PSI - Issue 17

C.A.R.P. Baptista et al. / Procedia Structural Integrity 17 (2019) 324–330 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

329

6

additional tests at R = 0.2 (specimens AR_3 and LP50_3, see Table 4) showed that these results are reproducible, whereas the specimen with increased overlapping rate (LP75_1) presented an intermediate behavior. In brief, the LSPwC treatment promoted a certain increment in the number of cycles for crack propagation, particularly in the second stretch, in which an increase of about 16% was observed. On the other hand, Table 5 results show that no beneficial effect was promoted by the laser processing in the tests with R = 0.5; on the contrary, the overall results show a decrease in the number of cycles for crack growth and, again, the increased overlapping rate apparently worsened the FCG results.

36

34

FCG raw data a versus N , R = 0.2 AR_1 LP50_1

32

30

28

26

a (mm)

24

22

20

18

16

0

10000

20000

30000

40000

50000

N (cycles)

Fig. 4. Plot of fatigue crack growth datasets for AR_1 and LP50_1 specimens tested at R = 0.2.

Table 4. Number of cycles for crack growth, specimens tested at R = 0.2. Specimen designation Cycles for 18 → 26 mm

Cycles for 26 → 34 mm

AR_1

30,851 32,305 31,452 31,692 32,448

6,739 8,128 7,610 7,300 8,829

LP50_1 LP75_1

AR_3

LP50_3

Table 5. Number of cycles for crack growth, specimens tested at R = 0.5. Specimen designation Cycles for 18 → 26 mm

Cycles for 26 → 34 mm

AR_2

107,848 110,728 91,714

21,586 19,909 19,093

LP50_2 LP75_2