6. Ductile fracture criteria

A number of models for predicting deformation at fracture take into account, on a microscopic scale, the limiting stage in the damage of the material under consideration. The criterion is then based on the description of this stage. For example, if fracture occurs as soon as cavities begin to form, the criterion will be based on principal stress. If the limiting stage is growth, we'll use a Rice and Tracey-type criterion.

In some cases, it is necessary to consider the evolution of all three stages of damage during deformation to be able to describe ductility correctly: the proposed criteria are then linked to models coupling behavior and damage.

Finally, other approaches, more or less empirical in nature, take into account only the relevant macroscopic mechanical quantities.

• Microscopic rupture...