OPT_PARAM

ID_NAME	= <`id_name_of_opt_param`>	Name of the `OPT_PARAM` definition.
OPTIMIZE	= <`name_of_optimize`>	Name of the optimization problem (`OPTIMIZE`) which is relevant for the parameter.
MOD_NEG_REL_CONSTR	= ON	Constraints with `MAGNITUDE=REL` are considered as relative constraints and thus the inequality operator changes when converting to an absolute constraint and `DRESP` value from optimization start is negative.
	=OFF	Behaviour like Tosca 7.x: The inequality operator is not changed.

Parameters for sensitivity-based bead, sizing and topology optimization

For eigenvalue optimization:

MODETRACKING		Switch for modetracking.
	= OFF	Modetracking is deactivated.
	= ON	Modetracking is activated.
	= ON, <`node_group`>	Modetracking is activated for specified nodegroup.
MODENUMBERS	= <`number_of_modes`> = 5	Number of modes included in the modetracking.
MODETRACK_REFERENCE	= INITIAL	Modes of present optimization iteration are tracked with respect to the modes of the initial optimization iteration.
	= PREVIOUS	Modes of present optimization iteration are tracked with respect to the modes of previous optimization iteration.

For frequency response optimization:

DAMP_STRUCTURAL_MASS	= <`real_value`>	Structural mass damping for design element (or elements at design nodes).
DAMP_STRUCTURAL_STIFF	= <`real_value`>	Structural stiffness damping for design element (or elements at design nodes).
DAMP_VISCOUS_MASS	= <`real_value`>	Viscous mass damping for design element (or elements at design nodes).
DAMP_VISCOUS_STIFF	= <`real_value`>	Viscous stiffness damping for design element (or elements at design nodes).
SUM_Q_FACTOR	= <`real_value`> = 6.0	Weighting function for peaks in frequency spectrum.

Parameters for controller based shape optimization

SCALE	= <`real_value`> = <`grow_scale`>, <`shrink_scale`> = 1	The displacements determined by the optimization algorithms are multiplied with the <`real_value`>. To switch the optimization direction of the controller a negative value can be entered (this is only available in the module SIMULIA Tosca Structure.nonlinear). If two values are defined, the first value is the scale for nodes with growth and the second value the scale for nodes with shrinkage. Both scale values must have the same sign.
MID_NODES		Treatment of the midside nodes during the optimization.
	= LINEAR	Midside node positions are linearly interpolated from the optimized position of the connected corner nodes.
	= INTERPOLATE	Midside node optimization displacements are interpolated from the optimization displacement of the corner nodes.
CURV_SMOOTH	= <`elem_edge_length`> = 5.0	The nodal optimization movement vector is modified in areas of high curvature to prevent a collapse of the mesh for large volume changes. A bigger radius causes a bigger curvature based modification of the optimization movement vector. (0.0 = OFF).
FILTER	= <`radius`>, <`sigma`>, <`exponent`> = <`radius`>, 0.2, 1.0	Filter for the nodal equivalence stress. The radius defines the maximum distance for influencing neighbour nodes, sigma defines the reduction of the radius depending on the surface bending, the exponent defines the weighting function depending on the distance.
VECTOR	= EVER = FIRST	Update of the shape basis vectors occurs in every (`EVER`) or only in the first (`FIRST`) design cycle.
DISP	= MINIMUM = AVERAGE	The permitted absolute step size is controlled by the medium node displacement (`AVERAGE`) or the minimum node displacement (`MINIMUM`).
TOL_VALUE	= <`real_value`> = 0.001	Tolerance value for the constraint (relative value).

Parameters for sensitivity based shape optimization

FILTER_RADIUS	= <`positive_real_value`>,[ABS\|REL]	Filter radius. It is used to filter the objective function sensitivities and half of the value is used as radius for filtering the constraint sensitivities and the design variables. The second parameter `ABS` or `REL` indicates if the radius is given in ABSolute units (default) or RELative i.e. in terms of medium edge length The default value is 4 * medium_edge_length Use `0` or a negative value to disable the filters (not recommended). Using the `FILTER_RADIUS=<value>` parameter is equivalent to using the three parameters `FILTER_SEN = <value> FILTER_CONSEN = 0.5<value> FILTER_DV = 0.5<value>`
FILTER_SEN	= <`positive_real_value`>,[ABS\|REL]	Filter radius for filtering the objective function sensitivities. The second parameter `ABS` or `REL` indicates if the radius is given in ABSolute units (default) or RELative i.e. in terms of medium edge length The default value is 4 * medium_edge_length This parameter is not available in Tosca Structure.gui.
FILTER_CONSEN	= <`positive_real_value`>,[ABS\|REL]	Filter radius for filtering the sensitivities of the constraints. The second parameter `ABS` or `REL` indicates if the radius is given in ABSolute units (default) or RELative i.e. in terms of medium edge length The default value is 2 * medium_edge_length This parameter is not available in Tosca Structure.gui.
FILTER_DV	= <`positive_real_value`>,[ABS\|REL]	Filter radius for filtering the design variables. The second parameter `ABS` or `REL` indicates if the radius is given in ABSolute units (default) or RELative i.e. in terms of medium edge length The default value is 2 * medium_edge_length This parameter is not available in Tosca Structure.gui.
USE_SOLVER_ELEMS	= YES \| NO	If Yes: Use solver element formulations instead own formulations. This will increase the number of fe solver calls.
NODAL_MOVE	= <`real_value`> = 0.1	Relative move limit of nodal optimization displacement per iteration. Value is between 0 and 1.
NODAL_UPDATE	= CONSERVATIVE = NORMAL = AGGRESSIVE	Parameter to determine how the nodal displacements are updated in the method of moving asymptotes (MMA).

Parameters for controller-based topology optimization

SPEED		`SPEED` size of increment.
	= VERY_SLOW	Very small step size.
	= SLOW	Small step size.
	= MODERATE	Moderate step size.
	= MEDIUM	Medium step size.
	= FAST	`FAST` large step size (only permitted in optimization of stiffness with volume constraint).
	= ITER, <`number_of_iterations`> = ITER,15	Step size is modified dynamically, so the optimization end after the given number of iterations.
START_DELETE	= <`operator`>, <`value`>	Setting the volume that can be removed immediately in the first design cycle.
<`operator`>	= PERC	Specifying the volume in percent.
	= ABS	Specifying the absolute volume.
<`value`>		Volume that is deleted in the first design cycle.
AUTO_FROZEN	= LOAD	All loaded elements and elements with loaded nodes are excluded from the optimization via an automated `DVCON_TOPO` `FROZEN` statement.
	= OFF	Loaded elements are treated normally (are optimizable).
	= SPC	Elements with boundary conditions are excluded from the optimization.
	= BOTH	All loaded elements and elements with loaded nodes and all with boundary conditions are excluded from the optimization via an automated `DVCON_TOPO` `FROZEN` statement.

Parameters for sensitivity-based topology optimization

DENSITY_UPDATE		Parameter for how the densities are updated in the method of moving asymptotes (MMA).
	= NORMAL	Normal strategy.
	= CONSERVATIVE	Conservative strategy.
	= AGGRESSIVE	Aggressive strategy.
DENSITY_INITIAL	= <`real_value`> = 0.5	Initial values of density (when no material constraint is present).
DENSITY_UPPER	= <`real_value`> = 1.0	Upper bound on design variables.
DENSITY_LOWER	= <`real_value`> = 0.001	Lower bound on design variables.
DENSITY_MOVE	= <`real_value`> = 0.25	Move limit on design variables.
FILTER_RADIUS	= <`radius`> = 1.3* <average_element_edge_length>	Filter for mesh independence and minimum size.
FILTER_TYPE	= STANDARD	The conventional filter applied in topology optimization.
	= LOW	A modified filter applied in topology optimization useful for coarse meshes.
MAT_INTERPOLATION		Material interpolation scheme (relation between relative density and relative element stiffness).
	= SIMP	Solid Isotropic Material with Penalization.
	= RAMP	Rational Approximation of Material Properties.
	= 4_TH	Material interpolation using 4th order polynomial. If this option is set the corresponding factors must be provided using the commands `MAT_0_TH_FACTOR, ... , MAT_4_TH_FACTOR`.
MAT_0_TH_FACTOR	= <`real_value`> = 0.0	Coefficient of the 4th order polynomial material interpolation which corresponds to the power of 0 term.
MAT_1_TH_FACTOR	= <`real_value`> = 0.0	Coefficient of the 4th order polynomial material interpolation which corresponds to the power of 1 term.
MAT_2_TH_FACTOR	= <`real_value`> = 0.0	Coefficient of the 4th order polynomial material interpolation which corresponds to the power of 2 term.
MAT_3_TH_FACTOR	= <`real_value`> = 3.0	Coefficient of the 4th order polynomial material interpolation which corresponds to the power of 3 term.
MAT_4_TH_FACTOR	= <`real_value`> = 0.0	Coefficient of the 4th order polynomial material interpolation which corresponds to the power of 4 term.
MAT_PENALTY	= <`real_value`> = 3.0	Penalty factor for interpolation scheme.
PROCESSORS		Number if CPU-processors for Abaqus in combination with sensitivity-based topology optimization.
	= SINGLE	Abaqus only, single CPU-processor in combination with sensitivity-based topology optimization.
	= MULTI	Abaqus only, several CPU-processors in combination with sensitivity-based topology optimization.
STOP_CRITERION_LEVEL	= BOTH = SINGLE	Parameter if both (`BOTH`) or just one (`SINGLE`) of two stop criteria should be fulfilled.
STOP_CRITERION_OBJ	= <`real_value`> = 0.001	Stop criterion based upon the change in objective function.
STOP_CRITERION_DENSITY	= <`real_value`> = 0.005	Stop criterion based upon the change in element densities.
STOP_CRITERION_ITER	= <`real_value`> = 4	Parameter defining from which optimization iteration should the two criteria be checked.
SOFT_DELETE_METHOD	= <`method`>, <`soft_delete_threshold_value`>
<`method`>		Method selection for `SOFT_DELETE`.
	= STANDARD	Removal of elements is done ensuring that there are no detached and floating elements caused by the soft delete.
	= AGGRESSIVE	Removal of elements is done based on the rel. density without detachment checks. In this case detached and floating elements can be caused by the soft delete. Some solvers have problems dealing with such elements but not the Abaqus solver. Note that check of elements in <`radius`> will still be performed but this procedure is independent of detachment checks.
	= MAX_SHEAR_STRAIN	Removal of elements is based upon maximum elemental shear strain (with positive shear threshold).
	= MIN_PRINCIPAL_STRAIN	Removal of elements based upon minimal elemental principal strain (with negative minimum principal threshold).
	= PLASTICITY	Removal of elements based upon maximum effective elastoplastic strain (only to use for elastoplastic constitutive material law).
	= VOLUME_CHANGE	Removal of elements based upon the minimum relative deformed elemental volume ((Vdeform - Vorg) / Vorg) with negative threshold value.
<`soft_delete_threshold_value`>	= <`value`>	Relative material density value for identification of elements to be removed (element with a value below will be removed from the finite element calculation file).
	= 0.05	For `METHOD = STANDARD` or `AGGRESSIVE`.
	no default value	For all other methods.
SOFT_DELETE	= <`el_group`>, <`radius`>
	<`el_group`>	Name of the element group in which the soft elements should be deleted during optimization.
	<`radius`>	For `METHOD = STANDARD` or `AGGRESSIVE` the default of this value is the average element edge length of the model. User defined value is considered to be an absolute one. This means that the corresponding units should be taken into account. If any of the elements enclosed in the sphere spanned by the <`radius`> has a relative density higher than the <`soft_delete_threshold_value`> then the element in origin will not be deleted.
AUTO_FROZEN
	= LOAD	All loaded elements and elements with loaded nodes are excluded from the optimization via a automated `DVCON_TOPO` `FROZEN` statement.
	= OFF	Loaded elements are treated normal (are optimizable).
	= SPC	Elements with boundary conditions are excluded from the optimization
	= BOTH	All loaded elements and elements with loaded nodes and all with boundary conditions are excluded from the optimization via an automated `DVCON_TOPO` `FROZEN` statement.

Parameters for sensitivity-based sizing optimization

THICKNESS_UPDATE		Parameter for how the thicknesses are updated in the method of moving asymptotes (MMA).
	= NORMAL	Normal strategy.
	= CONSERVATIVE	Conservative strategy.
	= AGGRESSIVE	Aggressive strategy.
THICKNESS_MOVE	= <`real_value`> = 0.25	Move limit on design variables.
FILTER_RADIUS	= <`radius`> = 1.3* <average_element_edge_length>	Filter for mesh independence and minimum size.
FILTER_TYPE	= STANDARD	The conventional filter applied in sizing optimization.
	= LOW	A modified filter applied in sizing optimization useful for coarse meshes.
STOP_CRITERION_LEVEL	= BOTH = SINGLE	Parameter if both (`BOTH`) or just one (`SINGLE`) of two stop criteria should be fulfilled.
STOP_CRITERION_OBJ	= <`real_value`> = 0.001	Stop criterion based upon the change in objective function.
STOP_CRITERION_THICKNESS	= <`real_value`> = 0.005	Stop criterion based upon the change in element densities.
STOP_CRITERION_ITER	= <`real_value`> = 4	Parameter defining from which optimization iteration should the two criteria be checked.
AUTO_FROZEN
	= LOAD	All loaded elements and elements with loaded nodes are excluded from the optimization via a automated `DVCON_TOPO` `FROZEN` statement.
	= OFF	Loaded elements are treated normal (are optimizable).
	= SPC	Elements with boundary conditions are excluded from the optimization
	= BOTH	All loaded elements and elements with loaded nodes and all with boundary conditions are excluded from the optimization via an automated `DVCON_TOPO` `FROZEN` statement.

Parameters for controller-based bead optimization

VECTOR	=FIRST =EVER	Update of the optimization displacement vector occurs in first or in each design cycle.
SCALE	= <`real_value`>	Definition of the direction of the optimization displacement.
BEAD_WIDTH	= <`real_value`>	Bead wide.
BEAD_ITER	= <`int_value`>	Definition of the number of iterations.
BEAD_MIN_STRESS	= <`real_value`> = 0.001	Value, relative to the highest Von Mises stress in the design area, under which, no optimization should be performed. Value between 0.0 and 1.0, where 1.0 is equal the highest Von Mises stress.
BEAD_MAX_MEMBRANE	= <`real_value`> = 1.0	Value of the maximal membrane stress relative to maximal bending stress in original model under which no optimization is performed. Value is greater than 0.
	= CONTINUOUS	Sorting filter values by the bending loads.
	= DISCRETE	Filtering whole design area.
CURV_SMOOTH	= <`elem_edge_length`> = 5.0	Filtering the normals, effect for curved geometries. Value is relative to the medium element edge length.
BEAD_NODE_SMOOTH	= <`real_value`> = 0.25 (of `BEAD_WIDTH`)	This defines the minimum distance between a node at zero optimization displacement and one at maximal bead height.

Parameters for sensitivity-based bead optimization

FILTER_RADIUS	= <`real_value`>, ABS = <`real_value`>, REL = 4.0, REL	Radius with which the sensitivties are filtered. `REL` is relative to medium edge length of elements in the design area. Values may also be set absolute (`ABS`).
ONLY_DES_NODES	= YES = NO	Calculate sensitivities for only design nodes (`YES`) or all nodes (`NO`) which is not recommended.
NODAL_MOVE	= <`real_value`> = 0.1	Relative move limit of nodal optimization displacement per iteration. Value is between 0 and1.
NODAL_UPDATE	= CONSERVATIVE = NORMAL = AGGRESSIVE	Parameter for how the nodal displacements are updated in the method of moving asymptotes (MMA).
PERTURBATION	= <`real_value`> = 0.0001	Sets perturbation size for finite differences (relative to medium element edge length).

Remarks

As the form of the component changes during optimization the shape basis vector must be continually adjusted. The settings VECTOR=FIRST is only to be used when a node displacement along the initial vector is explicitly required.
SCALE is the direction of the optimization displacement. 1.0 for the same direction as the surface normals, -1 for the opposite.
MODETRACKING can be activated for a specific node group (e.g. every fifth node on the surface). This results in a significant gain of performance.
Setting FILTER_TYPE = LOW can be recommend for optimizations having no casting constraints, a low mass constraint (<5%) and/or a coarse mesh. This will lead to less optimization iterations and more clear designs.
Generally, setting FILTER_TYPE = LOW gives raise more to clear solidvoid designs compared to FILTER_TYPE =STANDARD.
The main disadvantage of setting FILTER_TYPE = LOW is that the optimization result can contain checkerboard.
The setting of FILTER_TYPE has no impact upon the optimization results and history if the mass is the objective to be minimized.
The setting of FILTER_TYPE has no impact upon the optimization results if casting constraints are defined.
Setting FILTER_TYPE =LOW will lead to less optimization iterations.
The minimum member size restriction might not be completely enforced when applying FILTER_TYPE = LOW.
Changing the filter option has no effect when manufacturing constraints are present.

Examples

OPT_PARAM
 ID_NAME = optimization_control
 OPTIMIZE = bead_optimization
 SCALE = - 1.0
 BEAD_MIN_STRESS = 0.01
END_