Investigation of an approach to reduce lower limb injuries of drivers during frontal impact

Lower limb injuries often occur in the offset frontal impact. Besides the knee airbags, increasing the distance between the knee and the knee bolster is also worth being considered to reduce the injury risk of lower limb. An innovative knee bolster assembly was proposed in this study, which can increase the active survival space and reduce the injury risk of the lower extremity in the impact. This study establishes a numerical analysis model with a restrained human body and a car. Furthermore, the muscle function is activated in the lower extremity of the human model to simulate the emergency braking condition. Moreover, five sets of simulations are conducted under 40% offset frontal impact. Results showed that the new developed knee bolster can help to reduce the injury outcomes of the driver though the elastic stiffness of joint in the knee bolster is not play an important role. In detail, the impact force of the human femur could be reduced by more than 28% with the usage of innovative knee bolster assembly and the bending moment is reduced by over 10% compared with the drivers protected by classical knee bolster. Meanwhile, the tibia injury risk is reduced by around 29% through the comparison of tibia index. In terms of ligament performance, it is found that the use of innovative knee bolster assembly could significantly reduce the stretching and elongation change of posterior cruciate ligament. This study could provide a reference for reducing the risk of lower limb injuries for drivers.