Research On The Crashworthiness Of Frontal Collision Structure Of Passenger Car Based On Front Rail Optimization

In the vehicle occupant protection evaluation stipulated in the 2021 version of the "China New Car Evaluation Regulations",the occupant injuries of the frontal 50%overlapping offset collision(MPDB working condition)and 100% overlapping collision(FRB working condition)are more serious than other working conditions,and the proportion of penalty points in the vehicle safety star evaluation is also higher.The results show that the force transmission rate of the front side member is higher than 75%and the energy absorption rate is higher than 34.5% during the frontal collision of the vehicle,so the study of the deformation and energy absorption characteristics of the front side member plays an important role in the passive safety of the vehicle.However,the test results of the drop weight of the front side member cannot evaluate the crash performance of the whole vehicle,so this paper studies the influence of the energy absorption characteristics of the front side member on the crashworthiness of the frontal collision structure of passenger cars,so as to improve the collision performance of the whole vehicle and reduce the occupant injury.This thesis includes the following main contents:(1)Passive safety analysis and multi-objective optimization of front side beams.The front stringer drop weight test was set up by using the front stringer benchmark model,and the energy absorption characteristics of the front stringer were evaluated by analyzing the specific energy absorption SEA,average crushing force MCF and energy absorption efficiency Q of the front stringer.The sensitivity analysis of different parts of the front side beam was carried out,the thickness and material of the inner and outer plates of the front side beam were determined as the optimization goal,the parametric model of the response surface of the front side beam was established,60 sampling points were selected by the Hamersley sampling method,and the approximate mathematical model of the front side beam was obtained by moving the least squares method for polynomial fitting,and finally the energy absorption characteristics of the front side beam were optimized by the global response surface method,and the optimization results were obtained.After optimization,the SEA value of the front side member increased by 937.72 KJ,MCF increased by 47.52 KN,and Q increased by3.76%,and the results showed that the energy absorption characteristics of the front side member after optimization were improved.(2)Determination of vehicle verification scheme and evaluation index.In order to improve the accuracy of the verification results,this paper constructs the FRB working condition,MPDB working condition and FRB auxiliary constraint system model verification optimization results.The FRB working condition selects the acceleration and velocity zero moment at the lower end of the B-pillar,the deformation of the front side beam and the intrusion amount of the front fence to evaluate the crashworthiness of the vehicle structure,and the collision compatibility evaluation index is added on this basis under the MPDB working condition.(3)Comparison and evaluation of passive safety simulation results of basic model and optimization model of passenger car.In the MPDB condition,the peak acceleration at the lower end of the left B pillar decreased by 4.24 g,the peak acceleration at the lower end of the right B pillar decreased by 4.83 g,the deformation of the front side beam and the intrusion of the front fence were slightly improved,the collision compatibility penalty decreased by 0.44 points,and the OLC value decreased by 0.8g.In the FRB working condition,the peak acceleration at the lower end of the B-pillar on the left side of the optimization model decreased by 3.78 g and the right side decreased by 4.25 g,the deformation of the front longitudinal beam of the optimization model was slightly better than that of the basic model,the intrusion of the front fence was also reduced,and the optimization results of the auxiliary restraint system of the FRB working condition also met the regulatory requirements.In summary,in the two working conditions of frontal collision,the crashworthiness of the vehicle structure of the optimization model is significantly improved compared with the basic model,and the optimization of the front side member has practical significance for the improvement of the crashworthiness of the whole vehicle.