PSI - Issue 18

Fokion Oikonomidis et al. / Procedia Structural Integrity 18 (2019) 142–162 Dr Fokion Oikonomidis / Structural Integrity Procedia 00 (2019) 000 – 000

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The stress intensity factor calculated at the deepest point in the flaw due to the residual stress was K RS =-885.4N/mm 1.5 . Hence, equation (2) gives the stress intensity factor at the crack tip due to the applied load as K P =3257N/mm 1.5 . Using the graph in Fig. 10, the critical load for initiation of crack extension in the full-scale test at this value of K was estimated at 6117kN.

5. Pre-Charging

The whole chain link was pre-charged in 3.5% NaCl solution with CP -1100 mV (using Ag/AgCl reference electrodes) at room temperature (see Fig. 14). The chain link was pre-charged for a period longer than 400 days without interruptions, to ensure hydrogen saturation at a depth sufficiently below the fatigue pre-crack depth.

Fig. 14. Arrangement for the pre-charging of the chain link.

6. Testing

After the completion of pre-charging, the chain link was placed on a test machine capable of applying constant tensile loads in its longitudinal orientation (see Fig. 15). The chain link was fully submerged in the solution under CP for the duration of the test. The extension of the chain link was also monitored by a linear variable displacement transducer (LVDT) extensometer (Fig. 16). Acoustic emissions (AE) monitoring was used to detect crack growth during the loading (Fig. 17).