Research On Restitution Coefficient In Vehicle Frontal Impact Based On Finite Element

As the increase of vehicle registration, the problem of traffic safety has become more and more serious. According to the national statistics,there were 265204 traffic accidents in our country in 2008, whose result is 73484 dead and 304919 injured, as well as 10.1 billion in Yuan of financial losses. In total accidents of NHTSA in 2007, there were 54.5% car accidents and 36.9% frontal accidents, which caused the death and injury occupied 52.9% and 46.2% respectively in total. In view of the severe traffic safety condition, research on the vehicle accidents is very important and valuable.Traffic accident reconstruction, as an essential mean to analyze the reason and dispute resolution of traffic accident, has developed rapidly during these years. The essence of traffic accident reconstruction is to display the occurring process of accident in the form of dynamic simulation or description though modeling based on accident information, and collision theory plays an important role in accident reconstruction. The restitution coefficient, a scalar to describe elastic-plastic collision, is known as an important parameter to control and verify the accident reconstruction.Nowadays, the study on restitution coefficient mainly bases on data statistic of full scale vehicle crash test and the simplified mathematical model, so the efficiency and accuracy are both limited. The related theory of restitution coefficient is not yet perfect and quantified, and to some extent, the accuracy of accident reconstruction is accordingly affected. In this paper, the restitution coefficient in vehicle frontal impact is mainly studied because of the serious condition of vehicle frontal accident. First, though applying the related theory and rule of frontal impact, one dimensional impact model is established and the affect factors and law of restitution coefficient in frontal impact is studied. Furthermore, on the base of the dynamic nonlinear finite element method, simulation of frontal impact between car and rigid wall is carried out, the model of restitution coefficient is proposed and validated by full scale vehicle crash test. In addition, the change laws are contrasted between the front impact of car to rigid wall and car to car simulated by PC-CRASH. By this mean, the problem of efficiency and accuracy is well solved. The main performance of this paper is studied as followed:(1) After reviewing a large number of relevant documents, the status quo of restitution coefficient research at home and abroad are studied. Because of the high cost and long period of vehicle crash test as well as incomplete of simplified model, the simulation method of full scale vehicle crash test based on dynamic nonlinear finite element theory is proposed, which makes up the limitation of real vehicle crash text and simplified mathematical model accordingly. (2)Based on the data of related collision test and the analysis of collision theory, the influence of material nature, magnitude and direction of relative impact velocity, colliding position and geometry parameters is studied. According to kinematical theory analysis, the mathematical model of restitution coefficient in front collision is proposed and the relationship of restitution coefficient between cars and car to rigid wall is studied.(3)The theory of dynamic nonlinear finite element is introduced briefly, and the foundation of this theory and nonlinear characteristic about vehicle impact are expatiated emphatically, which provides the theory foundation for modeling.(4)The model of front impact between car and rigid wall is established by HyperMesh software, the detail of modeling process is described, and the validity reliability of vehicle is also verified by comparison between simulation and full scale vehicle crash test.(5)Appling the LS-DYNA, the simulation experiment is made and the v-t curves are analyzed among different impact velocities, then the model of restitution coefficient is proposed accordingly and contrasted with the statistic data of full scale vehicle crash test.(6)The data of the front accidents constructed by PC-CRASH are summarized, and the change laws of the restitution coefficient between the front impact car to rigid wall and car to car are contrasted and analyzed, and the relationship of them is studied. Taking a traffic accident for an example, the validity of restitution coefficient model is validated.The results of this paper propose a reliable and effective mean for restitution coefficient of vehicle and enrich the theory of restitution coefficient, which is foundational for further research as well as significant to accident reconstruction.