Fig. 1: Schematic visualization of in situ synchrotron and in situ SEM experiments.

Here, L, B, and W are the bending length, thickness and width of the cantilevers, respectively, while a is the crack length and BS indicates the beam stop (a). The cantilever deformed in SEM was continuously loaded, and a video recorded for tracking the spots to evaluate the total surface strains (b). Additionally, the elliptic lines in (b) show integration contours for J-integral evaluation, being small (8 µm), medium (16 µm) and wide (24 µm) ellipses at closest (1 µm) and maximum crack tip distance (13 µm) configurations, respectively. In (c) a detail of a SAXSM micrograph around the crack tip is shown with the coordinate system used to evaluate the relevant crack opening stress (COS) and growth direction stress (GDS) components parallel and perpendicular to the local crack tip coordinate system, respectively. The scale bars in (b and c) are 5 µm.