Tech Briefs Magazine - May 2024 - 12

Topology Optimization
In this case, our goal is to maximize
stiffness for a certain amount of material.
The load cases are symmetric, which
allows us to save time and computational
resources by only modeling a quarter of
the domain rather than the full drone.
The model is then replicated during the
results visualization step so we can see
the full, optimized design at the end of
the process (Figure 1).
When running this topology optimization
example, the computation starts
with only the drone battery at the center
and the four motors at the corners. We
see the quarter that was originally modeled
mirrored in the rest of the design
and watch as the software adds material
to connect the motors to each other and
the battery at the center. The stiffnessto-weight
ratio of the material is then
adjusted until the end result has a clear
physical interpretation.
Figure 1. Top: The topology optimization functionality in COMSOL Multiphysics® with the add-on
Optimization Module can be used to generate a drone model with good performance. Bottom: The
model is shown with the displacement magnitude to help us visualize the optimization process.
(Image: COMSOL)
components. It would fall to the designer
to decide how to balance the needs
of different components, such as determining
which parts could sacrifice presentation
for stronger performance, and
vice versa.
Taking a Closer Look at
Topology Optimization
When using topology optimization,
designers create a geometric virtual
space (often a box-like frame) for their
design and input some required parameters
into the software. The software then
fills out the design by iteratively removing
and adding material, producing an
optimized design that fits within this
geometric space.
Topology optimization is typically
employed early in the design process
because there is more flexibility at this
stage and thus more potential for performance
improvements related to to12
pological
changes of the design layout.
The closer a project gets to the production
stage, the fewer design changes
can be made, unless the designer
is willing to spend more resources to
revamp the design. With topology optimization,
the designer can decide on
an optimal design with good performance
and then, as they get closer to
the production stage, shift their focus
to simulation accuracy. Though simulation
accuracy is always important, it
is especially relevant in the latter half
of the design process, when designers
are using the simulation to predict how
the device will work once it becomes a
physical prototype.
To better understand the design freedom
of topology optimization, consider
the following example of creating the
structure of a drone. For this model, we
input two load cases, the volume fraction,
and a minimum length scale.
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Suitability for Manufacturing
When it is time to produce a design,
its complexity is a key factor in deciding
which manufacturing process to
use. The unique results of generative
design and topology optimization are
usually not suitable for traditional manufacturing
and mass production. For
this reason, designs created with these
methods, or a hybrid technique, often
go hand-in-hand with additive manufacturing.
For instance, the drone model
example is best suited for additive
manufacturing.
However, this compatibility does not
mean that additive manufacturing is the
only option for bringing software-generated
designs to life. Often, designers
may want to use topology optimization
to improve on their design ideas but
also need to manufacture products at
a lower cost or larger scale than what
additive manufacturing usually permits.
Preparing such a design for traditional
manufacturing may mean, for example,
that milling constraints need to be
considered in the optimization process.
Specialized functionality for topology
optimization available in the COMSOL®
simulation software can be used
to account for such constraints.
Consider a scenario where a topology-optimized
wheel rim design needs to
be produced using subtractive manufacturing.
Figure 2 shows such an example
modeled with the COMSOL® software:
A wheel rim design is generated with
optimal stiffness, and milling constraints
are added along its axis. However, addTech
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