Research On Reconstruction Analysis Model And Method Of Vehicle Three-Dimension Collision Accidents

Since automobile came out, road transportation cause began to rapidly development all over the world. However, road traffic accidents have became the negative aspect of the"double-edged sword"at the same time. It has been threatening people's life and property security. At roads without traffic video monitoring facilities, once traffic accidents occurred, it can not be replayed veritably. Because of these irreversible characteristics of road traffic accidents,it is difficult to determine some factors such as vehicles'driving speed, driving direction before collision or position of collision point accurately after accidents occurred. Furthermore, the description about the accident plot provided by accident parties may be different even contradictory from each other. In all kinds of road traffic accident, the three-dimension collision accident which accompanies vehicle rolling movement, is one of complex for its movement form, difficult for theoretical analysis and tedious for calculation. Therefore, how to use ralated theory to construct the reconstruction analysis models which are appropriate for automobile three-dimension collision accidents, and realize simulation reconstruction of this kind of accident, is an important issue in the field of accident reconstruction.At present, there exsist two main means to analyze automobile three-dimension collision accidents in domestic, one is depending on accident reconstruction software imported from foreign countries, the other is theoretically calculation after simplifying it to two-dimension collision accidents. The former is often constrained by foreign technology conditions. The latter's calculation precision is poor and cannot reconstruct accidents process completely. For the research purpose of reconstructing occurrence process of automobile three-dimension collision accidents, this paper studied the reconstruction analysis models and method of this kind of accidents, relying on the special subject of National High Technology Research and Development Program of China(863 Program)which was titled"Road Traffic Operation Safety Simulation Assessment and Accident Reconstruction Analysis System". There will be prominent practical application value in aspects of handling traffic accidents correctly, dividing accident responsibility clearly, and ensuring interests of accident parties impartially. It will also have great theoretical significance for further research of reconstruction analysis models and methods of more complicated accident types, such as multiple three-dimension collision.For the accident type of automobile to automobile single three-dimension collision, the problem of solving movement parameters at the moment of collision was studied. On the basis of analyzing dynamic characteristics of this kind of accident and referring existing movement parameters dynamics calculation model of two-dimension collision, collision impulse was extended to three-dimensional space. Based on the principles of classical mechanics, critical condition of vehicle's three-dimension movement was proposed. Based on classic dynamics theory, the three-dimension movement state parameters dynamic model for calculating vertical velocity, pitching angular velocity and rolling angular velocity at the moment of post-collision was constructed. Thus, the movement state parameters at the moment of pre-collision or post-collision could be calculated according to each.Aiming at the accident type of automobile to automobile collision,the automobile's centroid two-dimension movement trajectory models of turning driving were constructed on the basis of the automobile's centroid two-dimension movement trajectory models of no-turning driving. Furthermore, these models are also appropriate for describing automobile's movement trajectory of automobile to two-wheel vehicle collision accident. On the basis of the tires two-dimension movement trajectory model of automobile with two axles, the tires trajectory model of automobile with three axles was derived. Considering longitudinal and transverse slope at scene of accident, the calculation formula of gradient at the critical condition of automobile three-dimension movement was proposed. Taking three-dimension movement state parameters at the moment of post-collision as initial conditions, the centroid trajectory model of automobile three-dimension movement without ground reaction force was provided based on classic kinematics theory. On the basis of the existing automobile rolling model, the quadrangular prism rolling trajectory model and the hexagonal prism rolling trajectory model with ground reaction force were constructed.Aiming at the kind of automobile to two-wheel vehicle collision accident, the collision dynamics model and trajectory model were studied. On the basis of analyzing dynamic characteristics of automobile to two-wheel vehicle collision, the three- dimension movement parameters dynamics calculation model of this kind of collision was constructed. The two-wheel vehicle's centroid movement trajectory models at the rolling stage and sliping stage were constructed respectively. Based on this, the feature points movement trajectory model was derived, at the stage of two-wheel vehicle planar moving. For two cases of automobile's front colliding with two-wheel vehicle's side and two-wheel vehicle's front colliding with automobile's side, a simplified model for analyzing"occupant and vehicle separating"phenomenon was proposed.The dynamics model and trajectory models of automobile three-dimension collision which were constructed based on the classical mechanics theory were applied to road traffic accident reconstruction and studied. In the processes of actual accident reconstructions, the contents of accident scene survey and data collection were summarized. By using the reconstructed analysis model proposed in the paper and PC-Crash, two cases of automobile to automobile three-dimension collision and a case of automobile to motorcycle collision accidents were reconstructed respectively. The reconstruction results of the two methods were contrasted. The reconstruction results of the methods in this paper were also compared with the vehicles'stationary position, rolling way and pavement trace in the actual accident scene.According to the application situation of the automobile collision accident reconstruction analysis model which were constructed based on the classical mechanics theory, the application limitations of the classical mechanics method in collision accident reconstruction were analyzed and summaried. The theoretical framework of the classical mechanics and finite element comprehensive method in collision accident reconstruction were proposed. According to this framework and combined with an actual accident case, using ANSYS finite element analysis software, the finite element models of minibus and pickup can be constructed. By the finite element collision simulation experiment, the changes rule of velocity, acceleration and kinetic energy, the shape of deformation and the distribution state of Von mises stress of automobiles at collision process were all analyzed. Thus, the accident reconstruction application limitations of the classical mechanics analysis method were made up.