Interface to LS-DYNA

The LS-DYNA Interface enables you to export Midplane mesh models and some key material properties to LS-DYNA input files so that various analyses can be done with LS-DYNA.

Note: This feature is available only on Windows systems.

An API script, mpi2dyn.vbs, automatically converts the necessary output files into a format that LS-DYNA can use.

Injection molding-specific distributions resulting from a Warp analysis, such as initial stress and material properties, are the key elements of this interface. These distributions are written to separate LS-DYNA input files, including the *.sts file for initial stress distribution and the *.mts file for mechanical property distribution.

Release version 971 of LS-DYNA or later versions are required to work with this LS-DYNA Interface.

Interfacing to LS-DYNA

The LS-DYNA Interface passes three data types from this product to LS-DYNA according to LS-DYNA input specifications. These data types are:

1. mesh model data,
2. initial stress data, and
3. material data.

Another type of data is the control parameter set. In the LS-DYNA Interface, control parameters are grouped into a default set for predicting the warped part shape. However, the control parameters will differ depending on the situation and the solution level of difficulty, so users may choose to change the default options.

To view or change the LS-DYNA options for the current study, ensure that you have selected an analysis sequence that includes Fill+Pack. Click Analysis > Process Settings Wizard. If necessary, click Next one or more times to navigate to the Fill+Pack Settings page of the Wizard. Click Advanced options, click Edit in the Solver parameters group, click the Interface (tab), and then click LS-Dyna options.

Details about these options can be found in the LS-DYNA documentation; the default values are given in this LS-DYNA Options dialog.

Material model options

LS-DYNA includes more than 200 material models from which to choose. The LS-DYNA Interface includes four material model options considered most applicable to analysis of thermoplastics injection-molded parts.

• MAT_116 models the elastic responses of composite layups that have arbitrary layers through the part thickness and is based on the orthotropic assumption, so it is equivalent to the approach used in the Warp solver. This is the default material model option in the LS-DYNA Interface.
• MAT_022 is the composite damage model. However, the materials database does not include polymer matrix and fiber strength properties.
  Note: If you choose this option, you will need to fill in the actual strength values for impact analysis in LS-DYNA.
• MAT_023 is the orthotropic temperature dependency model. However, the materials database does not include relaxation moduli or a temperature dependency model for structural analysis.
  Note: Currently, only two sets of the same values corresponding to two temperatures are used in the LS-DYNA Interface. If necessary, you will need to replace the temperature dependent data and provide more temperature points in LS-DYNA.
• MAT_002 is the orthotropic elastic model. This is a simple model which should be used only with unfilled materials.

Solution method options

There are two basic solution method options available in LS-DYNA: static or quasi-static. In general, applications using unfilled materials can be solved easily by the static method, but for some applications using fiber-filled materials, the quasi-static method may be necessary. Users need to understand the time range and other control parameters associated with the quasi-static method in LS-DYNA.

Memory limit option

By default, the LS-DYNA Interface produces the LS-DYNA input file with a maximum of 300,000,000 words. However, interface files for typical models of 6,000 elements can exceed this default value, such that the Windows 32-bit version of LS-DYNA may not be able to handle them. Typically, for models having more than 6,000 elements and using fiber-filled materials, the LS-DYNA analysis must be run on a UNIX or LINUX workstation. In this case, you can change the default memory value in the LS-DYNA Options dialog to a higher value, or you can change the *KEYWORD value in the ASCII input file.

Other options

Refer to the LS-DYNA documentation for information about other element formulation options and parallel processing options.

Converting LS-DYNA interface files for use on UNIX/LINUX systems

Since the LS-DYNA Interface is only available on Windows systems, whereas the LS-DYNA application itself is often run on UNIX or LINUX systems, it is possible to convert interface files generated on Windows systems for use on UNIX/LINUX systems: in the C shell, type tr -d '\015' < filename.dyn > tmp, then type mv tmp filename.dyn.