Numerical investigation of 3-D constraint effects on brittle fracture in SE(B) and C(T) specimens

This investigation employs 3-D nonlinear finite element analyses to conduct an extensive parametric evaluation of crack front stress triaxiality for deep notch SE(B) and C(T) specimens and shallow notch SE(B) specimens, with and without side grooves. Crack front conditions are characterized in terms of J-Q trajectories and the constraint scaling model for cleavage fracture toughness proposed previously by Dodds and Anderson. The 3-D computational results imply that a significantly less strict size/deformation limit, relative to the limits indicated by previous plane-strain computations, is needed to maintain small-scale yielding conditions at fracture by a stress- controlled, cleavage mechanism in deep notch SE(B) and C(T) specimens. Additional new results made available from the 3-D analyses also include revised {eta}-plastic factors for use in experimental studies to convert measured work quantities to thickness average and maximum (local) J-values over the crack front

On the Anisotropy of the Ductile to Brittle Transition Behavior in a Wrought and in Two Oxide Dispersion Strengthened FeCrAl Steels

The directionality of the ductile-brittle transition behavior of two oxide-dispersion-strengthened (ODS) FeCrAl steels with similar chemical compositions, tensile properties, and sub-micrometric grain sizes but different processing routes, and a Zr-particle strengthened FeCrAl steel manufactured by high vacuum melting is discussed. Despite the similarities of the ODS FeCrAl steels, strong differences in the lower and upper shelf energy and the ductile to brittle transition temperature were observed for longitudinal through thickness notched specimens. Although the lower and upper shelf energies of longitudinal surface-notched specimens of ODS FeCrAl steels are similar, a strong difference in the ductile-to-brittle transition temperature is observed. For through-thickness notched and surface-notched specimens taken transversely, the analyzed ODS FeCrAl steels show a similar ductile-to-brittle behavior. In general, the FeCrAl alloy strengthened with Zr-particles presents a more isotropic behavior and a higher ductile-to-brittle transition temperature than the ODS FeCrAl steels. In addition, the upper shelf energy of the FeCrAl steel strengthened with Zr-particles is significantly higher than that of the ODS FeCrAl steels.The authors acknowledge financial support to Spanish Ministerio de Economia y Competitividad (MINECO) in the form of a Coordinate Project (MAT2016-80875-C3-1-R). The authors are grateful for the dilatometer tests by Phase Transformation laboratory. This work contributes to the Joint Programme on Nuclear Materials (JPNM) of the European Energy Research Alliance (EERA).Peer Reviewe