Vehicle Crashworthiness and Occupant Protection - Chapter 3

Finite Element Analytical Techniques
and Applications to Structural Design
Schelkle and Remensperger [58] discussed the development of an integrated
model of a passenger compartment and occupant using a single FE code. The
model simulated a sled test by 8,700 elements in frontal crash, and included an
unfolded air bag, steering system, knee bolster and seat. A 100 ms simulation
required 13 CPU hours on a CRAY-2 computer. Although the model exhibited
reasonable kinematics, the authors indicated that the contact algorithms were not
sufficiently robust to account for interactions between the dummy arms and the
deploying air bag.
Khalil and Sheh [51] developed an integrated model for frontal crash. This model
integrated the following components/subsystems into one FE model. These are
the primary components of the model:
• vehicle including a body-in-white structure of a four-door passenger sedan,
• engine, transmission, etc., weighing 1,750 kg,
• bucket car seat structure with the seat cushion,
• nergy absorbing steering column with a steering wheel and folded air bag,
• instrument panel, including a driver side knee bolster,
• door structure, and
• Hybrid III dummy
Model statistics:
• 70,000 shell elements
• 9,000 solid elements
• 300 beam elements
• 1,300 spot welds
• 300 parts
• 91,000 nodes
• 20 contact segments
Figure 3.6.4.1 shows the integrated model at time 0 and a deformed configuration
at 100 ms. The model kinematics, showing vehicle deformations, air bag deployment
and forward motion of the dummy and subsequent interactions with the air bag
and knee bolster are qualitatively similar to a barrier test (Figure 3.6.4.2). Figure
3.6.4.3 shows the energy balance for a typical run. It can be observed that the
total energy remained approximately constant throughout the 100 ms duration,
and the rise in internal energy and the decay in kinetic energy are smooth. This
attests to very little interpenetrating among the contacted segments. The vehicle
velocity response in time, at the rear rocker, is shown in Figure 3.6.4.4, along with
experimental data from one test. The velocity trace agreed quite well with test
data, particularly at the point where the vehicle velocity crosses the zero line.
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