PSI - Issue 28

7

Arroyo et al./ Structural Integrity Procedia 00 (2019) 000–000

B. Arroyo et al. / Procedia Structural Integrity 28 (2020) 180–187

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If we compare both techniques results, it is easily observed that the loading protocol had a similar trend and 3 samples were used for standard and for SPT cases, like stated in bibliography (Arroyo B. et al., 2019); the SPT proposal reflected the same behavior than the standard tests. Table 4 organizes the previous results, converting the threshold load (P th ) into threshold stress (σ th ). Figure 6 plots the results to facilitate comparison, incorporating some fractographies in order to show that the micromechanisms in both techniques for the same environment are similar too. This allows to conclude that the SPT proposal is representative of the interaction between material and environment. Therefore, the SPT proposal is able to reproduce the same trends than the ASTM F1624 standard. Furthermore, the linear fit from P th -σ th in the three environment conditions shows a very good correlation coefficient. Figure 5. S420 steel load-time registers obtained when tested under CP; the dashed lines show the planned steps that did not take place after specimen failure. On the left are shown the results of applying ASTM F1624 and on the right the SPT proposal based on the step loading technique; TOP: 1mA/cm 2 , CENTER: 5mA/cm 2 , BOTTOM: 10mA/cm 2 .

Table 4. Results obtained by applying ASTM F1624 and the SPT to S420 steel under CP at 1, 5 and 10 mA/cm 2 .

ASTM F1624

SPT Proposal

P th (N)

σ th (MPa)

P th-SPT (N)

Air

15445 10729

547 379 265 258

1465

1 mA/cm 2 5 mA/cm 2 10 mA/cm 2

812 625 594

7501 7282