On the link of the embrittlement mechanisms and microcrack nucleation and propagation properties for RPV steels. Part I. Materials, study strategy and deformation properties

Validation of local approach‐based statistical models for cleavage fracture of ferritic steels in uniaxial tension

“…(2). It agrees with the physical consensus of plastic deformation as a necessary condition for triggering cleavage fracture in steels 1–13 . In other words, cleavage fracture of ferritic steels does not occur in pure elastic deformation zone.…”

“…The experimental results were presented in tables. 13 Particularly, 10 sets of the experimental results in uniaxial smooth tension for each steel state at 77 K are summarized here in terms of yield stress σ YS (in MPa), true fracture strength σ F (in MPa), and the plastic strain at fracture ε F (dimensionless): For the steel in the initial state, (σ Note that the plastic strain at fracture ε F is calculated by ε F = À Ln(1-ψ F ) (ψ F is the relative area reduction at fracture) in general or by ε F = À Ln(1-δ F ) (δ F is the relative total elongation at fracture) when fracture occurs at uniform elongation. The data of ψ F and δ F were reported in in tables.…”

“…The data of ψ F and δ F were reported in in tables. 13 The diameter of the smooth round bar is 3 mm within the gauge length of 15 mm. The volume of the round bar within the gauge length gives the volume of plastic deformation zone V pl ¼ 106 mm 3 .…”

“…It agrees with the physical consensus of plastic deformation as a necessary condition for triggering cleavage fracture in steels. [1][2][3][4][5][6][7][8][9][10][11][12][13] In other words, cleavage fracture of ferritic steels does not occur in pure elastic deformation zone. In a brittle material, microdefects such as grain boundary cracks exist before it is in service, thus fracture occurs under elastic stress once it triggers the unstable propagation of microdefects.…”

“…C) is fitted with the two LA models Equation(13) and Equation (16) that bear a fixed-value threshold stress.Figure 2(D) is fitted with the LA model Equation (21) that assumes a threshold value equal to the yield stress σ th ¼ σ YS . Particularly, Figure 2(C) shows the two scenarios σ th < σ YS for the initial state (σ th ¼ 12:3 MPa, σ YS ¼ 972 $ 1024 MPaÞ and σ th ≥ σ YS for the H-embrittled state (σ th ¼ 1377:7 MPa, σ YS ¼ 1299 $ 1345 MPaÞ.…”