While systematic experimental data on fracture of blunted notched specimens (with notches of different root radii) loaded under mode I and mixed mode loading (I + II) have been recently provided , the results from blunted notched specimens under torsion loading are relatively scarce and the research activity has mainly considered cracked bars under torsion . Some
results were reported from ceramic notched components under combined tension and torsion, brittle glass and graphite under
pure torsion . In those papers the authors underlined that no other data were available in the literature