About Member Size Control

The maximum and minimum member size restrictions prevent parts of the model from becoming too thick or too thin.

This page discusses:

See Also
Defining a Maximum Truss Thickness (Maximum Member Size)
Defining a Minimum Truss Thickness (Minimum Member Size)

Minimum Member Size Control

Thin trusses in the resulting structure are often undesirable, depending on the manufacturing process. Defining a minimum thickness avoids the creation of small substructures in the final result.

The minimum member size control feature ensures the mesh independence of the results. A coarse mesh and a fine mesh lead to the same optimized topology if the minimum member sizes for both cases are set to the same absolute size.

Note: In both cases, the size must be larger than the average element edge length.

Optimized engine support with and without MINIMUM member size restriction is presented in the following figure:
Note:

  • It is impossible to ensure the accurate minimum thickness of the structures. For some cases, the results contain parts with a diameter smaller than the defined minimum member size.
  • The CPU-time for the calculation increases quadratically with the minimum member size. To save calculation time, the recommendation is to only define the restriction in areas of the model where thin parts must be avoided. To identify these areas, the first step is to perform an optimization without restrictions.

Maximum Member Size Control

The definition of a maximum truss thickness is often required to design castable components. With this restriction, thick parts are avoided by splitting them into several thinner parts.

Usually, the maximum member size control is also a minimum member size control. In the restriction area, the resulting structure contains trusses mainly of the given defined diameter. Generally, no thinner trusses exist. Usually, the combination of a maximum member size control and a minimum member size control is not required.

The following figure shows a plate designed with and without maximum member size control:



There are different algorithms for the maximum member size feature implemented, where both result in distinct optimization results. While the default METHOD = FILTER obtains clearer results, METHOD = LOCAL_VOLUME tends to be more robust in terms of optimization convergence (see Defining a Thickness Control for the Plate Model).