RD-E: 5102 Topology Optimization for Solids

This example outlines how to set up a topology optimization for solid elements part. A concentrated load is applied to the entire top of the part by using a rigid body. The lower part of the hook is the design space for the toplogy optimization.

Figure 1.
Topology optimization can be simulated with Altair Radioss by using the /DTPL option. The following typical topology optimization setup options are used.
  • Objective (minimize volume of the structure in this example)
  • Constraints (maximum displacement less than 5mm in this example)
  • Design variables (topology optimization of the design in hook example)

The setup of optimization requires an extra input optimization input file named <name>.radopt which defines the optimization objective, optimization constraints, design variables, and optimization responses.

For more Radioss optimization details, refer to Design Optimization in the User Guide.

Options and Keywords Used

  • Optimization objective (/DESOBJ)
  • Design Variable for Topology Optimization (/DTPL)
  • Optimization design response (/DRESP1)
  • Optimization design constraint (/DCONSTR)

Input Files

Refer to Access the Model Files to download the required model file(s).

The model files used in this example are available in:


Model Description

Units: mm, s, ton, N, and MPa

  • Objective: Minimize volume of hook (to saving materials)
  • Constraint: Maximum of total displacement in node group 120 less than 5.0 [mm]

Figure 2. Problem Description

Detailed Optimization Setup

Figure 3. Radioss Optimization Setup

Optimization Objective

/DESOBJ is used to define optimization objective. In this example, the objective is to minimize response #10.

Response #10 defines an optimization response that is the volume of defined optimization part.

The response type for an optimization run RTYPE=3 is Volume. PTYPE=3 and grpart=4 defined group part ID of 4 which is the design space where the optimization occurs.

Figure 4. Optimization Objective Setup in Radioss Optimization

Optimization Constraint

In this example, total displacement under concentrated load is limited to less than 5.0 mm to guarantee the quality of hook after topology optimization. In <name>.radopt file set total displacement of selected node group (ID) as response #11 and limit response #11 under maximum value 5.0. Depending on your own optimization criteria, the value in cmax may differ.

Figure 5. Optimization Constraint Setup in Radioss Optimization

Topology Optimization

Several parameters for topology design variables could be defined in /DTPL.
Minimum thickness
Stress constraint
Member Size Conrol
Mesh type
Draw Direction Constraints
Extrusion Constraints
Pattern Grouping
Pattern Repetition

Figure 6. Design Variable Setup in Radioss Optimization

The member size control function is enabled using MEMBSIZ=1 to improve the quality of the topology optimization. In this example the minimum diameter of members is set to MINDIM=2.5. It is recommended that MINDIM be at least 3 times, and no greater than 12 times, the average element size for all elements referenced by that /DTPL.

Draw direction for topology optimization is activated using DRAW=1. This results in a design that can be manufactored easier. DTYP is used to define the draw direction constraint type. In this example a “single die” type (DTYP=1) is used.


  1. Review the optimization results file to make sure that optimized design is satisfies the constraints and objective. This information is in the *.out file (hook_opt.out).
    Design is good
    Design does not meet the constraints defined

    The Radioss simulation for each design is included in the outer directories created during the simulation. All the animation results can be loaded by opening the hook_opt.mvw session file in HyperView.

  2. In the *.out file (hook_opt.out), check/verify the optimization definition. Objective Function: Minimize VOLUM, Run Type: Topology Optimization and so on. The Optimization results can be plotted in HyperGraph using the hook_opt.hgdata file.
  3. By running the Optimization in Radioss, an equivalent OptiStruct model will also be automatically created and named *.fem (hook_opt.fem).
Check the results in the hook_opt.eslout text file which contains the value of optimized objectives in each iterations.

Figure 7. Optimized Results in Each Iterations in *eslout File
The volume change of the design space:
  • In the original model, the volume is 324.7 mm3
  • After topology optimization, the volume is 251.0 mm3

After the topology optimization, the element densities of the different design iterations can be plotted in HyperView using the hook_opt_des.h3d file.

Figure 8. Optimized Results of Hook