The Correlation Behavior between Crack Growth and the Opening of a Ductile Crack in a Center Notched Plate of S15CK

摘要

The growth behavior of a ductile crack resulting from a notch root was investigated in tensile tests of a center notched plate of low carbon steel S 15 CK. Four different notch root radii, ρ, that is, ρ=0.0 (crack) , 0.08, 0.14 and 0.25 mm were prepared for testing. It was found by measurement of strain, e, and the notch shape in tension, that the notch root was blunting in the same way, independent of the notch root radius, before ductile crack initiation, The crack grew with mixed mode fracture which combined tensile mode and shear mode fracture. In the growth process of the ductile crack, the crack growth rate, da/dε, for the strain increment is proportional to crack length, a, and the proportional constants of the da/dε-a relation take nearly the same values independent of the notch root radius. The crack opening angle, COA, decreases with crack growth.