Extended Data Fig. 6: Polycrystal finite element model including the effect of boundary migration.
Once the bonds along GB24 are severed, then migration of GB34 causes a shear in the part of G4 through which the migration has occurred, as shown in (a). The shape of the resulting gap between G2 and G4 is shown in (b). The resultant difference in normal displacement of the top and bottom crack faces induced by migration of GB34 in (a–b). The red contour shows the locus of zero relative crack face displacement. The displacement is negative in a broad region at the crack tip and near one of the free surfaces, indicating a strong tendency toward crack closure.
