抄録
This paper considered the test specimen thickness (TST) effect on the fracture toughness of a material J_c in the transition temperature region for 3 point bending (3PB) specimens. Elastic-plastic finite element analyses (FEA) with standard test specimens, which are standard because the specimen thickness-to-width ratio B/W was 0.5, were conducted. Based on the FEA results, it was demonstrated that the "planar" (4δ_t,σ_<22c>) failure criterion-which states that cleavage fracture after significant plastic deformation occurs when the crack opening stress δ_22 at a distance from the crack-tip that is equal to 4times the crack-tip opening displacement δ_t exceeds a critical value δ_<22c>-effectively explain the TST effect on J_c of standard test specimens.
