In some designs, some elements may be desired to be solid or void (active or passive). In this tutorial you will learn how to set active and passive elements in the topology optimization program.
In some designs, some elements may be desired to be solid or void (active or passive). A $latex \texttt{nely} \times \texttt{nelx}\times \texttt{nelz}$ matrix with ones at elements desired to be solid, and a $latex \texttt{nely}\times \texttt{nelx}\times \texttt{nelz}$ matrix with zeros at elements desired to be void can be added to the program.

To solve the problem as shown below, the passive elements need to be defined first.

[expand title="Step.1: Define active/passive elements" expanded="true" tag="h5"]

The passive elements are defined by adding the following lines after line 62:

[matlab firstline="63"]
for ely = 1:nely
for elx = 1:nelx
if sqrt((ely-nely/2.)^2+(elx-nelx/3.)^2) < nely/3.
passive(ely,elx) = 1;
else
passive(ely,elx) = 0;
end
end
end
passive = repmat(passive,[1,1,nelz]);
x(find(passive)) = 0;
[/matlab]

[/expand]

[expand title="Step.2: Modify OC subroutine" expanded="true" tag="h5"]

One line is added in the OC subroutine under line 85:

[matlab firstline="86"]xnew(find(passive)) = 0;[/matlab]

[/expand]

[expand title="Step.3: Run the program" expanded="true" tag="h5"]

The optimized beam shown belown is promoted by the line

[matlab light="true"]top3d(60,20,4,0.3,3.0,1.5)[/matlab]

[/expand]