The user can define his/her own elements. In order to do so he/she has to:
- Give a name to the element. The name has to start with “U” followed by
maximal 4 characters. Any character from the ASCII character set can be
taken, but please note that lower case characters are converted into upper
case by CalculiX. Consequently, “Ubeam” and “UBEam” are the same
name. This reduces the character set from 256 to 230 characters.
- specify the number of integration points within the element (maximum 256), the number
of nodes belonging to the element (maximum 256) and the number of degrees of freedom in
each node (maximum 256) by using the *USER ELEMENT keyword card.
- write a FORTRAN subroutine resultsmech_uxxxx.f calculating the secondary
variables (usually strains, stresses, internal forces) from the primary
variables (= the solution of the equation system, usually displacements,
rotations....). Add a call to this routine in resultsmech_u.f
- write a FORTRAN subroutine e_c3d_uxxxx.f calculating the element stiffness
matrix and the element external force vector (and possibly the element mass
matrix). Add a call to this routine in e_c3d_u.f
- write a FORTRAN subroutine extrapolate_uxxxx.f calculating the value of
the secondary variables (usually strains, stresses..) at the nodes based on
their values at the integration points within the element. Add a call to
this routine in extrapolate_u.f
