====== BLZ2D ======
FIXME The prepro subroutine for BLZ2D seems to have been copy/pasted from [[elements:blz3d|BLZ3D]] and contains discrepancies (notably NNODE = 8 when NNODE should be = 4) \\
The prepro subroutine needs to be checked and corrected.
===== Description =====

Plane or axisymmetric state. \\ 
For the axisymmetric state, the symmetry axis is Y. The element is defined by 4 nodes. {{  :elements:plani.png?200|}} \\
Element type: 8 \\
Revised by: Y. Zhu (1991)

==== Files ====
Prepro: BLZ2DA.F \\
Lagamine: BLZ2DB.F

===== Input file =====
**Note**: The prepro subroutine for BLZ2D seems to have been copy/pasted from [[elements:blz3d|BLZ3D]]. However, it is highly uncertain that all the features available for BLZ3D are as well available for BLZ2D. The uncertain features are written below in italic.
^Title (A5)^^
|TITLE|"BLZ2D" in columns 1 to 5|
^ Control data (2I5) ^^
|NELEM| Number of elements |
|INDPP| 0 → Static \\ 1 → Dynamic|
|INSHE|= 0 for automatic calculation of shear locking parameter|
|:::  |//= 1 if shear coefficient taken into account//|
|//ILOAX//|//= 0 for global axis computation \\ ☛ Objectivity must be verified in the material law (with Jaumann correction)\\ ☛ No rotation of material axes//|
|:::|//< 0 for computation with constant and symetrical velocity gradients \\ pseudo local axes : use of local axes on the time step but no evolution of the local axes on the following time step \\ ☛ Objectivity is verified \\ ☛ No rotation of material axes//|
|:::|//> 0 for computation with local axes \\ ☛ Objectivity is verified \\ ☛ Rotation of material axes//|
|:::|//units: \\ = 1 for rotations incorporated in local tangent matrix :!: **Not available** \\ = 2 apply final rotation to local tangent matrix \\ = 3 apply initial rotation to local tangent matrix \\ = 4 compute tangent matrix through global perturbation method//|
|:::|//tens (only for ILOAX>0): \\ = 0 for local axes e<sub>1</sub>, e<sub>2</sub>, e<sub>3</sub> initially parallel to global axes e<sub>x</sub>, e<sub>y</sub>, e<sub>z</sub> \\ = 1 for local axes e<sub>1</sub>, e<sub>2</sub>  given (and e<sub>3</sub>=e<sub>1</sub>∧e<sub>2</sub>) \\ = 2 for local axes e<sub>1</sub>, e<sub>2</sub>  initially in the plane (e<sub>x</sub>, e<sub>y</sub>) forming an angle θ with e<sub>x</sub>, e<sub>y</sub> (and e<sub>3</sub>=e<sub>1</sub>∧e<sub>2</sub>)\\ = 3 same as 1 with different local axes for each element \\ = 4 same as 2 with different local axes for each element//|
|INSIG| 0 → No initial stresses \\ 1 → $\sigma_Y=\sigma_{Y0}+yd\sigma_Y$ \\ 3 → See [[elements:plxls|PLXLS]]|
^Specific weight - Only if INDPP = 1 (3G10.0)^^
|WSPE(1)| = specific weight in X direction|
|WSPE(2)| = specific weight in Y direction|
|WSPE(3)| = density| 
^//Shear coefficient - Only if INSHE > 0 (G10.0)//^^
|//PARSHE//| //Shear locking coefficient ∈ [0,1] \\ - close to 0: avoid shear locking but higher risk of hourglass modes (use for thin elements in flexion) \\ - close to 1: avoid hourglass modes but higher risk of shear locking (use for cubic elements in shear)//|
^Definition of the elements (2I5/4I5) ^^
|NINTE| Number of integration points (1, 2, or 4)|
|LMATE| Number of the material law|
|NODES(4)| List of nodes|
|SIG0(6)| List of initial stresses (Only if INSIG ≠ 0) \\ **If INSIG = 1 (3G10.0)**: \\ $\sigma_{Y0}$ - Effective stress $\sigma_Y$ at the axes origin \\ DSIGY - Gradient of effective stress along axis OY \\ AK0 - ratio $\sigma_X/\sigma_Y$ \\ **If INSIG = 3 (6G10.0)**: See [[elements:plxls|PLXLS]]|