Branching mechanism of intergranular crack propagation in three   dimensions
  We investigate the process of slow intergranular crack propagation by the finite element method model, and show that branching is induced by partial arresting of crack front owing to the geometrical randomness of grain boundaries. A possible scenario for branching instability of crack propagation in disordered continuum medium is also discussed. 
M.Itakura, H.Kaburaki and C.Arakawa