Checkerboard

0,1,2, or blank
(default = 0,
if card not in deck)

(Default = 1, if blank)

Controls checkerboarding. Use 0 for no checkerboard control. Use 1 or blank for global averaging over the entire design domain. This option generally yields a large number of semi-dense elements around fully dense elements. To reduce the number of semi-dense elements in the solution, restart the final iteration with checkerboard control off and run for 10-20 iterations. This may reintroduce some local checkerboarding. This method is used with plate/shell and solid design elements and is highly recommended for tetra elements. Nodal densities are output to the .res file if this option is used. Use 2 for averaging at local areas identified as checkerboarded. Since averaging is only applied locally, a much smaller number of semi-dense elements are found in the final iteration compared to the global averaging method. This method applies only to plate/shell design elements. If used in models with solid design elements, checkerboard control is not applied to solid elements.

OptiStruct errors out if this parameter is repeated on DOPTPRM in the bulk data section.

Discrete

<real>default = 1.0

Discreteness parameter. Influences the tendency for elements to converge to a material density of 0 or 1. Higher values decrease the number of elements that remain between 0 and 1. Recommended bounds are 0.0 and 2.0.

OptiStruct errors out if this parameter is repeated on DOPTPRM in the bulk data section.

Dcomp

<integer>

Shell elements with PCOMP PID given on this card will be placed in the topology design domain. This card overrides declarations in the bulk data deck.

Dshell

<integer>no def<real>def=0.0

Shell elements with PSHELL PID given in first field of DSHELL card will be placed into the topology design domain with T0 given in the second field. This card overrides declarations in the bulk data deck.

Dsolid

<integer>

Solid elements with PSOLID PID given on this card will be placed into the topology design domain. This card overrides declarations in bulk data deck.

Matinit

<real>def. = 0.9 or constraint val.

This card declares the initial material fraction. For runs with mass as the objective, default is 0.9. For runs with constrained mass, default is reset to constraint value.

OptiStruct errors out if this parameter is repeated on DOPTPRM in the bulk data section.

Maxiter

<integer>default = 30

Maximum number of iterations. Sets an upper limit on the number of iterations OptiStruct can perform before completion. If maxiter = 0, baseline analysis is conducted after initializing material fractions of all design elements at the matfrac value. If check is present, it overrides maxiter = 0. If analysis is present, it overrides maxiter = 0.

OptiStruct errors out if this parameter is repeated on DOPTPRM in the bulk data section.

Mindens

<real>default = 0.01

Minimum element material density. Sets a lower limit on the amount of material that can be assigned to any design element. Extremely low values for this parameter can result in an ill-conditioned stiffness matrix.

OptiStruct errors out if this parameter is repeated on DOPTPRM in the bulk data section.

Minmember

<real>no default<method> default= 2

Specifies the minimum diameter of members formed by OptiStruct.  This also eliminates checkerboard results. This command is used to eliminate small members. Method is either 1 or 2. Method 2 is set as default since it achieves more discrete solutions for most examples.

OptiStruct errors out if this parameter is repeated on DOPTPRM in the bulk data section.

Mmcheck

No input

The use of this card will ensure a checkerboard free solution, although with the undesired side effect of achieving a solution that involves a large number of semi-dense elements, similar to the result of using CHECKER=1. Therefore, use this card only when it is necessary.

OptiStruct errors out if this parameter is repeated on DOPTPRM in the bulk data section.

Objtol

<real>default = 0.005

Tolerance in objective function. If the fractional change in objective function is below this quantity for two consecutive iterations, the optimization is considered converged and is stopped.

OptiStruct errors out if this parameter is repeated on DOPTPRM in the bulk data section.

Smooth

<real>default = 0.7071

Solution smoothness. Influences the step size of the optimization iterations if the optimality criteria method is used for topology optimization. Changing this parameter generally results in changes in the solution topology. Larger values of this parameter create smoother topologies for shell element models. Leave this parameter at the default value, unless a different solution topology is desired. Recommended bounds are 0.5 and 0.9.

lbcon

<real>
<string>
no defaults

<integer*> <integer*>

Sets a lower bound constraint of value given in the first field of this card for the response given in the second field of the card. Supported responses are: volume, mass, disp, comp, freq, wcomp, wfreq, and comb. Global responses (volume, mass, wcomp, wfreq, and comb) must be located outside of all subcase declarations. Local responses (comp, freq, and disp) must be located within a subcase declaration. The third field is used for mode number declarations for freq responses or grid number declarations for disp responses. The fourth field is used for grid component declarations for disp responses.

Mass

<real>
no default

Mass of total model. If present, the matfrac parameter is not used. Input the total target mass for the part and OptiStruct calculates the material fraction automatically. If the computed material fraction is below 0.0 or above 1.0, OptiStruct returns an error. Not available if using multiple material types in the design domain.

Matfrac

<real>
default = 0.30
range = 0.0-1.0

Material fraction. Defines the amount of material to be distributed within the design domain as a fraction of the design domain. For shell elements, design volume is equal to (T - T0) * area. For solid elements, design volume is equal to the sum of the volume of the elements designated as design space. The design volume multiplied by the material fraction is the total amount of design material available. Material fractions for all design elements in the design space are initialized to matfrac value.

maxi

<string>
no default

<integer*> <integer*>

Sets objective function to maximize a response. Supported responses are: volume, mass, disp, comp, freq, wcomp, wfreq, and comb.  Global responses (volume, mass, wcomp, wfreq, and comb) must be located outside of all subcase declarations. Local responses (comp, freq, and disp) must be located within a subcase declaration. The second field is used for mode number declarations for freq responses or grid number declarations for disp responses. The fourth field is used for grid component declarations for disp responses.

mini

<string>
no default

<integer*> <integer*>

Sets objective function to minimize a response. Supported responses are: volume, mass, disp, comp, freq, wcomp, wfreq, and comb.  Global responses (volume, mass, wcomp, wfreq, and comb) must be located outside of all subcase declarations. Local responses (comp, freq, and disp) must be located within a subcase declaration. The second field is used for mode number declarations for freq responses or grid number declarations for disp responses. The fourth field is used for grid component declarations for disp responses.

Primary

<integer or blank>
default= lowest mode with highest weight if eigen.  Subcase no default if static.

This card sets which mode of eigenvalue solution is used to set material orientation angles. Primary mode declaration only applies to runs without static analyses and must be placed in the subcase declaration. If the card is placed in a static subcase, only that subcase is used to determine material orientation angle - no fields are necessary.

ubcon

<real>
<string>
no defaults

<integer*> <integer*>

Sets an upper bound constraint of value given in the first field of this card for the response given in the second field of the card. Supported responses are: volume, mass, disp, comp, freq, wcomp, wfreq, and comb. Global responses (volume, mass, wcomp, wfreq, and comb) must be located outside of all subcase declarations. Local responses (comp, freq, and disp) must be located within a subcase declaration. The third field is used for mode number declarations for freq responses or grid number declarations for disp responses. The fourth field is used for grid component declarations for disp responses.