In a general point of view, X-FEM plus level set representation of the interfaces reveals to be of great interest in the aim to couple experimental data with numerical simulations. This can be highly illustrated in the case of 3D fatigue crack growth simulations where the initial 3D “real crack” is extracted from tomo-graphic images. The experimentally observed fatigue crack propagation is compared to numerical simulations. Good agreement is found when a linear variation of closure stress along the crack front is taken into account in the “3D crack propagation law” used for the simulation. Furthermore, in order to take into account plasticity during fatigue crack growth, one develops an augmented Lagrangian formulation in the X-FEM framework that is able to deal with elastic-plastic crack growth with treatment of contact and friction. Numerical issues such as contact treatment and numerical integration are addressed, and finally numerical examples are shown to validate the method.