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3.1
Multibody Simulation
Numerical simulations with a biofidelic Hybrid III 50th percentile sitting cyclist male
model was used to assess the risk to injury in cyclist-vehicle impacts and further
optimize the cyclist protection in the early stages of the vehicle design process at
relatively low costs. The geometry of the bike was modelled by the authors with
particular effort to reflect the geometry and moments of inertia of a real-word road
bicycle frame. Further, the dummy was position and pre-simulated to reflect the
physical position of a cyclist. The vehicle front-end was modelled with simple
ellipsoids and surfaces, taken from MADYMO database - unlike the bicycle. The
attention was paid to reflect the dimensions, not the material properties of the vehicle.
Thus, the design automobile is regarded as a generic vehicle model. The authors
carried out multibody simulations using MADYMO (MAthematical DYnamic
MOdeling) code. As the distinct from the FE, for the kinematic analysis evaluation
there is no need to model detailed material characteristics. The geometry of the
impacting body - i.e. the vehicle - is the key factor for ensuring the cyclist safety
post-impact trajectory.
All of the below simulations runs depicted in Fig 1. and Fig. 2 mirror the
situations, where a vehicle strikes the side of the dummy model (a pedestrian or
cyclist) at 11.1 m/s (40 km/h).
3.2
Finite Element Coupled with MultiBody Simulation
The subsequent performed simulations entailed the combination of two different
numerical codes - i.e. Finite Element Analysis and MultiBody. Thus, to conduct the
simulations LS-DYNA-MADYMO coupling was applied (Fig. 3). This method
enabled combining the capabilities of the Multibody with Finite Element code, by
using them in a parallel simulation. It is considered a valuable tool during safety
examination. On the one hand MADYMO contains advanced, well-developed and
validated dummies; on the other hand LS-DYNA provides accurate contact
definitions and advanced materials models. An additional advantage of the coupling
process in the computational testing is time efficiency [9]. The use of the MADYMO
dummy instead of the FE model enabled reducing the duration of the numerical
calculations significantly. Therefore, embedding the MADYMO Hybrid III 50th
percentile pedestrian into LS-DYNA FE environment was considered a suitable
solution.
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