Optimization spreadsheet

When you create or edit a SOL 200 Design Optimization or SOL 200 Topology Optimization solution, you can specify the value of the MXCRTRSP parameter. This value determines whether Simcenter Nastran automatically creates a raw data .csv file during the solve, and what information that file contains.

MXCRTRSP value	Description
-1	No raw data file is created.
0	The raw data file includes the design objective value for each design cycle.For a SOL 200 Design Optimization solution, the file also includes the design variable value for each design cycle.
1–20	In addition to design objective values (and the design variable values for a SOL 200 Design Optimization solution), the raw data file includes design constraint values.The amount of design constraint information in the file varies, depending on the number of design constraints in the model and the MXCRTRSP value. For example, suppose the model has two design constraints, and each design constraint has a lower and upper limit (also called a bound). The file could contain four sets of constraint data:One set for the lower limit for the first constraintOne set for the upper limit for the first constraintOne set for the lower limit for the second constraintOne set for the upper limit for the second constraintHowever, if MXCRTRSP is set to 3, then the file would contain only three sets of data. Simcenter Nastran determines what information to include in the raw data file based on how greatly each constraint is violated (or close to being violated) during each design cycle—that is, which constraint has the most critical response.

The default value for MXCRTRSP is 5, so unless you change this parameter, the raw data file is created during the solve in the same folder where the Simulation file exists. Its file name is simulation_name-solution_name_sol200.csv, where simulation_name is the name of the Simulation file and solution_name is the name of the solution.

For each design cycle, this raw data file includes the design objective value, the design variable values (for a SOL 200 Design Optimization solution), and the values for up to the five most critical design constraints.

After you solve the solution, you can use the existing Optimization Spreadsheet command in Pre/Post to dynamically create a Microsoft Excel file. The first sheet in the spreadsheet displays the information from the raw data file. The subsequent sheets display graphs for the design objective, most critical design constraints, and design variables (only for a SOL 200 Design Optimization solution).

Note:

Comments in the raw data file that are preceded by the dollar sign character ($) are not included in the Excel spreadsheet.

Optimization sheet

For all solutions, the first sheet in the optimization spreadsheet includes a section with design objective and most critical design constraint values. For a SOL 200 Design Optimization solution, the spreadsheet also includes a section with design variable values.

(1) Design objective and most critical design constraint values; (2) Design variable values

In each section, the optimization spreadsheet includes one row of data for the model's initial state before any optimization occurs (design cycle 0) followed by one row for each design cycle.

Note:

When creating a SOL 200 Design Optimization solution, if you add user-defined text to the bulk data entries to specify that certain design variable values are limited to particular discrete values, the spreadsheet includes two rows for the last design cycle. You can optionally include two rows for other design cycles as well. To do this, set the DISBEG parameter for the solution. For more information, see Control the design optimization output.

The first row contains the data that does not impose the value limitation, and the second row contains the data that reflects the prescribed values. For example, suppose a particular design variable can have values of only 1.0, 1.5, or 2.0 rather than any value between 1.0 and 2.0. During the optimization process, Simcenter Nastran might generate results for which the design variable value is 1.45. That data appears in the first row. However, since 1.45 is not one of the prescribed values, the solver rounds it to one of the prescribed values, in this case 1.5. That data appears in the second row.

The design cycle ID for each rounded value is followed by the letter D. In the preceding example, the value 1.45 might appear in the row labeled 10, and the value 1.5 might appear in the row labeled 10D.

In the first section, the first column displays the design cycle number. The second column displays the progress made toward achieving the design objective. For example, if the design objective is to minimize the weight of the model, this column indicates the weight at each design cycle.

For each set of design constraint data, there are 11 columns under the heading Most critical constraint n, where n is an incrementing number that indicates the severity of the constraint violation. For example, if MXCRTRSP is set to 4, then 11 columns appear under each of the headings Most critical constraint 1, Most critical constraint 2, Most critical constraint 3, and Most critical constraint 4. The data that appears under Most critical constraint 1 reflects the most severe constraint violation; the data that appears under Most critical constraint 4 reflects the least severe violation (or no violation).

A constraint is considered violated when its normalized value is a positive number greater than the GMAX parameter for the solution, which is 0.005 by default. You can change this value when you create or edit the solution. When a constraint is violated, the normalized value appears in bold red text.

(1) Design cycle numbers; (2) Design objective values; (3) Most critical design constraint data

You can identify which design constraints are included in the spreadsheet by examining the information that appears in the Resp. Type and Resp. Label columns. For example, suppose a topology optimization model includes a global design constraint for weight and two subcase design constraints for displacement. If WEIGHT appears in the Resp. Type column, then the data in that row is related to the global design constraint for weight. If DISP appears in the Resp. Type column, you can look at the Resp. Label column to determine which of the two displacement constraints is involved.

The data that appears under each Most critical constraint heading can vary, depending on its normalized value, which indicates how greatly the constraint is violated. In the preceding graphic, for the first 31 design cycles, the normalized value is highest for the weight constraint, so weight data appears under Most critical constraint 1 for design cycles 1–31. However, for design cycle 32, the normalized value is highest for a displacement constraint. As a result, the displacement data appears under Most critical constraint 1 for design cycle 32.

Each set of design constraint data includes the following information.

Column title	Description
Constr. ID	An integer that identifies the design constraint.This value appears in the Label box in the Design Constraint dialog box in Pre/Post.
Norm. Value	A value that indicates whether the constraint is violated, and to what extent.A positive value greater than the GMAX parameter indicates a violated constraint; a negative value indicates that the constraint is within the defined limits. When a constraint is violated, the normalized value appears in bold red text.The greater the normalized value, the more significant the deviation.
Resp. Value	The actual response value as calculated by the solver.
Bound Type	An indicator that the response value is supposed to be either greater than or equal to a specified lower limit (>=), or less than or equal to a specified upper limit (<=).
Bound Value	The value that the response value should be greater than or equal to, or less than or equal to.This value appears as the lower or upper bound or limit in the Design Constraint dialog box.
Resp. ID	An integer that identifies the design response.For a SOL 200 Design Optimization solution, this value appears in the Label box in the Modeling Object group in the Design Response Quantities dialog box. For a SOL 200 Topology Optimization solution, this value appears in the Label box in the Design Constraint dialog box.
Resp. Label	A unique label that identifies the design response.For a SOL 200 Design Optimization solution, this value appears in the Label box in the Response Definition group in the Design Response Quantities dialog box. For a SOL 200 Topology Optimization solution, this value appears in the Response Label box in the Design Constraint dialog box.
Resp. Type	The type of response being constrained.This value appears in the Response Type list in the Design Response Quantities dialog box (for a SOL 200 Design Optimization solution) or the Design Constraint dialog box (for a SOL 200 Topology Optimization solution). Only the portion of the name that appears in parentheses (such as WEIGHT or DISP) appears in the spreadsheet.
Subcase	The ID used by Simcenter Nastran to identify the subcase associated with the constraint.Note: This subcase ID might differ from the subcase ID that appears in the Subcase Association Manager in Pre/Post.For global constraints in a SOL 200 Topology Optimization solution, this column displays N/A.
Location 1	A short string that describes the response definition.For example, if a displacement constraint applies in the Z-direction of a node, this column might display DOF: 3. More complex definitions might be identified by the Simcenter Nastran item code, such as CODE: 17. For more information, see Item Codes Overview and DRESP1.If the constraint is not location-specific (such as a weight constraint), this column displays N/A.
Location 2	A short string that describes the location of the object being constrained.For example, if a displacement constraint applies to node 7459, this column might display GRID: 7459. If a stress constraint applies to element 827, this column might display ELEM: 827.If the constraint is not location-specific (such as a weight constraint), this column displays N/A.

For a SOL 200 Design Optimization solution, the second section of the Optimization sheet includes two identifiers for each design variable. The first identifier (in the DVID row) corresponds to the modeling object label, which appears in the Label box in the Modeling Object group in the Design Variable dialog box in Pre/Post. The second identifier (in the Label row) corresponds to the Label box in the Design Variable (DESVAR) group in the same dialog box.

The subsequent rows display the design variable value for the initial state of the model and all design cycles. (The use of two rows for discrete values applies to this section as well.)

Note:

All cells that contain numbers use the General format to enhance readability. When a column is narrow, numbers with decimals are rounded. When a number has 12 or more digits, scientific notation (the E format) is used, regardless of the column width. Extraneous zeros are removed. For more information, refer to your Microsoft Excel documentation.

Graphs

In addition to the optimization data, the optimization spreadsheet includes graphs that plot various values as a function of the design cycles.

• Design Objective—This graph indicates which design cycles reflected improvements in achieving the design objective, and when the design objective values began to level off. Based on this information, you might want to adjust the number of design cycles in your solution.

• Most Critical Constraint n—For each set of design constraint data, the spreadsheet includes a graph of the normalized values. Although the value for each design cycle might be associated with a different design constraint, the graph provides insights into the changes in the normalized values over the course of the optimization process.

• Design Variable—For a SOL 200 Design Optimization solution, the spreadsheet includes a graph for each design variable (up to a maximum of 20). The name of each sheet is DV-DVID-Label, where DVID and Label are the identifiers used for the design variable in the first sheet. This graph indicates changes to the design variable values over the course of the optimization process.

Where do I find it?

MXCRTRSP or GMAX parameter

Application	Pre/Post
Prerequisites	A Simulation file as the work part and displayed partSimcenter Nastran as the specified solverStructural as the specified analysis typeSOL 200 Design Optimization or SOL 200 Topology Optimization as the specified solution type
Location in dialog box	Solution dialog box→Bulk Data page→Create Modeling Object next to Design Optimization Parameters (SOL 200 Design Optimization) or Topology Optimization Parameters (SOL 200 Topology Optimization)→E-Z group→GMAX or MXCRTRSP box

Optimization spreadsheet

Application	Pre/Post
Prerequisites	A Simulation file as the work part and displayed partSimcenter Nastran as the specified solverStructural as the specified analysis typeSOL 200 Design Optimization or SOL 200 Topology Optimization as the specified solution type
Simulation Navigator	Solution node→Results→right-click Structural→Optimization Spreadsheet

How do I

Create an optimization spreadsheet

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Optimization spreadsheet, Simcenter 3D 2021.1 Series

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