Study On Small Overlap Front Crashworthiness Of A SUV

Nowadays, 25% overlap front crash accident’s occurrence frequency is still very large. For example, the auto crash into oncoming vehicle, the roadside poles and trees, and other cylindrical objects. It has a high mortality. In 25% overlap frontal crash, due to the different collision position, vehicle longitudinal structures, like front side rails, which plays a major role of absorbing impact energy, do not engage frontal impact force that leads to potential risk for occupants. Therefore, it is very significant to research on the crashworthiness of small overlap front impact.According to the protocol and guidelines which was released by the Institute for Highway Safety(IIHS), a Finite Element Analysis model of a SUV is established by Hypermesh software. LS-DYNA is used as a solver for simulating 25% overlap front-crash. The following conclusions are gained by analyzing the small overlap impact results. The vehicle acceleration peak is larger. The crew cabin and the collision side a-pillar have severely deformation. Especially, the deformation of firewall,the threshold beam and hinge pillar exceed regulatory requirements. According to this special impact characteristic, the small overlap impact process is divided into three phases. The improved method is proposed to solve the above issues.Firstly, in order to make full use of the effect of front side rails energy absorption, the length of the front bumper is extended. Meanwhile, in order to transfer front impact force to front side rails, a double Y type sleeve structure is added to the front side rails. The position of the first brackets is optimized to further improve small overlap front crashworthiness. The results show that the vehicle acceleration peak and the deformation of the crew cabin are reduced effectively. Secondly, energy absorption guidance slot is designed in the shotgun to improve energy-absorbing deformation. And the cross section size of shotgun is increased in order to improve its collision energy absorption capacity and reduce the load to the crew cabin.Finally, to further reduce deformation of firewall, firewall is divided into two parts by the design method of laser tailor-welded plate. The thickness and material of each part are optimized. Test is arranged by orthogonal test. Using the vehicle acceleration peak, the max deformation of firewall and the left footrest as evaluation indexes, the optimal material and thickness are found by a comprehensive balance method. Then, the optimality of the result is validated.