Abstract:
This user's guide describes version 2.0 of the LSTC Free Motion Headform (FMH), an FEA model developed by Livermore Software Technology Corporation based on NHTSA's Free Motion Headform for use in upper interior head impact simulations in compliance with FMVSS 201U regulations. The model is distributed free of charge to licensed users of LSTC's LS-DYNA software. The new version features an entirely new mesh with a grid pattern to facilitate headform positioning and uses *MAT_OGDEN_RUBBER for the outer skin, replacing the *MAT_VISCOELASTIC material used in version 1.0. All other components are modeled using *MAT_RIGID The paper details the model's calibration against a series of three physical drop tests with initial velocities of 2.72m/s, 4.00m/s, and 6.71m/s, where the headform was impacted against a rigid surface at a 30-degree angle. The FEA results for peak lateral and resultant acceleration are summarized and compared against specified allowable ranges and physical test data from other sources, showing that the model's performance aligns with the required standards. The document also provides information on the model's mass and inertia properties, the location of the center of gravity and accelerometer, and the forehead impact zone grid. Additionally, it includes notes on applying initial velocity and recommended contact keywords. An appendix is included to explain how to transform the model into different unit systems, specifically to mm-s-tonne-N and English units, using the provided input files and scale factors. The document also includes a disclaimer stating that LSTC assumes no responsibility for the validity, accuracy, or applicability of the model or the results obtained from it.
