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1. The first step consists in loading the structure mesh (a) as well as the crack surface geometry (b).\r
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-2. The crack is then meshed (c). A length criterion defines the size of the extracted « Box ». This length is called the length of influence. Every element having a node within this zone is included in the « Box ». A second operation adds elements in the Box in order to have continuous faces (d).\r
+2. The crack is then meshed (c). A length criterion defines the size of the extracted « Box ». This length is called the length of influence. Every element of the structure mesh having a node within this zone is included in the « Box ». A second operation adds those elements in the Box in order to have continuous faces (d).\r
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3. A geometrical Box is reconstructed from the extracted Box mesh. The reconstruction is limited to faces which intersect the crack (e). A torus is created following the crack front (f).\r
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.. image:: images/longueur_influence.png\r
:width: 600\r
:align: center\r
+ :alt: The length of influence\r
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Every element having a node at a smaller distance to the crack than the length of influence is selected. Then a filling algorithm fulfill the Box with elements to get a Box. The Box is not limited to rectangular shapes. See the section on :ref:`test cases <test_cases>` to see examples.\r
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.. image:: images/schema_lignes1.png\r
:scale: 80\r
+ :alt: Crack front edges\r
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5) **Loss of element groups:**\r
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