In the optimization task editor, click the
Advanced tab.
Select the Condition-based optimization
algorithm.
Choose whether to Delete soft elements in region.
During the topology optimization process, the
Optimization module
distributes a given mass within the design area while it tries to satisfy the
constraints and optimize the objective. At the end of the optimization, the
structure contains hard (filled) and soft (void) elements. The soft elements
have a negligible influence on the stiffness of the structure; but they are
still relevant for the number of degrees of freedom of the structure and,
hence, influence the speed of the optimization process. The Delete
soft elements option allows you to select a region from which soft
elements that have only soft neighboring elements will be removed. The deleted
elements are reactivated if needed; for example, if the force flow changes
during the optimization.
If you chose to delete soft elements, you can prevent isolated soft
elements from being removed by choosing to delete only soft elements that have
neighboring soft elements. You can define a neighboring element as being within
the radius specified by the Average edge length (default)
or specified by a value that you enter. If the element edge length varies
considerably within the mesh, the radius calculated from the average edge
length can be misleading.
If you chose to delete soft elements, you can choose the method that
the
Optimization module
will use to delete elements:
-
Choose Standard deletion to check for
continuity before deleting soft elements. If the optimized model contains an
island of hard elements that are separated from the rest of the
model by soft elements, the
Optimization module
does not remove the soft elements. In addition, the
Optimization module
retains soft elements that are preventing hard elements from moving with
respect to each other; for example, hard elements that share a common edge but
not a common face.
-
Choose Aggressive deletion to delete soft
elements regardless of continuity.
If desired, enter the value of the Relative material density
threshold. An element is considered soft if its
relative material density that is less than this value, and the
Optimization module
removes it from the analysis.
Select the rate at which the
Optimization module
will modify the element properties during a topology optimization. You can
select the rate (Very small, Small,
Moderate, Medium, or
Large) and allow the
Optimization module
to calculate the number of design cycles required to meet this rate.
Alternatively, you can select Dynamic and enter
the maximum number of design cycles. The minimum number of design cycles is 10,
and the default value is 15. A reduction in the number of design cycles can
lead to undesired effects in the optimization. Although the resulting
structures have the same stiffness (the sum of the strain energy is almost
equal for the different results), changing the optimization speed can cause a
different truss configuration in the solution.
Select the volume deleted after the first cycle. You can enter a
percentage or an absolute value.
By default, the
Optimization module
removes 5% of the optimization region volume in the first iteration. In some
cases increasing this starting value will accelerate the optimization without
influencing the solution, especially for models where relatively low stresses
are present in large areas. Conversely, the
Optimization module
may remove too many elements in the first iteration if the starting value is
too high, leading to a failure in the optimization or a coarse structure.
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