LSDYNA Frequently Asked Questions

Q: Where can I download the latest version?

A: From LSTC’s FTP Site.

Q: How can I scale an entire model or a portion of a model?

1. With a keyword file loaded, go to the Page2 Scale Interface
2. Choose the appropriate local or global Scale Direction (ex: Global XYZ)
3. Enter the desired Scale Factor (ex: 25.4)
4. Choose scaling origin by Pick node or NodeID or XYZ coordinate (ex: 0,0,0)
5. Use the bottom panel Gen Select Interface to select the portion of the model to scale
6. Click Scale Up or Scale Down
7. Click Apply or Done to commit the operation

Q: How can I save display settings for a model so that they can be easily reapplied later?

1. With a keyword file or d3plots loaded, choose Misc. → Start Record from the top menu bar
2. Enter a Macro Name and click Ok
3. Do blanking, turn parts on/off, change colors, change transparency, etc…
4. Choose Misc. → Stop Record
5. Use the Page4 Macro Interface to load or execute a saved macro
Note: This approach can be useful for quickly reapplying settings after doing a File → Update.

Q: How can I play an animation and display a corresponding results curve simultaneously?

1. Load your d3plot files
2. Generate the desired curve using the XY Plotting Interface
3. Click Oper
4. Activate the “Timeline” checkbox in the lower right portion of the XY Plot window
5. Click Play in the Animation Controls Interface

Q: How do I get a force-deflection curve?

A: When you process ASCII files or time history data, individual or selected curves can be saved using the Save option in the XY Plotting sindow. If you have force-time and displacement-time curves, you can use the Cross option on the Page1 Xyplot Interface.

Q: How can I generate movies (AVI)?

1. Use File menu to load d3plots (File → Open → Binary Plot)
2. Select File → Movie…
3. Click Start

Q: How can I save images (PNG, GIF, TIFF)?

1. Select File → Print… from File menu
2. Select image format (PNG, GIF, TIFF, etc…)
3. Click Print

Q: How can I process ASCII time history files?

1. Go to the Page1 ASCII Interface
2. Select file type from the list (glstat, matsum, etc…)
3. Click Load or File (former loads file if in current directory, latter opens file selection dialog
4. Select desired entity from first list (example: node ID)
5. Select desired component from second list (example: x-displacement)
6. Click Plot (XY Plotting window pops up with time history curve)

Q: How can I filter time history data?

1. In XY Plotting window, click Filter
2. Select filter type (SAE, BW, FIR100, COS)
3. Select appropriate time units (SEC, MILLISECOND, MICROSECOND)
4. Select desired frequency (20, 50, 60, 180, 300, 600, 1000) or enter the desired cutoff frequency in the text field
5. Click Apply

Q: How can I check for and fix initial penetrations?

A: Please refer to the Page5 Conchk Interface documentation

Q: Can LS-PrePost do surface meshing?

A: The Page7 SurMesh Interface provides 2 types of surface meshing: AMesh and TMesh. AMesh is a topology mesher, and TMesh is a tool mesher specifically for metalforming applications.

Q: How can I renumber model entities (nodes, elements, parts, etc…)?

A: Use the Page2 Renum Interface. The entire model can be renumbered, or individual keyword types can be renumbered or offset. All associated data will be adjusted automatically. Renumbering and/or offsetting can also be perfomed while using the Save Keyword Dialog.

Q: Can I run LS-PrePost in batch mode?

A: Most operations can be performed in batch mode. Typically LS-PrePost is used in batch mode for extracting data from ASCII files. To run LS-PrePost in batch mode, use LS-PrePost c=commandfile -nographics, where “commandfile” is the file containing LS-PrePost commands.

Q: How can I write input file in a deformed configuration?

1. Using the animation controls, display the state to output
2. Go to the Page1 Output Interface
3. Select a format (Keyword, Movie BYU, Nastran, Dynain, InitDisp, STL)
4. Select Active Parts Only or Entire Model
5. Select desired data (Element, Nodal Coordinates, etc…)
6. Click Current to select the state
7. Click Write (pops up file selection dialog)
8. Enter output file name and click OK

Q: Can LS-PrePost read Nastran bulk data file?

A: Most Nastran bulk data is converted to LS-DYNA keyword data with a few exceptions. The remaining data can typically be created in LS-PrePost. Alternately, LS-DYNA has facilities to read Nastran files using *INCLUDE_NASTRAN. This allows users to run NASTRAN input files directly in LS-DYNA, and all data conversion is handled by LS-DYNA. (List of LS-PrePost supported Nastran cards)

Q: Can LS-PrePost animate multiple models simultaneously?

A: By using File → Open → Binary Plot, any number of models can be loaded into LS-PrePost. All loaded models are listed in the Page1 Model Interface. All models or any combination of selected models can be viewed together, and each model can be individually translated for making side by side comparisons (models can of course be directly overlaid as well). Using the Page1 Color Interface, each model can be assigned a unique color to help identify differences.

Q: Can LS-PrePost do hex meshing from CAD surface data?

A: HEX meshing capabilities are currently under development. The goal is to provide functions similar to what was available in LS-INGRID.

Q: Can LS-PrePost do tet-meshing?

A: Tet-Meshing can be performed using the Page7 TetMesh Interface. The input mesh can be either a solid or shell part. If the input is shells, then they must form a closed volume.

Q: How can I overlay curves (ex: analysis over test)?

A: External XY data can be imported into LS-PrePost using the Page1 Xyplot Interface.

Q: Can I graphically display contact definitions?

A: There are two methods:
1. On the Page3 *Contact Interface, select type from list, and click Edit. Then, on the keyword form, click Draw.
2. Use PageD

Q: How can I merge separate keyword files into one model?

1. File → Open → Keyword
2. File → Import → Keyword
3. File → Import → Keyword
4. etc…

Q: How can I animate a section cut?

1. Use the Page1 SPlane Interface
2. Define a plane and click Cut
3. Use the animation controls in the bottom panel to animate

Q: What is the difference between Group and View?

A: Group refers to a colletion of full parts. View can contain full and partial parts.

Q: How can I overlay a deformed shape on an un-deformed shape?

A: Use the Page1 State Interface

Q: How can I find free edges and merge duplicate nodes?

A: Click Show Free Edges on the Page2 DupNod Interface

Q: What does the History interface do? Why would I want to use it?

A: The Page1 History Interface is for plotting time histories of nodes, elements, materials (parts), and global data. This data can be from d3plot, d3thdt, or d3iff files which are binary files output by LS-DYNA.

Q: Can I calculate any injury criterion in LS-PrePost?

A: HIC (Head Injury Criterion) and CSI (Chest Injury index) can be calculated in 4 different ways:
1. From the d3thdt file using the Page 1 History Interface
2. From ASCII files using nodout file
3. From ASCII files using rbdout file
4. From XY Plotting window by clicking Oper and using Hic36

The gravitational constant and time units need to be selected to match the unit system you are using. This can be done by adjusting the Hic/Csi const. on the Page1 Setting Interface.

Q: Can I use my own forming limit curve?

A: FLD files can be imported through the Page1 FLD Interface by clicking Browse

Q: Can I display nodal time histories with respect to a rotating coordinate frame?

A: No. Time histories with respect to rotating coordinate frames have to be requested as LS-DYNA output using *DATABASE_HISTORY_LOCAL or *ELEMENT_SEATBELT_ACCELEROMETER and *DATABASE_NODOUT in LS-DYNA input files. The ASCII nodout file can then be processed using the Page1 ASCII Interface.

The distance between 2 nodes can be measured and time histories of displacements in global and local coordinate system can be plotted using the Page1 Measur Interface. This can be done while d3plot files are loaded for post-processing.

Q: What is *PARAM?

A: *PARAM is an LS-DYNA keyword. It allows users to define variables that can be assigned other keywords. Each keyword form has facilities to assign parameters. This capability can be used for optimization studies.

Q: How can I use curves created in LS-PrePost in the 2dmesher?

A: By choosing Blank on the Page2 Curves Interface and clicking Export To SB

Q: Can LS-PrePost handle master weld files?

A: LS-PrePost supports a number of masterweld file formats. Please refer to the Page 7 SWGen Interface.

Q: How can I output displayed parts only as a keyword file?

A: Once you have loaded a keyword file into LS-PrePost and displayed some parts, you can output a keyword file of only the active (displayed) parts using File → Save Active Keyword.

A: All buttons on the first 6 main pages can be re-configured, and this is done using Misc → Assign MenuButton. A list of menu buttons will pop up. First select a button from Page 1-6. Second, select an item from the pop up list to assign it to the button picked in the previous step. This preference can be saved in the .lspostrc file in the current working directory by clicking Save.

A: Use File → Save post.db. This interface allows saving lspost database files for selected elements or parts.

Q: How can I just save displacements?

A: The lspost database is designed to meet these needs. An lspost.db file can be created by extracting specific data from d3plot files or interactively in LS-PrePost. Only active as well as entire model can be saved as an lspost.db file. Please refer to commandfile documentation for more information.

Q: Can LS-PrePost project nodes to a mesh or a curve?

A: Use To Curve and To Mesh on the the Page2 Project Interface

Q: If I rotate a part that has stresses from a previous run, does LS-PrePost rotate the stresses?

A: Typically in metalforming applications, a dynain file containing thickness, stresses, and strains is output at the end of a stamping simulation. The stresses and strains are output in the keyword card definitions like *INITIAL_STRESS_SHELL etc… If such data is present in the model, and these parts get rotated, LS-PrePost rotates the stress and strain data accordingly.

Q: How can I post-process ALE results in LS-PrePost?

1. Click the Isos Rendering Hot Button
2. Choose Fluid type on the Page1 SelPar Interface
3. Click Misc for fluid components on the Page1 FComp Interface
4. Choose Fluid Surfaces on the Page1 Output Interface

Q: Can I animate mode shapes from eigenvalue analyses?

A: d3eigv files from LS-DYNA eigenvalue analyses can be loaded as binary plot files. Upon loading d3eigv files, the LS-PrePost Animation Control Interface will change automatically to allow animation of mode shapes.

Q: How can I plot time histories of all integration points through the shell thickness?

1. Choose Int.pt on the Page1 History Interface
2. Select shell elements from the display by left mouse clicking
3. Click Plot

Q: What is the difference between File → Open and File → Import?

A: Open reads the model in as a new model. Import appends the data to an existing model.

Q: What type of CAD data can LS-PrePost import and export?

A: IGES and VDA

Q: How can I fit belts to a dummy model?

A: Use the Page5 BeltFit Interface

Q: Is there a way to find and delete unreferenced data in my model?

A: Choose UnRef and click Check on the Page2 Refchk Interface

Q: What airbag folding methods are available in LS-PrePost?

A: thin, thick, tuck, spiral, and scrunch (see the Page5 ABFold Interface)

Q: Can I create initial velocities in a local coordinate system?

A: Initial velocities can be assigned to nodes using the Page5 IniVel Interface. Use Create Type=Local, and select a local CS from the list (the coordinate system must be pre-defined).

Q: When I load a keyword file, some buttons on page3 are Blue, and others are Black, Why?

A: Blue indicates keyword cards that are present in the current model. Black text indicates that the keyword is not used in the current model.

Q: Can I convert model units in LS-PrePost?

A: Direct unit conversion is not currently available in LS-PrePost, but LS-DYNA provides a method for converting model units using *INCLUDE_TRANSFORM, and this keyword can be setup in LS-PrePost.

A: Links to LS-DYNA information on the web:
LS-DYNA Blog (d3view.com)
LS-DYNA Examples (dynaexamples.com)
LS-DYNA Papers (dynalook.com)
LS-DYNA Support (dynamore.info)

Frequently Asked Questions