Simulation Analysis And Optimization Of Safety Of A Vehicle Seat Headrest

When the vehicle has a rear-end collision,the tail will have a huge impact force,which makes the head of the passenger to move backwards,and the relative displacement of the head and chest is too large,causing the passenger neck to be damaged.A large number of experiments have shown that the headrest can restrict the rearward movement of the adult head relative to their trunk,effectively absorb the external impact energy of the passenger,and reduce the damage of the external force on the human head and the cervical spine,therefore,it is very necessary to develop a safety seat headrest to protect the safety of the head and neck of passengers.In this thesis,HyperMesh pre-processor software,Ls-dyna and Radioss solver,Hyper-View post-processor are used to simulate and analyze the static strength of a vehicle seat structure,which provides a feasible basis for the improvement and optimization of the seat structure.The specific research contents are as follow:(1)A finite element simulation analysis model of the seat was establish,including the division of the mesh,the determination of the boundary conditions,the selection of the unit type,the setting of the connection relationship and material properties.(2)The analysis of the seat headrest static strength test was carried out.The HyperMesh software was applied to establishing the finite element model of middle-row seats of a domestic vehicle brand.In accordance with the load requirements of GB11550-2009,a simulation test of static strength for the headrest of seat was carried out by Ls-dyna.The simulation analysis shows that the seat headrest static strength test cannot meet the requirements of the regulations.Therefore,the headrest frame of the seat was required to further improve.Two schemes were propose in the paper.The supplement of reinforcing rib was applied to the headrest bar in the first proposal,frame structure of headrest bar was changed in the second proposal.(3)The energy absorption simulated analysis was carried out based on scheme NO.2.According to the requirements of the regulations,a simulate test of the energy absorption for the headrest of seat was carried out by Ls-dyna,and the deceleration curve of the fake head model was obtained.(4)According to the result of simulation analysis of the energy absorption of the headrest,the optimization analysis of the headrest cushion was carried out.By orthogonal analysis,the three factors of density,thickness and parcel of the headrest cushion are analyzed,9 different parameters are obtained,through re-analysis of the seat and the optimum parameters of the headrest cushion were found.The influence of the three factors on the peak value of the deceleration of the false head was determined by range analysis method,and then the significance of the three factors was determined by variance analysis method.(5)The static strength and the energy absorption of the headrest were tested on a special test bench of a company.The experimental date was compared with those finite element analysis to determine the accuracy and feasibility of the simulation analysis.(6)The numerical modal analysis method was used to study the modal of the overall skeleton of the seat without headrest and three headrest positions.The first two-order resonance frequency of the seat was calculated by the method of simulation analysis by linear vibration theory.And the two modes of the two representative seat structures were extracted in the post-processor.