PSI - Issue 51

Nils Wegner et al. / Procedia Structural Integrity 51 (2023) 122–128 N. Wegner et al. / Structural Integrity Procedia 00 (2022) 000–000

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354 and 500 ms, and a resolution of 5 µm. Evaluation of the reconstructed volumes was carried out using the software VGStudio Max 2.2 (Volume Graphics, Heidelberg, Germany). Multiple amplitude tests (MAT) were performed on an electro-mechanical testing system ElectroPuls E3000 (Instron, Norwood, MA, USA), enabling an evaluation of the mechanical stability through estimation of the residual fatigue strength. Starting from σ a,start = 10 MPa (stress ratio R = -1), the sinusoidal load (f = 10 Hz) was continuously increased by d σ a /dN = 10 MPa/10 4 . Instrumentation through an extensometer allowed the stress-strain hysteresis (plastic strain amplitude ε a,p , loss energy density w L ), and through a thermal camera, the temperature change to be evaluated. Due to higher stability, the uncorroded reference specimens were tested starting from σ a,start = 50 MPa. 3. Results Parts of the results have already been published in Wegner et al. (2022). Fig. 2 a) shows the results of the immersion tests under GSP with V H2,spec plotted over the normalized immersion time t/t max . The arithmetic means of the actual values and target values (based on Table 1) are plotted. Qualitatively, the actual curves of the coated and uncoated specimens are comparable. At the beginning of the respective days (t/t max = {0; 0.33; 0.67}) a progressive course is apparent, changing into a straight line. With the variation of the current density, a change in HER results. Quantitatively, WE43 achieves higher values than the PEO modified variant over the entire immersion time. Comparing target and actual values, it can be seen that qualitatively similar but quantitatively clearly different progressions are present, especially for WE43. The quantitative difference increases with increasing immersion time. For evaluation and validation of the method, m ሶ corr is plotted over the current density i in Fig. 2 b). The points of the previous tests on embedded WE43 samples (2D) and Equation 4 are plotted in gray. The tests on the three-dimensional (3D) specimens are colored. The majority of these data points lie above the calculation function, with only a few data points lying on it, meaning that higher corrosion rates are present for the respective current densities.

Fig. 2. Results of immersion tests of WE43 (PEO): a) mean hydrogen evolution at OCP and with GSP; b) corrosion rates calculated via HER for different current densities (Wegner et al., 2022).

Fig. 3. µ-Computed tomography images: a)–c) after immersion at OCP, d)–f) with GSP.