受路面随机激励作用车室低频耦合轰鸣声分析

摘要

为分析车室受路面随机激励作用产生的低频轰鸣声，采用白噪声过滤方法模拟路面随机激励，建立路面随机激励时域模型，根据拉格朗日原理建立整车七自由度振动动力学模型，利用Matlab建立受路面随机激励作用引起的悬架激励力仿真模型，并通过快速傅里叶变换得到悬架激励力幅频谱。利用Hypermesh建立车身结构有限元模型和空腔声场有限元模型，分别利用Nastran、Virtual. Lab计算车身结构模态和空腔声场模态，并采用模态叠加法计算声固耦合系统模态，最后施加悬架激励力载荷进行基于模态的耦合声学响应分析。分析结果表明：在频率20 Hz～50 Hz范围内，路面随机激励对车室低频耦合轰鸣声的贡献较大，以结构变形为主的耦合系统模态，受路面随机激励作用极易使车室空腔出现低频耦合轰鸣声。%To analyze the low frequency booming of the passenger compartments under road random excitation, the time domain model for road random-excitation simulation is established using white noise filtering method. Based on Lagrange principle, a 7-DOF dynamic model for the whole vehicle is set up. The simulation model for suspension excitation force caused by the road random excitation is built by means of Matlab and the amplitude frequency spectrum of the suspension excitation force is obtained by FFT method. A structural FEM for vehicle body and an acoustic FEM for interior cavity are established using Hypermesh. Structure modal analysis and cavity acoustic modal analysis are computed by using Nastran and Virtual.Lab. Then, the structure-acoustic coupling system modals are computed through modal superposition method. Finally, the coupled acoustic response analysis based on the modals is performed by applying the suspension excitation force load. The analysis results indicate that in the frequency range of 20 Hz-50 Hz, the road random excitation has a large contribution to the low frequency booming of the passenger compartments. The coupled system modals dominated by structure deformation can readily lead to low-frequency booming in the passenger compartments under the road random excitation.