On the measurement and physical meaning of the cleavage fracture stress in steel |
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Authors: | GZ Wang JH Chen JG Wang |
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Affiliation: | (1) Welding Research Institute, Gansu University of Technology, Lanzhou, Gansu, 730050, P.R. China |
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Abstract: | Elastic-plastic two-dimensional (2D) and three-dimensional (3D) finite element models (FEM) are used to analyze the stress distributions ahead of notches of four-point bending (4PB) and three-point bending (3PB) specimens with various sizes of a C-Mn steel. By accurately measuring the location of the cleavage initiation sites, the local cleavage fracture stress f and the macroscopic cleavage fracture stress F is accurately measured. The f and F measured by 2D FEM are higher than that by 3D FEM. f values are lower than the F, and the f values could be predicted by f=(0.8––1.0)F. With increasing specimen sizes (W,B and a) and specimen widths (B) and changing loading methods (4PB and 3PB), the fracture load P
f changes considerably, but the F and f remain nearly constant. The stable lower boundary F and f values could be obtained by using notched specimens with sizes larger than the Griffiths–Owen specimen. The local cleavage fracture stress f could be accurately used in the analysis of fracture micromechanism, and to characterize intrinsic toughness of steel. The macroscopic cleavage fracture stress F is suggested to be a potential engineering parameter which can be used to assess fracture toughness of steel and to design engineering structure. |
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Keywords: | Cleavage fracture stress finite element model specimen size steel stress distribution toughness |
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