Structure Optimization And Design Of Vehicle Safety Based On Comprehensive Pedestrain Protection

Automotive safety design has been attracting more and more concerns ofpassenger cars’ designers and consumers. Along with the development of this kind ofdemand, many countries have developed strict occupant protection laws andregulations, which make passenger cars own safety to new levels. However, asfollowed, the safety of pedestrians is facing unprecedented challenges in the collisionbetween pedestrian and vehicle, so many countries have introduced pedestrianprotection laws, which vehicles manufacturers have to fully follow when they arecompleting the platform operations of production and planning internationaldevelopment route. In this paper, based on the finite element model of a car, thestructure design for pedestrian’s leg and head comprehensive protection is finished,and the sequential quadratic programming and adaptive response surfacemethodology are used to optimize the design results.In accordance with the EEVC WG17regulation, the finite element numericalmodels of pedestrian lower legform impactor and headform impactor are establishedin the coupled software environment of Altair Hypermesh and LS-DYNA. Andpedestrian injury evaluation criteria are determined based on analysis of their injurymechanism in collision between pedestrian and vehicle. Through the requirement ofcalibration test, including static bending, static shearing and dynamic impacting testof lower legform impactor, the dynamic dropping and side impacting test of headformimpactor, dynamics response and biological fidelity performances of lower legformand headform impactor are effectively verified.In the impact test area which is divided through EEVC regulation, crashsimulation tests between pedestrian lower legform impactor and headform impactorand the original vehicle model are conducted at selected impact points, the pedestrianleg and head injury values under the original vehicle parameters are obtained. Theresults show that the key factors that determined pedestrian leg and headform injuriesis energy absorption performances of bumper system and rotational torque, andenergy absorption performances and deformation space of bonnet system.In this paper, thin-walled absorbing box structure is used to substitute theoriginal car’s energy absorbing foam, and a deputy bumper for supporting is designed, tests show that this design makes the energy absorption efficiency of bumper systemgreatly improved during a collision with a pedestrian, and reduces the rotationaltorque of pedestrian tibia. With orthogonal experimental design methods, it isdiscussed how the key structural parameters on the bumper system influencespedestrian leg injuries. Through range analysis of tests results, the optimal structuralparameters matching scheme for leg protection is determined. On the basis of the testdatas, the approximate function models of pedestrian leg injuries are established, andsequential quadratic programming method is used to optimize obtained results. Byexperimental verification, the optimized vehicle parameters are proved to have goodpedestrian leg protection effect.Based on the pedestrian head protection performance evaluation results oforiginal car, bonnet system materials and stiffness matching schemes which benefitpedestrian head protection are determined through simulation tests. Based on thematching tests of bonnet stiffness, approximation models of pedestrian head HIC andthe total mass of bonnet are fitted and established with adaptive response surfacemethod. Through iterative solution, the vehicle bonnet’s comprehensive optimizationdesign for pedestrian head protection and lightweight is finally established andverified.This study provides a feasible approach for vehicle safety structure design basedon comprehensive pedestrian protection, and creatively applies robust designalgorithms to engineering practice, and also provides a theoretical reference for thevehicle reliability development which benefit pedestrian protection.