1. Introduction

The ambition of cohesive models is to represent the evolution of the damage and/or rupture surfaces of a solid in 2D or 3D, initially healthy or already partially cracked, subjected to a very wide range of stresses (mixed mode, cyclic, thermal loads, etc.) in a quasi-static or dynamic regime for a material with or without nonlinearities in its behavior (elasticity, plasticity, viscosity, etc.). However, this ambition is limited, for the moment, to an evolution of surfaces whose direction is known a priori.

This approach, widely developed in the literature in recent years, is attractive for describing cracking phenomena. It is intermediate between the initiation criteria (energy return rate or stress criteria) and the continuous mechanics of the damage. When the geometric location of potential cracks is known, it provides a safe and robust framework for predicting propagation kinetics.

The purpose of this documentation is to provide users with a user guide. On the one hand to research units in order to maintain these models and make them evolve; but also to facilitate their use by engineering. In the first part, we summarize briefly the main lines of the models available in Code_Aster, their respective advantages and limitations as well as the references necessary for a more detailed understanding of their formulation. The precautions to be taken when creating the mesh are explained in the second part. The third is dedicated to advice for use in the various fields of fracture mechanics. Finally, we end this documentation with a commented example of use.