# the PDF - Altair University

```Topology optimization with Pattern
repetition using HyperMesh and
OptiStruct
hy do we need manufacturing constraints?
Firstly, why
Topology Optimization results sometimes give design which cannot be manufactured economically.
At this stage we need some constraints to apply on the design so that the end design results can be
manufactured within the available tools and costs.
OptiStruct offers few such manufacturing constraints to apply for the base design and get an output
design which can be easily manufactured. Few such manufacturing constraints are minimum and
maximum member size, Draw direction (Dv’s with PSOLID), Extrusion (Dv’s with PSOLID), pattern
grouping and pattern repetition.
In this tutorial we will discuss about pattern repetition manufacturing constraint
raint using modelled in
HyperMesh
sh and solved using Altair OptiStruct.
OptiStruct
Setting up the model:
Pattern repetition enforces same topology layout on different parts that can be scaled or
Overlap only partially.. For instance I have two
tw different components for a model with different loads
and boundary conditions and I need a similar topology layout for both the components. In such
cases pattern repetition comes in handy.
In this example, I have two plates with different thicknesses, BCs
boundary shells are made as non-design
non design space and the remaining is made as designable volume for
optimization.
Bottom plate has a thickness of 1 mm and upper plate has a thickness of 0.5mm. Material used for
both the plates is same.
Loads and boundary conditions are defined as shown in above picture:
picture
Create a linear static load case with the above
abov loads and boundary conditions.
Create topology design
constraints for the model:
variable
and
manufacturing
Create two design variables for top and bottom plate designable spaces with type as PSHELL
First, let us not create any pattern repetition manufacturing and check how the topology changes for
a given set of responses (objective and optimization
opti
design constraints)
Create responses,
constraints:
optimization
objective
and
design
I have two responses. One is compliance and the other is volume fraction. My objective for this
model is to minimize the compliance with a constraint on volume fraction
fraction of 0.3.
Run the analysis and post process the results.
Toggle the result to final iteration and look at the element density change.
Let’s add pattern repetition manufacturing constraint and see how the topology changes for both
the components.
Pattern repetition manufacturing constraint:
Go to the topology panel
nel and create pattern repetition manufacturing constraint.
constraint
We have created two DTPL cards (design variables) one is master and the other is slave. You can
have more than 1 slave DTPL card.
Switch to Pattern repetition in Topology panel and select master DTPL under devsar and select
anchor node and click update:
Similarly select slave for devsar and select anchor as shown:
The master and slaves are related through local coordinate system
system associated to master and slave
DTPL cards.
Scaling factors can be specified to slave components. For more information on pattern repetition
manufacturing constraints, please refer to OptiStruct user’s guide:
Altair OptiStruct > User's Guide > Design Optimization
Optimization > Manufacturing Constraints >
Manufacturability for Topology Optimization:
Update and run the analysis. If the run is successful you should see the following
Post-process
process the topology results in HyperView and observe the changes in the topology of the
model.
Pattern repetition manufacturing constraint can be used for both solid and shell elements and also
this can be clubbed with other manufacturing constraints in topology optimization.
```