Defines a structural analysis property as a function of a linear combination of design variables.
Entry Description:
DVPREL1 ID TYPE PID FID PMIN PMAX C0
DVID1 COEF1 DVID2 COEF2 DVID3
-etc.-Field Contents
ID Unique identification number. (Integer > 0).
TYPE Name of a property entry, such as “PBAR”, “PBEAM”, etc. (Character).
PID Property entry identification number. (Integer > 0).
FlD Field position of the property entry, or word position in the element property table of the analysis model. (Integer ≠ 0.0).
PMIN
Minimum value allowed for this property. If FID references a stress recovery location, then the default value for PMIN is -1.0+35. PMIN must be explicitly set to a negative number for properties that may be less than zero (for example, field ZO on the PCOMP entry). (Real; Default = 0.001).
PMAX Maximum value allowed for this property. (Real; Default = 1.0E20).
C0 Constant term of relation. (Real; Default = 0.0).
DVIDi DESVAR entry identification number. (Integer > 0).
COEFi Coefficient of linear relation. (Real).
Associated Entries:
Design variables are referenced on DVPREL1 entries by their DESVAR-defined IDs.
DESVAR ID LABEL XINIT XLB XUB DELXV DDVAL
Discussion:
An analysis model property can be expressed as a linear combination of design variables as
Equation 4-8.
Both independent as well as dependent design variables can appear in this relation (see the DLINK entry). This form is especially useful in the sense that it can be used to express not only a simple one-to-one correspondence between a design variable and a property, but more complex reduced basis formulations as well.
DVPREL2
Purpose:
Defines a structural property by reference to an equation defined on a DEQATN entry.
Entry Description:
DVPREL2 ID TYPE PID FID PMIN PMAX EQID
“DESVAR” DVID1 DVID2
-etc.-“DTABLE” LABL1 LABL2
-etc.-Field Contents
ID Unique identification number. (Integer > 0).
TYPE Name of a property entry, such as PBAR, PBEAM, etc. (Character).
PID Property entry identification number. (Integer > 0).
FID Field position of the property in the analysis model entry. (Integer ≠ 0.0).
PMIN
Minimum value allowed for this property. If FID references a stress recovery location field, then the default value for PMIN is -1.0+35. PMIN must be explicitly set to a negative number for properties that may be less than zero (for example, field ZO on the PCOMP entry). (Real; Default = 0.001).
PMAX Maximum value allowed for this property. (Real; Default = 1.0E20).
EQID DEQATN entry identification number. (Integer > 0).
“DESVAR” DESVAR flag. Indicates that the IDs of DESVAR entries follow. (Character).
DVIDi DESVAR entry identification number. (Integer > 0).
“DTABLE”
DTABLE flag. Indicates that the IDs for the constants in a DTABLE entry follow. This field may be omitted if there are no constants involved in this relation. (Character).
LABi Label for a constant on the DTABLE entry. (Integer > 0).
Associated Entries:
To define a synthetic property relation, the DVPREL2 entry identifies a DEQATN entry and declares the design variable (DESVAR) and any necessary table constant (DTABLE) arguments.
DEQATN EQID EQUATION
EQUATION (Cont.)
DESVAR ID LABEL XINIT XLB XUB DELXV DDVAL
DTABLE LABL1 VALU1 LABL2 VALU2 LABL3 VALU3 LABL4 VALU4
LABL5 VALU5 LABL6 VALU6
-etc.-Discussion:
For many applications, the linear design variable-to-property relations provided by the
DVPREL1 entry may not be sufficient. In these cases, equations may be defined to relate design variables to properties in a nonlinear fashion. The DVPREL2 entry provides the arguments to an equation defined on a DEQATN entry. These arguments may be design variables defined on DESVAR entries and table constants defined on a DTABLE entry.
Design Sensitivities and Type-2 Properties
Every property defined on a DVPREL2 entry becomes an independently varying property internally in NX Nastran. Design sensitivities are first computed with respect to these
independently varying properties, and then the chain rule applied to relate these sensitivities to changes in the design variables. Refer toDesign Sensitivity Analysis, for further details.
DVSHAP
Purpose:
Defines a shape basis vector as a linear combination of DBLOCATEd displacement vectors (in data block UGD) and assigns a design variable multiplier to the result.
Entry Description:
DVSHAP DVID COL1 SF1 COL2 SF2 COL3 SF3
Field Contents
DVID Design variable identification number on the DESVAR entry. (Integer > 0).
COLi Column number of the displacement matrix. (1 ≤ Integer ≤ maximum column number in the displacement matrix).
SFi Scaling factor applied to the COLi-th column of the displacement matrix.
(Real; Default = 1.0).
Associated Entries:
In shape optimization, shape basis vectors relate the changes in a design variable to changes in grid locations (see basis vectors in shape optimization inRelating Design Variables to Shape Changes). The design variables must first be defined using DESVAR entries.
DESVAR ID LABEL XINIT XLB XUB DELXV DDVAL
4.4 Parameters for Design Sensitivity and Optimization
In addition to the optimization control possible with Bulk Data entries such as DOPTPRM and DSCREEN, a set of parameters unique to design sensitivity and optimization is also available.
This section is intended to be a complete quick reference for all such Case Control and Bulk Data parameters. Refer toCommonly Used Commands for Design Optimizationfor further details.
CDIF Controls the selection of finite difference scheme used in sensitivity analysis.
YES: Selects central differences (default for shape optimization).
NO: Selects forward differences (default for property optimization only)
DESPCH Controls the frequency of updated DESVAR and GRID Bulk Data entry output to the PUNCH file.
N < 0: No output.
N = 0: Final design cycle (default).
N > 0: Every N-th, as well as final design cycles.
DSNOKD Indicates if the differential stiffness effect is to be included in buckling sensitivity analysis.
1.0: Include differential stiffness (default).
0.0: Do not include differential stiffness.
NASPRT Controls the frequency of NX Nastran output.
-1: No output.
0: Output on initial and final design cycles (default).
N: Output every N-th iteration and also prior to exit.
OPTEXIT Instructs the program to exit at one of six predetermined exit points.
0: No user-defined exit (default).
N > 0: Exit at one of the locations 1 through 7 (1 ≤ N ≤ 7).
SOFTEXIT Determines whether to terminate design cycles if soft convergence is indicated.
NO: Do not stop if soft convergence is indicated (default).
YES: Terminate design cycles if soft convergence is achieved.
UPDTBSH Controls the update of the boundary shapes in the analytic boundary shapes method for shape optimization.
NO: Do not update the boundary shapes (default).
YES: Update the boundary shapes.
Note
Regardless of the value of UPDTBSH, shape basis vectors are still updated for every design cycle (interpolation to the interior grids). UPDTBSH only controls updates on the boundary shapes.