PSI - Issue 28

Dimos Triantis et al. / Procedia Structural Integrity 28 (2020) 502–510 6 D. Triantis, I. Stavrakas, A. Kyriazopoulos, E. D. Pasiou, S. K. Kourkoulis / Structural Integrity Procedia 00 (2019) 000–000 mode at a constant stress rate) up to a strain level equal to about ε L = 0.0025, or, equivalently, at a time instant equal to about t L =295 s (see points A in Figs.4(a,b)). For the specific time interval 0

1200

0.0045

14 days

E

Β

D

800

0.0030

Axial strain

A

PSC [pA]

0.0015

400

Β΄

A΄

0

0.0000

1

10

100

(t f - t) [s]

Fig. 5. The PSC for a typical specimen of the “14 days” class, plotted versus the “time-to-failure” parameter, in juxtaposition to the respective evolution of the axial strain developed.

In general, the increasing period of the PSC values (A΄Ε interval) is characterized by three distinct regions: After the transient region (A΄Β΄), in which the PSC increases smoothly, the time evolution of PSC is described by a power law (corresponding to the Β΄D portion of the graph). The increase of PSC according to such a law has been recently verified experimentally by many protocols for a wide variety of materials and loading schemes (Triantis et al. 2020a;