====== CZM3D ======
3D cohesive zone model \\
:!: Still under development (?) - Last update: 2005 (C. Lequesne)
===== Description =====
{{  :elements:czm3d.png?300|}}
This element models the fracture of a material in case of monotonous loading or fatigue. \\ \\
This element, which models an interface of the crack, is composed with 4 nodes and linked with a 4 nodes foundation (ICODE=11), which models the other interface. \\ \\
Direction convention: The normal direction is defined by the vector cross product $\vec{n} = \vec{12} \wedge \vec{13}$ for the cohesive element and the foundation. The two normal vectors must penetrate the foundation. \\ \\
This element uses the cohesive law of Xu and Needleman (ITYPE=295), and can be coupled with the fatigue computed with the 3D Lemaitre and Chaboche fatigue damage law in the BLZ3D element and ARB law. \\ \\
Notes:
  * In case of fatigue it is required that ILIEN is equal to 1 (Prepro: 2<sup>nd</sup> line and 65<sup>th</sup> column)
  * In symmetric case, the symmetric plan must be the CZM3D and not the foundation
Type: 224 \\ 
Implemented by: C. Lequesne (2005)
==== Files ====
Prepro: CZM3DA.F \\
Lagamine: CZM3DB.F

===== Input file =====
^Title (A5)^^
|TITLE|"CZM3D" in the first 5 columns|
^Control data (2I5)^^
|NELEM|Number of elements|
|IMICRO| See details below|
^Definition of the elements (5I5/4I5)^^
|NINTE|Number of integration points (1, 4, or 9)|
|LMATM|Constitutive law|
|IFOND|Number of linked foundation|
|IFAT|Fatigue or not|
|ISYM|Symmetric case or not|
|NODES(4)|List of nodes|


 __IMICRO__

If =0, the tolerance of the distance between foundations and CZM3D nodes is 1.0E-4.

If =1, the tolerance is changed to 1.0E-6.
===== Results =====
__Stress:__ \\
Normal stress $T_n$ \\
Shear stress $T_p$ and $T_s$ \\
\\
__Internal variables:__ \\
  * The first ones are the variables computed by the constitutive law (cf. FCZM in law section)
  * The next ones is about the contact geometry:
    * ISEG: The number of the linked foundation's segment
    * DUN: The normal separation
    * DDUT: The shear separation
    * DDUN: The normal separation rate