This paper deals with two major subjects: (1) the elastic and elastic-plastic analyses of several kinds of compact tension (CT) specimens, and (2) crack growth analyses in the three-dimensional case. Firstly, CT specimens are analyzed elastically and elastic-plastically using the three-dimensional finite element method, and the three-dimensional J integral values along the crack front are evaluated. Several kinds of CT specimens, with various thicknesses and side groove depths, are analyzed elastically; four specimens are chosen for elastic-plastic analysis. For 1CT specimens without a side groove, the J value is maximum at the center of the specimen and minimum near the free surface. It is shown that the change in both values becomes smaller by introducing the curved crack front assuming the fatigue precrack. For the side-grooved specimens, it is shown that the experimental J value obtained from the load-displacement curve using the net thickness is better than that using the effective thickness. It is also shown that the J value is nearly equal along the crack front for 25% side-grooved specimens. In every case, the J values obtained by the load versus displacement curve coincide well with the average J values over the plate thickness.
Secondly, crack growth analyses are carried out. Using the method proposed by Nakagaki et al, which simulates the crack growth by moving the near-tip nodes forward along the crack growth direction, a smooth crack front is retained after crack growth even in the three-dimensional finite element analysis. Tunneling effects are observed for 1CT standard specimens; for the side-grooved specimen it is shown that the crack growth occurs equally along the crack front.