PSI - Issue 59

Jesús Toribio et al. / Procedia Structural Integrity 59 (2024) 198–205 Jesús Toribio / Procedia Structural Integrity 00 ( 2024) 000 – 000

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4. Fractographic analysis Hydrogen assisted microdamage (HAMD) started at the notch tip, and fractographic analysis by scanning electron microscopy (SEM) showed the tearing topography surface or TTS (Fig. 2), a term coined by Thompson and Chesnutt (1979) and Costa and Thompson (1982). It resembles micro-damage (Toribio et al ., 1991, 1992) and representing a slow crack growth mode (Toribio et al, 1991; Toribio, 1997). The TTS size decreases with the strain rate and it is influenced by the geometry in notched samples, reaching the location of the maximum hydrostatic stress point in quasi-static tests (Toribio et al. , 1992), consistent with hydrogen transport by diffusion. Fig. 3 shows the micro-fracture maps (MFM) at the fracture in the HE tests for the different notched specimens A, B, C and D.

Fig. 2. Tearing topography surface (TTS).

Fig. 3. Micro-fracture maps (MFM) at the fracture in the HE tests for the different notched specimens A, B, C and D with very distinct triaxiality levels; TTS: tearing topography surface ; C: cleavage-like topography .