Study On Three-dimensional Negative Poisson’s Ratio Structures And Their Application In Automobile

Cellular structures with negative Poisson’s ratio have extensive application prospects in automobile structural design due to their excellent properties such as light weight and high energy absorption under impact cases.However,most of the geometric configurations of negative Poisson’s ratio structures have high porosity,resulting in low utilization of spatial structures,which inevitably reduce their bearing capacity and impact resistance.In the application of energy absorption equipment or protection device,a novel negative Poisson’s ratio structure can achieve the energy absorption characteristics,but also improve the strength and stiffness of the structure is the core problem to be solved in this paper.In this paper,a novel negative Poisson’s ratio structure was proposed through the innovation of spatial topology,and the negative Poisson’s ratio structure was studied in terms of macroscopic mechanical properties,microstructural parameters,structural optimization,and the design and application of automobile structural.The research contents of this paper are as follows:1.The equivalent mechanical model of the tetra-double arrow negative Poisson’s ratio structure was established,which using the ABAQUS finite element analysis software to conduct a quasi-static study of the negative Poisson’s ratio structure,then the accuracy of equivalent mechanical model and the finite element model combined with the quasi-static compression test are verified.Which Using the LS-DYNA to research the dynamics of negative Poisson’s ratio structures,the solutions to the negative volume problem was summarized,and the influence of element types in the pre-simulation process on the simulation accuracy and cost was analyzed.The deformation mode,in-plane impact performance and energy absorption characteristics of the structure with negative Poisson’s ratio were studied,and the accuracy of the finite element model was verified by the in-plane impact experiment.2.A novel negative Poisson’s ratio structure with higher spatial utilization and porosity was proposed,the negative Poisson’s ratio structure is applied to the crash box,and the front bumper-collision trolley model was established.Under two different speed conditions,The finite element simulation of crash box filled with the negative Poisson’s ratio structure was carried out to analyze the deformation model,energy absorption mechanism and crashworthiness at different speeds conditions.The peak impact force,energy absorption,and specific energy absorption was defined as evaluation indexes,the protective effects of different negative Poisson ratio filling structures on automobile front end protection in medium and low speed collision were compared and studied.3.During the impact process,the influence of microstructural parameters such as cell angle,thickness and width on crashworthiness indicators which contains peak impact force and specific energy absorption were studied,and a multi-objective optimization algorithm combined optimal Latin hypercube sampling（LHS）,Response Surface Method（RSM）and Non-dominated Sorting Genetic Algorithms（NSGA-II）algorithm improved the crashworthiness of the structure microstructure parameters,which further guiding the geometric design of the structure with negative Poisson’s ratio.Considering the large number of uncertain factors in practical engineering problems,the 6-Sigma robustness analysis method was used to analyze the uncertainty of the crash box filled with negative Poisson’s ratio.In addition,a front bumper impact experiment was carried out between the negative Poisson’s ratio structure crash box and the traditional crash box,and the deformation model,energy absorption characteristics and crashworthiness under front bumper impact were compared and analyzed.The results show that filling with the negative Poisson’s ratio can effectively improve the crashworthiness of the automobile.4.By using the finite element simulation,the applications of negative Poisson’s ratio structure in electric vehicle door sill and engine hood were studied.Under the condition of side column collision,the protection ability of the negative Poisson’s ratio structure door sill to the battery module of electric vehicle was verified.Under the condition of adult head-shaped impact,the negative Poisson’s ratio structure engine hood was verified,it can also improve the protection ability of the automobile against pedestrians.