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Exporting MDL Models to LS-DYNA |
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Exporting MDL Models to LS-DYNA |
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MotionView MDL models can be exported to an LS-DYNA .key file.
This section explains how MotionView works with gravity, units, and solver parameters for DYNA.
Gravity is an implicit data set, meaning that its definition is created automatically by MotionView. The values for gravity can be accessed through the Forms panel while in the Misc system of a model. Default values for gravity are set in the std_inc file that is part of the MotionView installation. A Templex template is also included in std_inc. This template allows you to write the gravity to the DYNA input file.
Although MotionView is a "unitless" interface, it is often required that the units you are working with be communicated to the solver input deck. Therefore, the definitions of mass, length, time, and force are automatically generated by MotionView. To access this, go to the Forms panel and select Units under the Misc system. The default values as well as the Templex template used for exporting units to DYNA are generated from the std_inc file.
Solver parameters vary considerably between different solvers and are stored in datasets. There are two ways to generate solver parameter datasets.
| 1. | Data sets and their corresponding forms are created within the analysis task in the MDL library. If you are creating your own MDL library, you need to verify that the solver parameter datasets are defined in each analysis task. |
| 2. | No library is used to construct a model. This includes interactive model construction and the manual editing of .mdl files, or a combination of both. For this case, MotionView automatically generates the system containing the solver parameters based on a definition within the std_inc file. |
The mapping between MDL and the corresponding DYNA entities are described below.
| Note | All property data for these entities are set in the corresponding *Set() statements |
MDL Statement |
DYNA Entity |
|---|---|
*ActionOnlyForce() |
None |
*ActionReactionForce() |
None |
*AtPointJoint() |
Spherical (Joint) |
*BallJoint() |
Spherical (Joint) |
*Beam() |
None |
*Body() |
Part_Inertia |
*Bush() |
Element_Discrete |
*CoilSpring() |
None |
*ControlSISO() |
None |
*Coupler() |
None |
*Curve() |
AMPLITUDE |
*CVJoint() |
Constant_Velocity |
*CylJoint() |
Cylindrical |
*FixedJoint() |
Rigid_Bodies |
*Graphic() |
None |
*HookeJoint() |
Universal |
*InlineJoint() |
Trans+D.B.+Sph |
*InplaneJoint() |
Planar+D.B.+Univ |
*Marker() |
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*Motion() |
Constrained_Joint#_Motor |
*OrientJoint() |
Trans+D.B.+Tran+D.B.+Trans |
*Output() |
None |
*ParallelAxisJoint() |
Planar+D.B.+Trans |
*PerpAxisJoint() |
Cyl+D.B.+Planar |
*PlanarJoint() |
Planar |
*Polybeam() |
None |
*RevJoint() |
Revolute |
*SetFlexbodyComplaince() |
n/a |
*SolverArray() |
None |
*SolverDiffEquation() |
None |
*SolverString() |
None |
*SolverVariables() |
None |
*TorsionSpring() |
None |
*TransJoint() |
Translational |
*UniversalJoint() |
Universal |
CommandSets do not apply to the DYNA solver.
Templex templates can be used to export syntax directly to the solver input deck, including parametric substitution if required. For the LS-DYNA solver, there is a dependency on the position of the syntax within the solver input deck. The four keywords listed below allow you to position the extra text. These keywords must be the first line of the Templex template. The remaining text of the template is written according to the position specified.
<@ABAQ/MODEL/HEAD> |
Designates text that is written at the top of the model data. |
<@ABAQ/MODEL/TAIL> |
Indicates the end of the model data. |
<@ABAQ/HISTO/HEAD> |
Indicates the top of the history data. |
<@ABAQ/HISTO/TAIL> |
Indicates the end of the history data. |
One MDL model can be used to export to more than one solver. In this case, create the instance of the Templex template using the solvermode reserved keyword. This can be done in two ways:
For example, an MDL model containing:
if( solvermode == "DYNA" )
*Template(.....1...)
else
*Template(.....2...)
endif
results in the entire template 1 being used when DYNA is selected from the Solvers menu. When another solver is selected, template 2 is used. When a template is used, it means that it is displayed in the interface on the Templates panel and is acted upon when saving the solver input deck.
To use the keyword, put the required string in the first line of the template. For example, an MDL model containing:
*DefineTemplate(........)
<@DYNA/MODEL/HEAD>
text for dyna
*EndDefine()
results in "text for dyna" being exported to the input deck when you select DYNA as the solver. The same applies for the portion of template that is displayed in the user interface.
A Templex template can have several destinations as well as unique default behavior.
| • | A USER template does not get exported into any solver file but can be used to get parametrically based text into another file (by using the Templex open and close commands) or for text targeted for the GUI only. |
| • | A SOLVER_INPUT template results in the template text being exported to the .key file for DYNA. |
| • | The following templates do not apply to the DYNA solver: |
- SOLVER_PARAM
- GRAPHICS
- ADAMS
- ACF
MotionView supports function expressions for many of its entities. These expressions can be a function of time and state variables. You can create function expressions that are exported directly as part of a corresponding solver entity.
The solver neutrality is somewhat limited because the solver needs to handle the syntax that MotionView exports. For the DYNA solver, supported expressions and curves must be a function of time. Expressions that are a function of an axial distance between two points are also supported. MotionView converts these to X/Y pairs for the input deck.
Flexbodies are not supported in DYNA.
User subroutines do not apply to DYNA. Entities with a reference to user subs are not used when exporting to the solver input deck.
MotionView allows you to launch a process automatically after the solver input deck is exported. For LS-DYNA, the installation contains default launch sessions located in altair/utilities/mbd/launch_scripts. One or more of these launch sessions can be registered through the preferences.mvw file and then selected from the Run panel by using the *RegisterSolverScript() preference statement.
DYNA post-processing is described below:
Animation - Transient with Rigid Bodies Only
Rigid body model animation is not supported.
Plotting
Plotting rigid body model results is not supported.
