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

3164

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Figure 9 : plot of the tensile tests for both the two condition (a), image of the fracture surface of the “as built” sample where two pores are visible.

Table 2 : mechanical properties values recorded from the tensile tests.

As built

HIP

E [GPa] σ y [MPa]

112,7

108,7 849,7 962,3

1022,2 1092,4

σ max [MPa]

ε max

16,47

22,49

The fatigue curves were fitted with a SN curve in the form of:  P 50  a  b N f m

(1)

which is suitable to represent the knee exhibited by the curves around 10 6 fatigue cycles. The best-fit parameters a,b, and m are listed in Table …

Table 3: best-fit parameters for the as built and HIP fatigue tests.

As built

HIP

a b

343,13

369,53

7,21E+04

2,30E+06

m

0,573

0,897

The fatigue test results are shown in …… and……. The as built shows a gradual increase in the fatigue life when the load decrease and the sample tested at 325 MPa reaches 50 millions of cycles, the number of cycles that can be considered the endurance limit.The HIP lot of samples show results that can be distincted in two different groups. For values of the load higher than 400 MPa none of the samples survived even one million of cycles, while as soon as the load is decreased beneath 400 MPa many samples passed the test without failure. In this case the lower value of the load at wich a sample survived is 350 MPa that can be considered a safe limit.