PSI - Issue 41

Jesús Toribio et al. / Procedia Structural Integrity 41 (2022) 736–743 Jesús Toribio / Procedia Structural Integrity 00 (2022) 000–000

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Consideration should be given to the influence of external action  G , which makes the local strain rate d  L /dt change as the test proceeds, even keeping constant the global strain rate, as usually occurs in EAF tests, in which a constant displacement rate is externally applied on the sample.

Fig. 2. Relationship between local and global strain rates as a function of global strain.

4. Application to slow strain rate tests (SSRT) Slow strain rate tests (SSRT) were performed on round notched samples with the four geometries shown in Fig. 1, the sample diameter being D = 11.25 mm. The environment was an aqueous solution of 1 g/l Ca(OH) 2 plus 0.1 g/l (pH = 12.5). To promote hydrogen embrittlement, tests were performed with potentiostatic control at a constant potential of –1200 mV vs . SCE ( saturated calomel electrode ). A broad range of global displacement rates was covered. Test results appear in Fig. 3 for all geometries, where failure load in aggressive environment F C (normalized to failure load in air F O ) is plotted versus the crosshead speed. Such results show the classical trend of hydrogen embrittlement tests when plotted against displacement rate. The fracture load in a hydrogen environment increases as the applied strain rate increases.

1

0,9

0,8

0,7

A B C D

Fc/Fo

0,6

0,5

0,4

10 -9

10 -8

10 -7

10 -6

10 -5

CROSSHEAD SPEED (m/s)

Fig. 3. Experimental results of the SSRT: failure load in solution (divided by the same in air) vs. crosshead speed.