A parametric study of mixed-mode I/III ductile fracture in tough materials under small scale yielding

摘要

Mixed-mode I/III crack growth in high purity. tough materials under small-scale yielding conditions are studied using an elastic--plastic continuum model. The fracture process is controlled by the interaction of two mechanisms, the growth of theexisting voids and the nucleation of new voids under increased plastic strain. Crack growth is constrained to occur only along the initial crack plane because of the symmetry conditions of load and geometry. The effects of mode mixity on mixed-modefracture toughness are studied under different circumstances, and the effects of other factors. such a microstructural parameters. continuum properties of the solid and the crack-tip constraint. are also examined. The study indicates that mixed mode I/III fracture resistance. followed by some amount of ductile crack growth, displays a minimum at a critical phase angle[Φ = tan{sup}-1(K{sub}III / K{sub}I)] between 45° and 55°. This indicates a direction at which an initially flat mode I crack may reorient to cause slant fracture or formation of shear lips.