| Since 1990's the annual traffic fatalities in road vehicle accidents in China has been ranked the first in the world, which caused enormous economic losses. The vehicle safety issues must be paid a high degree of attention. As effective passive safety protection equipment, automobile airbag assistant restraint system can effectively reduce the impact force in a collision; it is an important and effective protection measure for occupants during collisions. At present, China's airbag market is at an increasing period, more and more vehicles are equipped with airbags. Airbag is a safety device with high technology, and advanced airbag technology is still in development. At mean time, how to enhance its protective effect and avoid its side effects is an important subject for safety researcher to improve efficiency of airbag system.In this paper the Logistic regression method is used to evaluate the airbag effectiveness, considering that other confounding variables are excluded, such as gender, age, seating position and pre-impact brake. The crash investigation data from the US Special Crash Investigations program (1994-2006) is studied in terms of the various factors which would relate to the airbag induced fatalities. The mechanisms of airbag induced injuries of head, neck, chest in traffic collisions are discussed. At last the Chi-squre test is used to analyze the relations between airbag induced occupant injuries and the presence of restraint system and pre-impact brake. In order to improve vehicle airbag performance, a new type of sandwiched tube-type airbag is studied in this paper. The new type of the airbag can reduce the impact force in its earlier stage of the deployment, and provide better protection for out of position occupants. The sled tests and virtual testing technique are used together to analyse the static deploying characteristics and protecting performance of the sandwiched tube-type airbag. In the airbag-parameter optimization studies, the airbag design variables which could influence its performance are discussed, such as tether collocation, tether length, vent hole size and location, inflator mass flow rate and inflator pressure slope. The 5% and 50% Hybrid III dummies are used to evaluate the protection performance of the sandwiched tube-type airbag. During the virtual tests, dummies seat in three testing configurations: two out-of-position configures,―chest centered on module‖,―forehead centered on module‖, and an in-position configure. And each seat configurations with three kinds of airbag state: the sandwiched tube-type airbag mounted, normal airbag mounted and no airbag.The airbag epidemiology study results indicate that the death probability in traffic accidents with airbag is 0.486 of the probability without airbag, in another words, airbag really plays a positive role to reduce traffic crash related deaths. And the probability of the age group―>60‖receiving airbag induced fatal injuries is 4.219 of the probability of the age group―0-14‖, is 4.878 of the probability of the age group―15-29‖, is 2.841 of the probability of the age group―30-60‖. The probability of the front right seated passenger receiving airbag induced fatal injuries is 0.832 of the probability of driver. The restriction system will help to reduce the probability of receiving airbag induced fatal injuries; the probability without restriction system is 7.04 of the probability with restriction system.The new sandwiched tube-type airbag study results indicate that the tube-type airbag deploys faster than the traditional airbag using less gas mass inflow and be of good controllable deploying mode with 35% lower leading deploying speed and lower internal pressure at the early deployment stage, so it could reduce the injury risk and provide better protections to the out of position occupants.The airbag-parameter optimization study results indicate that the design variables: vent hole size and location, inflator mass flow rate, inflator pressure slope and trigger time influence its performance significantly. And the ANOV analysis helps to determine the optimal range of these significant design variables.The protection performance research of sandwiched tube type airbag indicate that the 5% Hybrid III dummy seat in-position, in out-of position 1―chest centered on module‖and in out-of position 2―forehead centered on module‖, when using sandwiched tube type airbag, the peak value of head acceleration reduced 7.5%,15.7%,43.6% respectively; the peak value of chest acceleration reduced 32.7%,28.6%,40.5% respectively; the peak value of chest displacement reduced 66.7%,80%,81.7% respectively; the peak value of neck fx reduced 2%,45%,78.9% respectively; and the peak value of neck fz reduced 30%,20%,63.6% respectively. And the 50% Hybrid III dummy seat in-position, in out-of position 1―chest centered on module‖and in out-of position 2―forehead centered on module‖, when using sandwiched tube type airbag, the peak value of head acceleration reduced 28.6%,34.7%,52.4% respectively; the peak value of chest acceleration reduced 0%,79%,64.3% respectively; the peak value of chest displacement reduced 25%,57.1%,73.7% respectively; the peak value of neck fx reduced 33.3%,75%,76% respectively; and the peak value of neck fz reduced 40%,40%,46.7% respectively. The sandwiched tube type airbag not only meet the safety demand of in position occupants but also improve the protective performance for out of position occupants and small occupants.With the rapid development of the automotive industry and the dramatic increase of the vehicle fleet, it is very important to correctly evaluate airbag protective effect in real road accidents and the reason why airbag cause side effects, the development research on a new type of sandwiched tube type airbag as well as its parametric study, protective effect analysis and its application in a new vehicle type. This new type airbag has better performance, especially for the out of position occupants. The research results from this paper have a significant contribution to improvement of protective performance in new airbag design.
|
PDF Full Text Request