Virtual and numerical simulation of under-bonnet elements influence on pedestrian head impacts

摘要

Statistic studies carried out during last decades have underlined as pedestrians - with a prevalence of children and elderly - are a category with great risk in car accidents, particularly in the urban areas: according to recent investigations of a research committee of the European Community (CEC 2001), the risk of death in case of accident is, for pedestrians and cyclists, equal respectively to 9 and 8 times vehicle occupants' one. Particularly, in the European Union every year about 7000 pedestrians die (EEVC, European Enhanced Vehicle-safety Committee, "Improved test methods to evaluate pedestrian protection afforded by passenger cars," 1998; ETSC, European Transport Safety Council, "Safety of Pedestrian and Cyclists in Urban Areas,"[l, 5] 1999); that value represents around the 20% of the total of death caused from road accidents. In the world, this percentage varies from 14% in the United States (NTSHA, "Traffic safety facts 1994," 1995) at 47% in Thailandia (D. Mohan, J. Kajzer, K. Bawa Bhalla, S. Chawla, S.Sarabjit, Conference on the Biomechanics of Impacts, 1995). Sensitization of the public bodies and of the private companies towards the problem of pedestrian passive safety allowed the start of systematic study in subject, so that the European Committee, in 1988, appointed a working group (WG 10) which, in the 1994, at the end of its task, has defined a test protocol for the evaluation of the "aggressiveness" of the front part of the vehicle towards pedestrians. This protocol, partially revised in the 1998 by a followed working group (WG 17), establish the use of impactors for simulating, singularly, the body parts that, according to thorough statistic studies, have resulted as the mostly exposed to serious damages: knees, pelvis and the head. For each of these impacts it has been found the area statistically interested from greatest number of serious impacts in order to reach the definition of three types of test: legform to bumper test, upper legform (femur-pelvis) to bonnet leading edge test, head to bonnet top test, using, in that case, impactors of two different measures, adult and child.