How to Avoid Rectangular Patterns in Topology Optimization When Using Member Size Controls

Heiko_H_870106

Dear Community

I am working on an out-of-plane bending problem. My objective is to identify the optimal load path for a quadrilateral plate, ultimately defining a structure that resembles a framework of bars. 

Model Setup:

• The plate is fixed at four locations (rotational degrees of freedom a free), which are not at the corners.
• Five separate forces of equal magnitude are applied to the plate.
• Non-design spaces have been defined around the support locations and the points of force application.

Optimization Setup:

• Objective: Minimize the volume of the structure.
• Constraints: A maximum displacement constraint is applied at each of the five force application points.

The Issue:

When I run the topology optimization using only a minimum member size (MIN DIM on the DTPL card, set to 3x the average element size), I obtain a reasonable and expected result.

However, when I introduce a maximum member size (MAX DIM, set to 3x the minimum member size + MIN GAP 3x MAX DIM), the resulting topology forms a distinct and undesirable rectangular or grid-like pattern. Using a checkerboard control parameter does not resolve this issue.

Question:Is there a way to prevent the formation of these rectangular patterns when using maximum member size controls in topology optimization?

Thanks and regards

Heiko 

Optistruct 2022.3

HW 2022.3

solon

Hello,

MAXDIM must be at least twice MINDIM, and hence the minimum mesh requirement is that MAXDIM has to be at least 6 times the average element size for all elements referenced by that DTPL. This constraint is strongly enforced and an error termination will occur when this criteria is not met. In addition, MAXDIM should be less than half the width of the thinnest part of the design region.

One thing you can try is using an extrusion constraint through the thickness of the thinnest direction in the design space.