Abstract: High ductile steel are usually adopted for the piping material. The stress concentration and the plastic deformation can be found at the crack tip for the ductile material under external load which make stress and strain of crack tip domain redistributed and the blunting deformation appeared. Based on the relationship of the elastic-plastic material, 1/4 singular elements are used for crack front discretization, under the displacements control, the blunting process are simulated. The hardening zone and the fracture parameter are studied at different loading rates.