3.2152x107 cycles, N2 (point 2) at 3.2153x10 7 cycles and the number of cycles at fracture Nf to 3.2155x107 cycles. During the end of this test, the maximum temperature location moves from the left to the right of the specimen width in agreement with the increase of the fatigue crack length and the increase of the plastic zone ahead the fatigue crack tip. 4.2. Fractographic results The fracture surface and the polished specimen surface (where the temperature was recorded) were observed under Scanning Electron Microscope (Figure 4a and b). Until the point 5, the fracture surface is flat and correspond to the plane strain fatigue crack. Between the point 5 and 6, the fracture surface presents shear lips. Figure 4a and b: SEM observations of the whole fracture and polished surface a) 5 3 4 6 b) 1
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