Defines the thickness step
for discrete design variable definition. 15
Default = blank (Real > 0.0)
PMOPT
Ply selection options for
the PLYMAN constraint. Plies can be selected
based on:
BYANG (Default)
Orientation
BYSET
Ply sets
BYPLY
Ply IDs
Note:BYPLY is valid, if
PTYPE is either
STACK or
PCOMPG.
PMSET
Set ID of elements to
which the PLYMAN constraint is applied.
PMEXC
Exclusion flag indicating
that certain plies are excluded from the PLYMAN
constraint. Support options are:
NONE
Plies are not excluded.
CORE (Default)
The core is excluded.
CONST
Plies defined in the CONST constraint
are excluded.
BOTH
CORE and CONST are
considered.
BALANCE
Indicates that a balancing
constraint is applied. Multiple BALANCE
constraints are allowed.
BGRP1
First ply orientation in
degrees, ply sets or ply IDs, to which the
BALANCE constraint is applied, depending on
the BOPT selection.
No default (Real or
Integer)
BGRP2
Second ply orientation in
degrees, ply sets or ply IDs, to which the
BALANCE constraint is applied, depending on
the BOPT selection.
No default (Real or
Integer)
BOPT
Ply selection options for
the BALANCE constraint. Plies can be selected
based on:
BYANG (Default)
Orientation
BYSET
Ply sets
BYPLY
Ply IDs
Note:BYPLY is valid, if
PTYPE is either
STACK or
PCOMPG.
CONST
Indicates that a constant
thickness constraint is applied. Multiple CONST
constraints are allowed.
CGRP
Ply orientation in
degrees, ply sets or ply IDs, to which the CONST
constraint is applied, depending on the COPT
selection.
No default (Real or Integer)
CTHICK
Constant ply thickness for
the CONST constraint.
No default (Real >
0.0)
COPT
Ply selection options for
the CONST constraint. Plies can be selected based
on:
BYANG (Default)
Orientation
BYSET
Ply sets
BYPLY
Ply IDs
Note:BYPLY is valid, if
PTYPE is either
STACK or
PCOMPG.
PLYDRP
Indicates that ply
drop-off constraints are applied. Multiple PLYDRP
constraints are allowed.
PDGRP
Ply orientation in
degrees, ply sets or ply IDs, to which the PLYDRP
constraint is applied, depending on the PDOPT
selection.
No default (Real or Integer)
PDTYP
Specifies the type of the
drop-off constraint as: 10
PLYSLP (Default)
PLYDRP
TOTSLP
TOTDRP
PDMAX
Maximum allowed drop-off
for the PLYDRP constraint.
No default (Real >
0)
PDOPT
Ply selection options for
the PLYDRP constraint. Plies can be selected
based on:
BYANG (Default)
Orientation
BYSET
Ply sets
BYPLY
Ply IDs
PDSET
Set IDs of elements to
which the PLYDRP constraint is applied.
PDEXC
Exclusion flag indicates
that certain plies are excluded from the PLYDRP
constraint. Supported options are:
NONE
Plies are not excluded.
CORE (Default)
The core is excluded.
CONST
Plies defined in the CONST constraint
are excluded.
BOTH
CORE and CONST are
considered.
PDDEF
Optional definition to
fine-tune the drop-off constraint. Currently only
DIRECT is available to request directional
drop-off, in which case PDX,
PDY and PDZ specify the
drop-off direction. 11
PDX,
PDY, PDZ
Used to specify the
drop-off direction when DIRECT is input in the
PDDEF field. 11
PATRN
Indicates that pattern
grouping is active for the properties listed. Indicates that
information for pattern grouping is to follow.
Default = No pattern grouping
(1, 2, 3,
9, 10,
11, 20 or
21)
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. 1
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. 1
No default (Real in all three fields or
Integer in the 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. 1
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. 1
No default (Real in all three fields or
Integer in first field)
MASTER
Indicates that this design
variable may be used as a master pattern for pattern repetition.
2
SLAVE
Indicates that this design
variable is slave to the master pattern definition referenced by the
following DSIZE_ID entry. 2
DSIZE_ID
DSIZE
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. 2
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 flags are present.
CID
Coordinate system ID for a
rectangular coordinate system that may be used as the pattern
repetition coordinate system. 2
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. 2
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. 2
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. 2
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. 2
No default (Real in all three fields or
Integer in the first field)
FATIGUE
Indicates that fatigue
constraints are active and their definition is to follow.
FTYPE
Fatigue constraint
type:
DAMAGE
LIFE
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)
GROUP
Specifies the definition
of zone based free-sizing optimization. Indicates that element group
IDs will follow.
EG#
Element group numbers.
Element groups are created through element sets (Format 1). 6
No default (Integer > 0)
THRU
This keyword can be used
in the optional alternate format to define zone based free-sizing
optimization.
This keyword is used for ID range definition to
indicate that all ID's between the preceding ID
(EG1) and the following ID
(EG2) are to be included in the
set.
AUTO
Automatic creation of
Element groups for zone-based free-sizing optimization is activated
(Format 2). The element groups are automatically created based on
the SIZE field.
No default (should be set to
AUTO for Format 2)
SIZE
Specifies the size of the
patch to automatically define the element groups.
SIZE identifies the length of the edge of a
square wherein, all elements within this square are grouped
together.
Note: The elements mentioned in EG# in
Format 2 are excluded from the automatic grouping.
No
default (Real > 0.0)
EG#
Element group numbers
which are excluded from automatic grouping in Format 2. Element
groups are created through element sets (Format 2). 6
Default = blank (Format 2) (Integer >
0)
TAPE
The
TAPE flag to indicate that tape laying based
free-sizing definitions are active and corresponding parameters are
to follow. 121314
LTAPE
Minimum Tape length
No
default (Real > 0.0)
WTAPE
Tape width
No default
(Real > 0.0)
OFFSET
Allows selecting the
required option to offset contiguous patches.
LOFF
Contiguous tape patches are offset along the length
direction by a distance equal to half of the tape
length.
WOFF
Contiguous tape patches are offset along the width
direction by a distance equal to half of the tape
width.
blank (Default)
Comments
There are currently five pattern
grouping options for free-size optimization:
1-plane symmetry (TYP = 1)
This type of pattern grouping requires that the anchor point and the
first point 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 that the anchor point, first
point, and second point 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 that the anchor point, first
point, and second point 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 requires only the
TYP field to be set equal to 9. All elements
included in this DSIZE entry are automatically
considered for uniform pattern grouping. All elements on this
DSIZE entry are set equal to the same
thickness.
Cyclic (TYP = 10)
This type of pattern grouping requires that the anchor point, first
point, and number of cyclical repetitions 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 that the anchor point, first
point, second point, and number of cyclical repetitions 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.
Linear Pattern Grouping (TYP =
20)
Linear pattern grouping requires that the anchor point and first
point be defined. A vector from the anchor point to the first point
defines the direction in which the thickness is set to be constant.
Linear pattern grouping is typically designed to handle models with
minimal or no curvature in the specified vector direction (which is
typically orthogonal to the rolling direction in rolling
applications). For models with low curvature in the vector
direction, appropriate projections to the surface are used to
determine the direction on the surface. For models with high
curvature in the vector direction, depending on the direction of the
specified vector, the direction may become orthogonal to the surface
whereby the pattern grouping direction cannot be determined. In such
cases, Planar Pattern Grouping (TYP =
21) is recommended.
Planar Pattern Grouping (TYP =
21)
Planar pattern grouping requires that the anchor point and first
point be defined. A vector from the anchor point to the first point
is defined and thickness of the model in the various orthogonal
planes to this vector is set to be constant. Planar pattern grouping
is designed to handle models with high curvature in the orthogonal
planes of the defined vector, and with minimal or no curvature in
the direction of the defined vector. The vector defined in planar
pattern grouping should typically lie in the rolling direction in
rolling applications. This feature can handle large curvature in the
slicing plane orthogonal to the defined vector. Planar pattern
grouping cannot be used if large curvature exists in the rolling
direction.
Note: Multiple continuation lines defining pattern grouping is allowed.
However, this is currently only supported for
TYP=20 or
TYP=21 in conjunction with
TYP=1,
TYP=2, or
TYP=3.
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 DSIZE card may only contain one
MASTER or 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.
It is recommended that a
MINDIM value be chosen which allows for the formation of
members that are at least three elements thick. When pattern grouping
constraints are active, a MINDIM value of three times the
average element edge length is enforced, and user-defined values (which are
smaller than this value) will be replaced by this value.
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
and free-size stress constraints consists of many limitations. It is
recommended to use DRESP1-based Stress Responses
instead. 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.
The following manufacturing constraints
are available for composite free-sizing optimization:
Lower and upper bounds on the total thickness of the laminate
(LAMTHK).
Lower and upper bounds on the thickness of a given orientation
(PLYTHK).
Lower and upper bounds on the thickness percentage of a given
orientation (PLYPCT).
Linking between the thicknesses of two given orientations
(BALANCE).
Constant (non-designable) thickness of a given orientation
(CONST).
LAMTHK, PLYTHK,
PLYPCT, and PLYMAN can be
applied locally to sets of elements. There can be elements that do not
belong to any set.
Elements within each group will have
uniform ply thicknesses.
The core is designable by default. It
can be made non-designable through the CONST manufacturing
constraint. To facilitate this, the keyword CORE can be used
instead of a ply ID when BYPLY is activated.
The core is excluded from the
LAMTHK, PLYTHK,
PLYPCT and PLYMAN manufacturing
constraints by default.
Legacy data field
PTMAN (for manufacturable ply thickness) defined on the
PLYTHK and PLYPCT entries is
supported. However, it is now recommended to define the manufacturable ply
thickness in the PMMAN field through the
PLYMAN continuation line as this offers more
control.
The options for selecting the type of
drop-off constraints for PDTYP are defined for a set of
plies. Figure 1.
Assuming that the plies are stacked as shown above, you have the following
definitions: Figure 2. Figure 3. Figure 4. Figure 5.
When OUTPUT,FSTOSZ is used to
generate a Sizing input deck, the Ply drop-off manufacturing constraints are
converted into equivalent TOTDRP constraints. Check that the
estimated TOTDRP values on the DCOMP
entry(s) are meaningful, or adjust the values manually, if necessary.
The optional PDDEF
definition is used to fine-tune the drop-off constraint. Currently, only the
DIRECT option is available for the PDDEF
field.
PDDEF
DIRECT This option allows you to fine-tune the
drop-off constraint by requesting directional drop-off. The
direction of drop-off can be specified by defining a directional
vector with respect to the basic coordinate system. The directional
vector is defined using the PDX,
PDY and PDZ values.
PDX, PDY,
PDZ
PDX, PDY and
PDZ are real numbers.
These values are used to specify the drop-off direction when
DIRECT is input in the PDDEF
field. They specify the three components of a directional vector
defined with respect to the basic coordinate system.
Example: If drop-off control is required in the X-direction, then
1,0,0 can be defined in the PDX,
PDY, PDZ fields,
respectively. 0,1,0 can be defined for Y-direction drop-off
control.
Other manufacturing constraints (except
BALANCE) can be used along with tape laying.
If there are multiple plies of the same
orientation, the corresponding tapes are automatically offset with respect to
one another. This increases the design freedom by allowing OptiStruct to choose the optimum layout for a particular
configuration.
Symmetry is available only at the
laminate level for tape laying. Opposite orientations (for example, 45 degrees
and -45 degrees) are reflections of each other, instead of being reflected
across the plane of symmetry. 0 and 90 degree plies are still reflected across
the plane of symmetry.
Discrete design variables are
internally created based on the thickness step defined via
PMDIS. The thickness step indicates that the design
variables are created as integer multiples of the PMDIS
value. For example, if PMDIS is 0.2, then the design
variables can be 0.2, 0.4, 0.6 and so on.
Note:PMDIS and
PMMAN can be different. PMDIS is
inactive by default and PMMAN=PMDIS by
default if PMMAN is not specified.
This card is represented as an
optimization design variables in HyperMesh.
