Research On The Optimization For The Frontal Impact Pulse Of A Car

Research on the Optimization for the Frontal Impact Pulse of a CarVehicle frontal impact is the most serious condition which causes much death and serious injury of traffic accidents, the anti-collision performance of vehicle frontal collision is an important part of vehicle passive safety. When the vehicle occur frontal crash, the front structure of vehicle deforms, destructs, and absorbs the collision energy. During the collision period, the vehicle body is in a slow process, the decelerations of different points are different. The main energy absorption and deformation part of vehicle is the vehicle front structure, the structure after B pillar almost has no deformation. Therefore, the deceleration signal collected by B pillar is usually considered as the vehicle deceleration. During front collision, the vehicle deceleration-time history is called the vehicle frontal crash waveform. The Vehicle crash waveform is very important, and it is one of the frontal crashworthiness characteristics which can be easy to access, so it is important content of frontal impact design. The waveform not only can be used to measure the collision intensity, more importantly, it is closely related to occupant injury. If the collision energy is equivalent, suitable frontal crash waveform leads slighter occupant injury, so the optimization of the waveform has great significance.Frontal crash pulse is determined by frontal structure of the vehicle during the crash process, modifying the frontal structure can optimize crash pulse.In the traditional development process, structure is generally designed basing on the experience and verified by test or virtual method, repeated modification is needed to improve the pulse.The design method usually requires an iterative "trial and error" process, lacking of clear objective and heavy overload are the deficiency of it. In the concept design phase, introducing design for performance methodology, making the crash pulse as the goal, providing guidance for the design to reduce the "trial and error" circulation times, thereby the workload of the detail design stage is reducing. The paper improves the crashworthiness of the frontal structure of a passenger car for receiving a reasonable crash pulse by improved design. The reasonable pulse created in the crash is treated as the basic objective. The paper establishes the force-displacement characteristic curve which connects the pulse and the structure performance. The energy absorption of the sub-structure is evaluated from the energy curve which is integrated from force-displacement curve. The properties of substructures, as the sub-objectives, are obtained by energy management. The sub-objectives are expressed as some specific parameters. The designed substructures are integrated into the whole car after the modification to the structure and the way of connection. After the integration, the absorbed energy by the substructures is as much as the expected which reach the sub-objective and basic objectives. At last, the expected frontal crash pulse is realized.The paper researched into the relationship between the crash pulse and axial load vs. displacement of the car, the methodology to obtain the optimal pulse, the method to estimate the performance of the sub-structure based on the pulse objective. Mean while, the paper also discussed the design of the bumper, and the fast design method of the thin-wall beam that commonly used in the vehicle structures. A crash pulse optimization method of the car was summarized for concept design stage in the paper.The innovative of the paper is that took the optimal pulse as a goal, realized the top-down design of crash worthiness structures through target conversion and energy management method. The design process in the paper provided guidance to the detail design stage so that the circulation times of modification and test was apparently reduced. Therefore, the develop process was shortened. The paper provides a reference for other cars to optimal crash pulse.