Advances in the mechanism of cleavage fracture of low alloy steel at low temperature .3. Local fracture stress sigma f

Local fracture stress values af were measured accurately using 4PB, COD and Charpy V specimens. sigma f is the most stable parameter characterizing the fracture toughness of materials. It's scattering is analyzed to be determined only by the size distribution of the largest particles, accounting for less than 5 percent of the total particles of the weakest constituent, and is not subject to the influence of their locations. The toughness of a structurally heterogeneous zone such as a weldment could be characterized by a unique value of sigma f or sigma f/sigma y with a narrow band of scattering, sigma f or sigma f/sigma y is a potential engineering parameter used for assessment of fracture toughness of materials. The physical meaning of of associated with the surface energy is discussed in detail.