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radius, in which case the zero or blank must occupy either the RAD1 or RAD2 position.)
At least two of the values that you specify must be positive values; they will be used to
define the outer minor radius and the major radius.
To create the torus shown in Figure 5.16: "Torus Primitive", the command
TORUS,5,1,2 was issued. Due to the sizes of the specified radii values relative to one
another, 5, 1, and 2 were used to define the major radius, inner minor radius, and
outer minor radius of the torus, respectively. Since no values for THETA1 and THETA2
were specified, the default values of 0 and 360 were used as the starting and ending
angles of the torus. (See Figure 5.17: "Toroidal Sector" for a view of a toroidal sector
showing all radii.)
Figure 5.16 Torus Primitive
To create the toroidal sector shown in Figure 5.17: "Toroidal Sector", the command
TORUS,5,1,2,0,180 was issued; where 5, 1, and 2 are the major radius, inner minor
radius, and outer minor radius of the torus; and 0 and 180 are the starting and ending
angles of the torus.
Figure 5.17 Toroidal Sector
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5.4. Sculpting Your Model with Boolean Operations
Boolean algebra provides a means for combining sets of data, using such logical
operators as intersect, union, subtract, etc. The ANSYS program allows you to apply
these same Boolean operators to your solid model, so that you can modify your solid
model constructions more easily.
You can apply Boolean operations to almost any solid model construction, whether it
was created from the top down or from the bottom up. The only exceptions are that
Boolean operations are not valid for entities created by concatenation and that some
Boolean operations cannot always be performed on entities that contain degeneracies.
Also, all solid-model loads and element attributes should be defined after you complete
your Boolean operations. If you are using Booleans to modify an existing model, you
should take care to redefine your element attributes and solid-model loads.
Note
Boolean operations and other solid modeling operations can be unreliable, either failing
to work or corrupting/contaminating the database. You should SAVE a copy of your
database before a Boolean operation in order to cleanly recover from a failure.
5.4.1. Boolean Operation Settings
You can specify Boolean operation options using the BOPTN command (Main Menu>
Preprocessor> Modeling> Operate> Booleans> Settings).
When you perform a Boolean operation on two (or more) entities, you are faced with
the decision of whether or not you want to keep the original entities. You can control
this action with the KEEP label of the BOPTN,Lab,Value command, as illustrated
schematically in Figure 5.18: "Boolean Keep Options":
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Boolean operations on lower-order entities that are attached to higher-order entities are
generally permitted.
Boolean operations cannot be performed on meshed entities. You must clear the mesh
from the entity before performing the Boolean operation.
The label NWARN on the BOPTN command allows you to control warning messages. A
value of "0" will result in a warning message if a Boolean operation has no effect. A
value of "1" will suppress all warning or error messages if a Boolean operation has no
effect. A value of "-1" will allow error messages if a Boolean operation has no effect.
The default value of this label is "0".
The VERSION label can be used to control which numbering scheme ANSYS will use to
number the entities produced by Boolean operations. By default, ANSYS will number
entities using the Revision 5.2 numbering scheme, but you can force ANSYS to use the
Revision 5.1 numbering scheme instead. Normally, you will want to use the default
numbering scheme when running Revision 5.2 or newer versions. However, if you are
reading input that was created at Revision 5.1, you should activate Revision 5.1
numbering [BOPTN,VERSION,RV51] before reading in the file [/INPUT] so that the
input will run properly.
Note
A command input stream created at Revision 5.1 may produce different entity
numbering at Revision 5.2 or Revision 5.3 unless the Revision 5.1 numbering scheme is
specified [BOPTN,VERSION,RV51].
The label DEFA will reset all BOPTN settings to default values. The label STAT lists the
status of present settings.
5.4.2. Entity Numbering After Boolean Operations
The numbering scheme assigns numbers to Boolean output entities based on
information relating to their topology and geometry. The topology information used for
an area, for example, includes the number of loops it is defined by, the number of lines
(that is, 3-sided area, 4-sided area, etc.) making up the area, the line numbers of any
original lines (lines existing before the Boolean operation) in the area, keypoint
numbers of any original keypoints, etc. The geometry information used for an area
consists of the coordinates of its centroid, endpoints, and other "control points" relative
to some arbitrary reference coordinate system. "Control points" are defined by the
NURBS used to parametrically describe your model. The numbering scheme first assigns
numbers (beginning with the next available number) to those output entities that can
be uniquely identified by their topology. Any remaining entities are then assigned
numbers based on their geometry. Unfortunately, entity numbering based on geometry
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may not be consistent across design optimization loops, especially if the geometry
changes from loop to loop. Therefore, when geometry-based entity numbering occurs,
the program issues the following warning message:
*** WARNING ***
Entity numbers from the Boolean operation were assigned based on geometry.
If you are planning to do optimization, (or input looping), do not rely
on the entity numbers for loads, etc. To suppress this warning, issue "BOPT,NWARN,0".
5.4.3. Intersect
An intersection defines a new set of entities which is common to every original entity
included in the operation. In other words, an intersection represents the region of
overlap of two or more entities. The new set can be of the same or lower dimension as
the original entities. For instance, the intersection of two lines can be a keypoint (or a
set of keypoints), or it can be a line (or set of lines). The Boolean intersect commands
are as follows:
Create the
intersection of
Command
GUI
lines
LINL
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Intersect> Common> Lines
areas
AINA
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Intersect> Common> Areas
volumes
VINV
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Intersect> Common> Volumes
a line with an area
LINA
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Intersect> Line with Area
an area with a
volume
AINV
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Intersect> Area with Volume
a line with a volume LINV
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Intersect> Line with Volume
5.4.3.1. Illustrations of Intersection Operations
The following figures illustrate the intersection operations listed above:
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5.4.4. Pairwise Intersect
A pairwise intersection defines a new set of entities which is any overlapping set of
entities included in the operation. In other words, a pairwise intersection represents the
region of overlap of at least any two of the original entities. The new set can be of the
same or lower dimension as the original entities. For instance, the pairwise intersection
of a set of lines can be a keypoint (or a set of keypoints), or it can be a line (or set of
lines). The Boolean pairwise intersect commands are as follows:
Find the pairwise
intersection of
Command
GUI
lines
LINP
Main Menu> Preprocessor> Modeling>
Operate> Booleans> Intersect> Pairwise>
Lines
areas
AINP
Main Menu> Preprocessor> Modeling>
Operate> Booleans> Intersect> Pairwise>
Areas
volumes
VINP
Main Menu> Preprocessor> Modeling>
Operate> Booleans> Intersect> Pairwise>
Volumes
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5.4.4.1. Illustrations of Pairwise Intersection Operations
Figure 5.25: "LINP (Line Intersect Pairwise)", Figure 5.26: "AINP (Area Intersect
Pairwise)", and Figure 5.27: "VINP (Volume Intersect Pairwise)" illustrate the pairwise
intersection operations listed above:
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5.4.5. Add
An addition of entities defines a new entity that includes all parts of the originals. (This
operation is also known mathematically as a union, joining, or summation.) The
resulting entity is a single seamless whole, containing no internal divisions. (As a
practical matter, "added" entities will often not mesh as well as will "overlapped"
entities.) Only volumes or coplanar 2-D areas can be added in the ANSYS program.
Areas added may contain holes within the area; that is, internal loops. The Boolean add
commands are as follows:
Add
Command
GUI
separate areas to create a AADD
single area
Main Menu> Preprocessor> Modeling>
Operate> Booleans> Add> Areas
separate volumes to
create a single volume
Main Menu> Preprocessor> Modeling>
Operate> Booleans> Add> Volumes
VADD
5.4.5.1. Illustrations of Addition Operations
The following figures illustrate the add operations listed above.
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5.4.6. Subtract
If you subtract one entity (E2) from another (E1), you will obtain one of two results:
Either you will create a new entity or entities (E1 - E2
E3) that is of the same
dimensionality as E1 and that contains no overlap with E2, or, if the overlap is of a
lower dimensionality, you will simply divide E1 into two or more new entities (E1 - E2
E3 and E4).
If the command field SEPO on the subtract command is set to blank (default), the
subtraction of entities can result in lines with a common end point, or areas with a
common line boundary, or volumes sharing a common boundary area. If the command
field is set to "SEPO", the resulting entities will no longer share common boundaries but
have distinct but coincident boundaries. This latter operation is not valid if the overlap
of entities does not divide one of the input entities into at least two distinct lines, areas,
or volumes. The Boolean subtract commands (and their corresponding GUI paths) are
as follows:
Subtract
Command
lines from lines LSBL
GUI
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Subtract> Lines
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Subtract> With Options> Lines
Main Menu> Preprocessor> Modeling> Operate>
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Subtract
Command
GUI
Booleans> Divide> Line by Line
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> With Options> Line by Line
areas from
areas
ASBA
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Subtract> Areas
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Subtract> With Options> Areas
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> Area by Area
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> With Options> Area by Area
volumes from
volumes
VSBV
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Subtract> Volumes
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Subtract> With Options> Volumes
areas from
lines
LSBA
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> Line by Area
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> With Options> Line by Area
volumes from
lines
LSBV
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> Line by Volume
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> With Options> Line by Volume
volumes from
areas
ASBV
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> Area by Volume
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> With Options> Area by
Volume
lines from
areas
ASBL [1]
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> Area by Line
Main Menu> Preprocessor> Modeling> Operate>
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Subtract
Command
GUI
Booleans> Divide> With Options> Area by Line
areas from
volumes
VSBA
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> Volume by Area
Main Menu> Preprocessor> Modeling> Operate>
Booleans> Divide> With Options> Volume by
Area
1. The SEPO field is not available on the ASBL command.
You can subtract multiple entities from a single entity. All entity subtraction commands
are of the form eSBe, where "e" represents multiple or single entities.
You can set either entity field value of the subtract operation to ALL . If ALL is used in
the minuend field, the entity or entities listed or picked in the subtrahend field will be
removed from all selected entities. If ALL is used in the subtrahend field, all selected
entities will be subtracted from those listed in the minuend field. If ALL is used in both
minuend and subtrahend fields for subtraction of like entities, nothing will happen; that
is, the result will be your input entities.
The KEEP(X) argument fields of the entity subtraction commands allow you to
selectively keep or delete entities. For instance, the KEEPA and KEEPL arguments on the
ASBL command allow you to keep or delete the areas and/or lines used in an ASBL
operation. This is in contrast to the BOPTN,KEEP,Value command which demands you
either keep or delete all input entities. The KEEPL and KEEPA arguments override previous
settings made with the BOPTN command (Main Menu> Preprocessor> Modeling>
Operate> Booleans> Settings). If these two fields are left blank, the default
settings are controlled by the BOPTN command. The default setting for BOPTN is to
delete all entities that are used as inputs to entity subtraction commands.
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