Optimization and Crashworthiness Assessment of Vehicle Front-End Structures for Enhanced Pedestrian Injury Mitigation

Abstract

Pedestrians are one of the most vulnerable groups affected by road traffic accidents, and frontal vehicle geometry and stiffness are a major factor that explains the severity of injuries to pedestrians involved in car-to-pedestrian collisions for the World Health Organization (WHO), about one quarter of the 1.19 million people who die annually around the world in road-traffic accidents. In this paper, an integrated acting of finite-element (FE) simulation and multi-objective optimization approach is provided to design a bonnet; bonnet leading edge, bumper fascia, bumper beam, and crush-can assembly for a passenger-vehicle, to reduce simultaneously head injury criterion (HIC15), upperlegform bending moment and impact force on legform, tibia acceleration, and knee shear/bending response in crash response while keeping the added mass and manufacturing cost within limits. Eight geometric and material design variables were sampled by optimal Latin hypercube sampling, and, coupled with Euro NCAP/GTR-9 sub-system impactors (child and adult headform, upper-legform, and flexible pedestrian legform impactor, Flex-PLI), validated LS-DYNA front-end computer models were used to construct Kr-Su models. Then, we generated a Pareto-optimal design front over 120 generations using a non-dominated sorting genetic algorithm (NSGA-II). We conducted a PRISMA-guided systematic review to cover the state of the art in optimising bumpers, hoods, and energy absorbers and to present the framework proposed in the paper. Based on this optimized front-end configuration, the adult HIC15 dropped from 1340 to 861 (-35.7 %), the upper-legform bending moment to 246 (-33.9 %) N•m, tibia acceleration to 121 (-32.0 %) g and knee shear displacement to 5.1 (-38.1 %) mm for an additional structural mass of just 2.6 kg per vehicle side. An exploratory sensitivity analysis revealed that three design parameters were most sensitive: bonnet leading-edge height, bumper foam density, and hood inner-panel rib pattern. The results show that physically interpretable, regulation-driven multi-objective optimization pipeline can provide a pedestrian protection outcome while simultaneously imposing an almost imperceptible mass and geometric penalty for the Euro NCAP rating protocol, and future implications for light weight structural design, integration into autonomous-emergency-braking-based pre-crash mitigations, and future directions towards robust- and reliability-based optimization are discussed.