Keyword type: step
This procedure is used to perform a static analysis. The load consists of the sum of the load of the last *STATIC step and the load specified in the present step with replacement of redefined loads.
There are two optional parameters: SOLVER and DIRECT. SOLVER determines the package used to solve the ensuing system of equations. The following solvers can be selected:
Default is the SGI solver. If this solver is not installed, default is SPOOLES. If neither the SGI solver nor SPOOLES are installed, default is TAUCS. Finally, if neither the SGI solver, nor SPOOLES nor TAUCS are installed, the default is the iterative solver, which comes with the CalculiX package.
The SGI solver is the fastest, but is is proprietary: if you own SGI
hardware you might have gotten the scientific software package as well, which
contains the SGI sparse system solver. SPOOLES is also very fast, but has no
out-of-core capability: the size of systems you can solve is limited by your
RAM memory. With 2GB of RAM you can solve up to 250,000 equations. TAUCS is
also good, but my experience is limited to the decomposition, which
only applies to positive definite systems. It has an out-of-core capability
and also offers a
decomposition, however, I was not able to run either of
them so far. Next comes the iterative solver. If SOLVER=ITERATIVE SCALING is
selected, the preconditioning is limited to a scaling of the diagonal terms,
SOLVER=ITERATIVE CHOLESKY triggers Incomplete Cholesky
preconditioning. Cholesky preconditioning leads to a better convergence and
maybe to shorter execution times, however, it requires additional storage
roughly corresponding to the nonzeros in the matrix. If you are short of
memory, diagonal scaling might be your last resort. The iterative methods
perform well for truely three-dimensional structures. For instance,
calculations for a hemisphere were about nine times faster with the ITERATIVE
SCALING solver, and three times faster with the ITERATIVE CHOLESKY solver than
with SPOOLES. For two-dimensional structures such as plates or shells, the
performance might break down drastically and convergence often requires the
use of Cholesky preconditioning. SPOOLES (and any of the other direct solvers)
performs well in most situations with emphasis on slender structures but
requires much more storage than the iterative solver. Finally, there is the
PROFILE solver which performs well up to about 20,000 equations. For larger
systems is consumes too much memory and is slow. In CalculiX it can only be
used for linear calculations (no geometric or material nonlinearities allowed).
The parameter DIRECT is relevant for nonlinear calculations only, and indicates that automatic incrementation should be switched off.
In a static step, loads are by default applied in a linear way. Other loading patterns can be defined by an *AMPLITUDE card.
First line:
Example: *STATIC,DIRECT .1,1.
defines a static step and selects the SPOOLES solver as linear equation solver in the step (default). If the step is a linear one, the other parameters are of no importance. If the step is nonlinear, the second line indicates that the initial time increment is .1 and the total step time is 1. Furthermore, the parameter DIRECT leads to a fixed time increment. Thus, if successful, the calculation consists of 10 increments of length 0.1.
Example files: beampic, beampis.