▎ 摘　　要

A theoretical model is suggested which describes the formation of cracks at grain boundaries (GBs) containing partial (non-topological) disclinations and their dipoles in graphene. Such partial disclinations and their dipoles at GBs are associated with experimentally observed structural irregularities of real GBs in graphene. Within the suggested model, the dependences of the critical stress for crack formation on the parameters of sole disclinations and their dipole configurations at GBs are calculated. The results of the model effectively explain the experimental data (Huang et al 2011 Nature 469 389, Ruiz-Vargas et al 2011 Nano Lett. 11 2259) on crack formation in polycrystalline graphene at comparatively low levels of the applied stress and their discrepancy with the results of computer simulations (presented in the scientific literature) of strength exhibited by graphene bi-crystals with structurally perfect, periodic GBs.