SHPP, Lab, VALUE1, VALUE2
Controls element shape checking.
LabShape checking option. (When Lab = WARN, STATUS, SUMMARY, or DEFAULT, the remaining arguments are
ignored.)
ON | — | Activates element shape checking.
New elements, regardless of how they are created, are tested against
existing warning and error limits. (The existing limits may be the
default limits, or previously modified limits.) Elements that violate
error limits produce error messages
and either (a) cause a meshing failure, or (b) for element creation
or storage other than AMESH or VMESH, are not stored. Elements that
violate warning limits produce warning messages. If shape checking was previously turned off [SHPP,OFF] and you turn it on, existing elements are marked
as untested; use the CHECK command to retest them.
With this option, you may also specify a value for |
WARN | — | Activates element shape checking; however, in contrast to SHPP,ON, elements that violate error limits do not cause either a meshing or element storage failure. Instead, they produce warning messages to notify you that error limits have been violated. This option does not alter current shape parameter limits. Since the default shape parameter error limits are set to allow almost any usable element, the elements this option allows, which would otherwise be forbidden, are likely to be very poorly shaped. |
OFF | — | Deactivates element shape checking.
This setting does not alter current shape parameter limits. Use
of this option is risky, since poorly shaped elements can lead to
analysis results that are less accurate than would otherwise be expected
for a given mesh density. With this option, you may also specify
a value for |
SILENT | — | Determines whether element shape
checking runs in silent mode. In silent mode, ANSYS checks elements
without issuing warnings, with the exception
of the generic warnings that it issues at solution. With
this option, you must also specify a value for |
STATUS | — | Lists the shape parameter limits currently in effect, along with status information about element shape checking (for example, whether any individual shape tests are off, whether any of the shape parameter limits have been modified, and so on). |
SUMMARY | — | Lists a summary of element shape test results for all selected elements. |
DEFAULT | — | Resets element shape parameter limits to their default values. Also, if any individual tests were turned off, turns them back on. (The SHPP,DEFAULT command may be useful if any parameter limits were previously altered by using the MODIFY option.) |
OBJECT | — | Determines whether element shape
test results data is stored in memory. When this option is turned on, an "object" is created for storing
test results in memory. When this option is turned off, no object
is created and no data is stored; thus, any operation that requires
shape parameters for an existing element (such as use of the CHECK command) causes the shape parameters to be recomputed.
(Note the distinction between storing the data in memory and storing
it in the database; regardless of whether this option is turned on
or off, no element shape test results data will be stored in the database.
The element shape parameter object is deleted automatically before
any solution.) This setting is independent of shape checking status,
with one exception--if shape checking is turned off [SHPP,OFF], the object is not created. Keep in mind that recomputing
shape parameters is more computationally expensive than retrieving
them from the object. With this option, you must also specify a value
for the |
LSTET | — | Determines, for Jacobian ratio tests,
whether sampling is done at integration points (DesignSpace product method),
or at corner nodes. When this option is turned on, sampling is done
at integration points, and the default limits for h-element Jacobian
ratios are a warning tolerance of 10 and an error tolerance of 40.
When this option is turned off, sampling is done at corner nodes,
and the corresponding default limits are a warning tolerance of 30
and an error tolerance of 1000. Sampling at the integration points
(option on) results in a lower Jacobian ratio, but that ratio is also
subjected to a more restrictive error limit. Some elements that have
passed the integration point sampling criterion, have failed the corner
mode sampling criterion. Because of this, use integration point sampling
only for simple linear analyses. For other types of analyses (e.g.,
nonlinear, electromagnetic), use sampling at corner nodes, which is
the more conservative approach. With this option, you must also specify
a value for the |
MODIFY | — | Indicates that you want to respecify
a shape parameter limit. With this option, you must also specify
values for the |
FLAT | — | Determines the warning and error
limits used to test elements that may exhibit nonzero/nonconstant
Z coordinates. With this option, you must also specify values for
the |
VALUE1Valid for the ON, OFF, SILENT, OBJECT, LSTET, MODIFY, and FLAT options only. When
Lab = ON or OFF, use VALUE1 to
individually control (that is, turn off or turn on) specific element shape tests. Thus,
VALUE1 can be ASPECT (aspect ratio tests), PARAL (deviation from
parallelism of opposite edges tests), MAXANG (maximum corner angle tests), JACRAT (Jacobian
ratio tests), WARP (warping factor tests), or ALL (all tests). When
Lab = SILENT, VALUE1 can be ON (to turn
silent mode on) or OFF (to turn silent mode off). When Lab =
OBJECT, VALUE1 can be either 1, YES, or ON to turn on storage of
element shape test data (the default); or it can be 0, NO, or OFF to turn off storage of
element shape test data (delete the data and recompute as necessary). When
Lab = LSTET, VALUE1 can be either 1,
YES, or ON to choose Jacobian sampling at integration points; or it can be 0, NO, or OFF to
choose Jacobian sampling at nodes (the default). When Lab = MODIFY,
VALUE1 is the numeric location (within the shape parameter limit
array) of the shape parameter limit to be modified. Locations are identified in the element
shape checking status listing [SHPP,STATUS]. For more information, see the
examples in the Notes section. When
Lab = FLAT, VALUE1 is the warning limit
for XY element constant Z sets performed at CHECK or
SOLVE. The default is 1.0e-8.
VALUE2Valid for the MODIFY and FLAT options only. When Lab = MODIFY, specifies the new limit for the shape
parameter that is in the location indicated by the VALUE1 argument. See the examples in the Notes section. When Lab = FLAT, VALUE2 is the error limit. The default is 1.0e-2.
All shape checking tests are on [SHPP,ON,ALL] with default shape parameter limits. Silent mode is off. Memory object storage of element shape parameters is on.
The following examples illustrate how to use the SHPP,MODIFY,VALUE1,VALUE2 command to respecify shape parameter limits. Assume that you issued
the SHPP,STATUS command, and you received the output
below:
ASPECT RATIO (EXCEPT EMAG)
QUAD OR TRIANGLE ELEMENT OR FACE
WARNING TOLERANCE ( 1) = 20.00000
ERROR TOLERANCE ( 2) = 1000000.
.
.
.
MAXIMUM CORNER ANGLE IN DEGREES (EXCEPT OR EMAG)
TRIANGLE ELEMENT OR FACE
WARNING TOLERANCE (15) = 165.0000
ERROR TOLERANCE (16) = 179.9000
Notice that in the sample output, the warning tolerance for aspect ratios is set to 20. Now assume that you want to "loosen" this shape parameter limit so that it is less restrictive. To allow elements with aspect ratios of up to 500 without causing warning messages, you would issue this command:
SHPP,MODIFY,1,500Also notice that each shape parameter's numeric location within
the shape parameter limit array appears in the sample output within
parentheses. For example, the numeric location of the aspect ratio
shape parameter (for warning tolerance) is 1, which is why "1" is
specified for the VALUE1 argument in the
example command above.
Now notice that the sample output indicates that any triangle element with an internal angle that is greater than 179.9 degrees will produce an error message. Suppose that you want to "tighten" this shape parameter limit, so that it is more restrictive. To cause any triangle or tetrahedron with an internal angle greater than 170 degrees to produce an error message, you would issue this command:
SHPP,MODIFY,16,170The existence of badly shaped elements in a model may lead to certain computational errors that can cause your system to abort during ANSYS solution. Therefore, you run the risk of a system abort during solution any time that you turn element shape checking off entirely, run shape checking in warning-only mode, turn off individual shape checks, or loosen shape parameter limits.
Changing any shape parameter limit marks all existing elements as untested; use the CHECK command to retest them.
Since the shape parameter limit array was completely reorganized at ANSYS 5.4, you should revise any input files created prior to 5.4 that contain limit changes so that they reflect the reorganized data structure.
For more information about element shape checking, see Meshing Your Solid Model in the Modeling and Meshing Guide.
This command is also valid for rezoning.