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Exporting MDL Models to Nastran |
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Exporting MDL Models to Nastran |
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MotionView can export MDL models to Nastran. It performs a linearization of the model about its design position, utilizes a tree generation algorithm to define independent coordinates, and exports the system model. Nastran export also works on models containing flexbodies.
This section explains how MotionView works with gravity, units, and solver parameters for Nastran.
Gravity is not used with the Nastran export.
Although MotionView is a "unitless" interface, units that the modeler is working in must often be communicated to the solver input deck. Therefore, the definitions of mass, length, time, and force are automatically generated by MotionView. These selections can be accessed through the Units form located in the Misc system. The default values as well as the Templex template used for exporting units to Nastran are generated from the std_inc file.
No solver parameters are included in the standard include.
The mapping between MDL and the corresponding Nastran entities is described below.
| Note: | All entities implicitly create required markers. All property data for these entities are set in corresponding *Set statements. |
Statement |
Maps to |
|
|---|---|---|
*ActionOnlyForce |
N/A in linearized model |
N/A in linearized model |
*ActionReactionForce |
N/A in linearized model |
N/A in linearized model |
*AtPointJoint |
RBE2 (123) |
MPCs |
*BallJoint |
RBE2 (123) |
MPCs |
*Beam |
CBEAM |
CBEAM |
*Body |
CONM2, RBE2s |
CONM2, RBE2s |
*Bush |
CBUSH |
CBUSH |
*CoilSpring |
CELAS2, CDAMP2 |
CELAS2, CDAMP2 |
*ControlSISO |
MPCs, SPOINTs,CELAS2s |
MPCs |
*Coupler |
-- |
-- |
*Curve |
(Slope evaluated) |
(Slope evaluated) |
*CVJoint |
RBE2 (123) + 1 MPC |
MPCs |
*CylJoint |
RBE2 (1245) |
MPCs, PLOTEL |
*FixedJoint |
RBE2 (123456) |
MPCs |
*Graphic |
-- |
-- |
*InlineJoint |
converted to joints |
MPCs |
*InplaneJoint |
converted to joints |
MPCs |
*Marker |
CORD |
CORD |
*Motion |
add DOF in RBE2 |
MPCs |
*OrientJoint |
converted to joints |
MPCs |
*Output |
-- |
-- |
*ParallelAxisJoint |
converted to joints |
MPCs |
*PerpAxisJoint |
converted to joints |
MPCs |
*PlanarJoint |
RBE2 (345) |
MPCs, PLOTEL |
*Polybeam |
CBEAM |
CBEAM |
*RevJoint |
RBE2 (12345) |
MPCs |
*SolverArray |
-- |
-- |
*SolverDiffEquation |
-- |
-- |
*SolverString |
-- |
-- |
*SolverVariables |
-- |
-- |
*TorsionSpring |
CELAS2, CDAMP2 |
CELAS2, CDAMP2 |
*TransJoint |
RBE2 (12456) |
MPCs, PLOTEL |
*UniversalJoint |
RBE2 (1235) |
MPCs |
CommandSets do not apply to Nastran export.
Templex templates can be used to directly export syntax to the solver input deck including parametric substitution (if required). Since there are no position or order requirements of deck syntax for the Nastran solver, the Templex template does not require the use of keywords for positioning and ordering.
It is possible that one MDL model will be exported to more than one solver. In this case, it is best to wrap either the contents within the Templex template or the instance of the Templex template using the solvermode reserved keyword. This can be done at two levels.
| • | The first is to wrap the entire instance of the Templex template such that the existence of the template will depend on the solvermode. For example, an MDL model containing: |
if( solvermode == "NASTRAN" )
*Template(.....1...)
else
*Template(.....2...)
endif
| results in the entire template #1 being utilized when Nastran is selected from the Solvers menu. When another solver is selected, template #2 is utilized. When a template is utilized, it is displayed in the templates panel and is acted upon when the solver input deck is saved. |
| • | The second is to wrap text within a Templex template such that only a portion of the template applies to a particular solver. For example, an MDL model containing: |
*DefineTemplate(........)
{if (solvermode == "NASTRAN" ) }
text for nastran
{else}
text for other
{endif}
text for all
*EndDefine()
| results in "text for nastran" and "text for all" being exported to the input deck when Nastran was selected as the solver, but "text for other" and "text for all" if any other solver was selected at the time of model export. The same applies for the portion of template that would be displayed in the user interface. |
A Templex template can have several destinations as well as unique default behavior.
A USER template is not exported into a solver file but can be useful for getting parametrically based text into another file (by using the Templex open & close commands) or for text targeted for GUI only.
A SOLVER_INPUT template results in the template text being exported to the .bdf file for Nastran.
A SOLVER_PARAM template does not apply to the Nastran solver
A GRAPHICS template does not apply to the Nastran solver
An ADAMS template does not apply to the Nastran solver
An ACF template does not apply to the Nastran solver
Only function expressions of constant value are utilized when exporting to Nastran.
User subroutines do not apply to Nastran export.
MotionView provides the capability to automatically launch a process after the solver input deck is exported. For Nastran, this mode may apply less than other solvers. The intent of Nastran export is for the resulting model to be imported to an FEA pre-processor for further processing.
Post-processing can be performed using the animation windows capabilities for Nastran. See the HyperView online help for detailed instructions.
See also
