Parametric Finite Element Model of Sport Utility Vehicle
Perhaps the most drastic automotive design verification comes from
vehicle collision tests. Not only do they bring perspective to
everyday driving, but also make one more appreciative of challenges
facing vehicle designers. The amounts of energy and deformation
involved in collision are enormous and must be well understood to be
harnessed into mechanisms which will protect vehicle occupants. In
recent years considerable effort has been directed towards development
of computational methodologies for simulating the mechanical response
of automotive structures in collisions. It has become a standard
practice in vehicle design to evaluate new and existing vehicles using
computational simulations using large and complex models based on
finite element method (FEM).
Computational vehicle models need to capture complex deformation and
interaction of vehicle parts and subsystems occurring during impact.
The accuracy with which the crash behavior of the vehicle is simulated
can be related to the density of the computational cells (finite
elements) employed in the vehicle regions that experience significant
permanent deformations. Therefore, a single vehicle crash model that
would accurately simulate a wide range of impact conditions (frontal,
side, offset, oblique impact, roll-over) would require high density of
finite elements over the entire vehicle. Such a model, aside from
being computationally tractable only on supercomputers, would
generally not yield a better accuracy than a set of models that are
tuned to specific impact conditions.
The problem then becomes one of generating a modeling environment that
can be used for rapid generation of crash situation-specific models.
These models have finite element discretization tuned to specific
impact scenario, required accuracy, and computational resources that
are available for the simulation. Such models will then execute much
faster than a uniformly-detailed discretized model and
correspondingly, allow for simpler and more efficient visualization
and analysis of simulated events.
The modeling environment has been developed at ORNL that enables
researches to access the vehicle models over the network through
Virtual Reality Modeling Language (VRML) interface. Users are able to
analyze the model, modify it by changing the provided control
parameters, and generate new FEM models suited to their specific
simulation objectives.
Another distinctive advantage of the parametric approach to the finite
element mesh discretization is that convergence of simulation results
can be easily tested by proportionally increasing or decreasing the
FEM mesh density employed for the model. The FEM models that have only
single finite element discretization cannot generally provide a
measure of computational convergence and usually require excessive FEM
mesh to ensure that the convergence is achieved. Parametric FEM model
can in addition be used to develop measures that can be used for
determining the type, extent, and distribution of FEM discretization
for different impact situations.
Acknowledgment
Research sponsored by the National
Highway Traffic Safety Administration, U.S. Department of
Transportation, under Interagency agreement DOE No. 2117-I027-AI,
NHTSA No. DTNH22-95-X-07229, under contract DE-AC05-00OR22725
with UT-Battelle, LLC.
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