Structure Analysis And Modal Optimization Of An Automobile Seat

Automobile seats are an important assembly unit that connects driver and passengers and the automobile,and it directly influences the safety and comfort of the driver and passengers,so there is no doubt that the importance of automobile seats cannot be over emphasized.Country and enterprises have made relative regulations and test requirements on automobile seats,and now test process,test equipment and finite element method analysis are all very well-established,which has a significant importance on improving the whole level of automobile seat filed and safety of drivers and passengers.At the same time,the vibration of automobile seats influences the comfort of seat,and the increase of seat's modal frequency is one of an effective ways to avoid resonance.The main contents of this paper are as follows:(1)the Construction and Analysis of Dynamic Simulation Model.Based on the CATIA geometry model of an automobile seat,the finite element pre-processing is done by the HyperMesh software,and then there are four solving models,the strength test of seat system,the test of seat headrest performance and the test of 50% Hybrid ? dummy front collision and back collision,respectively.These two types of operating conditions can be solved by OptiStruct and LS-DYNA software,respectively,and then the performance results can be analyzed.(2)Modal Test,the Analysis and Verification of Modal Simulation Model.The modal test of the seat is done.To validate the effectiveness of the modal test's result,the value of MAC(Modal Assurance Criterion),MPC(Modal Phase Collinearity)and MPD(Mean Phase Deflection)are calculated.Considering the difficult of modeling of small components and getting the stiffness parameters between two components,this paper does numerical analysis about these parameters and gets a modal simulation model with a little error compared with experiment results.The Cross MAC(Cross Modal Assurance Criterion)is used to validate the effectiveness of modal simulation model.(3)the Frequency Optimization of the Seat.Based on the modal model obtained from previous step and according to route from “concept design” to “detail design”,the current paper uses 4 optimization methods,method of modal strain energy,topography optimization,topology optimization and size optimization,to optimize the automobile seat's first frequency step-by-step.The compliance constraints added to the size optimization.After these optimization,the seat's first frequency increases to 19.64 Hz,increases by 3.06 Hz,and this meets the enterprise's newest requirement.(4)the Validation of Seat's Dynamic Operating Conditions after Optimization.After the optimization,the seat is needed to validate in the national standards and enterprise standards.The new seat model is imported into the four dynamic operating conditions and the results are analyzed.Because in some operating conditions the seat cannot meet the requirements,in order not to increase the mass of the seat,some components in the seat are replaced with other better materials,and then the seat meets all requirements.Finally,after all optimization and modification,the seat's first frequency increases by 3.06 Hz,but the mass of the seat decreases by 0.31 Kg.Under the condition that the seat meets all dynamic requirements,the aim of lightweight is obtained.