Fatigue endurance limit and crack front evolution in metallic glass

Fatigue fracture mechanism of amorphous materials from a density-based coarse-grained model

“…Thus, crack-like shear-band propagation from preexisting defects (a heterogeneous mechanism) also plays a critical role. For example, an experimental work by Lei et al 73 showed significant roles of preexisting cavities in fracture of metallic glasses. Furthermore, the presence of nanocavities was observed for metallic glasses via electron microscopy 71 , which may be responsible for more than two types of shear band nucleation sites that operate at different stress levels 72 .…”

“…This criterion for brittle fracture, γ c ¼ ð∂G=∂p L Þ À1 , estimated from the experimentally measured P-dependence of G, is consistent with the critical strain for the brittle fracture of poly(methyl methacrylate) 67 . However, the predicted critical strain ( ~10%) was much larger than experimental ones (a few %) for metallic glasses 67 , which might be due to pre-existing defects or voids [71][72][73] or nucleation-growth-type fracture, although it has to be examined carefully (see also the later discussion). We note that the intrinsic critical strain can be much larger than the experimental values obtained from macroscopic experiments, as supported by recent simulations and small-sample-size experiments on metallic glass fracture 74,75 .…”

Damage due to start-stop cycles of turbine runners under high-cycle fatigue

“…Buxbaum & Ostermann, 1983) or (Sonsino & Dieterich, 1990). Figure 5 displays a nominal S-N curve and the corresponding fatigue endurance limit (FEL) under which the stress amplitude 𝜎 will not lead to a failure, whatever the number N of cycles (see Lei et al 2021). Figure 5 also displays a design curve.…”