Structure Optimization Of A Passenger Vehicle Based On Small Overlap Frontal Collision Target Decomposition Analysis

Nowadays,vehicle collision accident occurrence rate becomes higher and higher,especially the frontal collision which results in the highest incidence and casualty rate among all the traffic accidents.25% of these deaths are caused by small overlap frontal collision.As the collisions happen at the corner of the vehicle,traditional buffering energy absorption components show a low crushing rate and a poor energy absorption performance,resulting in a higher level of intrusion into passenger compartment and more severe passenger injury.Therefore,it is of great significance to study the crashworthiness of vehicles under a small overlap frontal collision condition.Vehicle crashworthiness optimization is a complex issue.The target decomposition method uses the crashworthiness of a vehicle as the overall target,and gradually decomposes it into sub-goals in the following design steps,always aiming at achieving the overall goal.In this thesis,the crashworthiness overall goal is decomposed into the target energy absorption of the front compartment sub-structures and the target axial force interval.Eventually,the overall requirements were met with the completion of the sub-structure designs.Although this method will increase the workload in early design stage,it can reduce the trail and error process for the detail design phase,and increase the success rate.This thesis based on the study of a passenger vehicle.First,CAE simulation was carried out to analyze the small overlap frontal collision.Then,considered the critical value of the passenger compartment intrusion,the target adsorption of front compartment sub-structure can be obtained through calculating the new collisions velocity with golden section method.Finally,by changing the structure thickness and form as well as adjusting the sub-structure axial force,the relationship between the axial force and the crashworthiness can be found and thus the target range of the sub-structure axial force can be determined.According to the axial force distribution range of the front compartment and the target energy adsorption of its substructures,the front structure design of the vehicle body was accomplished following the conventional thin-walled beam crushing theory.Furthermore,this improved scheme was assessed with CAE simulation for full width frontal collision,the 40%offset frontal collision,and the small overlap frontal collision respectively.The results indicate that the improved scheme can meet the crashworthiness requirements in frontal collisions.At last,two types of vehicles were improved with lightweight method,for safety,energy saving and environmental protection purposes.Combined the optimal Latin hypercube design,the response surface methodology,and multi-objective genetic algorithm,the multi-objective optimization was performed for light weight without sacrificing the crashworthiness.Eventually,in these two multi-objective optimization strategies,the total weight of the components decreased by 9.5% and 11.1%,respectively.