It is a common technique in modelling cracked bodies with finite element method, to refine the mesh near the crack tip. It is mentioned in text books, mesh refinement is nessecary to increase the acuuracy of the computed stress intensity factor for the crack tip. Is meshrefinement nessecary for computing eigen-properties ( natural frequencies and natural modes ) as well as SIF? or eigen properties are not affected much by the near crack tip field?