Study On SUV Crashworthiness Based On Load Path

Nowadays, automotive industry is highly developed; people pay more and moreattention to the vehicle safety and treat the safety performance as one of the majorconsiderations when they make up their mind to purchase a car. So the research ofvehicle safety, such as the improvement of vehicle crashworthiness has become themost important problem of automobile industry. Sport utility vehicle (SUV) hasbecome one of the most popular urban vehicles for its large interior space, good powerand trafficability characteristic. Although the SUV has huge and stiff body, some stillcan not achieve good crashworthiness, especially for the unitized body SUV studied inthe paper. For that vehicle, the longitudinal turning aside envelope wheel radius bendsearily, and longitudinal ends of the firewall come earily large deformation in the frontcollision. Longitudinal cause the vehicle to absorb dynamic energy inefficiently,consequently, higher acceleration and severe deformation of passenger cab will begenerated. These results are disadvantaged seriously for passenger protection.A great number of references and predecessors’ achievements have beenreviewed and summarized.This paper briefly describes the calculation of impact forceunder the axisymmetric crush，and the ideal formula for calculating impact forcewhich is based on the design concept of equivalent double-trapezoidal wave and thecollision force calculation of energy conservation. Quantify the concept of the impactforce in the automotive collision. Based on the optimization of the impact forcetransmission， three improvement programs has been proposed. In program1,two-point bracket as internal reinforcements were welded between firewall andA-pillar, increasing the longitudinal force at the end of local support. In program2,three-point brackets were welded on it, guiding the flow of impact force from the railstoward the end of the threshold beam. In program3, support points were optimizedbased on the cross-section area of the longitudinal beam, not only enhance firewalllocal stiffness but also improve the transmission path of longitudinal end of theimpact force.In this paper, the finite element model of vehicle crash was developed byHPERMESH and the model was analyzed by LS-DYNA. The finite element model ofthe sport utility vehicle was developed according to the CAD model and modelingstandards.According to the provisions of C-NCAP test conditions, different kinds of finite element simulation were conducted, for instance, frontal impact,40%offsetdeformable barrier impact and side impact with a moving deformable barrier.According to the crash simulation, from the peak value of acceleration, thedeformation of entire car, energy absorption ratio, the crash force, maximum intrusionto the two pedals in the X and Z direction, and energy-absorbing ability of main parts,crashworthiness of the vehicle body structure has been analyzed.The results shows that the proposed improvement scheme, especially for the case5in program3can effectively improve the impact force of the longitudinal in thepathway and reduce the maximum intrusion of the firewall and pedal intrusion, reducethe peak value of acceleration in the front collision and meet the most intrusion andthe maximum speed of B pillar etc expected engineering requirements in side impactwith a moving deformable barrier. Stable folding mode of vehicle front rails duringfrontal impact is the key to achieve desired deceleration pulse under the improvedvehicle. The above theories and methods are applied with good results through severalpractical vehicles’ crashworthiness design and improvement.