DENSITY_MOVE |
This option decides the maximum possible change of the pseudo density values
within each optimization iteration. Smaller values of this
parameter help to overcome convergence issues. But at the
same time, the convergence rate can be slower when compared
to the default settings. The default value is
DENSITY_MOVE=0.25. In cases where it is
observed that either the objective function or some of the
constraints are oscillating, the recommendation is to set
DENSITY_MOVE=0.1. |
DENSITY_UPDATE |
This option affects the behavior of CSA (Algorithm based on Convex Separable
Approximations). The two available schemes of density update
are CONSERVATIVE and
NORMAL. Conservative update method is
considered to be more stable. The default is
DENSITY_UPDATE=NORMAL. In cases where it is
observed that either the objective function or some of the
constraints are oscillating, the recommendation is
DENSITY_UPDATE=CONSERVATIVE. |
DENSITY_INITIAL |
Material properties of design elements are scaled (solid and void properties
are interpolated) based on the pseudo density values.
Different material interpolation schemes like
SIMP and RAMP are
available in Tosca Structure. The initial pseudo density values can be set by the
DENSITY_INITIAL option. If one of the
constraints is based on volume design response, then the
initial density is set equal to the value of the volume
constraint by default. In all other cases, the initial
density value is set equal to 0.5. Note, to compare the
DRESP value of Tosca Structure with the solver results set DENSITY_INITIAL =
1 and use the DRESP value from design cycle 0. |
DENSITY_LOWER |
In topology optimization, the voids are not created by deleting the finite
elements from the mesh, but are simulated scaling the
stiffness of the design elements to a very low value. Zero
elemental stiffness would lead to the loss of positive
definiteness of the global structural stiffness matrix. The
corresponding system of equations would not be solved.
Hence, a minimum value of pseudo density is used within
topology optimization. The default value is
DENSITY_LOWER=0.001 but can be modified by
the user. |
SOFT_DELETE_METHOD |
In a topology optimization process, the structure consists of hard (filled)
and soft (void) elements. The soft elements have a
negligible influence on the stiffness of the resulting
structure but they are still relevant for the solution of
the system of equilibrium equations. The soft delete option
activates a procedure that looks for elements that could be
potentially distorted during the optimization procedure
based on the user-defined criteria and deletes them from the
finite element mesh. The deleted elements are reactivated if
required, in case that the force flow changes during the
optimization. Note, this procedure is useful to stabilize
the optimization in the context of nonlinear structural
analysis and helps to overcome solver instabilities. By
default, it is not activated. |
AUTO_FROZEN |
This option is used to keep elements with loaded nodes and boundary
conditions from being optimized. There are four settings
available: LOAD, SPC,
BOTH, and OFF.
LOAD and SPC constrain
elements with loaded nodes or boundary conditions,
respectively, from being optimized, while
BOTH simultaneously freezes all elements
with either load and boundary condition. The default setting
is AUTO_FROZEN=LOAD. |