Influence of narrow starter notches on the initial crack growth resistance curve of ceramics

In experimental R-curve investigations crack development usually starts from notches. The validity of R-curves depends on the size of the notch root radius. This influence is completely ignored in most cases. In this theoretical study it is shown how the notch radius affects the formally computed crack resistance curve. First, the influence of the notch radius on the starting point of the R-curve, the so-called crack-tip toughness K _I0, will be addressed. Then, the effect of the notch on the shielding stress intensity factor will be discussed, and, finally, the influence on T-stress and the consequences on local path stability will be shown.