Defining a Minimum Truss Thickness (Minimum Member Size)

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.

This task shows you how to:

Related Topics
In Other Guides
DVCON_TOPO

Context:

The minimum member size control technique also 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 should 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 not possible 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 restriction should only be defined in the areas of the model where thin parts should be avoided. To identify these areas, the first step is to perform an optimization without restrictions.

Define a Minimum Member Size in Tosca ANSA® environment

  1. Choose DV_CONSTRAINTS and select New > MEMBERSIZE_CONTROL.

  2. In MEMBER_SIZE_CONTROL dialog, enter the element group and the desired minimum thickness using MEMBER_SIZE = MIN.

Define a Minimum Member Size in Tosca Structure.gui

  1. Choose Command > DVCON_TOPO in Tosca Structure.pre.

  2. Define the Minimum Member Size as shown in the following figure:

  3. Or use the DVCON_TOPO command:

    DVCON_TOPO
 ID_NAME = <Name of DVCON object>

 EL_GROUP = <Element group to be restricted>

 CHECK_TYPE = MIN_MEMBER

 THICKNESS = <minimum thickness of structures>
END_

    The result of the minimum / maximum member size control looks like follows:



Define a Minimum Member Size in Tosca Extension for ANSYS® Workbench

  1. To add a Membersize Control, select Topology > Membersize Control.

  2. In Details View window, select MIN_MEMBER as Check Type and insert the desired membersize as Thickness.