Minimizing the Volume of the Crankshaft Model (Tosca Structure.gui)

This example shows how to add rotational displacement constraints and a center of gravity constraint.

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About Checking the Quality of the Optimization Result

  1. Start Tosca Structure.pre to define the optimization task.

  2. Import the analysis model crank_shaft.ext (ext=inp, bdf, dat...). If no groups are defined in the analysis input (e.g. for MSC Nastran® input) import the groups from the file groups.bdf which can be found in the same directory as the analysis input. For more details please refer to the Tosca Structure Getting Started manual.

  3. Create the design variable area. The group DESIGN_ELEMENTS contains the design elements.

  4. Add a design response for the volume as a sum of all design elements volumes.

  5. Create a design response for the rotational displacement on node 2 along the z axis. Select the first load case to refer the design response to.



  6. Create a second design response for rotational displacement on node 2 similar to the previous one. Select the rotation along the x axis and the assign the second load case to the design response.

  7. Create a design response for the y location of the center of gravity of the whole model. Make sure to switch the Group Oper to Sum.



  8. Define the objective function to minimize the design volume.

  9. Define constraints to maintain the torsional and bending stiffness as well as to set the y location of the gravity center. In the first constraint set the maximal value of 2.0e-6 for the z rotation of node 2. In the second constraint set the maximal value of 1.2e-6 for the x rotation of node 2. In the third constraint set a maximal value of -18 for the y coordinate of the center of gravity. All constraint types should be less or equal and the magnitude values should be set to ABS.

  10. Compose the optimization task (OPTIMIZE) and select the predefined definitions. Choose the TOPO_SENSITIVITY optimization strategy. Make sure to reference all defined CONSTRAINT items in the OPTIMIZE command

  11. Define some additional optimization parameters via the OPT_PARAM command. Increase the initial density from 0.5 to 0.9.

  12. Start the complete SIMULIA Tosca Structure optimization using the start option type = all.

The optimization is finished after approx. 20 design cycles. The results in form of material distribution are as follows: