DTPG

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

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DTPG ID TYPE PID1/

SID1

/

DVID

PID2/

SID2

PID3/

SID3

PID4/

SID4

PID5/

SID5

PID6/

SID6

 
    PID7/

SID7

etc etc etc etc etc etc  
  MW ANG BF HGT Norm/

XD

YD ZD SKIP  
  MAXW MAXWTH MINHGT ZEROB          
  PATRN TYP AID/

XA

YA ZA FID/

XF

YF ZF  
  PATRN2 UCYC SID/

XS

YS ZS        
  BOUNDS LB UB INIT DDVAL        
  AUTOBEAD LAYER REMESH            
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 DTPG_ID SX SY SZ        
  COORD CID CAID/

XCA

YCA ZCA CFID/

XCF

YCF ZCF  
      CSID/

XCS

YCS ZCS CTID/

XCT

YCT ZCT  

Example 1

This example defines a topography design variable which allows for swages to be created in components referencing the PSHELL properties 1, 9, and 23. The swages will have a minimum width of 3 units, a draw angle of 600, and a maximum height of 5 units. The draw direction will be in the element's normal direction, but the swages may grow in either the positive or negative direction. The swages should be grouped such that they form a cyclical pattern, of 1200 intervals about the z-axis, through the point (0,25,0), and they also should be symmetrical about the xy plane.
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DTPG 1 PSHELL 1 9 23        
  3.0 60.0 Yes 5.0 Norm     both  
  PATRN 50 0.0 25.0 0.0 0.0 1.0 0.0  
  PATRN2 3 1.0 0.0 0.0        
  BOUNDS -1.0 1.0            

Example 2

This example defines a topography design variable that references the shape variables defined by the DVGRIDs with ID 1. The swages will have a minimum width of 5 units and a draw angle of 750. The height and draw direction of the swages is defined by the DVGRID cards. Also ensure that the swages can only grow in the positive direction as defined by the DVGRID cards.
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DTPG 1 DVGRID 1            
  5.0 75.0 YES            
  BOUNDS 0.0 1.0            

Definitions

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

No default (Integer > 0)

 
TYPE Indicate whether DTPG card is defined for PSHELL, PCOMP, DVGRID, SET or STACK (Laminate).

No default

 
PID#/SID#/DVID If TYPE is PSHELL or PCOMP, then this entry is a Property identification number. Use ALL if it applies to all properties of type PTYPE in the model. Numerous PIDs may be given.

If TYPE is DVGRID, this entry is the Design Variable number for a set of DVGRIDs. Only one DVID may be given.

If TYPE is SET, this entry is a SET identification number referring to a set of elements.

If TYPE is STACK, this entry is a STACK (Laminate) identification number. Numerous STACK ID's may be provided.

Default = ALL (Integer > 0, blank or ALL)

 
MW Bead minimum width. This parameter controls the width of the beads in the model [recommended value between 1.5 and 2.5 times the average element width]. 1

No default (Real > 0.0)

 
ANG Draw angle in degrees. This parameter controls the angle of the sides of the beads (recommended value between 60 and 75 degrees). 1

No default (1.0 < Real < 89.0)

 
BF Buffer zone. This parameter will establish a buffer zone between elements in the design domain and elements outside the design domain. 2
YES (Default)
NO
 
HGT Draw height. This parameter sets the maximum height of the beads to be drawn. This field is only valid if TYPE is PSHELL or PCOMP.

No default (Real > 0.0)

 
norm/XD,YD,ZD Draw direction. If norm/XD field is 'norm', the shape variables will be created in the normal directions of the elements. If all the fields are real, the shape variable will be created in the direction specified by the xyz vector defined by the three fields. The X, Y, and Z values are in the global coordinate system. This field is only valid if TYPE is PSHELL or PCOMP.

Default = NORM (NORM in norm/XD field or Real in all three fields)

 
SKIP Boundary skip. This parameter tells OptiStruct to leave certain nodes out of the design domain.
NONE
All nodes attached to elements whose PIDs are specified, will be a part of the shape variables.
BC or SPC
Any nodes which have SPC or SPC1 declarations are omitted from the design domain.
LOAD
Any nodes which have FORCE, FORCE1, MOMENT, MOMENT1, or SPCD declarations are omitted from the design domain.
BOTH (Default)
Nodes with either SPC or LOAD declarations are omitted from the design domain. This field is only valid if TYPE is PSHELL or PCOMP.
 
MAXW Indicates that maximum bead width control is active.  
MAXWTH Maximum width of beads. This parameter can be used to prevent the formation of large beads. It should be at least twice the value of the minimum bead width (MW).

No default (Real > 0.0)

 
MINHGT Minimum height ratio to be considered as bead. Only the beads with height greater than MINHGT*HGT would be counted in maximum width constraint.

Default = 0.5 (Real ≥ 0.0)

 
ZEROB Indicates whether the width control is applied to the beads with zero height.
YES
NO (Default)
 
PATRN Indicates that variable pattern grouping is active. Indicates that information about the pattern group will follow.  
TYP Type of variable grouping pattern. Required if any symmetry or variable pattern grouping is desired. If zero or blank, anchor node, first vector, and second vector definitions are ignored. If less than 20, second vector definition is ignored. 4

Default = 0 (Integer ≥ 0)

 
AID/XA,YA,ZA Variable grouping pattern anchor point. These fields define a point that determines how grids are grouped into variables. 3 The X, Y, and Z values are in the global coordinate system. You may put a grid ID in the AID/XA field to define the anchor point.

Default = origin (Real in all three fields or Integer in AID/XA field)

 
FID/XF,YF,ZF Direction of first vector for variable pattern grouping. These fields define a xyz vector which determines how grids are grouped into variables. 3 The X, Y, and Z values are in the global coordinate system. You may put a grid ID in the FID/XF field to define the first vector. This vector goes from the anchor point to this grid. If all fields are blank and the TYP field is not blank or zero, OptiStruct gives an error.

No default

 
PATRN2 Indicates variable pattern grouping continuation card. This card is only required when a second vector is needed to define the pattern grouping.  
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. 4

Default = 0 (Integer ≥ 0 or blank)

 
SID/XS,YS,ZS Direction used to determine second vector for variable pattern grouping. These fields define a xyz vector which, when combined with the first vector, form a plane. The second vector is calculated to lie in that plane and is perpendicular to the first vector. The second vector is sometimes required to determine how grids are grouped into variables. 3 The X, Y, and Z values are in the global coordinate system. You may put a grid ID in the SID/XS field to define the second vector. This vector goes from the anchor point to this grid. If all fields are blank and the TYP field contains a value of 20 or higher, OptiStruct gives an error.

No default

 
BOUNDS Indicates that information on upper and lower limits and the initial value for grid movement are to follow.  
LB Lower bound on variables controlling grid movement. This sets the lower bound on grid movement equal to LB*HGT.

Default = 0.0 (Real < UB)

 
UB Upper bound on variables controlling grid movement. This sets the upper bound on grid movement equal to UB*HGT.

Default = 1.0 (Real > LB)

 
INIT The initial value of the variables controlling grid movement. This sets the initial value on grid movement equal to INIT*HGT.

Default = LB + factor*(UB-LB), if LB > 0.0 and UB > 0.0

Default = UB - factor*(UB-LB), if LB < 0.0 and UB < 0.0

Default = factor*max(abs(LB),UB), if LB < 0.0 and UB > 0.0

where:
  • factor = 0.0 if this DTPG is not used in a BEADFRAC response or is used in a BEADFRAC response that is neither chosen as the objective nor constrained.
  • factor = 0.9 if this DTPG is used in a BEADFRAC response that is chosen as the objective.
  • factor = constraint_value if this DTPG is used in a BEADFRAC response that is constrained.
(LB < Real < UB)
 
DDVAL ID of DDVAL entry that provides a set of discrete values.

(Blank or Integer > 0; Default = blank for continuous design variables)

 
AUTOBEAD Indicates that AUTOBEAD of OSSmooth is used to interpret the results as one or two level beads.  
LAYER Indicates the number of layers.

Default = 1 (Integer: 1 or 2)

 
REMESH Indicates the element size for remeshing.
0.0 (Default)
REMESH of OSSmooth is inactive

(Real ≥ 0.0)

 
MAIN Indicates that this design variable may be used as a main pattern for pattern repetition.  
COORD Indicates information regarding the coordinate system for pattern repetition is to follow. This is required if either MAIN or SECOND flags are present.  
CID Coordinate system ID for a rectangular coordinate system that may be used as the pattern repetition coordinate system. 6

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. 6

No default (Real in all three fields or Integer in the 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. 6

No default (Real in all three fields or Integer in the 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. 6

No default (Real in all three fields or Integer in the 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. 6

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

 
SECOND Indicates that this design variable is secondary to the main pattern definition referenced by the following DTPG_ID entry. 6  
DTPG_ID DTPG identification number for a main pattern definition.

No default (Integer > 0)

 
SX, SY, SZ Scale factors for pattern repetition in X, Y, and Z directions, respectively. 6

Default = 1.0 (Real > 0.0)

 

Comments

  1. The bead minimum width and draw angles are used to determine the geometry of the shape variables. Figure 1 shows a cross-section of a single shape variable fully extended normal to the plane of the design elements. The top of the bead is flat across the circular area with a diameter equal to the minimum bead width parameter. The sides of the bead taper down at an angle equal to the draw angle parameter.


    Figure 1. Bead Width and Draw Angle Definitions
  2. The buffer zone is a parameter that controls how the interfaces between design and non-design elements are treated. If active, OptiStruct will place the shape variables far enough away from the non-design elements so that the proper bead widths and draw angles are maintained. If inactive, the boundary between the beads and non-design elements will have an abrupt transition. Any nodes that were skipped due to the boundary skip parameter (field 10) will also have a buffer zone created around them.


    Figure 2. Transitions Between Design and Non-design Elements With and Without Buffer Zone
  3. Symmetry of topography optimization can be enforced across one, two, or three planes. Defining symmetry planes for symmetric model and loading conditions is recommended because automatic variable generation may not be symmetric if it is not enforced. A symmetric mesh is not necessary, OptiStruct will create variables that are very close to identical across the plane(s) of symmetry. If the mesh is larger on one side of the plane(s) of symmetry than the other, OptiStruct will reflect variables created on the 'positive' side of the plane(s) of symmetry to the other side(s) but will not create variables on the 'negative' side(s) of the plane(s) of symmetry that do not overlap with the positive side. The positive side of the plane(s) of symmetry is the one in which the first vector, second vector, and cross product thereof are pointing toward.
  4. Variable pattern grouping may be defined for a DTPG card. OptiStruct will generate shape variables based on the type of pattern selected in field 20. For variable grouping pattern types 1 through 14, only the first vector and anchor node need to be defined. For variable pattern grouping types 20 or higher, the first and second vectors need to be defined as well as the anchor node. If a grid is used to define the first vector, the normal vector will begin at the anchor point and extend towards the given grid (see below). Grids or xyz data may be used for either the first vector, second vector, or anchor point and can be a mixture, (that is the anchor point may be determined by a grid and the first vector determined by xyz data or vice-versa).
    One very useful feature for topography optimization in OptiStruct is the automatic generation of shape variables in simple patterns. In many cases, due to manufacturing constraints or the risk of elements being collapsed upon them during shape optimization, it is required to create shape variables in patterns that conform to the desired shape of the part. In basic topography optimization (TYP = 0), OptiStruct creates shape variables that are circular. OptiStruct contains a library of different shape variable patterns which can be accessed using the TYP parameter on the DTPG card.

    beadfig3
    Figure 3. Defining the First Vector Using a Grid Point
    The second vector is calculated by taking the grid point or vector defined in fields 22, 23, and 24 and projecting it onto plane 1. If a grid point was used to define the second vector, the second vector is a vector running from the anchor node to the projected grid point. If a vector was used to define the second vector, the base of the projected vector is placed at the anchor point.

    beadfig4
    Figure 4. Second Vector is Normal to Plane 2

    beadfig5
    Figure 5. Plane 3 is Determined to be Normal to Both Plane 1 and Plane 2
  5. For a list of patterns supported by OptiStruct, refer to Pattern Grouping Options.
  6. Pattern repetition allows similar regions of the design domain to be linked together so as to produce similar topographical layouts. This is facilitated through the definition of "Main" and "Secondary" regions. A DTPG card may only contain one MAIN or SECOND flag. Bead parameters will not be exported for any DTPG 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. 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 "Secondary" may reference the same "Main".

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

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

  7. REMESH function uses mixed type of elements, if input mesh contains any QUAD elements; otherwise, it only uses TRIA elements.
  8. This card is represented as an optimization design variable in HyperMesh.