Macroscopicmode I ductile crack propagation in thin metallic sheets often starts in mode I as a flat triangle whose normal corresponds to the loading direction. After some limited extension, the crack becomes slanted and propagates under local mixed mode I/III. Modeling and understanding this phenomenon is challenging. In this work, the computational cell methodology proposed in , which uses a predefined crack path, is used to study flat to slant fracture transition. The energy dissipation rate is studied as a function of the meshed crack tilt angle. It is shown that a minimum is always reached for an angle equal to 45◦. This correlates well with the variation of the crack tip opening angle (CTOA) or the mean plastic deformation along the crack path. Stress and strain states in the stable tearing region hardly depend on the assumed tilt angle. A parametric study shows that flat to slant fracture transition is less likely to occur in materials having high work hardening and favored if additional damage is caused by the local stress/strain state (plane strain, low Lode parameter) in the stable tearing region.
Citation: Engineering Fracture Mechanics
Pub Type: Journals
Ductile rupture, CTOA specimen, Slant fracture, X100 steel