轿车车身怠速共振分析

Idle resonance analysis and test of car body-in-white

针对某轿车在怠速工况下车身容易产生共振,采用有限元技术和模态试验相结合的方法对该轿车白车身进行模态分析,找出车身振动的根本原因。首先建立白车身有限元模型,重点研究点焊单元的模拟方法,通过模态分析得到该白车身模态参数;然后搭建白车身模型的模态测试系统,采用随机子空间法识别得到白车身模型的模态动态响应参数。通过对比计算模态和试验模态,误差在5.3%内。结果表明,发动机激励频率（23~25 Hz）与车身1阶试验模态频率（25.53 Hz）相近是导致怠速工况下车身振动的主要原因,应增强车身发动机盖和顶板强度,这为车身的动态和结构设计提供了参考依据。

Because the resonance usually appeared in idle condition, modal test and finite element method were used to carry out modal analysis for car body-in-white in order to find out the main reason that made car-body vibrate. Firstly, the finite element model of body-in-white was established. The simulation method of spot-weld unit was studied, and the modal parameters of body-in-white were obtained by modal analysis. Then,the modal test system for body-in-white was built and modal dynamic-response parameters of body-in-white were get by stochastic subspace identification-method. The error was within 5.3% by results comparison between calculation modal and test modal.The result shows that incentive frequency（23~25 Hz） from engine in idle condition and the first-order experimental modal-frequency（25.53 Hz） from car-body are so similar,which is the main reason of vibration of car-body idle-condition. So, stiffness of hood and roof of car-body should be enhanced. The research provides a reference for structural design of car-body.