二方向荷重下での脆性破壊発生特性(第2報) : 大規模および全面降伏を伴う場合

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In the previous report, the brittle fracture initiation characteristics of plate subjected to bi-axial tension was investigated on the cruciform specimens of PMMA (Polymethylmethacrylate) and SM 41 (mild steel), each of which contains an inclined crack. The experiments showed that the fracture of the PMMA specimens was perfectly brittle and that of SM 41 specimens was with a small scale yielding. In this report, brittle fracture initiation characteristics with large scale yielding were investigated. A series of experiments was conducted on the cruciform specimens of SM 41 under bi-axial tension, of which load ratios were 0/1, 1/2, and 1/1. Elastic-plastic stress analysis was also carried out using the finite element method. The results obtained by the experiments and the finite element analysis lead to the following conclusions. ( 1 ) The direction of fracture initiation is nearly normal to the vector of crack opening displacement (COD) near the notch tip analyzed by FEM. ( 2 ) The brittle fracture stress under mixed mode condition may be conservatively predicted by the application of COD-concept in which the critical COD is evaluated as the one for the opening mode.
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