Citation

Konosu A, Ishikawa H, Tanahashi M. Proc. Int. Tech. Conf. Enhanced Safety Vehicles 2001; 2001: 9 p..

Copyright

(Copyright © 2001, In public domain, Publisher National Highway Traffic Safety Administration)

DOI

unavailable

PMID

unavailable

Abstract

The legform impactor proposed by EEVC/WG17 is composed of a rigid thigh segment and a rigid lower leg segment. Human bone, however, has flexibility, causing some differences between the EEVC rigid legform impactor and the human leg. This research analyzes the influence of the differences (rigid versus flexible) on the injury criteria. It also reanalyzes the upper tibia acceleration with regard to the fracture index. The rigid legform impactor cannot simulate bone bending motion, so the injury criteria should consider the legform rigidity. It means the injury criteria need to include the bone bending effect. From several PMHS test results, the shearing displacement becomes 23mm and 20 degrees for bending angle including the bone bending effect. However, the bone bending effect will change with the loading conditions. Therefore, to establish a certain injury criteria for a rigid legform impactor is impossible. To solve this problem, a flexible legform impactor seems to be needed. If a flexible legform impactor exists, the relationship between rigid bone and flexible bone need not be considered, and the pure ligament tolerance can be applied. The threshold of upper tibia acceleration as for lower leg fracture (fibula/tibia/tibia+fibula fracture) was found to be 198G for 50% injury risk, but if the focus is on the tibia fracture (tibia/tibia+fibula fracture), with the fibula-only fracture cases excluded, the threshold becomes 247G. To use only the upper tibia acceleration as the leg fracture index is problematic. The relationship between upper tibia acceleration and fracture was obtained from a PMHS test series which was conducted with normal bumper height, but if the impact point is changed, the upper tibia acceleration becomes lower but leg fracture occurs. Therefore, if the acceleration is used for the leg fracture index, the accelerometer should be attached in the proper position. More seriously, the tibia acceleration from the rigid impactor is completely different from the human leg because of its rigidity. Therefore, the acceleration from a rigid legform impactor should not be used for the estimation. If the legform impactor is flexible, the acceleration is appropriate and proper estimation can be made.