Influence of a finite notch root radius on fracture toughness

The validity of fracture toughness data from tests with V-notched bending bars depends in the notch root radius and the presence of an R-curve behaviour. In a theoretical study it is shown how the notch radius affects the formally computed conventional toughnesses. These are computed under the assumption that the introduced notch with a small crack at the notch root acts as a long crack of the same total size and, in a stronger simplification, that the crack length is identical with the depth of the notch.