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Morfeo/crack for Abaqus

  • Extended description of Morfeo/crack for Abaqus
Morfeo/Crack for Abaqus relies on the implementation of the XFEM method available in Abaqus since version 6.10. The functionality of Abaqus is however limited to the calculation of stationary cracks. Morfeo/Crack for Abaqus enhances Abaqus and is capable of performing crack propagation simulations in complex geometries. The method is based on calling Abaqus/Standard at each propagation step. Between each step, it reads the Abaqus solution, recovers a richer, improved XFEM solution in a small area surrounding the crack using a tailored integration rule, accurately computes the stress intensity factors which determine the crack advance and updates the Abaqus input file with the new crack position. Moreover, Morfeo/Crack for Abaqus profits from the nice and intuitive user interface Abaqus/CAE since it is integrated in the latter as a plug-in for the definition of the initial crack position and the specific data for fatigue crack propagation. Finally, Morfeo/Crack for Abaqus offers the choice between post-processing the results in Abaqus/CAE as usual or in a freely available post-processor (gmsh), which renders the solution at the crack tip with a better accuracy and eases the realization of crack propagation movies.
  • Features
    • Problem definition and initial crack positioning in Abaqus/CAE
    • Automatic Abaqus/Standard execution at each propagation step with an input file updated with the current crack position
    • Recovered extended finite element solution in a small area surrounding the crack, called the crack area hereafter
    • Improved solution visualization in gmsh with respect to the visualization in Abaqus/CAE
    • J-integral computation with the equivalent domain integral method
    • Stress intensity factors extraction with the interaction integral method
    • Crack representation with the level-set method
    • Crack update with the fast marching method

 

  • Added value

Given that Abaqus has an XFEM implementation since v6.9-EF, one may wonder what it the added value of
Morfeo/Crack for Abaqus.
 
XFEM in Abaqus refers to 2 different features:
    • One is XFEM for propagating crack: the crack is roughly modelled by cohesive segments propagating through the elements. This method is useful for modeling delamination or a displacement-controlled low-cycle fatigue.
    • The other is XFEM for stationary crack: the current crack position is accurately modelled by a geometry, the stress intensity at the crack front is precidely considered and the stress intensity factors may be computed. This method is useful for assessing the stability of a given crack and the crack growth rate under a (high-cycle) fatigue loading may be predicted.
 
  
Morfeo/Crack for Abaqus actually extends the second feature above (XFEM for stationary cracks) to fatigue crack propagation. The distinctive features of Morfeo/crack for Abaqus over Abaqus alone are:
    • High precision tailored integration rules at the crack front
    • Enlarged enriched domain at the crack front where the stress singularity is precisely captured
    • Stress intensity factors computation accounting for
      • thermal strain
      • initial stress
      • crack curvature
→ Dispersion error of the stress intensity factors around the exact value is one order of magnitude smaller with Morfeo/crack for Abaqus compared to Abaqus
    • Fatigue propagation law
    • Unique algorithms based on the level set method for modelling the propagation of multiple, 3D cracks with no limitation on the crack shape