OS-E: 0845 Control Arm with Local Stress Constraint

Demonstrates the use of Stress Constraint in Topology Optimization on a control arm.

The finite element mesh containing designable (red) and non-designable regions (brown) is shown in Figure 1.

Figure 1. FE Model

Model Files

Before you begin, copy the file(s) used in this example to your working directory.

Model Description

Topology optimization of control arm is solved for:
Analysis Type
Linear Static
Force and Moment
Objective: Min Volume
Subject to: Local stress constraint

New stress responses for Topology and Free-Size optimization can be defined via the DRESP1 Bulk Data Entry. The Stress Responses are internally aggregated using the Stress-NORM approach to maintain the number of created responses at a reasonable number.

The Stress-NORM method is used to approximately calculate the maximum value of the stresses of all the elements included in a particular response. This is also scaled with the stress bounds specified for each element. Therefore, to minimize the maximum stresses in a particular element set, the resulting Stress NORM value is internally constrained to a value lower than 1.0. For more information on the Stress-NORM method, refer to the DRESP1 Bulk Data Entry in the Reference Guide.
FE Model
Elements Types
The linear material properties are:
Young’s Modulus
1.6E5 MPa
Poisson's Ratio
Initial Density
7.1E-9 Mg/mm3


Figure 2. Element Stress Plot
OptiStruct provides the Element density information for all of the iterations (Figure 3 and Figure 4). In addition, OptiStruct will also show Displacement and von Mises stress results of a linear static analysis for iteration 0 and iteration 44 (Figure 2).

Figure 3. Element Density Contour

Figure 4. Element Density Contour (different view)