抄録
The main object in this study is a proposal for establishment of fracture toughness value at initiation of crack growth. We measured the exact crack growth by coloring for improving of precision. Futhermore, we examined to use the sound at crack initiation to determine the fracture toughness value. As a result, we could propose the measurement method of internal crack growth with coloring and defined the appropriate fracture toughness value. Additionally we understood that the sound at generation of crack is useful to determine the fracture toughness value simply.
