Small and large scale crack arrest tests

In structures containing gradients in toughness or stress, a crack may initiate in a region of either low toughness or high stress, or both, and arrest in another region of either high toughness or lower stress, or both. The value of the stress intensity factor at the arrest of a fast running crack is a measure of the ability of the material to stop such an unstable crack propagation. Even though dynamic effects are influencing fast running cracks in specimens and structures as well, the ASTM Standard E 121-88 neglects these effects by using static methods of analysing the material behaviour. This engineering approach is only applicable as long as the dynamic effects are small. In all other cases the crack arrest values determined according to the ASTM standard underestimate the actual material properties, which are measured in large scale tests. (authors). 2 refs., 5 figs