Use Analysis
Analysis Optimization in the FEA Editor or Results environment to access the Design Optimization dialog. The Performance tab is used to specify the objectives of the design optimization and the constraints for each. What result will be minimized or maximized or otherwise limited? Use the Add Row button to add additional objectives and the Delete Row button to remove an existing objective.
The input for the Performance tab is as follows:
Objective/Constraint
Select a cell in the Objective/Constraint column and use the drop-down list to select one of the available objectives. The available objectives are as follows:
- Volume
- Max Stress will use the beam Worst Stress for beam parts and the von Mises stress for all other parts. These are unsmoothed values.
- Max Displacement will use the displacement magnitude.
- Frequency will use the specified frequency in cycles/time.
- Max Strain Energy Density will use the calculated strain energy density (linear static stress, plate elements only)
Loadcase
The Loadcase column indicates which set of results to use for the objective. Acceptable entries are 0 or a specific number. Zero (0) indicates that all load cases are used for the Objective/Constraint. The load case number has the following correlation to the analysis type:
- Static Stress with Linear Material Models: one load case from the analysis
- Natural Frequency (Modal) or Natural Frequency (Modal) with Nonlinear Material Models: one mode shape/frequency from the analysis.
- MES with Nonlinear Material Models, MES Riks Analysis, or Static Stress with Nonlinear Material Models: one time step number from the analysis.
Type
Specify how the objective will be treated using the Type column. Each design optimization must have either one objective minimized or maximized, but it cannot have more than one. Any number of objectives can be set to upper limit and lower limit.
- Technically speaking, the objective of the analysis is the entry that is either minimized or maximized. The other items with upper or lower limits are constraints.
- Since only one objective can be specified, use an upper limit or lower limit constraint to minimize or maximize a second objective. For example, it is not possible to minimize the volume and maximize the displacement. Instead, choose to minimize the volume and set a lower limit on the displacement.
Part
Use the Part column to indicate which part the objective will be based on. Acceptable entries are 0, All, or a specific part number. Zero (0) or the word All (without the quotation marks) indicates that all parts in the model are used for the Objective/Constraint. For example, if the objective is Max Stress and the part is set to All, then the stress in all parts will be checked. Therefore, a stress in a part that is not being optimized could be selected as the maximum stress. Since such stresses may not be affected by changing other parts, an option instead of specifying All would be to repeat the objective row multiple times but specify a single part each objective in the Part column.
Current Value
Use the Current Value column to indicate the current value of the objective, based on the current values of the design variables (not necessarily the values entered when creating the model). Although these values should be accurate, they do not need to be precise. The optimization algorithm uses the current values of the objectives as a starting point in the solution. These parameters are normalized by the design variable current values and used in the algorithm. So the more accurate the values that are entered, the better the solution. The design optimization results graphs also begin at the user-entered current value.
Limit Value
Use the Limit Value column to specify the limiting value for the objective. For an upper limit constraint, the limit value would be the maximum acceptable value. For a lower limit constraint, the limiting value would be the minimum acceptable value.