遅れ破壊き裂発生挙動に及ぼす試験片形状の影響（見掛けの応力拡大係数による検討）

Abstract

The crack initiation behavior in delayed failure was studied on various specimen configurations, using the apparent stress intensity factor, Ka, which is obtained by substituting notch length for crack length in the equation of stress intensity factor K.When Ka is constant, the time to crack initiation is independent of notch length a0 and loading methods, but is dependent on specimen thickness B and notch root radius ρ. When the crack initiation time is constant, the next experimental equation holds:Ka=KI(B0/B)δ(ρ/ρ0)λ, ρ≥ρ0where KI is the stress intensity factor under plane strain state, B0 is the critical specimen thickness over which crack initiation time is constant, ρ0 is the critical notch root radius under which Ka at crack initiation is constant, and δ and λ are constant. ρ0 varies with crack initiation time and seems to depend not only on mechanical factors but also on chemical factors, such as the formation of protective film on the notch root surface.