*compute_midmesh_thickness

Calculates the thickness of a midmesh and assigns properties.

Syntax

*compute_midmesh_thickness mesh_entity_type mesh_mark_id geom_entity_type geom_mark_id string_array number_of_strings

Type

HyperMesh Tcl Modify Command

Description

Computes the thickness of the midmesh elements based on the proximity with the geometry. New properties are created with thickness assigned. The command expects a baseline property with the name t0 to exist before execution. It estimates thickness and assigns the thicknesses to new properties, using the t0 property as a template. Optionally, an expected minimum and maximum thicknesses can be supplied, which will be used and a guide for the computation.

This functionality is currently supported for the OptiStruct, Radioss, Nastran, Abaqus, LS-DYNA and ANSYS user profiles.

Inputs

mesh_entity_type
Entity type used for mesh input. Valid values are:
  • Elements
  • Components
mesh_mark_id
The ID of the mark containing the mesh input. Valid values are 1 and 2.
geom_entity_type
Entity type used for geometry input. Valid values are:
  • solids
  • surfaces
  • elements
  • components
geom_mark_id
The ID of the mark containing the geometry input. Valid values are 1 and 2.
string_array
The ID of the string array that contains the additional input parameters. The string array is created using the *createstringarray command. This should always be set to 1.
Valid parameters and their syntax are:
AbsoluteGroupingTolerance: <tolerance>
The band width of the thickness group. This is applicable only when ThicknessOutputOption is PropertyOnElements or PropertyOnComponents, or when GroupThickness is enabled.
Range > 0
Default = 0, which means this option is ignored and GroupingTolerance is used.
AppendToTable: <value>
If set to 1, when run for the second time, the current computation results will be added to an existing table. This option is valid only for Radioss.
AssignMidIntervalAsThickness: <value>
Specifies whether to use the mid-value of the interval as the thickness of the group. Valid values are:
  • 0 - Assigns the average thickness of all elements in the group.
  • 1 - Assigns the mid-value of the interval.
  • -1 - The command chooses the behavior (for FixedInterval = 1, behaves as 1, 0 otherwise). Default if not specified.
CardImage: <card image name>
The card image to be used to create new properties. This is applicable only if the ThicknessOutputOption is set to PropertyOnElements or PropertyOnComponents.
Default - A suitable default card image is used according to the selected solver profile.
ConnectionInterpolationFactor: <factor>
The factor used in interpolating the thickness values near a connection (sharp corners, t/x-junctions). Valid factors are:
  • 0 - Approximate mass conserved thickness estimation at connections.
  • 0 < factor < 1 - Thickness linearly decreases towards the connection.
  • 1 - Thickness is interpolated constantly (default).
  • > 1 - Thickness linearly increases towards the connection.
CornerThicknessCorrectionThreshold: <value>
The ratio of the maximum thickness allowed at corners to the maximum thickness of the rest of the face. If a thickness exceeds this ratio at the corners, it will be corrected. The inverse of this ratio is used to limit the maximum thickness at the corners as well.
Range > 1.0
Default - 1.5
FeatureAngle: <value>
The angle used to decide the features of the mid-mesh. The corner scaling options are applied to these features.
Range - (0, 180)
Default - 30
FixedInterval: <value>
User defined “fixed” thickness interval value for each group of elements.
GroupThickness: <value>
Defines whether the calculated exact thickness needs to be grouped and an average value needs to be assigned. This helps reduce the number of different thickness values, at the cost of accuracy of the results. This is applicable only if ThicknessOutputOption is Element. This is always turned on if ThicknessOutputOption is PropertyOnElements or PropertyOnComponents, and always turned off if ThicknessOutputOption is Node or ElementNodal.
  • 0 - Do not group thickness (default).
  • 1 - Group thickness.
GroupingTolerance: <tolerance>
The relative band width of the thickness group (in terms of a factor of the average group thickness). This is applicable only when ThicknessOutputOption is PropertyOnElements or PropertyOnComponents, or when GroupThickness is enabled. This is ignored if, AbsoluteGroupingTolerance is provided.
Range - (0, 1.0)
Default - 0.2
HighlightCorrected: <value>
0 - Assign an extrapolated thickness value to any mesh outside the solid.
1 - Highlight the corrected entities.
LogFile: <file>
The full path and name of the file where the command execution information is to be logged.
MaxInclinationOfMidMeshWithSolid: <angle>
The maximum angle that the mid-mesh makes with the solid, beyond which the estimated thickness will be ignored and corrected.
Range - (0, 90)
Default - 35
MaxInclinationOfMidMeshWithSolidAtFreeEdges: <angle>
The maximum angle that the mid-mesh makes with the solid at the free edges of the mid-mesh, beyond which the estimated thickness will be ignored and corrected.
Range - (0, 90)
Default - 35
MaxRelativeChordalDeviation: <value>
The maximum chordal deviation to use when generating facets used for internal calculations, relative to the minimum thickness. Applicable only if geom_entity_type is surfaces or solids. The default is 0.1, which means for a minimum thickness of 1.0, the geometry faceting will use a maximum chordal deviation of 0.1.
MaxSearchDistance: <distance>
The maximum proximity distance which is considered for the thickness calculation.
Range ≥ 0, where 0 means the max distance is calculated internally, based on the model bounding box dimensions.
MaxThickness: <value>
The maximum thickness expected in the model. Any thickness estimated more than this is set to this value.
MaxThicknessGradient: <factor>
The maximum change in thickness allowed across two adjacent measurement locations, as a factor of the distance between the locations.
Range - (0, 10.0]
Default - 2.0
MinThickness: <value>
The minimum thickness expected in the model. Any thickness less than this is corrected.
NeedOffset: <value>
Defines whether element offset values are required or not.
  • 0 - Offset values are not needed (default).
  • 1 - Offset values are needed.
NewPropertyPrefix: <prefix>
The prefix to be used for naming the newly created properties/components. This is applicable only if the ThicknessOutputOption is set to PropertyOnElements or PropertyOnComponents.
Default - 'thickness'. If SampleProperty is supplied, its name is used instead.
NumDecimals: <value>
The number of decimal digits to use in the output. The output will be truncated with the given value.
  • > 0 - The number of digits required after the decimal point.
  • 0 - Rounded off to nearest integer.
  • < 0 - The minimum number of zeros required before the decimal point.
  • auto - 1% of the estimated min thickness.
  • AbsoluteGroupingTolerance - Use the same precision as AbsoluteGroupingTolerance.
Examples:
NumDecimals: 2
  • 303.2134 --> 303.21
  • 316.6666 --> 316.67
NumDecimals: 0
  • 303.2134 --> 303
  • 316.6666 --> 307
NumDecimals: -1
  • 303.2134 --> 300
  • 316.6666 --> 310
NumDecimals: auto
  • 303.2134 --> 303
  • 4316.6666 --> 4320
RegroupThicknessVariationFactor:<value>
The tolerance factor used to determine if element is going to be regrouped in case of merging isolated elements into adjacent groups. For example, if the value is 0.2, elements can only be regrouped if the percentage change in thickness is going to be less than 20%.
Range - (0, 1.0)
Default – 0.2
RenameRetainedComponents:<value>
New components are created only if the existing component contains more than one thickness groups. If all the elements in an existing component have the same thickness, the component is retained as it is. In that case, setting this option to 1 ensures that the retained component is renamed as per the naming rules for new components. This is applicable only when the ThicknessOutputOption value is set to PropertyOnComponents2.
SampleProperty: <property name>
If CardImage is not supplied, a sample property can be supplied which will be used as a template to create the new properties. This is applicable only if the ThicknessOutputOption is set to PropertyOnElements or PropertyOnComponents. This is also applicable when the CardImage option is not supported by this command.
SkipOutsideMeshFromCorrection: <value>
0 - Assign an extrapolated thickness value to any mesh outside the solid (default).
1 - Do not assign any thickness to any mesh which is determined to be outside the solid, even if it is connected to the mid-mesh inside.
StartThickness: <value>
User defined “fixed” start thickness value of the first group. This is applicable only for the user-defined fixed interval scheme.
ThicknessAssignMethod:<option>
The method of assigning thickness. If set to “Average”, the thickness assigned to the group will be the average thickness value of all the elements in that group. Similarly, if set to “Min-interval”, the thickness assigned to the group will be set to the minimum thickness element in that group if automatic method is chosen, and the left boundary thickness if fixed interval method is chosen.
Valid values are: Average (default), Min-interval, Mid-interval, and Max-interval.
ThicknessCorrectionMethod: <method>
The method to be used to correct the thickness on elements/nodes where thickness could not be estimated, or estimated incorrectly. Valid methods are:
  • Interpolation - Interpolates the thickness from the neighborhood (default).
  • UseMinOrMaxThickness - Resets the estimated thicknesses which exceeds the min or max limits to the set limits.
ThicknessOutputOption: <option>
Specify how the thickness data should be output. Valid options are:
  • Node - Thickness assigned on node card.
  • Element - Thickness assigned on element card (default for Radioss).
  • ElementNodal - Thickness assigned as nodal thickness on element card (default for LS-DYNA).
  • PropertyOnComponents2 – Thickness assigned on component properties, additionally make sure that elements originally from different components are not grouped into the same component because they have the same thickness. This is achieved by creating components with naming scheme <component_name>_<prefix>_<thickness>
  • PropertyOnElements - Thickness assigned on element properties (default for OptiStruct, Abaqus and Nastran).
WriteToInclude: <value>
If set to 1, the computation results will be written to an include file. This option is valid only for Radioss.
number_of_strings
Integer indicating the size (number of strings) in the string array created using *createstringarray.

Examples

To calculate the midmesh thickness for all shell elements, based off of the displayed surfaces, using a min thickness of 0.1 and a max thickness of 1.0:
*createmark elems 1 all
*createmark surfs 1 displayed
*createstringarray 2 {MinThickness: 0.1} {MaxThickness: 1.0}
*compute_midmesh_thickness elems 1 surfs 1 1 2
To calculate the midmesh thickness for all shell elements, based off of the displayed surfaces, using a min thickness of 0.1 and a max thickness of 1.0 with REAL SET for ANSYS:
*createmark elems 1 all
*createmark surfs 1 displayed
*createstringarray 14 "ThicknessOutputOption : PROPERTYONCOMPONENTS" "NeedOffset : 0" \
  "ThicknessCorrectionMethod : Interpolation" "ConnectionInterpolationFactor : 1.0" \
  "LogFile : C:/Users/ Temp/__ThicknessCalculationLog263.log" \
  "CardImage : SHELL63p" "GroupingTolerance : 0.2" "NumDecimals : Automatic" \
  "NumDecimalsOffset : Automatic" "MaxInclinationOfMidMeshWithSolid : 35" "MaxThicknessGradient : 2.0" \
  "ThicknessMeasurementLocation : Default" "SkipOutsideMeshFromCorrection : 0" \
  "MaxRelativeChordalDeviation : 0.1"
*compute_midmesh_thickness elems 1 surfs 1 1 2
To calculate the midmesh thickness for all shell elements, based off of the displayed surfaces, using a min thickness of 0.1 and a max thickness of 1.0 with SECTYPE for ANSYS:
*createmark elems 1 all
*createmark surfs 1 displayed
*createstringarray 14 "ThicknessOutputOption : PROPERTYONCOMPONENTS" "NeedOffset : 0" \
  "ThicknessCorrectionMethod : Interpolation" "ConnectionInterpolationFactor : 1.0" \
  "LogFile : C:/Users/Temp/__ThicknessCalculationLog263.log" \
  " CardImage : SECTYPE" "GroupingTolerance : 0.2" "NumDecimals : Automatic" \
  "NumDecimalsOffset : Automatic" "MaxInclinationOfMidMeshWithSolid : 35" "MaxThicknessGradient : 2.0" \
  "ThicknessMeasurementLocation : Default" "SkipOutsideMeshFromCorrection : 0" \
  "MaxRelativeChordalDeviation : 0.1"
*compute_midmesh_thickness elems 1 surfs 1 1 2

Errors

Incorrect usage results in a Tcl error. To detect errors, you can use the catch command:
if { [ catch {command_name...} ] } {
   # Handle error
}

Version History

11.0.101

2017.1 - New options AssignMidIntervalAsThickness, FixedInterval and StartThickness added to support thickness grouping into intervals.

2021.1 - New options RegroupThicknessVariationFactor,RenameRetainedComponents, and ThicknessAssignMethod to enhance thickness grouping. Removed ThicknessOutputOption value PropertyOnComponents.