Study On 3D Reconstruction Of Plastic Deformation And Finite Element Plastic Performance Calculation Of Accident Vehicle

With the rapid growth of car ownership in China,the number of road traffic safety accidents in China is also on the rise.In actual road traffic accidents,it is very difficult to reproduce and analyze the vehicle collision accident accurately and obtain the vehicle speed before the collision because the vehicle scene is easy to be damaged and the trajectory is difficult to measure.Therefore,it is an important method to obtain the vehicle speed by calculating the plastic deformation energy of the accident vehicle.However,the traditional methods for calculating plastic deformation energy of accident vehicles have some limitations,such as large workload in deformation data measurement,two-dimensional measurement data and no change in stiffness during calculation.Aiming at these limitations,this study will acquire the deformation data of the accident vehicle by image three-dimensional reconstruction technology.Combining with the finite element analysis model,the incremental method will be used to deal with the material non-linearity problem and realize the finite element calculation of the plastic deformation energy of the vehicle deformation structure.Thus,the plastic energy solution of the plastic deformation of the vehicle structure in the body,door,front and rear circumferences in low and medium speed collision accidents can be solved.Firstly,aiming at the problem that it is difficult to acquire the deformation data of vehicle body by traditional methods,this paper uses three-dimensional reconstruction to acquire the model of deformed vehicle surface.Based on the theory of image three-dimensional reconstruction,the three-dimensional reconstruction of a mini-car door is realized by collecting photos of the real car door from different angles and using MATLAB platform,and the three-dimensional model of the deformed car door is obtained.Then,the three-dimensional reconstruction technology is connected with the traditional method to reconstruct the model,and the residual deformation of the deformed door is obtained.By consulting the collision stiffness coefficient of the model,the plastic deformation energy of the deformed door is calculated by the traditional method.At the same time,the deformation data obtained by laser scanner are used to verify the accuracy of the deformation data measured by three-dimensional reconstruction and the plastic deformation energy calculated by traditional methods.Thirdly,in the traditional method of calculating plastic deformation energy of collision vehicles,the data of material stiffness and other data need the help of foreign databases,and the data of deformation adopted by the traditional method are two-dimensional data,and the calculation results of rigidity as a fixed value have large errors.In this paper,the method of calculating the plastic properties of accident vehicles by finite element method is studied.That is to say,triangular shell element suitable for the actual situation of car body is established.On the platform of MATLAB,the joint force calculation and stiffness matrix calculation are realized by self-compiling finite element program.Combining with the tensile test data of materials,the incremental method is adopted to solve the material non-linearity problem.The deformation data used in this method are three-dimensional.According to this,and the stiffness value will be changed reasonably,the limitations of the traditional method will be improved.Finally,the deformation data of the specimens are obtained by using the three-dimensional reconstruction technology through the simulation loading test on the MTS dynamic environment simulation system of specially designed specimens,and the plastic deformation energy of the specimens is calculated by combining the finite element calculation program.In order to verify the correctness of the calculation results,HyperWorks is used to simulate and analyze the specimens.By comparison,the difference between the two methods is 14.49%.It shows that the three-dimensional reconstruction technology based on image combined with finite element calculation of deformed structure is a relatively fast,simple and more accurate method for reappearance analysis of mid-and low-speed collision accidents and plastic performance calculation of vehicles.