PSI - Issue 2_A

M. Benedetti et al. / Procedia Structural Integrity 2 (2016) 3158–3167 M.Benedetti et al./ Structural Integrity Procedia 00 (2016) 000–000

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observed in the high-cycle fatigue regime makes the as-built structure more sensitive to defects in the high-cycle fatigue regime. In Fig.11 to 14 are shown the most meaningful fracture surfaces of part of the investigate samples. As it is possible to observe the nucleation site of the crack is in all cases on the surface or near it. From other observations, also at higher magnification, this evidence was confirmed. Even if on the fracture surfaces of the as built samples many pores were found, none of them acted as nucleation site for the crack.

Figure 11: fracture surface of the as built (350 MPa - 5,55E+05 cycles) sample at 30X (a) and 80X (b).

Figure 12: fracture surface of the as built (400 MPa - 3,06E+05 cycles) sample at 30X (a) and 80X (b).

Figure 13: fracture surface of the HIP (375 MPa - 7,15E+06 cycles) sample at 30X (a) and 80X (b).