Simulation Study Of Automotive In Low-speed Impact

Security contains one of human and the other of physical. Automobile collisionin low-speed does not cause casualties, while damage to vehicle leads to greateconomic loss. The security of low-speed impact is as important as high-speed impactin car crash safety, which plays an important role in vehicle passive safety.Crash boxis key absorbing energy component in low-speed impact.In this paper, aimed at this shortage, to analysis the crashworthiness of crash boxunder the condition of the whole vehicle in low-speed impact. A finite element modelof a whole car of high-speed impact was constructed, and verified its effectiveness bycompared with crash test experiment. Based on the verified car model, a low-speedcrash finite element model was constructed according to the RCAR (ResearchCouncil for Automobile Repairs) test. The result shows that the compression distanceof crash-box is93.4mm, more than the safety distance of88.6mm, which causeradiator damaged. Two schemes were proposed to improve the crashworthiness ofcrash-box in low-speed impact. One is to change the material and the other one isstructural optimization.In the first scheme, toreplace the crash-box original material with yield strengthof380MPa and420MPa steels, then the simulation result shows that the compressiondistance of crash-box reduce to87.2mm and82.8mm, both of thoseare shorter than88.6mm. And the crash force get to101.886kN and115.074kN, while the plasticdeformation of front longeron enlarge to4.962%and27.818%. Only the former isless than the allowable value of5%to meet the requirements.It shows that to increasethe yield strength of a single part may not always bring beneficial effects to the wholecar impact safety.A multi-objective optimization problem based on the compression distance ofcrash-box, crash force and energy absorption in the scheme of structure optimization,has been put forward. After analyzing the parameters of the structures of thecrash-box, taking thickness of crash-box and width of groove as design variables, thefeasible design area is obtained.To generate the test sample points by orthogonal arrays experimental design. A global optimized of the structures was preformed basedon the RSM approximation model. To get Pareto Optimal Solution Set by NSGA-Ⅱ(Non-Dominated Sorting Genetic Algorithm Ⅱ) multi-objective genetic algorithmand choose one of those to verify the effect optimization. The simulation shows thatthe compression distance of the optimized crash-box becomes87.7mm, then there isno contact between the radiator and the bumper. The crash force increases to98.087kN, and the plastic deformation of front longeron enlarge to4.759%. Theoptimized crash-boxmeets the requirements of RCAR low-speed collision. Andenergy absorption forms5.703kJ gets to6.728kJ, an increase of17.97%.This paperprovides a reference to improve the passenger car impact security in low speedcollision research.