Factor Influences Of 40% Offset Collision Simulation Accuracy For A Passenger Car

According to the all types of car accidents,the probability of frontal collision was the highest,and the injury and death rate of passengers was the highest when the overlap rate of frontal collision was 30%~40%.Therefore,C-NCAP sets 40% offset deformable barrier impact to investigate the structural crashworthiness of vehicle body.Due to the disadvantages of the experiment method,such as expensive test costs,limited information and long cycle of design,the finite element simulation method was widely used in the study of vehicle crash safety performance by major automobile manufacturers.At present,there was still some deviation between the results of finite element simulation and the results of frontal offset impact experiment,such as the difference between the acceleration curve of finite element simulation and that of experiment;the common connection failure problems in the experiment cannot be well simulated in the finite element simulation and so on.Finite element simulation accuracy would be affected by various factors.How to improve the simulation accuracy of finite element simulation was the hotspot of crash simulation all the time.Therefore,this paper studied the influence of key simulation parameters,mechanical properties of materials,connection modeling methods on the accuracy of the finite element simulation results from the factors that affect the accuracy of the finite element simulation.Finally,the best combination of the factors was found out by orthogonal test,which improved the accuracy of simulation model.The main work was summarized as follows:(1)The basic finite element simulation model of a passenger car was built by using finite element preprocessing software,and compared with the test collision timing and B-pillar acceleration.The accuracy of the simulation results was evaluated by Correlation Rating(CORA).The larger the CORA,the higher the simulation accuracy.The CORA of B-pillar acceleration of the basic finite element simulation model was 72.77%.(2)The influence of key simulation parameters on the simulation accuracy was studied.Firstly,the influence of geometric accuracy and integral point setting on the simulation result was studied by single hat column finite element model.Then the influence of different mesh size,integration point setting and friction coefficient on the simulation accuracy of vehicle collision was compared on the basic model.The result shows that the detailed fillet,the appropriate mesh size and integral point setting,and the smaller friction coefficient could improve the CORA of the left B-pillar acceleration.(3)The influence of mechanical properties of materials on the simulation accuracy was studied.The elastic modulus,Poisson’s ratio and other basic mechanical parameters of the front rails material were obtained by tensile test,and then the influence of different strain rate parameters on simulation accuracy was studied.The result shows that different strain rate parameters had a great influence on CORA of the left B-pillar acceleration.The strain rate parameters must be set accurately in the simulation model.(4)The influence of connection modeling methods on the simulation accuracy was studied.Through the analysis of different solder joint modeling methods,it was found that the CORA of left B-pillar acceleration of the Hex spotweld was generally higher than that of the Beam spotweld,and when the Hex spotweld element was Hex8,the CORA of left B-pillar acceleration was the highest;then a bolt modeling method which could predict failure and pull off was established and used in the basic model.Finally,the Beam element contact method was used to simulate the weld connection,and the diameter and yield strength of Beam element were calculated by the Reversing Method.The simulation result shows that the Beam element contact method can improve the CORA of the left B-pillar acceleration.(5)The parameters which had great influence on the Cora of left B-pillar acceleration were selected by one-way anova.Then,the orthogonal experiment was designed to consider the influence of key simulation parameters,mechanical properties of materials,connection modeling methods on the simulation accuracy of finite element simulation,and the optimal combination was found.The accuracy of the finite element model was significantly improved,which layed the foundation for the next step of improving the crashworthiness of the whole vehicle.