Modeling And Optimization Of Side Restraint System Of Passenger Car

Automobile production and sales of China has surpassed the United States since2009, and it maintains a stable growth trend all these years. However, traffic accidents always shock people, so how to protect occupants from traffic injury becomes an important issue in vehicle safety design. Because of the limited buffer space and closer distance between the driver and the impact area in side impact, the driver’s injury is more serious, thus the side impact leads to the highest proportion of bad injuries among all collision types. By using sub-model in MADYMO with the simulation results of side impact finite element as input, this paper equips and studies the side restraint system for a passenger car model. Besides, in order to minimize the driver’s injury, the design parameters of airbag are optimized by using the multi-objective method.Firstly, to get the displacement information of side structure nodes, side impact finite element simulation analysis is conducted based on C-NCAP. A mobile deformable barrier validation model is built and the results show that the force-deformation curve, absorbed energy and displacement of the energy absorption block meets the regulatory requirements. So the model is reliable. Full-size vehicle simulation model in side impact based on C-NCAP is also built. And the simulation results show that the model is reliable too. Thus, the results can be used in restraint system as input.Secondly, side restraint system is built including door trim, seats, seat belts and thorax airbags with displacement information of side structure node as input. Sensitive areas detailed modeling method is adopted to establish a sub-structure of the side impact with MADYMO, and the door trim system connected to the input boundary conditions is strictly accordance with the connection of the finite element model. Simulation results show that the injury of dummy’s head and hip are within the rules of the high-performance range and have been well protected. The thorax rib deformation, viscosity index and abdominal force are beyond the low-performance value. To improve serious injury of thorax and abdomen, the effect of thickness and stiffness of door trim area which cause serious injury is studied. The results show that the stiffness of area which causes injury of dummy thorax improves the dummy injury remarkably and different combinations of interior parameters cause different injury of dummy body. For further research, seatbelt and thorax airbags to PSM model are matched. Results show that thorax airbag between the dummy and the door trim in the narrow space plays a great role of absorbing enrgy and buffering impact load. Airbag avoids hard contact between dummy and side structure, and all kinds of the dummy injury are reduced.Finally, for minimizing injury of the driver, response surface model and NSGA-Ⅱ multi-objective optimization algorithm is used to optimize airbag design parameters including the mass flow rate factor of the inflator, the airbag deployment thickness and the trigger time of airbag. The Pareto optimal set is got through the optimization. The optimization results show that the stiffness of thorax airbags hardness is increased. Most importantly, head injury, abdomen force, thorax rib deformation, viscosity index and hip injury has all reduced.