A boundary element method, which does not require a special function for the treatment of the singularity at the crack tip, is used in the analysis of two dimensional crack problems. A method for determination of stress intensity factors from the crack opening displacement is studied.
With the point, at which one-point formular is used, being varied along the crack, the stress intensity factors are calculated. The results for edge crack and center crack are compared with the other approximations.
It is shown that the stress intensity factors calculated at the second node are more accurate than those calculated at the first node. Such a result may be due to the poor estimation of tractions in the crack tip element. The displacement at the first node from the crack tip may be strongly affected by this. Accordingly, it is recommended that the one-point formular be used at the second node from the crack tip.