Abstract
Change from a slowly propagating crack such as a fatigue crack or any other types of crack, which was initiated from a stress concentrated region or a weld defect, into a brittle crack at a critical crack length is very significant from a viewpoint of safety of welded steel structures.
One of the authors succeeded previously by using the deep notch test specimens newly developed in evaluation of brittle fracture initiation characteristics for a high strength steel under only static tension, without superposition of any factors such as welding residual stress, impact stress, concentrated stress, impact stress, concentrated stress due to structural discontinuity, metallurgical change in notch ductility, etc.
The stress-temperature relationships at fracture initiation for various crack lengths can be obtained by using 2 or 3 deep notch test specimens and applying the Griffith-Orowan energy condition.
In this paper, the brittle fracture initiation characteristics for various kinds of steel, such as mild steel, WES-HW 36, 40, 50, 63, 70, 80, 90 or 60, 70, 80, 100 kg/mm2 high strength steels, 2.5, 3.5, 9% Ni steels and 33, 37, 58 kg/mm2 yield strength Al-killed quenched and tempered steels as the low temperature steel, which were lately manufactured by leading steel makers in Japan, were investigated.
