Fracture Toughness Testing with Notched Round Bars
SourceA method to simplify fracture toughness testing and reduce testing costs is discussed. An alternative specimen geometry, the notched round bar (NRB), has been combined with a simpler testing methodology. A multispecimen technique using notched round bars with finite notch root radii ρ was applied to 2024-T351 and overaged 2024 aluminum alloy. No fatigue precracking was used. A graph of apparent fracture toughness Kρ versus the square root of notch root radius √ρ was extrapolated to ρ = 0, corresponding to a fatigue precracked configuration. The resulting fracture toughness values were the same as those obtained from ASTM E 399 tests. Apparent fracture toughness Jρ, determined from NRB J-R curves for overaged 2024, was graphed versus notch root radius ρ. The extrapolated value of fracture toughness was the same as that obtained from ASTM E 813 and E 1152 tests.