# DTPL

Bulk Data Entry Defines parameters for the generation of topology design variables.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DTPL ID PTYPE PID1 PID2 PID3 PID4 PID5 PID6
PID7 etc etc etc etc etc etc
etc etc
Optional continuation lines for minimum thickness definition:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
TMIN T0
Optional continuation lines for stress constraint definition:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
STRESS UBOUND
Optional continuation lines for member size constraint definition:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MEMBSIZ MINDIM MAXDIM MINGAP
Optional continuation lines for mesh type definition:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MESH MTYP
Optional continuation lines for draw direction constraint definition:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DRAW DTYP DAID/XDA YDA ZDA DFID/XDF YDF ZDF
OBST OPID1 OPID2 OPID3 OPID4 OPID5 OPID6 OPID7
OPID8 etc etc etc etc etc etc
NOHOLE
STAMP TSTAMP
Optional continuation lines for extrusion constraint definition:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
EXTR ETYP
EPATH1 EP1_ID1 EP1_ID2 EP1_ID3 EP1_ID4 EP1_ID5 EP1_ID6 EP1_ID7
EP1_ID8 etc etc etc etc etc etc
etc etc
EPATH2 EP2_ID1 EP2_ID2 EP2_ID3 EP2_ID4 EP2_ID5 EP2_ID6 EP2_ID7
EP2_ID8 etc etc etc etc etc etc
etc etc
Optional continuation lines for "Main" definition for pattern repetition constraint:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MAIN
COORD CID CAID/

XCA

YCA ZCA CFID/

XCF

YCF ZCF
CSID/

XCS

YCS ZCS CTID/

XCT

YCT ZCT
Optional continuation lines for "Secondary" definition for pattern repetition constraint:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
SECOND DTPL_ID
COORD CID CAID/

XCA

YCA ZCA CFID/

XCF

YCF ZCF
CSID/

XCS

YCS ZCS CTID/

XCT

YCT ZCT
Optional continuation lines for "Coordinate System" definition for Multi-Model Optimization:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
COORD CID CAID/

XCA

YCA ZCA CFID/

XCF

YCF ZCF
CSID/

XCS

YCS ZCS CFTID/

XCT

YCT ZCT
Optional continuation lines for "Scaling" definition for pattern repetition and Multi-Model Optimization:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
SCALE SX SY SZ
Optional continuation lines for defining DTPL-dependent initial material fraction definition:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MATINIT VALUE
Optional continuation lines for pattern grouping constraint definition:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
PATRN TYP AID/

XA

YA ZA FID/

XF

YF ZF
UCYC SID/

XS

YS ZS
Optional continuation lines for material definition if PTYPE=COMP:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MAT MATOPT
Optional continuation lines for fatigue constraint definition:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
FATIGUE FTYPE FBOUND
Optional continuation lines for Level Set Method (Topology Optimization) definition:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
LEVELSET HOLEINST HOLERAD NHOLESX NHOLESY NHOLESZ
Optional continuation lines for Lattice Structure Optimization:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
LATTICE LT LB UB LATSTR
Optional continuation lines for Failsafe Topology Optimization:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
FAILSAFE SFAIL DFAIL TFAIL DFAIL PFAIL
Optional continuation lines for Multiple Materials Topology Optimization:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MMAT MID1 MID2 MID3 MID4 MID5 MID6 MID7
MID8 MID9
Optional continuation lines for Overhang Constraint:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
OVERHANG ANGLE GID1/

X1

Y1 Z1 GID2/

X2

Y2 Z2
METHOD STEP/

PENFAC

PENSCHE NONDES HOLES ANGTOL DISTOL
SUPPSET

## Example 1

Define a topology design variable that allows the thickness of components referencing the PSHELL properties 7, 8, and 17 to vary between 1.0 and 5.0 (the thickness defined on PSHELL definitions with PID 7, 8, and 17 is 5.0). The optimized design should contain members whose width is no less than 60.0 units.
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DTPL 1 PSHELL 7 8 17
MEMBSIZ 60.0
TMIN 1.0

## Example 2

Define a topology design variable for components referencing the PSOLID properties 4, 5, and 6. The optimized design should contain members whose diameter is no less than 60.0 units. The final design will be manufactured using a casting process, where the draw direction lies along the x-axis. The components referencing PSOLID properties 10, 11, and 12 are non-designable, but will form part of the same casting as the designable components.
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DTPL 1 PSOLID 4 5 6
MEMBSIZ 60.0
DRAW SPLIT 0.0 0.0 0.0 1.0 0.0 0.0
OBST 10 11 12

## Definitions

Field Contents SI Unit Example
ID Each DTPL card must have a unique ID.

No default (Integer > 0)

PTYPE Property type or Laminate for which the DTPL card is defined.
PBAR
PBARL
PBEAM
PBEAML
PBUSH
PROD
PWELD
PSHELL
PCOMP
PSOLID
STACK

No default

PID# Property or Laminate (STACK) identification numbers. List of properties or laminates of PTYPE for which this DTPL card is defined.

If PIDs are not listed, OptiStruct will check all properties or laminates of type PTYPE to see if they are to be included in the design space (see PCOMP, PSHELL, PSOLID, STACK, and so on). If any properties satisfy this search, then they will be affected by entries on this card. In this situation (where PIDs are not defined), only one DTPL card can be defined for the given PTYPE.

Default = blank (Integer > 0 or blank)

TMIN Indicates that minimum thickness value will follow. Only valid when PTYPE=PSHELL.

If not present when PTYPE=PSHELL, the minimum thickness will default to the T0 value defined on the PSHELL card. If a T0 value is not defined on the PSHELL card, the minimum thickness will default to 0.0.

T0 Minimum thickness for PSHELL properties when the referenced material is of type MAT1.

If PSHELL references a material which is not of type MAT1, this value is ignored and T0=0.0 is used.

If a value is not entered for T0, the T0 value on the PSHELL card is used. If T0 is not defined on the PSHELL card, then T0=0.0 is assumed.

Default = blank (Real > 0.0)

STRESS Indicates that stress constraints are active and that an upper bound value for stress is to follow. 1
UBOUND Upper bound constraint on stress.

No default (Real > 0.0)

MEMBSIZ Indicates that member size control is active for the properties listed and if MINDIM and possibly MAXDIM are to follow.
MINDIM Specifies the minimum diameter of members formed. This command is used to eliminate small members. It also eliminates checkerboard results. 2

Default = No Minimum Member Size Control (Real > 0.0)

MAXDIM Specifies the maximum diameter of members formed. This command is used to prevent the formation of large members. Only used in combination with MINDIM. 3

Default = No Maximum Member Size Control (Real > 0.0)

MINGAP Defines the minimum spacing between structural members formed. Only used in conjunction with MAXDIM. 3

Default = blank (Real > MAXDIM)

MESH Indicates that mesh type information is to follow.
MTYP Indicates that the mesh conforms to certain rules for which the optimizer is tuned. Currently, the only option available is ALIGN, which indicates when manufacturing constraints are active, the mesh is aligned with the draw direction or extrusion path. 4

Default = blank (ALIGN or blank)

DRAW Indicates that casting constraints are being applied and that draw direction information is to follow.

Only valid if PTYPE=PSOLID. OptiStruct will terminate with an error, if present for other PTYPEs.

DTYP Draw direction constraint type to be used.
SINGLE
Indicates that a single die will be used, the die being withdrawn in the given draw direction.
SPLIT (Default)
Allows the optimization of the splitting surface of two dies, with both dies moving apart in the given draw direction.
SPLIT2 and SPLIT3
Provide alternative methods to optimize the splitting surface. These should only be used in the case where SPLIT creates non-castable cavities.
Provides a radial draw direction. The DAID and DFID fields can be used to identify the Z-axis of the cylinder for radial draw direction. 26
SPHERICA
Spherical draw direction, provides an option to specify draw around a single grid point, specified via DAID. 26

DAID/XDA, YDA, ZDA Draw direction anchor point. These fields define the anchor point for draw direction of the casting. The point may be defined by entering a grid ID in the DAID field or by entering X, Y, and Z coordinates in the XDA, YDA, and ZDA fields, these coordinates will be in the basic coordinate system.

Default = origin (Real in all three fields or Integer in first field)

DFID/XDF, YDF, ZDF Direction of vector for draw direction definition. These fields define a point. The vector goes from the anchor point to this point. The point may be defined by entering a grid ID in the DFID field or by entering X, Y, and Z coordinates in the XDF, YDF, and ZDF fields, these coordinates will be in the basic coordinate system.

No default (Real in all three fields or Integer in first field)

OBST Indicates that a list of PIDs will follow which are non-designable, but their interaction with designable parts needs to be considered with regards to the defined draw direction. OBST stands for obstacle.

Only recognized if DRAW flag is also present on the same DTPL card. OptiStruct will terminate with an error, if OBST flag is present without DRAW flag.

OPID# Obstacle property identification number. List of non-designable properties that are to be considered with regards to the defined draw direction. These must be PSOLID.

No default (Integer > 0, blank or ALL)

NOHOLE Prevents the formation of through-holes in the draw direction.
Note: It does not prevent holes perpendicular to the draw direction. The assumed minimum thickness in the draw direction is twice the average mesh size.

STAMP Forcing the design to evolve into a 3D shell structure. Indicates that thickness (TSTAMP) is to follow. 5
TSTAMP Defines the thickness of the 3D shell structure that is evolved with the STAMP option. The recommended minimum thickness is three times the average mesh size. 5

No default (Real > 0.0)

EXTR Indicates that extrusion constraints are being applied and that extrusion information is to follow.

Only valid if PTYPE=PSOLID. OptiStruct will terminate with an error, if present for other PTYPEs.

ETYP Extrusion constraint type to be used.
NOTWIST (Default)
Indicates that the cross-section cannot twist about the neutral axis, in which case only one path needs to be defined.
TWIST
Indicates that the cross-section can twist about the neutral axis, in which case two paths need to be defined.

EPATH1 Indicates that a list of grid IDs will follow to define the primary extrusion path.

Only recognized if EXTR flag is also present on the same DTPL card. OptiStruct will terminate with an error, if EPATH1 flag is present without EXTR flag.

EP1_ID# Primary extrusion path identification numbers. List of grid IDs that define the primary extrusion path.

No default (Integer > 0 or blank)

EPATH2 Indicates that a list of grid IDs will follow to define the secondary extrusion path. This is only required when ETYP has been set to TWIST.

Only recognized if EXTR flag is present on the same DTPL card. OptiStruct will terminate with an error, if EPATH2 flag is present without EXTR flag.

EP2_ID# Secondary extrusion path identification numbers. List of grid IDs that define the secondary extrusion path.

No default (Integer > 0 or blank)

MAIN Indicates that this design variable may be used as a main pattern for pattern repetition. 7
COORD Indicates information regarding the coordinate system for pattern repetition is to follow. This is required if either MAIN or SECOND flag is present.
CID Coordinate system ID for a rectangular coordinate system that may be used as the pattern repetition coordinate system. 7

Default = 0 (Integer ≥ 0)

CAID/XCA, YCA, ZCA Anchor point for pattern repetition coordinate system. The point may be defined by entering a grid ID in the CAID field or by entering X, Y, and Z coordinates in the XCA, YCA, and ZCA fields. These coordinates will be in the basic coordinate system. 7

No default (Real in all three fields or Integer in first field)

CFID/XCF, YCF, ZCF First point for pattern repetition coordinate system. The point may be defined by entering a grid ID in the CFID field or by entering X, Y, and Z coordinates in the XCF, YCF, and ZCF fields. These coordinates will be in the basic coordinate system. 7

No default (Real in all three fields or Integer in first field)

CSID/XCS, YCS, ZCS Second point for pattern repetition coordinate system. The point may be defined by entering a grid ID in the CSID field or by entering X, Y, and Z coordinates in the XCS, YCS, and ZCS fields. These coordinates will be in the basic coordinate system. 7

No default (Real in all three fields or Integer in first field)

CTID/XCT, YCT, ZCT Third point for pattern repetition coordinate system. The point may be defined by entering a grid ID in the CTID field or by entering X, Y, and Z coordinates in the XCT, YCT, and ZCT fields. These coordinates will be in the basic coordinate system. 7

No default (Real in all three fields or Integer in first field)

SECOND Indicates that this design variable is secondary to the main pattern definition referenced by the following DTPL_ID entry. 7
DTPL_ID DTPL identification number for a main pattern definition.

No default (Integer > 0)

COORD Indicates information regarding the coordinate system for pattern repetition is to follow. This is required if either MAIN or SECOND flag is present.
CID Coordinate system ID for a rectangular coordinate system that may be used as the pattern repetition coordinate system. 7.

Default = 0 (Integer > 0)

CAID/XCA, YCA, ZCA Anchor point for pattern repetition coordinate system. The point may be defined by entering a grid ID in the CAID field or by entering X, Y, and Z coordinates in the XCA, YCA, and ZCA fields. These coordinates will be in the basic coordinate system. 7

No default (Real in all three fields or Integer in first field)

CFID/XCF, YCF, ZCF First point for pattern repetition coordinate system. The point may be defined by entering a grid ID in the CFID field or by entering X, Y, and Z coordinates in the XCF, YCF, and ZCF fields. These coordinates will be in the basic coordinate system. 7

No default (Real in all three fields or Integer in first field)

CSID/XCS, YCS, ZCS Second point for pattern repetition coordinate system. The point may be defined by entering a grid ID in the CSID field or by entering X, Y, and Z coordinates in the XCS, YCS, and ZCS fields. These coordinates will be in the basic coordinate system. 7

No default (Real in all three fields or Integer in first field)

CTID/XCT, YCT, ZCT Third point for pattern repetition coordinate system. The point may be defined by entering a grid ID in the CTID field or by entering X, Y, and Z coordinates in the XCT, YCT, and ZCT fields. These coordinates will be in the basic coordinate system. 7

No default (Real in all three fields or Integer in first field)

SCALE This is applicable to Pattern Repetition and Multi-Model Optimization (MMO) functionalities.

Indicates that scaling factors for pattern repetition (Main-Secondary) in a model or for Multi-Model Optimization (across multiple models) is active.

SX, SY, SZ Scale factors for pattern repetition or Multi-Model Optimization in X, Y, and Z directions, respectively. 7

Default = 1.0 (Real)

COORD Indicates information regarding the coordinate system for Multi-Model Optimization is to follow. This is required for Multi-Model Optimization runs (unless individual pattern repetition within each model is active using MAIN/SECOND continuation lines).
CAID/XCA, YCA, ZCA Anchor point for coordinate system used in Multi-Model Optimization. The point may be defined by entering a grid ID in the CAID field or by entering X, Y, and Z coordinates in the XCA, YCA, and ZCA fields. These coordinates will be in the basic coordinate system. 14

No default (Real in all three fields or Integer in first field)

CFID/XCF, YCF, ZCF First point for coordinate system used in Multi-Model Optimization. The point may be defined by entering a grid ID in the CFID field or by entering X, Y, and Z coordinates in the XCF, YCF, and ZCF fields. These coordinates will be in the basic coordinate system. 14

No default (Real in all three fields or Integer in first field)

CSID/XCS, YCS, ZCS Second point for coordinate system used in Multi-Model Optimization. The point may be defined by entering a grid ID in the CSID field or by entering X, Y, and Z coordinates in the XCS, YCS, and ZCS fields. These coordinates will be in the basic coordinate system. 14

No default (Real in all three fields or Integer in first field)

CTID/XCT, YCT, ZCT Third point for coordinate system used in Multi-Model Optimization. The point may be defined by entering a grid ID in the CTID field or by entering X, Y, and Z coordinates in the XCT, YCT, and ZCT fields. These coordinates will be in the basic coordinate system. 14

No default (Real in all three fields or Integer in first field)

PATRN Indicates that pattern grouping is active for the properties listed and that information for pattern grouping is to follow.

Only valid if PTYPE=PCOMP, PSHELL, or PSOLID. OptiStruct will terminate with an error, if present for other PTYPEs.

TYP Indicates the type of pattern grouping requested. 10

Default = No Pattern Grouping (1, 2, 3, 9, 10, or 11)

AID/XA, YA, ZA Anchor point for pattern grouping. The point may be defined by entering a grid ID in the AID field or by entering X, Y, and Z coordinates in the XA, YA, and ZA fields. These coordinates will be in the basic coordinate system. 10

Default = origin (Real in all three fields or Integer in first field)

FID/XF, YF, ZF First point for pattern grouping. The point may be defined by entering a grid ID in the FID field or by entering X, Y, and Z coordinates in the XF, YF, and ZF fields. These coordinates will be in the basic coordinate system. 10

No default (Real in all three fields or Integer in first field)

UCYC Number of cyclical repetitions for cyclical symmetry. This field defines the number of radial "wedges" for cyclical symmetry. The angle of each wedge is computed as 360.0/UCYC. 10

Default = blank (Integer > 0 or blank)

SID/XS, YS, ZS Second point for pattern grouping. The point may be defined by entering a grid ID in the SID field or by entering X, Y, and Z coordinates in the XS, YS, and ZS fields. These coordinates will be in the basic coordinate system. 10

No default (Real in all three fields or Integer in first field)

MATINIT Continuation line to define the DTPL-dependent initial material fraction.
VALUE Default = 0.9 for optimization with mass as the objective, Default is reset to the constraint value for runs with constrained mass. If mass is not the objective function and is not constrained, then the default is 0.6.
Blank (Default)
0.0 ≤ Real ≤ 1.0
Initial material fraction.

This continuation line takes precedence over DOPTPRM,MATINIT for this design variable.

MAT Indicates the type of composite topology optimization. Only considered for PTYPE=PCOMP.
MATOPT
PLY (Default)
Indicates that the optimization should be performed at the ply level. Topology design variables are applied to each ply individually. This method allows the optimization process to determine which orientation is preferred for each element.
HOMO
Indicates that the optimization should be performed on the homogenized shell. This is the method which was used in previous versions of OptiStruct.

FATIGUE Indicates that fatigue constraints are active and their definitions are to follow.
FTYPE Fatigue constraint type.
DAMAGE
LIFE
FOS

FBOUND Specifies the bound value.

If FTYPE=DAMAGE, FBOUND will be the upper bound of fatigue damage.

If FTYPE=LIFE or FOS, FBOUND will be the lower bound of fatigue life (LIFE) or Factor of Safety (FOS), respectively.

No default (Real)

LEVELSET Indicates that the Level Set method (for topology optimization) is activated and the definitions of the required parameters follow. 23 - 27
HOLEINST Method used to insert holes into the design.
blank
It is set to ADAPT by default.
NONE
Indicates that there are no holes in the initial design, and it will work similar to shape optimization.
Indicates that the optimization will start with a cheese-like initial design, where the holes are adaptively inserted into the design domain, as illustrated in Figure 3. This works well with irregular design domains.
ALIGN
Indicates that the optimization will start with evenly distributed holes aligned with axes X and Y (and Z for 3D) of the basic coordinate system, as illustrated in Figure 4. This option is specially developed for regular design domains.
TOPDER
Indicates that OptiStruct will automatically identify locations for the insertion of holes during the optimization process.

A real number that specifies the initial radius of the holes.
blank
The radius will be set to 5 times the average mesh size.

Default = 5 times the average mesh size

NHOLESX / NHOLESY / NHOLESZ <POSITIVE INTEGER>
A positive integer that specifies the number of holes in X direction (when HOLEINST= ALIGN).
blank
OptiStruct will automatically assign a number based on HOLERAD and the dimensions of the domain.

NHOLESY and NHOLESZ can be inferred by analogy.

LATTICE Indicates that Lattice Structure Optimization is activated and the definitions of the required parameters are to follow.
LT Lattice type (only applicable to hexahedral elements). For other element types (tetrahedron, pyramid, and pentahedron), there is only one lattice type and it is active by default. 11 12

Default = 1 (Integer: 1, 2, 3, or 4)

LB Density lower bound. 11 12

Default = 0.1 (0.0 ≤ Real ≤ 1.0)

UB Density upper bound. 11 12

Default = 0.8 (0.0 ≤ Real ≤ 1.0)

LATSTR Stress constraint for Phase 2 of Lattice Optimization (see Stress Constraints in the User Guide).

No default (Real)

FAILSAFE Indicates that Failsafe Topology Optimization is activated and the definitions of the required parameters are to follow. 13
SFAIL Size of the individual Failure Zones in a particular layer. This is the edge length for CUBE failure zone (see TFAIL) and the diameter for SPHERE.

No default (Real > 0.0)

DFAIL Distance (spacing) between Failure Zones in a particular layer. This is the distance between the center of one failure zone to the next.

Default = SFAIL (Real > 0.0)

TFAIL Failure Zone type.
CUBE (Default)
The Failure Zones are cubes (or squares) of equal edges.
SPHERE
The Failure Zones are spheres (or circles).

OFAIL Activates the Overlap (second) Failure Zone in addition to the first Failure zone.
YES (Default)
An Overlap (second) Failure Zone is added. This second failure zone is offset by a distance of half of DFAIL in X, Y, and Z directions (wherever applicable).
NO
An Overlap (second) Failure Zone is not added.

PFAIL Defines the ratio (fraction) of total design volume below which the volume is not considered as a Damage Zone.

Default = 0.0 (Real > 0.0)

MMAT Indicates that Multiple Materials Topology Optimization is activated and the definitions of the required parameters are to follow. 15
MAT# Candidate material identification numbers. List of candidate materials used for multiple material optimization. 16

No default (Integer > 0 or blank)

OVERHANG Indicates that Overhang Constraints are active and the definitions of the required parameters are to follow.
ANGLE Orientation angle for the Overhang Constraint. This angle is measured from the build direction, and a larger angle implies more design freedom.

No default (Real ≥ 0.0)

GID1, GID2 Grid point identification numbers which identify the orientation. The orientation can also be identified by defining coordinates (X#, Y#, Z#).

Default = Blank (Integer > 0)

X#, Y#, Z# Coordinates of two points which identifies the orientation.

Default = Blank (Real)

METHOD Overhang Constraint Method. 20
CONSTR (Default)
The overhang angle constraint (ANGLE field) is strictly applied. The step length is determined by the STEP field.
PENALTY
The overhang angle constraint (ANGLE field) is mostly applied, however it is allowed to be violated depending on the chosen penalty factor (PENFAC field).
Blank

STEP/ PENFAC
STEP
Step length control for the CONSTR Overhang constraint method. 18
1 (Default)
Larger step length for overhang constraint is activated.
2
Moderate step length for overhang constraint is activated.
blank
PENFAC
Indicates the penalty level if the METHOD field is set to PENALTY.
Lower penalty indicates that higher violation of the overhang constraint is allowed. The levels of violation of the overhang constraint decreases from LOW to ULTRA.
This is to penalize the amount of overhang violation and the penalty will be included in optimization problem and will be minimized during the optimization process.
LOW (Default)
MEDIUM
HIGH
ULTRA
Blank

PENSCHE Penalization scheme. 17
SIMP
Solid isotropic material with penalty.
Default for PENALTY method.
RAMP
Rational approximation for material properties.
Default for CONSTR method.

NONDES Indicates if the non-design area is supported or unsupported.
SUPP (Default)
Non-design area is supported
UNSUPP
Non-design area is unsupported

HOLES Indicates if the holes are supported or unsupported.
SUPP (Default)
Holes are supported
UNSUPP
Holes are unsupported

ANGTOL Tolerance angle which identifies the elements of the design space for which the overhang constraint is not applied. The identified layer will be assumed as supported by the optimizer. 21
Default = 90.0 (0.0 ≤ Real ≤ 90.0)
Note: For ANGTOL=90.0, only the first layer of elements on the surface of the model (encountered when traveling in the build direction) is supported.

DISTOL Distance which characterizes the layer of design space for which the overhang constraint is not applied. The identified layer will be assumed as supported by the optimizer. 21
Default = 0.0 (Real ≥ 0.0)
Note: For DISTOL=0.0, only the first layer of elements on the surface of the model (encountered when traveling in the build direction) is supported.

SUPPSET References the identification number of a SET of grid points which identifies regions of the model that are considered to be supported.

Default = Blank (Integer > 0)

1. The von Mises stress constraints may be defined for topology and free-size optimization through the STRESS optional continuation line on the DTPL or the DSIZE card. There are a number of restrictions with this constraint:
• The definition of stress constraints is limited to a single von Mises permissible stress. The phenomenon of singular topology is pronounced when different materials with different permissible stresses exist in a structure. Singular topology refers to the problem associated with the conditional nature of stress constraints, that is, the stress constraint of an element disappears when the element vanishes. This creates another problem in that a huge number of reduced problems exist with solutions that cannot usually be found by a gradient-based optimizer in the full design space.
• Stress constraints for a partial domain of the structure are not allowed because they often create an ill-posed optimization problem since elimination of the partial domain would remove all stress constraints. Consequently, the stress constraint applies to the entire model when active, including both design and non-design regions, and stress constraint settings must be identical for all DSIZE and DTPL cards.
• The capability has built-in intelligence to filter out artificial stress concentrations around point loads and point boundary conditions. Stress concentrations, due to boundary geometry are also filtered to some extent as they can be improved more effectively with local shape optimization.
• Due to the large number of elements with active stress constraints, no element stress report is given in the table of retained constraints in the .out file. The iterative history of the stress state of the model can be viewed in HyperView or HyperMesh.
• Stress constraints do not apply to 1D elements.
• Stress constraints may not be used when enforced displacements are present in the model.
Note: The functionality of the STRESS continuation line to define topology stress constraints consists of many limitations. It is recommended to use DRESP1-based Stress Responses. Actual Stress Responses for Topology and Free-Size (Parameter) Optimization are available through corresponding Stress response RTYPE's on the DRESP1 Bulk Data Entry. The Stress-NORM aggregation is internally used to calculate the Stress Responses for groups of elements in the model.
2. It is recommended that a MINDIM value be chosen such that it is at least 3 times, and no greater than 12 times, the average element size. When pattern grouping, draw direction, or extrusion constraints are active, a MINDIM value of 3 times the average element size is enforced, and user-defined values (which are smaller than this value) will be replaced by this value. However, in cases where a MINDIM greater than 12 times the average element size is defined, irrespective of whether, or not other manufacturing constraints are defined, the value is reset to be equal to 12 times the average element size. If DOPTPRM,TOPDISC is present in the model, a MINDIM value equal to 2 times the average element size is enforced.

If MINDIM is defined, but no other manufacturing constraint exists, MINDIM will not be reset to the recommended lower bound value for PTYPE=PSHELL or PSOLID, if the defined value is less than the recommended value. For PTYPE=PCOMP, MINDIM will be reset in the absence of manufacturing constraints.

3. MAXDIM should be at least twice the value of MINDIM. If the input value of MAXDIM is too small, OptiStruct automatically resets the value and an INFORMATION message is printed.

The MAXDIM constraint introduces significant restriction to the design problem. Therefore, it should only be used when it is a necessary design requirement. A study without MAXDIM should always be carried out in order to compare the impact of this additional constraint.

MAXDIM implies the application of a MINGAP constraint of the same value as MAXDIM, as well. Therefore, for MINGAP to be effective, it should be greater than MAXDIM.

It is important to pay attention to volume fraction as the achievable volume is below 50% when MAXDIM is defined, and further decreases as MINGAP increases.

4. MTYP=ALIGN may be used in conjunction with draw direction or extrusion manufacturing constraints to indicate that a mesh is aligned with a draw direction or extrusion path.

Mesh 1 is "aligned" for draw direction 1 in the example shown, but not for draw direction 2.

MTYP=ALIGN may also be used in conjunction with manufacturing constraints (minimum member, maximum member, pattern grouping, and pattern repetition) other than draw direction and extrusion, and Mesh 1 is considered "aligned" for those manufacturing constraints, too.

In both cases, this will enable OptiStruct to use a smaller minimum member size and smaller maximum member sizes. The default minimum member size is three times the average element edge length; with an "aligned" mesh, the default size can be two times the average element edge length.

Mesh 2 in the example shown is not "aligned" in any case.

5. The stamping constraint is available for only one sheet, which is defined by the combination of STAMP and DTYP as SINGLE.

It is recommended that the stamping thickness, TSTAMP, be chosen such that it is at least 3 times the average element size. If TSTAMP is defined less than the minimum recommended value, TSTAMP will be reset to the minimum recommended value.

STAMP and NOHOLE can be a good combination as this helps to produce a continuous/spread shell structure.
Note: Attention should be paid to the compatibility between thickness and target volume.
6. Extrusion constraints cannot be combined with draw direction constraints.
7. Pattern repetition allows similar regions of the design domain to be linked together so as to produce similar topological layouts. This is facilitated through the definition of "Main" and "Secondary" regions. A DTPL card may only contain one MAIN or SECOND flag. Parameters will not be exported for any DTPL cards containing the SECOND flag. For both "Main" and "Secondary" regions, a pattern repetition coordinate system is required and is described following the COORD flag. To facilitate reflection, the coordinate system may be a left-handed or right-handed Cartesian system. The coordinate system may be defined in one of two ways, listed here in order of precedence:
• Four points are defined and these are utilized as follows to define the coordinate system (this is the only way to define a left-handed system):
• A vector from the anchor point to the first point defines the x-axis.
• The second point lies on the x-y plane, indicating the positive sense of the y-axis.
• The third point indicates the positive sense of the z-axis.
• A rectangular coordinate system and an anchor point are defined. If only an anchor point is defined, it is assumed that the basic coordinate system is to be used.

Multiple "Secondary" may reference the same "Main."

Scale factors may be defined for "Secondary" regions, allowing the "Main" layout to be adjusted via the SCALE continuation line.

For a more detailed description, refer to Pattern Repetition contained within the User Guide section Topology Optimization Manufacturability.

8. Pattern grouping is applicable for PCOMP, PSHELL, and PSOLID components only.
9. For historic reasons, the SYMM flag may be used in place of the PATRN flag.
10. Currently there are six pattern grouping options:

1-plane symmetry (TYP=1)

This type of pattern grouping requires the anchor point and first point to be defined. A vector from the anchor point to the first point is normal to the plane of symmetry.

2-plane symmetry (TYP=2)

This type of pattern grouping requires the anchor point, first point, and second point to be defined. A vector from the anchor point to the first point is normal to the first plane of symmetry. The second point is projected normally onto the first plane of symmetry. A vector from the anchor point to this projected point is normal to the second plane of symmetry.

3-plane symmetry (TYP=3)

This type of pattern grouping requires the anchor point, first point, and second point to be defined. A vector from the anchor point to the first point is normal to the first plane of symmetry. The second point is projected normally onto the first plane of symmetry. A vector from the anchor point to this projected point is normal to the second plane of symmetry. The third plane of symmetry is orthogonal to both the first and second planes of symmetry, passing through the anchor point.

Uniform Pattern Grouping (TYP=9)

This type of pattern grouping does not require any additional input. It only requires the TYP field to be set equal to 9. All elements included in this DTPL entry are automatically considered for uniform pattern grouping. All elements on this DTPL entry are set equal to the same element density with respect to one another.

Cyclic (TYP=10)

This type of pattern grouping requires the anchor point, first point, and number of cyclical repetitions to be defined. A vector from the anchor point to the first point defines the axis of symmetry.

Cyclic with symmetry (TYP=11)

This type of pattern grouping requires the anchor point, first point, second point, and number of cyclical repetitions to be defined. A vector from the anchor point to the first point defines the axis of symmetry. The anchor point, first point, and second point all lay on a plane of symmetry. A plane of symmetry lies at the center of each cyclical repetition.

For a more detailed description, refer to Pattern Grouping contained within the User Guide section Topology Optimization Manufacturability.

11. The LT field can be used to specify the lattice type used in Lattice Structure Optimization for hexahedral elements.
12. The density thresholds are defined using the LB and UB fields on the LATTICE continuation line. Elements with densities below LB (real) are considered voids and removed for the second phase. Elements with densities above UB (real) are considered solid and are retained as solid elements for the second phase. Elements with densities between LB and UB are considered as porous phases and elements having these densities are replaced by lattice structures. The amount of intermediate densities (between 0.0 and 1.0) is controlled using DOPTPRM, POROSITY. Refer to Lattice Structure Optimization in the User Guide for further information.
13. FailSafe topology optimization runs in SPMD mode and requires the -fso script option. Refer to Failsafe Topology Optimization in the User Guide for further information.
14. Multi-Model Optimization requires the definition of the COORD continuation line to allow mapping of the design domains among multiple models. If individual pattern repetition is defined on all models, then this continuation line is not required as the COORD data from the pattern repetition section is used instead. The coordinate system can be defined in one of two different ways:
• Four points are defined, and these are utilized as follows to define the coordinate system (this is the only way to define a left-handed system):

A vector from the anchor point to the first point defines the x-axis.

The second point lies on the x-y plane, indicating the positive sense of the y-axis.

The third point indicates the positive sense of the z-axis.

• A rectangular coordinate system and an anchor point are defined. If only an anchor point is defined, it is assumed that the basic coordinate system is to be used.
15. Both solids and shells are supported in multiple materials topology optimization. The following two limitations apply to PSHELLs in the design space for multiple materials topology optimization.
• For any PSHELL entry part of the design space, then all material reference fields (MID# fields) on each PSHELL entry should point to the same material entry.
• Additionally, if multiple PSHELL entries are part of the design space, then all MID# fields on all PSHELL entries should point to the same material entry.
16. The original material defined by its property will be taken as one of the candidate material by default. Besides the original one, the maximum number of candidate materials is nine (9). Only isotropic material MAT1 is supported on the MID# fields.
17. The Rational Approximation for Material Properties (RAMP) method uses the following equation for penalization.(1)
$\stackrel{˜}{K}\left(\rho \right)=\left(\frac{\rho }{1+p\left(1-\rho \right)}\right)K$
Where,
$\stackrel{˜}{K}\left(\rho \right)$
Penalized stiffness matrix of an element (as a function of density)
$K$
Actual stiffness matrix of an element
$\rho$
Density
$p$
Penalization factor

For information about Solid Isotropic Material with Penalty (SIMP) method, see the Design Elements section.

18. For overhang constraints, STEP=1 allows aggressive move limits and typically converges fast. It generally produces good results for a majority of situations. However, it may show large fluctuations in convergence. In such cases, STEP=2 can be tried, which moves conservatively and follows a smoother convergence curve. It may sometimes offer faster convergence and better designs.
19. This card is represented as an optimization design variable in HyperMesh.
20. If the METHOD field is set to CONSTR, then the following considerations are available:
• Depending on the model, CONSTR method can pose a significant reduction of the design freedom for the optimization. Which may lead to a reduction in performance compared to the run without overhang constraints.
• If a volume or mass constraint is used in addition to the overhang constraint with CONSTR, then the target may be too low for the optimizer to find a good design. In such cases, you can try increasing the volume or mass target.
• If the impact on the performance or the volume/mass target is too large, then try the PENALTY method.
If the METHOD field is set to PENALTY, then the following considerations are available:
• This method is good at removing members that are overhanging but have a small or medium impact on the performance. This method may not remove members which are very important to performance. If the goal is to remove such high impact members, try the CONSTR method instead.
• For PENALTY method, the violations of overhang angle are output to H3D file.
21. The ANGTOL and DISTOL fields can be used to define elements that are considered to always be supported during optimization. Candidate elements are all those elements in the first layer encountered when traveling in the build direction. If this layer is inclined more than ANGTOL, and lies within DISTOL, it is always supported.
The elements which are always supported are output to the H3D file under the “Predefined Support” results type. For the actual manufacturing of the part, some sections of this predefined support might require support structure.
22. LATPRM,LATSUP can be used to define the maximum volume fraction of the lattice support regions when overhang constraints are used in Topology Optimization.
23. The level set method can merge existing holes but cannot nucleate new holes in the design domain, unless TOPDER is defined. Therefore, creating an initial design with holes is necessary, especially for 2D design problems (For 3D design problems, new holes can be “tunneled” when two surfaces merged).
24. By default, OptiStruct will automatically create a Cheese-like initial design with holes adaptively distributed over the design domain (Figure 3) The default hole radius is 5.0 times the average mesh size.
25. Changing the value of HOLERAD can result in different initial designs. Figure 3(right) shows an initial design filled with holes possessing a doubled hole radius when compared to Figure 3(left). If you want to create an initial design with evenly distributed and well aligned holes (this may be preferable for regular design domains), HOLEINST can be set to ALIGN. The number of holes in each direction can be further specified by using NHOLESX, NHOLESY and NHOLESZ (Figure 4).
26. The Radial draw direction option allows you to define manufacturing constraints for draw such that the die can be withdrawn in a radially outward direction away from the cylindrical axis defined by DAIDDFID. The Spherical draw direction option allows you to define manufacturing constraints for draw such that the die can be withdrawn in a spherically outward direction away from the central point defined by DAID. The anchor grid for spherical draw direction is recommended to be placed in the center of geometry.
27. For more information, refer to Level Set Method in the User Guide.
28. This card is represented as an optimization designvariable in HyperMesh.