Development of Injury Probability Functions for the Flexible Pedestrian Legform Impactor 2012-01-0277

The goal of this study was to develop injury probability functions for the leg bending moment and MCL (Medial Collateral Ligament) elongation of the Flexible Pedestrian Legform Impactor (Flex-PLI) based on human response data available from the literature. Data for the leg bending moment at fracture in dynamic 3-point bending were geometrically scaled to an average male using the standard lengths obtained from the anthropometric study, based on which the dimensions of the Flex-PLI were determined. Both male and female data were included since there was no statistically significant difference in bone material property. Since the data included both right censored and uncensored data, the Weibull Survival Model was used to develop a human leg fracture probability function. As for the MCL failure, since one of the two data sources does not provide tabulated data, two MCL failure probability functions as a function of the knee bending angle developed using the Weibull Survival Model were averaged over the knee bending angle. The functions developed for the human leg fracture and the MCL failure were converted to those for the Flex-PLI using the results of the previous study that investigated the correlation between human and Flex-PLI injury measures using human and Flex-PLI finite element (FE) models and simplified vehicle models. 10% increase in failure tolerance due to muscle tone estimated from the literature was taken into account when converting the function for the MCL. Since the conversion of the MCL failure probability function was made using the correlation function between different human and Flex-PLI injury measures, the correlation between the different measures both for human was investigated for validating the conversion. The injury thresholds proposed for the Flex-PLI were evaluated in terms of equivalence to the current injury thresholds for the TRL legform specified in the global technical regulation (gtr) on pedestrian safety by developing an injury probability function for the tibia fracture measure used for the TRL legform. The results showed that the protection level provided by the currently proposed injury thresholds for the Flex-PLI is similar to that for the TRL legform in terms of injury probability.