The Automobile Body Frontal Structure Design For Vehicle 25% Overlap Frontal Collision

Currently,frontal collisions occur frequently and lead to serious occupant injury.In all frontal collision fatalities,small overlap frontal collision accounts for about a quarter.However,among all the safety regulations and evaluation rules,only the IIHS commenced 25%overlap frontal collision vehicle evaluations in 2012.This paper selects 30 typical vehicles and statistically analyzes the evaluation results respectively in the conditions of full width frontal collision,40%offset frontal collision and 25%overlap frontal collision,and finds that the full mark rate for IIHS 25%overlap is the lowest,the passenger compartment intrusion is larger,and the occupant injury is more serious.However,the current research enterprises and institutions work on the automobile body modification for 25%overlap frontal collision which is usually based on the lack of energy absorption and the passenger compartment intrusion of certain car models appeared in the test conditions and then verified by test or CAE methods.Such structural modification is very difficult to grasp the reduction extent of the passenger compartment intrusion which must repeatedly modify the structure based on the occupant injury to achieve the purpose of protecting the occupant and increase the risk of project development.This paper aims to explore a frontal structure design method which starts from the passenger compartment critical intrusion and then proposes the design requirements of the total energy absorption and energy distribution,transmission characteristics of the collision force to satisfy the automobile body structure requirements.This can provide the design goal for the primary stage which is used for designing the topologies,sections and materials for the frontal structure.Firstly,this paper established the finite element dummy-vehicle model for 25%overlap frontal collision based on Pam-Crash/Safe software.And then this paper evaluated the occupant leg and foot injuries and got three related force transmission path.The main energy-absorbing parts were found by the analysis of deformation characteristic and energy distribution.Secondly,this paper established equivalent simplified model based on the relationship between the occupant leg and foot injuries and passenger compartment and verified its effectiveness.Then this paper established three simplified models based on the equivalent simplified model,explored the characteristics of the energy absorption and force transmission with or without the sub-frame,and proposed design points of frontal structure respectively.Finally,this paper designed the topologies,sections and materials for the frontal structure based on the characteristics of the energy absorption and force transmission,and verified them separately in full width frontal collision,40%offset frontal collision and 25%overlap frontal collision.The explored structure design method of frontal automobile body for 25%overlap frontal collision can get some design points of frontal structure based on energy absorption and force transmission in order to meet the vehicle crashworthiness requirements for 25%overlap frontal collision.Compared to traditional CAE analysis method,this method can reduce the repeated trial process,improve development efficiency,and reduce development costs.