To Set Up an Optimization Study

1. Click Home >

Optimization Study. The Optimization Study Setup dialog box opens.

3. To select items to include in the study, select check boxes from the following lists:

4. If required, click Advanced Settings, and set any of the following advanced settings in the Optimization Study Advanced Settings dialog box:

1. Diagnostic code (DIAG)—Type the code number to specify the level of the diagnostic output.

2. Memory limit in MB—Type a value in megabytes to specify the maximum memory.

3. Processors (THREADS)—Type a value to specify the number of processors (threads).

4. Automatic SPC (single point constraint)—Select Yes to automatically constrain the degrees of freedom, with little or no stiffness.

5. Parameters—Expand the list, click

to add a row, and then type the parameter name and value to add parameters that control the analysis settings.

1. Max. design cycles (DESMAX)—Type a value to specify the maximum number of design cycles allowed for the optimization study.

2. Topology index—Select an option to specify the method for defining the compliance index objective function:

▪ Normalized Reciprocal (TINDEXM=0)—Responses are normalized by their values in the first design cycle. The compliance index objective function terms are calculated using reciprocals for negative weighting factors.

▪ Normalized Direct (TINDEXM=1)—Responses are normalized by their values in the first design cycle. The compliance index objective function is a straight summation.

▪ Reciprocal (TINDEXM=2)—Responses are not normalized. The compliance index objective function terms are calculated using reciprocals for negative weighting factors.

▪ Direct (TINDEXM=3)—Responses are not normalized. The compliance index objective function is a straight summation.

3. Linearization (LINAPR)—Select an option to specify the method for controlling the approximation optimization method:

▪ Regular (LINAPR=0)—Use the fast linear approximations method when all approximations are linear. If any approximations are nonlinear, then the program will use its standard hybrid approximations.

▪ Aggressive (LINAPR=1)—Use the fast linear approximations method for all responses.

4. Convergence—Type values to specify when the optimization process is complete. The optimization considers both hard convergence and soft convergence. Soft convergence is when no further progress can be made (design variables do not change). Hard convergence is when two consecutive design cycles do not improve the objective values, though there is significant change in the design variables.

▪ Hard absolute (CONV2)—Specifies the absolute change criterion to detect hard convergence of the overall optimization process. Optimization terminates if the absolute change in the objective function is less than the given value for two consecutive design cycles and all constraints are satisfied.

▪ Hard relative (CONV1)—Specifies the relative change criterion to detect hard convergence of the overall optimization process. Optimization terminates if the relative change in the objective function is less than the given value for two consecutive design cycles and all constraints are satisfied.

▪ Hard max. violation (GMAX)—Specifies the maximum constraint violation allowed at the optimum. Constraints are normalized so a value of 0.005 represents a 0.5 percent constraint violation.

▪ Soft constraint (CONVCN)—Specifies the allowable change in the maximum constraint value for soft convergence. Optimization terminates if the change in the maximum constraint value is less than the given value, and the Soft Variable check is satisfied during the approximate optimization.

▪ Soft variable (CONVDV)—Specifies the relative change criterion to detect soft convergence of the overall optimization process. Optimization terminates if the maximum relative change in the design variables is less than the given value and the Soft Constraint check is satisfied during the approximate optimization.

5. Move Limits—Type values to limit the amount that design variables can change during a design cycle.

▪ Fractional topology (DELT)—Specifies the fractional change allowed for each topology design variable during the approximate optimization.

▪ Min. topology (DTMIN)—Specifies the minimum move limit fraction imposed for topology design variables at a given design cycle.

6. Screening (DSCREEN)—Type values for Truncation threshold (TRS) and Max. retained constraints (NSTR) next to each constraint to keep only the constraints that are potentially critical for the current design cycle.

7. Parameters—Expand the list, click

to add a row, and then type the parameter name and value to add parameters that control the design settings.

1. Design post output—Select the cycles from the list to specify the design cycles for which results are requested in the optimization post-processing files (*DENS.pch).

2. Analysis post output—Select the cycles from the list to specify the design cycles for which results are requested in the analysis post-processing files (*.pch).

3. Recorded Results—Expand the list, and select the check boxes next to the results to record in the output file.

6. In the Optimization Study Setup dialog box, click one of the commands described below:

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Save—Save the optimization study with the model. The dialog box remains open.