２Ｖシャルピ衝撃試験の破面遷移温度とＣＯＤ試験によるぜい性破壊発生温度との相関

Abstract

The relationship between the fracture appearance transition temperature υTrs in the V-notch Charpy test and the brittle fracture initiation temperature in the COD test has been investigated. The obtained results can be summarized as follows:-(1) The relationship can be expressed by the equation, [Tδ]^σ=σ_c=c = (0.006121δy+0.4704)νTrs+8.26√t+0.608δy[{1n(c/40)(2σ/δy)2}+{c(2σ/δy)2-40}/100]-90.2(°K)where [Tδ]^σ=σ_c=c is the critical temperature at which the brittle fracture is initiated in an infinite plate with a crack of a length 2C and application of an uniform stress σ, δy is the nominal yield strength and t is the thickness of steel plates.(2) For preventing brittle fracture in welded structures made with HT60 or HT80, the required value of νTrs for the welds should be lowered with an increase in the strength and the thickness of steel plates, the design stress and the length of the crack in the welds. And the maximum acceptable crack length should be decreased with an increase in the strength and the thickness of steel plates, the design stress and νTrs.(3) The maximum acceptable crack length, for preventing brittle fracture in welds of HT60 or HT80 welded with the same heat input of 40-50 kj/cm, increases with the plate thickness up to the thickness of 40 mm and decreases with the plate thickness in a range of more than 40 mm.