Experience in the use of DYNA3D
Constructing and Evaluating Virtual Collisions of Vehicles

In 1990 Dr. Hallquist of LSTC referred Mr. Cheva of General Motors to Dr. Schwer to develop for Mr. Cheva a DYNA3D model of an energy absorbing bumper mechanism planned for use with the Oldsmobile and Buick platforms. Dr. Schwer developed a viscoelastic model that was successfully validated with experimental data provided by General Motors. Nonproprietary aspects of this modeling effort appear as a chapter in a specialty book:

Schwer, L.E., W. Cheva, and J.O. Hallquist, ``A Simple Viscoelastic Model for Energy Absorbers Used in Vehicle-Barrier Impact,'' in Computational Aspects of Contact, Impact, and Penetration, Edited by R.F. Kulak and L.E. Schwer, Elmepress International, Lausanne, Switzerland, pp. 99-117, 1991.
This work is also cited in the LS-DYNA Theoretical Manual on page 13.8 of the May 1998 version under the description of the l inear viscoelastic discrete element.

In 1994 Dr. Schwer joined U.S. Electricar as Director of OEM Vehicle Crashworthiness. In this position Dr. Schwer was responsible for the development of numerical models of conventional steel-based vehicle designs and new all composite-based vehicle designs for simulation of front and side dynamic impact and quasi-static roof crush tests for compliance with the Federal Motor Vehicle Safety Standards (FMVSS). The main product at U.S. Electricar was the conversion of OEM internal combustion vehicles, 1994 Geo Prizm sedan and 1994 Chevrolet S-10 pickup, to electric drive for resale. The conversion to electric drive increased the vehicle curb weight significantly, primarily due to the addition of batteries, and substantially modified the vehicle’s frame. Both of these changes in the OEM vehicle necessitated the re-certification under FMVSS. The approach taken was to develop DYNA3D models of the OEM internal combustion vehicles, which had already been certified by the OEM, and validate these models under virtual compliance with the FMVSS. The vehicle models were then converted to the electric drive configuration and the FMVSS simulations repeated; design iterations were perform as indicated by the simulation results. Finally vehicle certification was obtained through crashworthiness tests performed by certified FMVSS testing facilities. Dr. Schwer developed the internal combustion crashworthiness DYNA3D model of a third OEM vehicle platform, 1995 Ford Ranger pickup, however U.S. Electricar terminated this vehicle platform before the crashworthiness validation phase was completed.

As part of the FMVSS side impact certification requirements, the impacting vehicle used in the certification tests is a so called ‘moving deformable barrier’ (MDB) which comprises a rudimentary vehicle frame with a large block of crushable honeycomb aluminum at the impacting end of the vehicle. U.S. Electricar requested and received a DYNA3D model of the MDB, developed at the John A. Volpe National Transportation Systems Center, for the National Highway Traffic Safety Administration (NHTSA). In the process of re-validating this model, Dr. Schwer discovered several model anomalies. When these anomalies were corrected the resulting model no longer provided a correlation with the experimental data used for validation. Subsequent MDB model modification incorporated by Dr. Schwer did validate the model. The results of this effort were communicated to Ms. Randa Samaha of NHTSA who was then planning an upgrade of this model for NHTSA. Dr. Schwer’s MDB model developments also appear in the peer reviewed publication:

Schwer, L.E. and R.G. Whirley, ``Lessons Learned in Modeling a Moving Deformable Barrier (MDB) Impacting a Rigid Wall,'' International Journal of Crashworthiness, Vol. 1, No. 1, pp.73-92, 1996.

Also during this period, Dr. Schwer developed a DYNA3D model of a 30 foot electric powered passenger bus designed by US Electricar. Unlike the other vehicle model development performed by Dr. Schwer, the emphasis of this modeling effort was not crashworthiness, but rather structural integrity and durability associated with developing a new bus design. The model comprised the vehicles frame, side and roof structure and details of the suspension including the airbags used in place of more traditional springs used in passenger vehicles. A detailed model of the vehicle’s roof structure was developed and a virtual simulation of the quasi-static roof crush requirement for passenger buses was perform to asses the adequacy of the roof design.

In 1996, as a consultant to TransMotive Technologies Inc, Dr. Schwer developed a DYNA3D crashworthiness model of the U.S. Postal Service’s (USPS) Long Life Vehicle (LLV) that is widely used by letter carriers in mail delivery nation wide. The program’s goal was to assess the crashworthiness, structural integrity, and durability of an electric drive version of the LLV designed and built by U.S. Electricar. Using an approach similar to that described above for virtual crashworthiness other OEM vehicles, both an internal combustion and electric drive vehicle models were developed and the simulation results compared. Unlike other on-road vehicles, all USPS vehicles are exempt from FMVSS regulations. However, in this case the objective was to provide an assurance that the electric power vehicle performed as well or better than the internal combustion version of the vehicle in frontal barrier impacts.; similar virtual assessments were made for the vehicle’s structural integrity and durability.

In 1997 Dr. Schwer developed a DYNA3D model of a hybrid powered natural gas and electric drive bus under a consulting agreement with Columbine Bus Company for the Denver Transit District. The bus modeling effort was similar to that described above for 30 foot US Electricar passenger bus in that structural integrity of the new design was the objective of the modeling effort.