Extended Data Fig. 5: Polycrystal finite element analysis indicating crack closure at the crack tip.

(a) Continuum-level version of the triple junction model shown in main text, Fig. 3a. The arrows on the top and bottom surfaces indicate the direction of the tensile axis; (b) the difference in normal displacement of the top and bottom crack faces induced by the non-uniform triple junction stresses in (a). The red contour shows the locus of zero relative crack face displacement. Near the crack tip, the displacement is negative, indicating crack closure.