The Design And Optimization Of Crash Box Based On 3-D Negative Poisson's Ratio Structure

Crash box is a part of the bumper system.When the car happens to a crash,the crash box can absorb the energy of crash to protect the other automobile components from damaged.So,the crash box has a significant meaning to improve the safety of automobiles and reduce the maintenance cost under the low-velocity accidents.In order to enhance the crash box's mechanics performance and reduce its mass,a new crash box,made from negative poisson's ratio cellular structure,is designed.In this paper,the energy absorption mechanism of the negative poisson's ratio structure is explained by analysising its stress-strain curve and deformation feature.Then,the constant-velocity models of crash box are established to analysis the effects of its geometrical parameters to its mechanical properties.While,the parameters of the crash box are selected from its design space by Optimal Latin Hypercube method.At last,the crash box is optimized by cubic RSM model and NCGA method.The result meets the RCAR rule.In order to reduce the mass of negative poisson's ratio crash box,the concept of functional grade is adopted to the crash box design.According to the mechanical properties of the crash box in different relative density,a gradient negative poisson's ratio crash box is designed.Then the gradient negative poisson's ratio crash box is optimized by cubic RSM model and NSGA-II.The result is better than the former crash box.At last,the gradient negative poisson's ratio crash box is equipped on the bumper to verify its practicality.The test model is the 40% offset crash model.Because of the bumper's geometrical shape,a joint device is designed to combine the bumper and the crash box.Simulation result meets the RCAR rule.This paper proved that: Combining RSM model with optimization method can improve the efficiency of the structure optimization;The negative poisson's ratio crash box can meet the RCAR test;The concept of functional grade can make the crash box more lighter and enhance its performance;Negative poisson's ratio structure has a great practicability in crash box design.