Automobile collision deformation is related with the collision speed of vehicle, so many accidents of judicial identification or accident analysis by car to car collision velocity calculation of deformation. There are some mistakes in it

  The theoretical basis of 1. , people can make use of the deformation and speed is the deformation energy is equal to the kinetic energy consumption. First of all, available data or empirical formulas from the car on the screen wall collision experiments, and the experiment of vehicle collision speed is generally 49+/-1km/h, there are some test speed is 60km/h. In general, the deformation is larger than 600mm, has exceeded the range of experimental results have, has no practical significance. In practice, the accident identification in the needs of people in many cases, the speed is effectively out of range data or formula, so some calculation results serious deviation from the actual.

  2 use the deformation experiment data calculation speed is frontal crash screen wall, namely the automobile the entire front uniformly deformed. Therefore, large deformation (more than 600mm), offset collision, the existing data or empirical formula was not applicable. For example, an accident is a form of Chinese car rear end large trucks, cars, longitudinal deformation total size is 1600mm, thus a judicial authentication institution of the appraisal conclusion is car collision velocity is 135km/h. Read the report found that: the car bumper and grille overall deformation is small, is estimated to be less than 200mm; the engine cover the whole deformation estimate of longitudinal deformation is about 800mm, the height direction is about 100mm; the windshield deformation breakage, bilateral A column deformation is not more than 200mm; thus, the car at full width overall deformation is not more than 600mm, in fact less! Obviously the results of speed is much higher than that of the collision speed. In addition, even if the car deformation is 1600mm, because the speed is much higher than the existing experimental data or empirical formula based on experimental data, the formula is not applicable!

  The 3 speed identification for speed higher than 50km/h, accident, the best use of computer simulation method, and assuming that the recovery coefficient is equal to zero (0.05-0.1) simulation.

 4 in the use of experimental data or a formula to calculate the collision speed, must consider the accident form, applicable conditions of the formula, the parameters of the actual range. If the accident conditions and experimental conditions, the actual vehicle, the actual environment is different, do not blindly applied experimental data or empirical formula. Each formula is obtained under certain conditions, especially the analysis of accident rate formula, different forms of collision, different models, different years, different accident environment has the very big difference!