PSI - Issue 17

Jürgen Bär et al. / Procedia Structural Integrity 17 (2019) 300–307 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

304

5

3.2. Fractographic Evaluation

Figure 3 shows a typical cross cut through the crack surface of a specimen tested at RT and in LH2, respectively. In case of RT the topography of the crack surface is macroscopic and microscopic smooth with only a low roughness. All specimens tested in LH2 exhibit a pronounced topography with many steps, resulting in a rough surface. The cross section shows also several secondary cracks parallel to the loading direction which indicate the dissection of the material into several plates parallel to the loading direction.

LH2

RT

Fig. 3. Cross section of crack surfaces of a specimen fatigued at room temperature (RT) and in liquid hydrogen (LH2).

RT

LH2

LH2

RT

Fig. 4. Typical crack surfaces of specimens fatigued at room temperature (RT) and in liquid hydrogen (LH2).