On the Determination of Crack Initiation Using Standard Test Methods

The results presented in this paper were obtained by participation in an ASTM experimental round-robin exercise. The roundrobin was aimed at verifying the appropriateness of ASTM Draft Test Method for Crack Tip Opening Displacement (CTOD) Testing. It was demonstrated that the Draft Method is suitable for determining initiation values of CTOD and that more unequivocal values are obtained if the crack length is measured as the average of ten instead of three individual values distributed over the specimen thickness. This is consistent with the recent revision of the Draft Method.