Simplified Models for Optimization of Curtain Air Bag for US NCAP

The main role of CAB(side curtain airbag) is to protect the occupant's head in the event of side crash. The updated US NCAP for model year 2010 requires more extended coverage of CAB. It is not only required to cover the 50^th%ile driver but also the 5^th%ile driver and rear passenger. Although the general safety analysis model using only concerned sub-structure of the vehicle and prescribed structural motion is sufficient to handle frequent jobs, the analysis model with increased efficiency is needed when optimization is to be studied as it requires more runs and the model gets enlarged to consider extended sub-structure. In this study, three types of simplified analysis models are introduced. The first has an impactor which is composed of the head and neck with prescribed translational motions. It only uses the upper parts of the original sub-structure hence the run time is saved by 60∼70%. However the efficiency is still insufficient and it shows relatively high sensitivity to initial conditions. The other two models are combinations of a linear impactor with the head or the head and neck together with simplified structure with a two dimensional fixture which has been transformed from the three dimensional original structure. These methods save about 90% of the simulation time. Among the three models, two are chosen based on the accuracy and the robustness against initial conditions. With the two selected models, DOE(Design Of Experiments) are studied to find out the most competent model for optimization.