Running the Analysis
Use Analysis
Analysis Optimization in the FEA Editor or Results environment to access the Design Optimization dialog. The Analysis pull-down menu is used to run the analysis. From the pull-down menu, choose either of these choices:
- Perform Design Study: A design study will analyze the model with two analyses for each design variable. The results are presented only in the Design Optimization dialog as a series to sensitivity graphs.
- Perform Design Optimization: A design optimization analyzes the model with various combinations of the design variables, but not necessarily all combinations, to find the optimum set of variables that fit the objectives. The results are a series of graphs that are displayed in the Design Optimization dialog, a complete FEA model with the design variable set to the optimized value, and results for the model which can be viewed in the Results environment. The optimized model is named modelname_dsN_opt.fem. where N in _dsN is the number of the design scenario optimized.
During the analysis, the display window will show the on-going results by displaying the processor log file. After performing a Design Optimization, check the last iteration in the log file. Make sure the text ** The change of constraints are less than limit! appears to indicate that it was able to converge. If it did not converge, then the text ** Maximum iteration has been reached! will appear.
Regardless of whether the optimization converged or the maximum number of iterations has been reached, check the Optimum objective/Constraint value table (see Figure 1). The constraint values should be close to the lower or upper limit, but depending on the user-entered tolerance value, the constraint values may not be fully within the limit. You can decide whether the results are sufficient or not. If the amount of violation (outside of the limits) is not acceptable, increase the Maximum Iterations and run the analysis again.
| 01 | ** The change of constraints are less than limit! | ||||
| 02 | |||||
| 03 | ** Finished Optimization after 11 Iterations | ||||
| 04 | |||||
| 05 | ** Optimum Design Variables ** | ||||
| 06 | |||||
| 07 | Design | Current Value | Lower Limit | Start Value | Upper Limit |
| 08 | |||||
| 09 | 1 | 4.3402e-001 | 3.0000e-001 | 4.8000e-001 | 1.0000e+000 |
| 10 | 2 | 3.6666e-001 | 3.0000e-001 | 4.8000e-001 | 1.0000e+000 |
| 11 | 3 | 3.4084e-001 | 3.0000e-001 | 4.8000e-001 | 1.0000e+000 |
| 12 | 4 | 3.0001e-001 | 3.0000e-001 | 4.8000e-001 | 1.0000e+000 |
| 13 | |||||
| 14 | |||||
| 15 | ** Optimum Objective/Constraint Value ** | ||||
| 16 | |||||
| 17 | Obj/Const | Current Value | Limit Value | Change/Violation | |
| 18 | |||||
| 19 | Objective | 3.60380e+000 | 4.80000e+000 | 24.92083 % Decreased | |
| 20 | 1 th Const | 3.00000e+004 | 3.00000e+004 | 0.000052 % Violated | |
| 21 | 2 th Const | 5.06292e-001 | 5.00000e-001 | 1.258394 % Violated | |
| 22 | |||||
| 23 | ** Finished Optimization !! ** | ||||
| 24 | |||||
| 25 | >> Optimization log was saved at beam.ds_data\2\ds_opt\ds.opt1optlog | ||||
|
Figure 1: The Last Iteration of a Converged Design Optimization Analysis
Line numbers were added to help with the following description. |
|||||
The analysis has converged (line 01) because the change in the two user-entered constraints from one iteration to the next are less than the user-entered tolerance. Line 19 shows the objective (volume, being minimized). The Change/Violation column indicates the optimum design is 24.9% less than the user-entered current value. The first constraint (line 20, stress) had an upper limit of 30,000 specified. The final optimum value was essentially at this limit. The second constraint (line 21, displacement) was over the intended upper limit of 0.5 inches by 1.26%. Is the final optimum displacement of 0.506 inches acceptable? You will need to decide. (Text shown in bold is highlighted to correspond with this description.)