.. _R7.02.19:

**r7.02.19** Cohesive elements with X- FEM
=========================================

**Summary:**

This document presents the various cohesive elements available with the extended finite element method (X- FEM). Three types of cohesive laws are available. The law introduced first is a regularized law, available for linear elements, a function of the displacement jump only. Following the limits of this last one, two mixed laws were introduced: one for linear elements, the other for quadratic elements. A crack propagation procedure with cohesive elements is implemented. It is based on linear mixed elements.

Cohesive elements are implemented in*Code_Aster* in 2D and 3D. They can be used with two types of discontinuities: through interfaces (keyword TYPE_DISCONTINUITE =' INTERFACE 'in DEFI_FISS_XFEM) and cohesive cracks (keyword TYPE_DISCONTINUITE =' COHESIF') that are used for propagation studies on an unknown path. The cohesive law is defined in STAT_NON_LINE, the resolution is performed with the command STAT_NON_LINE [:external:ref:`U4.51.03 <U4.51.03>`]. For a propagation study on an unknown path, the update of the cracked surface is done by the command PROPA_FISS, and the directional criterion is calculated by the command CALC_G.

     Table of Contents


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.. toctree::
    :hidden:

    self

.. toctree::
    :maxdepth: 2
    :numbered:

    Introduction
    Formulation_forte_du_probl_me_coh_sif
    Formulations_variationnelles
    Strat_gie_de_r_solution
    Expression_matricielle_du_probl_me
    Propagation_d_une_fissure_coh_sive
    Bibliographie
    Description_des_versions