v-K-data for silica from interrupted lifetime measurements

Different methods were applied so far in order to determine subcritical crack growth for silica. Mostly, fracture mechanics standard tests with macro cracks were used for this purpose. In this report, we evaluated the subcritical crack growth curves from interrupted lifetime tests on silica bending specimens containing small natural flaws. The resulting v-K-curve showed crack growth rates down to 10${}^{-14}$ m/s indicating a threshold for subcritical crack growth at
K${}_{th}$$\approxeq$0.31 MPa$\sqrt{m}$
In the plot of v=f(K/K${}_{Ic}$) slight material differences could be eliminated and suitable agreement with macro-crack results by Wiederhorn and Bolz [1] on DCB-specimens and Michalske et al. [2] on DCDC-specimens could be stated.