Assessing Femur and Pelvis Injury Risk in Car‐pedestrian Collisions: Comparison of Full Body Pmto Impacts, and a Human Body Finite Element Model

A considerable potential for reducing fatalities of pedestrians and other vulnerable road users lies in the design of car front shapes. Vehicle safety tests have been proposed by the EEVC WG17, and are currently in discussion by legal entities, as well as car makers. In this study, we first present numerical simulations of various pedestrian impacts against several different simplified hood shapes. Impacts were simulated using a detailed finite element model of a mid-size pedestrian that has been extensively validated in previous studies. As expected, the model revealed that biomechanical loading patterns are heavily influenced by hood leading edge shape. In a second step, femoral and pelvic bone surface strains were measured in five full body PMTO impacts at 40 kph using physical representations of the simulated car shapes. Each PMTO was instrumented with strain gauges on the impact side: four on the femoral shaft, three on the femoral neck, and three on the superior ramus of the pelvis. Accelerometers were placed on the dorsal aspect of vertebra T6 and L5. High speed digital video was recorded at 1,000 frames per second from the side. Fracture risk was examined with respect to car geometry, pedestrian stature, and bone quality as indicated by peripheral quantitative computed tomography (pQCT) of the femoral neck. Experimental results indicated a remarkable predictive ability of the finite element model in assessing femur and pelvic injury risk. Strain data yielded valuable insight into the failure threshold of the pelvic rami, which was observed to fracture in three of the tests. The largest factor in pelvic fracture was low bone quality, rather than car geometry. Based upon results of the model and PMTO experiments, recommendations are offered for a more appropriate characterization of the hood shape with regard to pelvis and femur injury risk.