Download models and reports
Here you can download the FEM models and reports for the project. The available FEM models are:
- standalone models for tractors and trailers
- crash scenario models
Crash scenario models include tractor, trailer, ballast, barrier and coupling between the tractor and the trailer. These models also can have large initiatialization files for accounting for gravity initialization.
Orienting vehicle and barrier models for a particular simulation should not be done manually by moving nodes/elements in a pre-processor. Use the *DEFINE_TRANSFORMATION and the *INCLUDE_TRANSFORM options in LS-Dyna (in the 00Main.k file) only for any re-orientation of the vehicle or the barrier. The reasons for this are:
- There are several inertias defined that are not exactly orthogonal to the global coordinate system, but they are defined in the global coordinate system.
- The shell element stress tensors defined for the front suspension preload are defined relative to each element's local coordinate system. Changing the orientation of the tractor or the trailer with a pre-processor may not properly account for the correct orientation of specified inertias and initial stress information.
Transformations and orientations that are done within LS-Dyna using *DEFINE_TRANSFORMATION and *INCLUDE_TRANSFORM will guarantee that stresses and inertias are accounted for properly. The tractor and trailer models are oriented orthogonal to the global coordinate system such that X is forward, Y is to the left, and Z is up. Barriers or other targets can then be oriented relative to the vehicle (global) coordinate system. All the various tractor and trailer FE models, the Airide suspension models, and to some extent the ballast FE models are designed to be modular and can be interchanged relatively easily to facilitate other combinations of tractors and trailers. This is most easily done using the *INCLUDE and *TRANSFORM options via a 00Main*.k file. A minor bug in LS-PrePost when writing an FE model that has the *MAT_SIMPLIFIED_RUBBER_WITH_DAMAGE option is that the unloading load curve number is written in scientific notation to 4 significant digits rather than as an integer. This creates an error condition when LS-Dyna tries to read the keyword file because LS-Dyna is expecting an integer.
The LS-Dyna FE model of the tractor-semitrailer vehicle is organized using the *INCLUDE options in LS-Dyna. This organizational strategy allows users to easily reconfigure the simulated crash vehicle and the simulated crash-test device. All of the model input files required for a particular simulation are brought together in a "main" file. This main file is typically named 00Main.k. The intent of the leading zeros are to place the main file at the top of the file list in the directory. One advantage of using the LS-Dyna *INCLUDE file option is that entire (keyword file) models can be positioned via the *TRANSFORM option and can also be conveniently renumbered into ranges that are meaningful and useful to the analyst. Figures 5 and 6 show an example of a "00Main.k" file annotated with explanations of the *INCLUDE command inputs. This assumes the standard analysis-file organization "convention" for LS-Dyna/Linux environments of creating a separate directory for each simulation. The baseline tractor vehicle FE Model is based on the original NCAC-developed FE model of a sleeper-cab style tractor with a 242-inch wheelbase. Variations on this baseline FE model are accomplished using the ADAP scripts developed by ORNL. Variations include a day-cab style model and various (shorter) wheelbases. Completed variations are available for the day cab tractors used in MwRSF and TTI crash tests TL5CMB2 and 7069-13. Note that the position of the semitrailer rear wheelset assembly (bogey) is adjustable (fore-aft) by the user for any cargo box length and bogey position. Some care must be taken when doing this. In the FE model, the part of the bogey frame that adjusts its relative position on the trailer longitudinal rails is connected using *MAT_SPOTWELD (solid) elements. These elements are a type of tied contact, so they do not have to be "manually" disconnected and reconnected when the bogey position is adjusted. The bogey and these *MAT_SPOTWELD elements are selected and then translated using LS-PrePost. The direction of this fore-aft motion is not *exactly* along the global X direction because the trailer is angled 2° downward from the rear wheels to the kingpin. Given this, the actual translation should be done by choosing the appropriate "N1-to-N2" reference nodes in the translation utility in LS-PrePost. Also, when the wheels are moved, the locations of the wheel rotation *JOINTs and the rotation centers for the *INITIAL_VELOCITY option must be updated by the user. If the user needs to make this adjustment for several different cases, separating the bogey assembly into its own keyword file with specific joint and initial velocity definitions may be preferable. The user can call this separate bogey k file into the 00Main file using the *INCLUDE_TRANSFORM option.
Many of the keyword files themselves contain comment lines with information about the content of the particular file as well as comments about revisions and modifications to the content.
Project reports are provided for each year of the project. The User Manual describes combination vehicle models used in simulations of the test crashes.