====== BEM3D ======
3D boundary element
===== Description =====
Boundary element using the "BEM" method in linear elastic mechanical analysis. \\ 
A group of BEM boundary elements defines a region considered as an equivalent finite element. \\
No volumetric force is taken into account. \\
Type: 61 \\
Implemented by: Y.S. Jiang, 1991
==== Files ====
Prepro: BE3DIM.F, BEM3DA.F \\
Lagamine: BEM3DB.F
===== Input file =====
^Title (A4)^^
|TITLE|"BEM3D" in the first 5 columns|
^Control data (I5)^^
|NEFEQ| Number of equivalent finite elements|
|NX| = 1 if the problem is symmetrical with respect to a plane perpendicular to axis X \\ = 0 else|
|NY| = 1 if the problem is symmetrical with respect to a plane perpendicular to axis Y \\ = 0 else|
|NZ| = 1 if the problem is symmetrical with respect to a plane perpendicular to axis Z (not available yet) \\ = 0 else|
|X|Coordinate of the symmetry plane along X|
|Y|Coordinate of the symmetry plane along Y|
|Z|Coordinate of the symmetry plane along Z|
==== Definition of an equivalent finite element ====
This section must be repeated NEFEQ times.
^Control data (9I5)^^
|LMATE|Material law - only the elastic material is accessible|
|NSUBE|Number of boundary BEM elements|
|NSUBD|Total number of nodes taken into account in the boundary elements|
|NSIGP|Number of interior points where stresses should be computed|
|NORET|Index for rigid body rotation (:!: Not available)|
|NTRAC|Number of surface traction (:!: Not available)|
|IFTRA|Index for the calculation of nodal traction at each step (:!: Not available):  \\ = 1 Yes \\ ≠ 1 No|
|NRI|Index for the control of rigid body rotation (:!: Not available)|
|INSOL|Index for the choice of fundamental solution (:!: Not available): \\ = 1 Green (fluid mechanics, problem of potential) \\ = 2 Kelvin (solid mechanics) \\ = 2 Mindlin (solid mechanics)|
|NINF|Index for the type of domain: \\ = 0 Finite domain \\ = 1 Infinite domain|
^Definition of the BEM elements (2I5/NELND(I5)) - Repeated NSUBE times^^
|NELND|Number of nodes of the boundary element (3, 4, 6 or 8)|
|NINP|Number of Gauss integration points (1, 4, or 9)|
|NODE(I) \\ I=1,NELND|List of nodes of the BEM element|
^Definition of the points of stress computation 3G10.0) - repeated NSIGP times^^
|XP|Coordinates of the point where the stress must be computed|
|YP|:::|
|ZP|:::|

=== Remarks ===
4 types of boundary elements are available:
{{  :elements:bem3d.png?500  |}}
The numbering direction must be done in order to get a normal to the element surface directed outwards of the domain.