MINIMUM SPECIMEN SIZE REQUIREMENTS AND VALIDITY CRITERIA FOR K_(IIC)-TESTS

摘要

From a discussion of the sizes of the plastic zones at the tip of a crack under shear (mode-II) and tensile (mode-I) conditions of loading hypotheses on minimum specimen size requirements for the determination of valid values of the shear fracture toughness K_(IIc) are derived. The minimum specimen thickness for a K_(IIc)-test should be smaller, but the minimum inplane specimen dimensions should be larger than for a K_(Ic)-test. Mode-I and mode-II fracture toughnesses are measured for the aluminium alloy 7075 with specimens of different sizes to verify the hypotheses.