Abstract
According to Oda et al., 2008, the proportional method does not give reliable results if the relative crack size is considerably deep (say, a/W 0.4 ). The efficiency and accuracy of the improved proportional method is demonstrated by pursuing a convergence study in this research. The effects of the minimum element size e and the number of refined layers NL around the singular region on the mode I SIF values of several examples are discussed. A linear relationship between the stress intensity factors and the minimum element size has been observed in the convergence study. Finally, it is concluded that the exact results can be obtained through linear extrapolation.
