The Optimization Design Research On Automobile Inner Door Panel Oriented To Vibration Problems

As an essential part of vehicle,the vibration performance of door will directly affect the NVH performance ofthe vehicle,thereby affecting the ride comfort of passengers.The car door vibrates with the excitation of the motor,engine and road during the car works.If thedesign of the door structure is improper,the resonance phenomenon will appear because the frequenciesof excitationsclose to the natural frequencies of door.For this reason,it is valuable to study the vibration performance of door and perform the optimization design research of car door structure.The main content of this thesis is as follows.So as to get the natural frequencies and vibrational modes andevaluate the vibration characteristics of the car door,FEM is built by ABAQUS to perform freemodal analysis.To verify the accuracy of the modal analysis results,experimentmodal analysis is carried out by using LMS.Test.Lab test system,in which multiple input single output method is applied.The modal parameters are extracted by using PolyMax modal fitting method.The door modal vibration modes of experiment are consistent with that of finite element modal analysis.The natural frequenciesare also close,and the maximum error is 7.9%,which within the permissible range of error.So the accuracy of the finite element modal analysis is verified.According to the results of modal analysis,the natural frequencies of the dooravoid the frequencies of the excitation sources.While the first order natural frequency 41.1Hz of the door close to the forth order natural frequency 41.44 Hz of BIW(body in white).So optimization is needed to improve the natural frequency.Aimed at the vibration problem of the door,OptiStruct software is used to perform the single target topography optimization with the first order natural frequency as optimization objective and the abdomen of inner door panel as design domain.And the optimal valuesof different reinforcement parameters are determined.After optimization,the first-order natural frequency of car door has increased by 7.7% compared with that before optimization,which is 2.82 Hz higher than the fourth order frequency of BIW and 5.39 Hz lower than the fifth order frequency of BIW,avoiding the frequencies of excitations at the same time.So resonance phenomenon will not appear after single target optimization.The multi-targetstopography optimization study of car door is performed,in which compromise programming method is adopted to establish a comprehensive objective function with the vertical stiffness and the first three order vibration frequencies as the optimization goal.And the optimal values of different reinforcement parameters are determined.After optimization,the first-order natural frequency of car door has increased by 8.1% compared with that before optimization,which is 2.99 Hz higher than the fourth order frequency of BIW and 5.22 Hz lower than the fifth order frequency of BIW,avoiding the frequencies of excitations at the same time.So resonance phenomenon will not appear after multi-targets optimization.Compared with these two methods,there is little difference betweenthe optimization result of single objective and that of multi-objective optimization.But the efficiency of single objective optimization is higher than that of multi-objective optimization,and modeling process is easier compared with the latter.When meeting the similar problems in the engineering practice,the single objective optimization method is recommended.This thesis reached the purpose of optimization design.In the product development phase,the optimization design research has been completed,which provide the guidance for the design of car door and can save the development cycle and cost of enterprise.