Analytical modeling of the shear mode and opening mode of ductile fracture

Strain localization in the vicinity of a surface is a precursor to ductile fracture of materials. It can be analyzed by considering the stability of a linear perturbation. For a broad class of materials : plastic, rate dependent, with void growth damage... and loading conditions : three-dimensional, thermomechanical and dynamic, a closed form solution is obtained for the stability condition. From this condition, the mode of ductile fracture can be predicted : shear or opening. In a plastically incompressible or nearly incompressible material (no or low void growth damage), the shear mode of fracture only is obtained; it results from a competition between strain hardening and thermal softening. In a void growth damaging material, the opening mode prevails and it is promoted by stress triaxiality. The analytical results are in agreement with experimental observations and numerical results from the literature.