Metal alloys used in industrial applications most often have a ductile fracture mode involving nucleation, growth, and coalescence of internal cavities. The cavities appear as a result of the rupture of inclusions and grow under mechanical loading until they join together, leading to the failure of the structure. Resistance to crack initiation and propagation results from this mechanism. The prediction of toughness therefore requires the modeling of the plasticity of porous materials. The behavior of porous materials has been extensively studied from an experimental, theoretical, and numerical point of view in the case of monotonic mechanical loading under large deformations, leading to constitutive equations that can be used to simulate ductile fracture of structures. The case of cyclic mechanical loading and / or involving low levels of deformation / low number of cycles has been comparatively little studied, even though this type of loading is of interest in industrial applications, for example in the case of earthquakes. In this thesis, the effect of oligocyclic loading on ductile fracture properties will be investigated systematically from an experimental, theoretical, and
numerical point of view. Test campaigns will be carried out on various materials used in nuclear applications and under different mechanical stress conditions in order to quantify the effect of oligocyclic loading on fracture deformation and toughness. At the same time, numerical simulations will be performed to obtain an extensive database on the plastic behavior of porous materials under cyclic loading, with a particular focus on the effects of elasticity, porosity, mechanical loading, and spatial distribution of cavities. These numerical simulations will be used to validate analytical models developed during the thesis to predict the evolution of porosity and yield stress. Finally, the models will be implemented in the form of constitutive equations and used to simulate experimental tests.