A study on three-dimensional crack tip fields

In this paper several kinds of crack problems are numerically analyzed by the three-dimensional finite element method. They are (1) CT specimens with different thicknesses; (2) stable crack growth in CT specimens: (3) surface cracked plate subjected to bending: (4) pipe with surface crack subjected to bending: (5) CT and surface cracked specimens made of welded plate. The crack tip singular fields are compared with HRR solutions and the Q-factor is evaluated. The effects of the J-integral and Q-factor on the crack growth behavious are discussed with the comparison of the experimental results. It is concluded that the J-integral does not uniquely control the stable crack growth behaviors in many three-dimensional crack problems. It is also found that both J-integral and Q-factor play important roles in the stable crack growth especially in the welded plate.