The three dimensional J-integral expressions were introduced and evaluated by using finite element method.
The thick plate with a through crack and the compact type specimens were elastically analyzed, and the distributions of the JX values along the crack front were obtained. By changing the thickness of the specimen, the thickness effects were studied. It was shown that the second term of the three dimensional J-integral expression was the main factor for the thickness effect. The CT specimens with several depths of side groove were also analyzed. For a quarter inch thickness specimen, it was shown that 10% side groove gave the equal J values along the crack front.
