DTPL

Bulk Data Entry

DTPL – Design Variable for Topology Optimization

Description

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	…	…	…	…	…	…
		…	…

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	…	…	…	…	…	…
	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	…	…	…	…	…	…
		…	…
	EPATH2	EP2_ID1	EP2_ID2	EP2_ID3	EP2_ID4	EP2_ID5	EP2_ID6	EP2_ID7
		EP2_ID8	…	…	…	…	…	…
		…	…

Optional continuation lines for "Master" definition for pattern repetition constraint:

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
	MASTER
	COORD	CID	CAID/XCA	YCA	ZCA	CFID/XCF	YCF	ZCF
			CSID/XCS	YCS	ZCS	CTID/XCT	YCT	ZCT

Optional continuation lines for "Slave" definition for pattern repetition constraint:

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
	SLAVE	DTPL_ID	SX	SY	SZ
	COORD	CID	CAID/XCA	YCA	ZCA	CFID/XCF	YCF	ZCF
			CSID/XCS	YCS	ZCS	CTID/XCT	YCT	ZCT

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) activation:

(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	OFAIL	PFAIL

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

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

Field	Contents
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. No default (PBAR, PBARL, PBEAM, PBEAML, PBUSH, PROD, PWELD, PSHELL, PCOMP, PSOLID, or STACK)
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. See comment 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. See comment 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. See comment 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. See comment 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. See comment 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	Type of draw direction constraint to be used. SINGLE indicates that a single die will be used, the die being withdrawn in the given draw direction. SPLIT 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. Default = SPLIT (SINGLE, SPLIT, SPLIT2, or SPLIT3)
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 regard 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 regard 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 that 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. See comment 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. See comment 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 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. Default = NOTWIST (NOTWIST or TWIST)
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)
MASTER	Indicates that this design variable may be used as a master pattern for pattern repetition. See comment 7.
COORD	Indicates information regarding the coordinate system for pattern repetition is to follow. This is required if either MASTER or SLAVE flag is present.
CID	Coordinate system ID for a rectangular coordinate system that may be used as the pattern repetition coordinate system. See comment 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. See comment 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. See comment 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. See comment 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. See comment 7. No default (Real in all three fields or Integer in first field)
SLAVE	Indicates that this design variable is slave to the master pattern definition referenced by the following DTPL_ID entry. See comment 7.
DTPL_ID	DTPL identification number for a master pattern definition. No default (Integer > 0)
SX, SY, SZ	Scale factors for pattern repetition in X, Y, and Z directions, respectively. See comment 7. Default = 1.0 (Real > 0.0)
COORD	Indicates information regarding the coordinate system for pattern repetition is to follow. This is required if either MASTER or SLAVE flag is present.
CID	Coordinate system ID for a rectangular coordinate system that may be used as the pattern repetition coordinate system. See comment 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. See comment 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. See comment 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. See comment 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. See comment 7. 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. See comment 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. See comment 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. See comment 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. See comment 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. See comment 10. No default (Real in all three fields or Integer in first field)
MAT	Indicates the type of composite topology optimization. Only considered for PTYPE=PCOMP.
MATOPT	PLY: 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. Default = PLY
FATIGUE	Indicates that fatigue constraints are active and their definitions are to follow.
FTYPE	Specifies the type of fatigue constraint; it can be DAMAGE, LIFE or FOS.
FBOUND	Specifies the bound value. If FTYPE is DAMAGE, FBOUND will be the upper bound of fatigue damage. If FTYPE is 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.
HOLEINST	Defines the method used to insert holes into the design. Default = ADAPT (NONE, ADAPT, ALIGN or TOPDER) NONE: Indicates that there are no holes in the initial design, and it will work similar to shape optimization. ADAPT: 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 2. 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 3. 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. If the HOLEINST field is blank, it is set to ADAPT by default.
HOLERAD	<REAL NUMBER> Default = 4 times the average mesh size A real number that specifies the initial radius of the holes. If blank, the radius will be set to 4 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). If 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 (see comments 15 and 16) Default = 1 (Integer: 1, 2, 3, or 4)
LB	Density lower bound (see comments 15 and 16) Default = 0.1 (0.0 ≤ Real ≤ 1.0)
UB	Density upper bound (see comments 15 and 16) Default = 0.8 (0.0 ≤ Real ≤ 1.0)
LATSTR	Stress constraint for Phase 2 of Lattice Optimization (see Stress Constraints in the User's Guide). No default (Real)
FAILSAFE	Indicates that Failsafe Topology Optimization is activated and the definitions of the required parameters are to follow. See comment 17.
SFAIL	Size of the individual Failure Zones in a particular layer. This is the edge length for CUBE failure zone (see TFAIL option) 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: Default = CUBE (CUBE or SPHERE) CUBE: 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. Default = YES (YES or NO) YES: 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)

Comments

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 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.

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.

DTPL_comment_9

Figure 1: Draw direction

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 that attention should be paid to the compatibility between thickness and target volume.

6.	Extrusion constraints cannot be combined with draw direction constraints.

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 "Master" and "Slave" regions. A DTPL card may only contain one MASTER or SLAVE flag. Parameters will not be exported for any DTPL cards containing the SLAVE flag. For both "Master" and "Slave" regions, a pattern repetition coordinate system is required and is described following the COORD flag. In order 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 "Slaves" may reference the same "Master."

Scale factors may be defined for "Slave" regions, allowing the "Master" layout to be adjusted.

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

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)

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's Guide section Manufacturability for Topology Optimization.

11.	The level set method can merge existing holes but cannot nucleate new holes in the design domain. 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).

12.	By default, OptiStruct will automatically create a Cheese-like initial design with holes adaptively distributed over the design domain, as shown in Figure 2. The default hole radius is 4.0 times the average mesh size.

DTPL_fig2

Figure 2: A Cheese-like Initial design generated with (left) the default setting, and (right) double hole radius.

13.

Changing the value of HOLERAD can result in different initial designs. Figure 2 (right) shows an initial design filled with holes possessing a doubled hole radius when compared to Figure 2 (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, as shown in Figure 3.

DTPL_fig3

Figure 3: A Cheese-like initial design with 3-by-5 evenly distributed holes generated using the following settings:
HOLEINST=ALIGN, NHOLESX=5 and NHOLESY=3

14.	Currently, level set supports both SINGLE and SPLIT draw direction constraints. When multiple DTPL cards are involved, the draw directions need to be the same. The information needed for draw direction constraint is read from the DTPL cards and thus no extra settings are required.

15.	The LT field can be used to specify the lattice type used in Lattice Structure Optimization.

Refer to Lattice Structure Optimization in the User’s Guide for further information.

16.

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’s Guide for further information.

17.	FailSafe topology optimization runs in SPMD mode and requires the –fso script option. Refer to Failsafe Topology Optimization in the User’s Guide for further information.

18.	This card is represented as an optimization designvariable in HyperMesh.