PSI - Issue 28

Sabrina Vantadori et al. / Procedia Structural Integrity 28 (2020) 1055–1061 Author name / Structural Integrity Procedia 00 (2019) 000–000

1060 6

40

12.5

20

80

Fig. 3. Specimen sizes (in mm).

The testing machines used were servo-hydraulic machines, and all tests were performed under load control. The fracture criterion was the complete separation of failed specimens. Run-out tests were stopped at a number of loading cycles equal to about 3 million cycles. The details of the experimental loading conditions examined are reported in Tovo et al. (2014): they consisted in tensile loading (4 values of the fatigue ratio R were examined), torsional loadings (2 values of R were examined), and combined tensile and torsional loading (phase shift β was equal to 0° or 90° and R was equal to -1). The mechanical and fatigue properties of the ductile cast iron EN-GJS-400-18 are listed in Table 2.

Table 2. Mechanical and fatigue properties of the ductile cast iron EN-GJS-400-18. Properties u   460 MPa 1 af ,   173MPa 1 af ,   167MPa m 12.85 m* 10.07 0 N 2(10) 6

4. Results and discussion In Fig.4, the experimental fatigue lives are compared with the calculated ones. The solid line indicates cal exp N N  (all results above such a line are conservative), the dashed lines correspond to / cal exp N N equal to 0.5 and 2, respectively, and the dash-dot lines correspond to / cal exp N N equal to 1/3 and 3, respectively.

7

7

10 7

(c)

(b)

(a)

Scatter band 3X Scatter band 2X Scatter band 3X

Scatter band 3X Scatter band 2X Scatter band 3X

Scatter band 3X Scatter band 2X Scatter band 3X

6

6

10 6

5

5

N exp [cycles] 10 5

R

-3.0 -1.0 0.0 0.5



4

R

4

-1.0 0.0

0° 90°

3

3

10 4

10 3

10 4

10 5

10 6

10 7

10 3

10 4

10 5

10 6

10 7

10 4

10 5

10 6

10 7

N cal [cycles]

N cal [cycles]

N cal [cycles]

cal N under: (a) tension; (b) torsion; (c) combined tension and torsion.

exp N against

Fig. 4.